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 Jackson Hole  -> Yellowstone National Park > Wildlife in Yellowstone National Park

Yellowstone National Park

Yellowstone’s Wildlife

Yellowstone's Amphibians

General

• Cool, dry conditions limit Yellowstone's amphibians to four species.
• Population numbers for these species are not known.
• Amphibians: boreal toad, chorus frog, spotted frog, tiger salamander.

Status

• The spotted frog may be declining in the West.
• Some researchers suspect that there are more amphibians in Yellowstone than are currently known, but this has not been documented yet.

Yellowstone is home for a small variety of amphibians. Glacial activity and current cool and dry conditions are likely responsible for their relatively low numbers in Yellowstone.

In 1991 park staff began cooperating with researchers from Idaho State University to sample additional park habitats for reptiles and amphibians. This led to establishment of long-term monitoring sites in the park (map, page 119). The relatively undisturbed nature of the park and the baseline data may prove useful in testing hypotheses concerning the apparent declines of several species of toads and frogs in the western United States. Reptile and amphibian population declines may be caused by such factors as drought, pollution, disease, predation, habitat loss and fragmentation, introduced fish and other non-native species.

Although no Yellowstone reptile or amphibian species are currently listed as threatened or endangered, several-including the boreal toad-are thought to be declining in the West. Surveys and monitoring are underway to try to determine if amphibian populations are declining in Yellowstone National Park

BLOTCHED TIGER SALAMANDER

 

Identification

• The only salamander in Yellowstone.
• Adults range up to about 9 inches, including the tail.
• Head is broad, with a wide mouth.
• Color ranges from light olive or brown to nearly black, often with yellows blotches or streaks on back and sides; belly is dull lemon yellow with irregular black spots.
• Larvae, which are aquatic, have a uniform color and large feathery gills behind the head; they can reach sizes comparable to adults but are considerably heavier.

Habitat

• Breeds in ponds and fishless lakes.
• Widespread in Yellowstone in a great variety of habitats, with sizable populations in the Lamar Valley.

Behavior

• Adult salamanders come out from
  hibernation in late April to June, depending on elevation, and migrate to breeding ponds where they lay their eggs.
• Mass migrations of salamanders crossing roads are sometimes encountered, particularly during or after rain.
• After migration, return to their moist homes under rocks and logs and in burrows.
• Feed on adult insects, insect nymphs and larvae, small aquatic invertebrates, frogs, tadpoles, and even small vertebrates.
• Preyed upon by a wide variety of animals, including mammals, fish, snakes, and birds such as sandhill cranes and great blue herons.

BOREAL TOAD

 

Identification

• Yellowstone's only toad.
• Adults range up to about 4 inches, juveniles just metamorphosed from
  tadpoles are only one inch long.
• Stocky body and blunt nose.
• Brown, gray, or olive green with irregular black spots, lots of "warts," and usually a white or cream colored stripe down the back.
• Tadpoles are usually black and often congregate in large groups.

Habitat

• Once common throughout the park, now appears to be much rarer than spotted frogs and chorus frogs; scientists fear this species has experienced a decline in the Greater Yellowstone Ecosystem.
• Adults can range far from wetlands because of their ability to soak up water from tiny puddles or moist areas.
• Lay eggs in shallow, sun-warmed water, such as ponds, lake edges, slow streams, and river backwaters.

Behavior

• Tadpoles eat aquatic plants; adults eat insects, especially ants and beetles, worms and other small invertebrates.
• Sometimes active at night.
• Defends itself against predators by secreting an irritating fluid from numerous glands on its back and behind the eyes.
• Eaten by snakes, mammals, ravens, and large wading birds.

COLUMBIA SPOTTED FROG

 

Identification

• Abundant and best known amphibian in Yellowstone.
• Maximum length is 3.2 inches, newly metamorphosed juveniles less than one inch long.
• Upper surface of the adult is gray-brown to dark olive or even green, with irregular black spots; skin is bumpy; underside is white splashed with brilliant orange on the thighs and arms on many but not all individuals.
• Tadpoles have long tails and may grow to 3 inches long.

Habitat

• Found all summer along or in rivers, streams, smaller lakes, marshes, ponds, and rain pools.
• Lay eggs in stagnant or quiet water, in globular masses surrounded by jelly.

Behavior

• Breeds in May or early June, depending on temperatures.
• Tadpoles mature and change into adults between July and September.
• Tadpoles eat aquatic plants, adults mostly eat insects but are highly opportunistic in their food habits (like many other adult amphibians).

BOREAL CHORUS FROG

 

Identification

• Adults reach 1 to 1 1/2 inches in length, and females are usually larger than males; newly metamorphosed froglets are less than one inch long.
• Brown, olive, tan, or green (sometimes bi-colored) with a prominent black stripe on each side from the nostril through the eye and down the sides to the groin; three dark stripes down the back, often incomplete or broken into blotches.

Habitat

• Common, but seldom seen due to its small size and secretive habits.
• Live in moist meadows and forests near wetlands.
• Lays eggs in loose irregular clusters attached to submerged vegetation in quiet water.

Behavior

• Breeds in shallow temporary pools or ponds during the late spring.
• Calls are very conspicuous, resembles the sound of a thumb running along the teeth of a comb.
• Males call and respond, producing a loud and continuous chorus at good breeding sites, from April to early July, depending on elevation and weather.
• Usually call in late afternoon and evening.
• Tadpoles eat aquatic plants; adults mostly eat insects.
• Eaten by fish, predacious aquatic insect
  larvae, other amphibians, garter snakes, mammals, and birds.

Never approach closer then 100 Yards to
Bears and 25 Yards to Other Wildlife

The grizzly bear population within the Yellowstone ecosystem is estimated to be approximately 280-610 (Eberhardt and Knight 1996) bears. The park does not have a current estimate of the black bear population; black bears are considered to be common in the park.

Black Bear

Color: Varies from pure black to brown, cinnamon, or blonde; in the Rocky Mountains, approximately 50% are black with a light brown muzzle.

Height: About 3 ft (0.9 m) at the shoulder.

Weight: Male: 210-315 lbs (95-143 kg); Female: 135-160 lbs (61-73 kg) (Barnes and Bray 1967).

Home Range Size: Males: 6-124 mi² (16-321 km²); Females: 2-45 mi² (5-117 km²) (Mack 1988).

Life Expectancy: 15 - 20 years in the wild; 30+ years in captivity.

Grizzly Bear

Color: Varies from black to blonde; frequently with white-tipped fur giving a grizzled, "silver-tipped" appearance. In the Yellowstone ecosystem, many grizzly bears have a light brown girth band.

Height: About 3-1/2 ft (1.0 m) at the shoulder.

Weight: Male: 216-717 lbs (98-325 kg); Female: 200-428 lbs (91-194 kg) (Blanchard 1987).

Home Range Size: Males: 813-2075 mi² (2106-5374 km²); Females: 309-537 mi² (801-1391 km²)

(Blanchard and Knight 1991).

Life Expectancy: 15 - 20 years in the wild; 30+ years in captivity.

Physical and Behavioral Characteristics

The physical and behavioral differences between black bears and grizzly bears have been described in detail by Herrero (1978). Black bears are primarily adapted to use forested areas and their edges and clearings. Although grizzly bears make substantial use of forested areas, they also make much more use of large, non-forested meadows and valleys than do black bears. Black bears have short, curved claws better suited to climbing trees than digging. This enables black bears to forage for certain foods, such as mast, by climbing trees. In contrast, grizzly bears have longer, less curved claws and a larger shoulder muscle mass better suited to digging than climbing. This enables grizzly bears to efficiently forage for foods which must be dug from the soil such as roots, bulbs, corms, and tubers, as well as rodents and their caches. The primary difference between the food habits of black bears and grizzly bears in the Yellowstone ecosystem is the absence of roots in the diet of black bears (Knight et al. 1988).

Behaviorally, black bears are generally much less aggressive than grizzly bears and rely on their ability to climb trees to allow themselves and their cubs to escape predators such as wolves, grizzly bears, or other black bears. Grizzly bears are generally one and one-half to two times larger than black bears of the same sex and age class within the same geographic region. Grizzly bears are also more aggressive than black bears and more likely to rely on their size and aggressiveness to protect themselves and their cubs from predators or other perceived threats.

Another behavioral difference between black bears and grizzly bears is the length of time cubs are under their mother's care. Black bear cubs are born in the winter den, spend the summer following birth with their mother, den with her again in the fall, then separate from her early the next summer as yearlings. Grizzly bear cubs spend two and one-half and sometimes three and one-half years under their mother's care before separation.

 Hibernation

Hibernation is an adaptation to a seasonal shortage of food, low environmental temperatures, and snow cover on the ground (Crowed and Crowed 1972; Tietje and Ruff 1980). Bears hibernate during the winter months in most areas of the world. Duration of winter denning is dependent upon latitude and varies from a few days or weeks for black bears in Mexico to 6 months or more for bears in Alaska (Kolenosky and Strathearn 1987). The denning period in YNP is approximately 5 months.

For many years bears were not considered to be true hibernators. Mammals considered true, or deep hibernators, such as chipmunks and ground squirrels, experience a drastic decrease in body temperature during hibernation. Body temperature for a hibernating bear remains above 88° F (31° C) which is within 12° F (11° C) of their normal body temperature of 100° - 101° F (37.7° - 38.3° C) (Bagget 1984). This allows bears to react to danger quicker than hibernators whose body temperature may be less than 40° F (4° C) and who have to warm up before they can move quickly (Bagget 1984). Many researchers now consider bears to be super-hibernators. Due to the highly insulative pelts of bears and their lower surface area to mass ratio than smaller hibernators, body heat is lost slowly which enables bears to cut their metabolic rate by 50-60% (Crowed and Crowed 1972; Rogers 1981). Respirations in bears decrease from 6-10 breaths per minute normally, to 1 breath every 45 seconds during hibernation. They experience a drop in heart rate from 40-50 beats per minute during the summer to 8-19 beats per minute during hibernation. Mammals that experience lower body temperatures during hibernation, such as chipmunks and ground squirrels, must awaken every few days to raise their body temperature, move around, urinate, and eat (Rogers 1981). Grizzly bears and black bears generally do not eat, drink, defecate, or urinate during hibernation. Bears live off of a layer of fat built up during the summer and fall months prior to hibernation. Waste products are produced, however, instead of disposing of their metabolic waste, bears recycle it. The urea produced from fat metabolism (fatal at high levels) is broken down and the resulting nitrogen is used by the bear to build protein which allows them to maintain muscle mass and organ tissues (Rogers 1981). Bears lose fat and may actually increase lean-body mass while hibernating due to this nitrogen recycling (Wickelgren 1988). Bears may loose 15-30 % of their body weight during hibernation (Rogers 1981). It was once thought that bears ate roughage prior to den entrance to scour their digestive tract and form a plug in the anus to prevent them from eating any more food that fall. Actually, the plug, made up of feces, dead intestinal cells, hair, and bedding material, forms during hibernation and not before (Rogers 1981). Bears continue to produce some feces during hibernation yet they do not defecate (Rogers 1981). It is possible this plug may keep the bear from defecating inside the den during hibernation as fecal plugs are found just inside or outside the dens of bears that have just emerged (Rogers 1981).

It was once believed that bears obtained nutrients from sucking their paws during hibernation. This idea most likely arose from observations of bears licking the bottom of their paws during the last half of the denning period when their old, calloused foot pads slough off (Rogers 1977). The sucking and licking action apparently helps toughen the new foot pads so bears can walk on them without pain or difficulty when they emerge from the den and begin searching for food (Beecham et al. 1983).

In the Yellowstone ecosystem, grizzly bears tend to dig or locate dens on the mid to upper one-third of 30° - 60° slopes with northern exposures between 6,562 - 10,006 ft,  =8103 ft (2,000 - 3,050 meters,  =2,470 m) in elevation (Judd et al. 1986). Black bears locate or excavate dens on 20° - 40° slopes ( =27.8°) with northerly aspects between 5,800 - 8,599 ft,  =7,346 ft (1,768 - 2,621 meters,  =2,239 m) in elevation (Mack 1990). There are several different types of dens utilized by bears. Black bears tend to excavate dens, den under windfalls, in hollow trees or caves, and in previously occupied dens (Jonkel 1980). Grizzly bears tend to excavate dens at the base of large trees often on densely vegetated north-facing slopes. This is advantageous in the Yellowstone ecosystem due to prevailing SW winds which accumulate snow on northerly slopes and insulate dens from temperatures which often drop as low as -40° F to -60° F (-40° C - -51° C) (Crowed and Crowed 1972; Jonkel 1980; Vroom et al. 1980). Grizzly bears in YNP usually dig new dens but on occasion, dens (especially natural cavities) are re-utilized. (Crowed and Crowed 1972; Judd et al. 1986; Miller 1990). Most dens are dug in sandy loam soils with some occurring in clay loams and rocky silt soils (Judd et al. 1986). Reuse of excavated dens is rare but does occasionally occur. Usually excavated dens collapse the spring after they are dug due to runoff and are unusable. Some grizzly bears excavate dens long before the onset of hibernation while other bears tend to wait to almost the last minute to construct dens (Crowed and Crowed 1972). Major den excavation is completed in 3-7 days during which a bear may move up to a ton of material (Brown 1993; Crowed and Crowed 1972). After completion of a den (which consists of an entrance, a short tunnel, and a chamber) bears will cover the chamber floor with bedding material ranging from spruce boughs to duff. The bedding material has many air pockets which trap body heat and form a microclimate around the bear helping to keep it warm (Crowed and Crowed 1972). These bedding materials are related to availability at the den site and not on the bears preference (Judd et al. 1986). The den entrance is usually just large enough for the bear to squeeze through. This minimal opening size helps prevent heat loss during hibernation since a smaller opening will be covered with snow more quickly than a large opening. The tunnel is dug straight into a hillside or at a slightly upward angle to keep heat in the den chamber. The chamber is dug slightly larger than the bear allowing for efficient heat retention. Males and females with young usually dig the largest dens.

Movement to dens is correlated to weather and snow conditions with most movement usually occurring from late October to mid November (Judd et al. 1986). However, Crowed and Crowed (1972) found hibernation onset varied by as much as one month depending on weather conditions. Bears will remain in the area of their den for a few weeks and enter a state of lethargy during which they eat nothing and sleep frequently (Crowed and Crowed 1972). According to Crowed and Crowed (1972) and Servheen and Klaver (1983), final den entry occurs during severe snowstorms. In theory the fresh snow will hide any tracks or other evidence of where the bear's den is located. Solitary females usually enter dens first, followed by females with young, subadults, and lastly, adult males. Grizzly and black bears breed from May through July but the embryonic implantation does not occur until around December, about 1 month after solitary females den. The cubs are then born in late January or early February and are naked, blind, and helpless (Roger 1981). They measure only about 8 inches (20 cm) long and weigh from 8-12 ounces (224-336 g). The cubs do not hibernate. They sleep next to the sow, nurse, and grow rapidly. When black bear cubs emerge from the den at about three moths of age, they weigh about 4-8 pounds (1.8-3.6 kg) and are able to follow the sow around in search of food (Rogers 198). At ten weeks of age, grizzly bear cubs weigh about 10-20 pounds (4.5-9.0 kg) (Brown 1993),

When temperatures warm up and food is available in the form of winter-killed ungulates or early spring vegetation, bears emerge form their dens. First to emerge are adult males in mid March (= number of days denned =113), followed by subadults, and solitary females in late March to early April (= days denned =132). The last to emerge are females with young in early to mid April (number days denned = 170) (Judd et al. 1986, Beecham et al. 1983). The males, subadults, and solitary females usually leave the vicinity of their den within a week of emergence while females with young remain in the general vicinity for 2-3 weeks (Lindzey and Meslow 1976).

Several physiological processes bears undergo during hibernation are of interest to medical researchers. When bears are hibernating and metabolizing body fat, their cholesterol levels are twice as high as during the summer and twice as high as the cholesterol levels of most humans (Bagget 1984). Bears, however, do not suffer from hardening of the arteries (arteriosclerosis) or gallstones, conditions which result from high levels of cholesterol in humans. The bear's liver secretes a substance that dissolves gallstones in humans without surgery. Another mystery of hibernation is that bears do not lose bone mass during hibernation. All other mammals which maintain non-weight bearing positions for an extended period of time suffer from osteoporosis, or a weakening of the bones (Wickelgren 1988). When the substance for this phenomenon is discovered it may help people who suffer from weak bones.

  Bear Deaths 1992-1997

 a Includes bears killed accidentally during management actions.

 From 1980-2002, over 62 million people visited Yellowstone National Park (YNP). During the same period, 32 people were injured by bears. The chance of being injured by a bear while in the park is approximately 1 in 1.9 million.

Injuries to Humans - Grizzly Bears

Grizzly bear-inflicted injuries to humans in developed areas averaged approximately 1 per year during the 1930's through the 1950's and 4 per year during the 1960's. Grizzly bear-caused human injuries in developed areas then decreased to 1 injury every 2 years (0.5/year) during the 1970's. In the last 20 years (1980-2002), there have been only 2 grizzly bear-caused human injuries in a developed area.

Human injuries from grizzly bears in the backcountry, a rare occurrence before 1970, increased to an average of approximately 1 per year during the 1970's, 1980's, and 1990's. The slight increase in backcountry injuries from the 1970's through the 1990's may be related to the increase in backcountry recreational use since the early 1970's.

Injuries to Humans - Black Bears

Human injuries from black bears have decreased from averages of 46 per year from 1931-1969, to 4 per year during the 1970's and less than one (0.17) per year from 1980-2002. Undoubtedly, some minor injuries were not reported by park visitors. Only 7 of the 45 injuries caused by black bears from 1970-2002 were in backcountry areas, and 2 of these were from females "defending cubs." Thirty-four injuries were from black bears along roadsides as a result of visitors getting too close while attempting to feed, take pictures, or get a better view of bears. Three injuries were from black bears in developed areas, and 1 injury was during a bear-relocation accident.

Human Fatalities

Five known bear-caused human fatalities and 1 possible fatality have occurred within YNP. In addition, 1 fatality occurred in the Gallatin National Forest outside of the park.

In October of 1986, the fifth fatality in YNP occurred when a photographer approached an adult female grizzly bear too closely in Hayden Valley. The fourth fatality occurred in July 1984, when a grizzly bear killed a backpacker in a backcountry campsite located on the southern end of White Lake. The third fatality occurred in June 1972, when a man returned at night to an illegally established camp and approached to within 50 feet of a grizzly bear that was feeding on food that was left out. The second fatality occurred in August 1942, in the Old Faithful campground. The species of bear involved could not be determined. The first fatality occurred in 1916 when a grizzly bear killed a man in a roadside camp. A possible fatality supposedly occurred in 1907 when a man was attacked by a female grizzly bear after he prodded her cub with an umbrella. However, the validity of this incident is questionable. In late June 1983, a fatality occurred in the Gallatin National Forest outside the park when an adult male grizzly bear attacked a camper in the Rainbow Point Campground.

Where are all the bears?

Bears were once commonly observed along roadsides and within developed areas of Yellowstone National Park (YNP). Bears were attracted to these areas by the availability of human foods in the form of handouts and unsecured camp groceries and garbage. Although having bears readily visible along roadsides and within developed areas was very popular with the park visitors, it was also considered to be the primary cause of an average of 48 bear-caused human injuries per year from 1930 through 1969 (Cole 1974).

In 1970, YNP initiated an intensive bear management program with the objectives of restoring the grizzly bear and black bear populations to subsistence on natural forage and reducing bear-caused injuries to humans (Cole 1976, Meagher and Phillips 1983). As part of the bear management program implemented in 1970, regulations prohibiting the feeding of bears were strictly enforced, as were regulations requiring that human food be kept secured from bears. In addition, garbage cans were bear-proofed and garbage dumps within the park were closed.

Although bears are less frequently observed along roadsides and within developed areas today than in the past, many people still see bears each year. From 1979 - 2002 over 31,000 bear sightings have been reported to park managers.

Grizzly bears are active primarily during nocturnal (night time) and crepuscular (dawn and dusk) time periods (Schleyer 1983, Harting 1985, Gunther 1991). Look for grizzly bears with a high power spotting scope in open meadows just after sunrise and just before sunset. Grizzly bears are most commonly observed along the road corridor from Tower south through Canyon, Lake, and Fishing Bridge, to the East Entrance of the park. Grizzly bears are also commonly observed in the area south and east of Yellowstone Lake and in the Gallatin Mountains in the northwest corner of the park. Black bears are active primarily during crepuscular and diurnal (daylight) time periods (Mack 1988). Look for black bears in small openings within or near forested areas. Black bears are most commonly observed on the northern range along the road corridor from Mammoth east through Tower to the Northeast Entrance of the park. Black bears are also commonly observed in the Old Faithful, Madison, and Canyon areas as well as the Bechler region in the southwest corner of the park.

Bighorn Sheep

Bighorn sheep (Ovis canadensis) once numbered in the millions in western United States and were an important food source for humans. The "Sheepeaters", related to the Shoshoni tribe, lived year-round in Yellowstone until 1880. Their principal food was bighorn sheep and they made their bows from sheep horns. By 1900, during an "epoch of relentless destruction by the skin hunters" (Seton 1913), bighorn numbers were reduced to a few hundred in the United States. In 1897 Seton spent several months roaming the upper ranges of Yellowstone Park and did not see any, although about 100-150 were estimated to be present. He reported that by 1912, despite a disease (scab) contracted from domestic sheep, bighorns in the park had increased to more than 200 and travelers could find them with fair certainty by devoting a few days to searching around Mt. Everts, Mt. Washburn or other well-known ranges. In winter, small bands of sheep could then be seen every day between Mammoth and Gardiner ..."4 great rams with about 40 other sheep...so tame that one could get pictures within ten feet..."

Bighorn sheep are named for the large, curved horns borne by the males, or rams. Females, or ewes, also have horns, but they are short with only a slight curvature. Sheep range in color from light brown to grayish or dark, chocolate brown, with a white rump and lining on the back of all four legs. Rocky Mountain bighorn females weigh up to 200 pounds, and males occasionally exceed 300 pounds. During the mating season or "rut", occurring in November and December, the rams butt heads in apparent sparring for females. Rams’ horns can weigh more than 40 pounds, and frequently show broken or "broomed" tips from repeated clashes. Lambs, usually only one per mother, are born in May and June. They graze on grasses and browse shrubby plants, particularly in fall and winter, and seek minerals at natural salt licks. Bighorns are well adapted to climbing steep terrain where they seek cover from predators such as coyotes, eagles, and mountain lions. They are susceptible to disease such as lungworm, and sometimes fall off cliffs.

By 1914 there were about 210 sheep in Yellowstone and by 1922 there were 300 (Seton 1929). Censuses since the 1920s have never indicated more than 500 sheep. In recent years, bighorns have been systematically counted by aerial surveys in early spring. An annual ground count is also conducted on the winter range in the northern part of the park.

In the winter of 1981-82, an outbreak of pinkeye occurred among bighorns in the Mt. Everts area. Many sheep were blinded and/or killed on the adjacent park road or by falling from cliffs. No evidence of the disease, a natural occurrence, has been seen since. Winter visitors to the park still enjoy watching and photographing bighorns along the cliffs between Gardiner and Mammoth, as they did 80 years ago. Annual surveys of bighorn indicate that the resident herd on Yellowstone's northern range consists of at least 150-225 animals.

In 1997, a new study done by researchers at Montana State University began to investigate bighorn population status and behavior in northern Yellowstone. Of particular interest to these investigators is the effect of road use on the bighorns' ability to use their summer and winter range. Sheep are commonly seen along the road through the Gardner River Canyon, where visitors should be alert for bighorns crossing between their preferred cliffs and the river where they drink.

Summering bands are found in the Gallatin and Washburn Ranges, the Absarokas, and occasionally in the Red Mountains. On Dunraven Pass, a section of the Grand Loop Road in the park, a band of ewes and lambs has become somewhat habituated to summer traffic. These bighorns cause numerous traffic jams and are sometimes illegally fed by visitors, posing traffic hazards and danger to sheep. Park staff and visitors are encouraged to educate others about the importance of the "no feeding" regulation to the long-term welfare of wild animals.

Sandhill Crane

Identification

The sandhill crane is a large tall bird with long legs and neck but a relatively medium length bill.  It's color is typically gray, although in Yellowstone the birds often appear to be reddish brown, a result of  red soil (iron oxide) picked up on their beaks and spread on their plumage during preening which helps camouflaging the bird during nesting. They also have an unmistakable red crown on the tip of the head.  

While in flight their neck is extended straight as compared with the Great Blue Heron who flies with its neck folded.  The call of the sandhill crane can be heard at great distances and sounds like a long rattle - "garooo a a a" guttural call.  Once you have heard this call you will not likely mistake it for any other bird.

Habitat

Sandhill Cranes prefer small open wet meadows  but  can also be found in dry meadows and along the edge of aspen groves, willows and lodgepole  pine stands.

Behavior

The sandhill cranes that call Yellowstone home in summer spend their winters in the Rio Grande Valley of New Mexico and Mexico. While on their wintering grounds, sandhill cranes  feed on a variety of seeds including newly planted or harvested wheat, corn and sorghum, and insects, worms, etc.  In summer they feed more in marshy and wet meadows on a variety of insects, amphibians and rodents.  They are very good at walking and may walk great distances while feeding.

During summer months, sandhills are found in pairs and tend to be reclusive.  During migration, however, on their way to their wintering grounds they form large family flocks of up to 200 birds.  When these flocks join together in staging areas it is not uncommon to see a thousand cranes in a field or meadow.

One of the Crane's most unique and enjoyable behaviors to watch is their courtship dance.  If you are lucky enough to see this dance you will find yourself captivated by this behavior.  The dance which usually occurs between paired birds can go on for quite some time.  It begins with the birds high stepping on the ground while at the same time partially raising their wings.  They then take turns leaping into the air, wings partially spread and legs hanging below.  Interspersed throughout this mating ritual are various forms of neck and head bending and bowing.

The sandhill cranes of Yellowstone are much easier to hear than see, so listen for them to arrive sometime late March to early April.  If you are determined to see the cranes your best chances of finding them in Yellowstone are in the Bechler and Fountain Flats areas or the park.  They normally leave the park in September, thus completing a year in the life of a Yellowstone sandhill crane.

Common Raven

Identification

The Common Raven is a large, black bird, standing approximately 24 inches tall. It has a thick bill, a shaggy hackles on the throat and a wedge-shaped tail.  Its identifying calls include a hoarse croaking "kraak" and  "kloo-klok that is usually made during flight. 

Ravens are often confused with American Crows, but crows can be distinguished in a couple of ways. Crows are generally smaller, have a more rounded fanned tail, and make a light "caw" sound. American crows are rather uncommon in Yellowstone.

Habitat

A year round resident of the Yellowstone area, Ravens are found commonly throughout the park, often migrating to lower elevations during the winter. However, some pairs do not migrate.

Behavior

These opportunistic feeders take a variety of foods.  They take advantage of seasonal berries, small mammals, young birds and amphibians and of course are always present to feast on carrion. When food is plentiful, such as is found in the summer, ravens are more spread out and function primarily as predators. When food is scarce, such as is the case in the winter, ravens are in groups functioning as scavenger/carrion guides and feeders. A flock of ravens is a good indicator of a predator kill often appearing at the carcass only minutes after the kill.  

Although smaller than eagles, ravens are often seen harassing both bald and golden eagles and it is not uncommon for a group of  ravens to successfully keep these birds away from a carcass. They have also adapted to human activity/habitation and will take advantage of any available food, stealing off of picnic tables and rummaging through back packs to find something to eat.  In winter, many snowmobilers have returned from a short hike to find their belongings scattered about the parking lot, with the raven stealing both food and valuables from visitors.  

Ravens are some of the earliest birds to re-establish and defend nesting territories.  This can begin as early as February. As spring progresses look for paired ravens sitting side by side, riding the air currents and performing impressive aerial acrobats. Ravens provide the visitor with sheer entertainment because of their curious behavior, for you never know what a raven is up to.

Bald Eagle

Identification

A very large bird, the bald eagle  stands about 30-45 inches tall.  Adults over 5 years old have a white head, neck and tail, dark brown to black body and yellow bill.  Immatures are brown with whitish wing linings and blotches on the underparts.  Their head and tail will whiten  with each molt as they reach adulthood.  

Habitat

Bald eagles are found along the lakes and rivers of  Yellowstone National Park where they perch in nearby trees watching for fish below.  The best areas to watch for these majestic birds include Yellowstone River and Lake.   Although some adult bald eagles will winter in the park most migrate to lower elevations. During these winter months, look for them, sometimes in groups of five or six along the Yellowstone River north of the park.

Behavior

In the summer, bald eagles eat mostly fish and waterfowl.  Their fishing skills, however, are not as polished as those of the Osprey  and they have been watched on numerous occasions harassing these fisher birds until they drop their catch and fly off leaving the fish on the ground for the eagle to scavenge.   During winter months they feed primarily on waterfowl and carrion.  It is not uncommon to see bald eagles feeding on an elk carcass along side ravens, magpies, golden eagles and coyotes.

Yellowstone Data

In 1995, the U.S. Fish and Wildlife Service downlisted the Bald Eagle from endangered to threatened due to significant population gains made over the last three decades. Certain specific populations, however, are not completely recovered due to heavy metal contamination problems in the Great Lakes region, and habitat encroachment and development problems associated with riparian zones in the desert southwest.

In Yellowstone National Park, a total of 14 eaglets fledged from 26 active nests during 1999. Nest substrate instability, a result of the 1988 Yellowstone wildfires, caused minimal problems for nesting pairs; however, in following decades we expect large numbers of trees to topple to the ground. This will undoubtedly result in nest failure, loss of nest sites, and sudden changes in the locations of nesting territories. Although it has occasionally been documented that Bald Eagles will take over previously occupied Osprey nests, the incidence of takeover appears to be increasing due to the competition for nest sites. In 1999 alone, two previously known Osprey nest sites were occupied by Bald Eagles.

Trumpeter Swan Facts

The following are some facts about trumpeter swans that should help answer any questions you may have regarding this most interesting species.

·         The trumpeter swan gets its name from its trumpet-like call.

·         It is regarded as the largest of all North American wildfowl.  Male mute swans can actually get larger at times, but the mute swan is not native to North America.

• There are four species of swans that are considered free-flying in North America.  Two are wild native species (trumpeter swan and tundra swan), one Eurasian species (whooper swan) is accidental in North America, and one species (the mute swan) escaped from captivity and is now a free-flying swan in certain areas of the country.  The mute swan is the species of swan typically found in city parks, however it has the ability to overpopulate and is a severe threat to wild swans and other waterfowl.  Mute swans are native to Eurasia and should not be encouraged in North America unless they are placed in a cage or are permanently incapable of flight. Wild swans need all the help they can get.
• The trumpeter swan has a trumpet-like call whereas the tundra swan has a whistling call, and the mute swan is relatively silent.
• In a standing position, trumpeter swans are approximately 4 feet high.  However, if the neck and legs are outstretched they can measure nearly 6 feet long from bill to feet.
• The wingspan (length from wing tip to wint tip) of the trumpeter swan varies between young and adults and between females and males.  Wingspans in adults can vary from 6to 8 feet.
• Male swans are called "cobs", female swans are called "pens" and young swans up to one year of age are called "cygnets".
• Males are typically larger  than females.  Sexes can not be told apart, since both have identical white plumage with black bills and feet.  Although cob and pen sizes can be told apart if they are side by side, there is still a fair degree of individual variation.  Therefore, the only reliable way to sex individual swans is through a cloacal examination.
• Trumpet swan cygnets are typically born gray in color and steadily lose their gray plumage becoming pure white by the time they are one year old.  Sometimes rare white cygnets are born, these cygnets are termed "leucistic" meaning white, and retain white plumage throughout their juvenile and adult years.  The bill of adult leucistic trumpeter swans remains black.
• Adult male swans can vary from 21-32 lbs., but more typically weigh 26-30 lbs.
• Adult female trumpeter swans weigh between 20-25 lbs, averaging about 21-22 lbs.
• Trumpeter swans have been known to live 29 years in the wild, whereas a swan raised in captivity survived for 32 1/2 years.  In the wild, however, typical survival age ranges from 15-25 years.
• Trumpeter swans feed on submerged aquatic vegetation and on occasion aquatic invertebrates.  Sometimes in the spring, they can be observed feeding on green grass.  But this is very rare.
• They feed in slow shallow water and dip their heads below the surface of the water.  In deep water, they can only feed as deep as their neck will extend.  Under these circumstances they balance with their legs and tail out of the water.
• Every year adult swans go through a flightless period in which they molt all their feathers at once thus making them flightless for a 1-2 month period of time.  This typically occurs during the warmest months, namely July and August.
• A trumpeter swan nest commonly consists of a mass of emergent vegetation such as cattail or bulrush.  It is large measuring 5 feet in diameter, 1-2 feet high, and weighing hundreds of pounds.  Sometimes they will nest on a muskrat house or beaver lodge.
• They build their nests in May, and the young usually hatch in June.  The eggs are cream-colored, and they normally lay 4-6 eggs.  The female does most of the incubating.  It takes 33-37 days for the eggs to hatch.
• Cygnets fledge (fly for the first time) in late September and early October.  So it can take up to 110-120 days , to go from the time they are born to the time they fledge.
• Trumpeter swans can fly between 40-80 miles per hour.  They are very susceptible to collisions with wires, especially when they migrate.
• There are basically two trumpeter swan flocks in Yellowstone., a resident year-round population and a migratory winter population.  The resident population can vary from 28-55 swans, whereas the winter population varies from 75-119 swans.
• Migrants that visit Yellowstone in the winter are a combination of swans from the Yellowstone/Greater Yellowstone area including swans from Canada (primarily Grande Prairie, Alberta).
• Weather plays an important role in cygnet and juvenile swan survival and in swan productivity in general.  Mild weather conditions usually are good for swan production.  Higher winter survival also occurs during milder winters.
• Nest flooding is the primary cause of nest failure.  Egg predation by coyotes, ravens, and otters does occur.
• Coyote predation is the major cause of swan mortality in the winter.
• For the last five years, there have been 8-10 nest attempts per year, fledging 0-7 cygnets per year.
• The Trumpeter Swan is one of the most imperiled birds in Yellowstone National Park. 2000 population estimates:  20 adults, 7 cygnets.

Bison

Bison are the largest mammals in Yellowstone National Park. They are strictly vegetarian, a grazer of grasslands and sedges in the meadows, the foothills, and even the high-elevation, forested plateaus of Yellowstone. Bison males, called bulls, can weigh upwards of 1,800 pounds. Females (cows) average about 1,000 pounds. Both stand approximately six feet tall at the shoulder, and can move with surprising speed to defend their young or when approached too closely by people. Bison breed from mid-July to mid-August, and bear one calf in April and May. Some wolf predation of bison is documented in Canada and has recently been observed in Yellowstone.

Yellowstone is the only place in the lower 48 states where a population of wild bison has persisted since prehistoric times, although fewer than 50 native bison remained here in 1902. Fearing extinction, the park imported 21 bison from two privately-owned herds, as foundation stock for a bison ranching project that spanned 50 years at the Buffalo Ranch in Yellowstone's Lamar Valley. Activities there included irrigation, hay-feeding, roundups, culling, and predator control, to artificially ensure herd survival. By the 1920s, some intermingling of the introduced and wild bison had begun. With protection from poaching, the native and transplanted populations increased. In 1936, bison were transplanted to historic habitats in the Firehole River and Hayden Valley. In 1954, the entire population numbered 1,477. Bison were trapped and herds periodically reduced until 1967, when only 397 bison were counted park wide. All bison herd reduction activities were phased out after 1966, again allowing natural ecological processes to determine bison numbers and distribution. Although winterkill takes a toll, by 1996 bison numbers had increased to about 3,500.

Bison are nomadic grazers, wandering high on Yellowstone’s grassy plateaus in summer. Despite their slow gait, bison are surprisingly fast for animals that weigh more than half a ton. In winter, they use their large heads like a plow to push aside snow and find winter food. In the park interior where snows are deep, they winter in thermally influenced areas and around the geyser basins. Bison also move to winter range in the northern part of Yellowstone.

Bison are enjoyed by visitors, celebrated by conservationists, and revered by Native Americans. Why are they a management challenge? One reason is that about half of Yellowstone's bison have been exposed to brucellosis, a bacterial disease that came to this continent with European cattle and may cause cattle to abort their first pregnancy after exposure to Brucella bacteria. The disease has few population level effects. Outside the park wild bison from the Yellowstone population have not been known to transmit brucellosis to a visitor or to domestic livestock. The State of Montana believes its "brucellosis-free" status may be jeopardized if bison commingle with cattle. The risk of Yellowstone bison transmitting brucellosis to nearby livestock is very low. However, if livestock are infected, ranchers can be prevented from shipping livestock out of state until stringent testing and quarantine requirements are met. Some elk in the Greater Yellowstone ecosystem also carry the disease.

Most Yellowstone wildlife move freely across administrative boundaries set a century ago. Bison however, are not always welcome outside the park. Managers have tried to limit bison use of lands outside the park through public hunting, hazing bison back inside park boundaries, capture, testing for exposure to brucellosis, and shipping them to slaughter.

The NPS, U.S.D.A. Forest Service, U.S.D.A. Animal and Plant Health Inspection Service, and the State of Montana completed an Environmental Impact Statement for the Interagency Bison Management Plan for the State of Montana and Yellowstone National Park in November 2000. Alternatives considered ranged from: allowing bison to freely range over a large portion of public land inside and outside the park; managing bison like elk and other wildlife through controlled hunting outside park boundaries; and attempting to eradicate brucellosis by capturing, testing, and slaughtering infected bison at numerous facilities constructed inside the park. Additional options included purchase of additional winter range; attacking brucellosis with a safe and effective vaccine for bison; and quarantine of animals at appropriate locations such as Indian Reservations or other suitable sites outside Yellowstone.

State and Federal Records of Decision were signed in December 2000. The purpose of the IBMP is to maintain a wild free-ranging bison population and to address the risk of brucellosis transmissions to protect the economic interest and viability of the livestock industry in Montana. The principles of the Interagency Bison Management Plan include the following concepts:

• The State of Montana is responsible for managing bison when they leave the park and is the lead agency when conducting capture operations in the western Special Management Area
• National Park Service is responsible for all actions conducted within the park and is responsible (currently) for keeping bison from leaving the park in the area of Reese Creek along the northern Special Management Area
• Abundance and distribution of bison are monitored throughout the year
• When bison move beyond an established tolerance area the following procedures are implemented to enforce spatial and temporal separation between bison and cattle:
   
• All cattle within and near special management zones adjacent to YNP are vaccinated
• Vaccinate eligible bison (initially calf and yearling animals)
• An Adaptive Management strategy is incorporated for systematically increasing tolerance of bison on low elevation winter range outside of Yellowstone National Park:

Bobcat

Bobcats (Felix rufus) are small wild cats with reddish-brown or yellowish-brown coats, streaked with black or dark brown. They have prominent, pointed ears with a tuft of black hair at the tip. Females average 20 pounds and males weigh from 16 to 30 pounds. They breed in late winter or early spring and have a gestation period of about two months. A female may have one to six kittens each year. Although adapted to a variety of habitats across the country, they do not tolerate the deep snows found in much of Yellowstone, and thus they are usually reported in the northern portion of the park. Bobcats move about their home ranges most actively in the hours near dawn and dusk, hunting small mammals such as mice, rabbits, hares, and deer. They seek cover in conifer stands and on rocky ledges.

In the early years of this century, bobcats were reported as "somewhat common" in the park. In the last 64 years, there have been at least 43 reports of bobcats sighted in the park, 9 to 14 reports in each decade since 1960. These sightings have occurred throughout the park; about 80 percent have occurred in the northern half. Bobcats have been reported in about equal numbers during all seasons. In 1960, a bobcat was killed by a car near Squaw Lake (now Indian Pond) on the north shore of Yellowstone Lake; its skull was deposited in the Yellowstone Museum collection. Other roadkilled bobcats were reported in 1993 and 1996. In 1960, a young bobcat was reported on the porch of the administration building at Mammoth; other young bobcats have been reported at Pebble Creek bridge (Feb. 1977) and at Canyon campground (July 1986), where one accompanied an adult bobcat.

No research has been conducted in Yellowstone to determine the numbers or distribution of this elusive animal that usually is solitary, nocturnal, and widely scattered over its range.

Unlike lynx, which they resemble, bobcats elsewhere have been highly adaptable to human-caused changes in environmental conditions; some biologists believe that there are more bobcats in the United States today than in colonial times. Yellowstone has many rock outcrops, canyons bordered by rock ledges, conifer forests, and semi-open areas that seem to offer conditions favorable for bobcats—adequate shelter, a variety of rodents, rabbits, hares, birds, and other small animals as well as seasonal carrion, for food. Carrion is seldom used if live prey is available. Studies elsewhere have shown that bobcats also may kill both young and adult antelope and deer; they stalk bedded adults and may be carried long distances while biting their prey in the neck.

Bobcats are known to hole-up and wait out severe winter storms elsewhere, but whether they are able to tolerate the severe midwinter conditions of the park interior is unknown. These elusive cats are most active at night, so even those who study them seldom have an opportunity to see one. If you are so fortunate, look for the black bars on the inside of the forelegs. Black bars mean bobcat, and not the similar-looking lynx! If you see tracks, measure and photograph them carefully, then consult a track field guide. Bobcat tracks seldom exceed 2 1/4 inches in length; lynx tracks usually are longer than 3 1/2 inches.

If you see a bobcat or bobcat tracks, please report them promptly to a ranger or visitor center. For animals so seldom recorded, every observation is useful and important.

Coyotes

Yellowstone's coyotes (Canis latrans) are among the largest coyotes in the United States; adults average about 30 lbs. and some weigh around 40 lbs. This canid (member of the dog family) stands less than two feet tall and varies in color from gray to tan with sometimes a reddish tint to its coat. Coyotes live an average of about 6 years, although one Yellowstone coyote lived to be more than 13 before she was killed and eaten by a cougar. A coyote’s ears and nose appear long and pointed, especially in relation to the size of its head. It can generally be distinguished from its much larger relative, the gray wolf, by its overall slight appearance compared to the massive 75 to 125-pound stockiness of the bigger dog. The coyote is a common predator in the park, often seen alone or in packs, traveling through the park's wide open valleys hunting small mammals. But they are widely distributed and their sign can also be found in the forests and thermal areas throughout Yellowstone. They are capable of killing large prey, especially when they cooperatively hunt.

Pre-Wolf Research

In 1989, research was undertaken to investigate the basic ecological role of coyotes in Yellowstone. The park is one of the few places where the natural behavior of coyotes is not strongly influenced by trapping or predator control programs. Here, a unique opportunity existed for scientists to study the social behavior of coyotes and their interactions with prey and other predators, such as bears, mountain lions, and to document their ecology in Yellowstone prior to the proposed return of gray wolves.

Researchers captured and radio-collared coyotes, mainly on Yellowstone's northern range, to study movements and behavior. Males and females were sampled from at least 16 different resident packs. Researchers estimated that 85 to 90% of coyotes on the northern range belong to packs. Average pack size during the winters of 1990-93 ranged from 6.2 to 7.1 animals, typically a dominant, mated alpha-pair and subordinate beta individuals. The betas are pups from previous litters that remain in the area in which they were born. Evidence strongly indicated that coyote territories are traditional, with some coyotes using the same natal dens documented in 1940, when Adolph Murie studied coyote ecology in the Lamar Valley. Wolf extirpation in the first decades of the 20th century probably resulted in high coyote population densities and coyotes at least partially slid into this vacant niche.

Small mammals are an important component of coyotes’ diets. In Yellowstone, such prey include microtines or voles (Microtus spp.), mice (Peromyscus spp.), pocket gophers (Thomomys talpoides), small birds such as grouse, and in spring and summer, Uinta ground squirrels (Spermophilus armatus). In one study (Gese et al. 1996), scientists observed 4,439 predation attempts by coyotes, 35% of which (1,545) were successful. Young, inexperienced coyotes detected and attacked small mammals at a higher rate than did older coyotes. Older animals were more selective, making fewer attempts at small mammal predation, but interestingly, pups and older coyotes captured similar numbers of small mammals per hour. The depth and hardness of snow influenced how well coyotes detected and killed small prey, which was most successful in moist meadows and sagebrush grasslands. The coyotes capturing small mammals consumed 98.6% of their kills, only rarely caching or immediately sharing the prey. However, coyotes often regurgitate their prey to help feed pack members. Alpha males were seen delivering whole prey to their mates during the time of gestation and pup rearing. Alphas, betas, and older pups brought food to the current year’s litter of pups at den sites.

Carrion from winterkilled ungulates (elk, deer, bison, moose, pronghorn, and bighorn sheep), as well as predation on these larger mammals, also provides vital coyote food. Coyotes appeared to affect ungulate numbers in three ways: predation on calves and fawns shortly after birth, predation on "short-yearlings" (animals just shy of one year old) and adults during winter, and indirect impacts from harassment of other predators at ungulate kills. Researchers in Yellowstone and elsewhere have observed both successful and unsuccessful attempts at predation of elk calves and mule deer fawns. Observations of coyotes preying on adult elk and deer are more rare, although Gese and Grothe (1995) observed 9 such winter attempts in the park, 5 of which were successful. In all but one case, the alpha male coyote led the attack. In all cases, the coyotes attacked from the rear and/or the flanks of their prey. Occasionally they also grabbed the neck and head, pulling the animal down to the ground. Successful attacks lasted from 14 minutes to about 21 hours; even unsuccessful ones varied from 2 minutes to more than 8 hours before the coyotes abandoned the effort. Depth of snow affected the likelihood of success, although two or more adult coyotes could kill both calf and adult elk even during deep snow conditions, if the prey were in poor condition. In 3 of the 4 unsuccessful attempts, the intended prey fled into water, and researchers observed several other instances in which coyotes approached prey but did not pursue when the elk or deer entered a river. The researchers noted that some coyote pack members stayed nearby watching while 2 or 3 animals made the kill; in contrast, in other study areas all pack members appear to all be involved in the chase and kill.

Coyotes were also observed harassing both mountain lions and grizzly bears from their kills. And coyotes were sometimes killed by other carnivores, especially mountain lions, and by vehicular collisions. Coyotes are also subject to disease, including several pathogens that are known to kill coyotes in their first 3 months of life. Park coyotes have also shown exposure to canine parvovirus, canine distemper, plague (Yersinia pestis), tularemia, and leptospirosis, but not brucellosis. These diseases may be transmitted to coyotes from other wild canids, or from domestic dogs coming into the park.

Post-Wolf Research

In 1995, wolves were returned to Yellowstone. Throughout the restoration project, coyote research has continued, with an eye toward identifying the interactions between coyotes and wolves and on assessing the effects of wolves on coyote populations. During planning and environmental assessment of the effects of wolf restoration, biologists anticipated that coyotes would compete with the larger canid, perhaps resulting in disruption of packs and numerical declines.

Although early in the post-wolf study period, scientists have already observed some changes in the northern range coyote population as a result of restoring the larger canid. Shortly after wolves arrived in Yellowstone, coyote vocalizations increased in and around wolf acclimation pens and territories. During 1995-1997, coyote pack territories shifted and, in some cases, packs disintegrated as a result of one or more of the alpha coyotes was killed. Coyote den sites are more likely to be under rocks or closer to the park roadway perhaps because humans pose less threat to coyotes than do wolves. Coyote pup survival and weight have increased, as has group cohesion among coyotes; this is likely a result of their banding together for protection against wolves. Researchers documented that wolves killed at least 13 adults coyotes in the winter of 1995-1996 and 7 coyotes during 1996-1997. Coyote numbers have declined, although the species is still abundant and well-distributed throughout the park. It is expected that the two species will settle into a pattern of coexistence such as existed prior to the establishment of Yellowstone National Park—a pattern that is newly being discovered by many observers of the ecosystem.

Coyote-Human Interactions

Coyotes occasionally lose their wariness of humans and frequent roadsides or developed areas, becoming conditioned to human food by receiving handouts or picking up food scraps. They can quickly learn bad habits like roadside begging behavior. This leads to potential danger for humans and coyotes. Several instances of coyote aggression toward humans have occurred in the park, including one that involved an actual attack. Habituation most likely played a role in this unusual coyote behavior.

Beginning in 1988, park staff increased monitoring of coyotes along park roadsides. We experimented with scaring unwary coyotes from visitor use areas with cracker shell rounds, bear repellent spray, or other negative stimuli, but there is little indication that such techniques caused long-term term changes in individual coyote behavior. Those animals that continue to pose a threat to themselves or to humans may be translocated to other areas of the park, or even removed from the park ecosystem. Signs, interpretive brochures, and park staff continue to remind visitors that coyotes and other park wildlife are wild and potentially dangerous. They should never be fed or approached too closely, for the protection of humans and the animals.

Elk

Elk (Cervus elaphus) are the most abundant large mammal found in Yellowstone; paleontological evidence confirms their continuous presence for at least 1,000 years. Yellowstone National Park was established in 1872, when market hunting of all large grazing animals was rampant. Not until after 1886, when the U.S. Army was called in to protect the park and wildlife slaughter was brought under control, did the large animals increase in number.

More than 30,000 elk from 7-8 different herds summer in Yellowstone and approximately 15,000 to 22,000 winter in the park. The subspecies of elk that lives here are found from Arizona to northern Canada along the Rocky Mountain chain; other species of elk were historically distributed from coast to coast, but disappeared from the eastern United States in the early 1800s. Some other subspecies of elk still occupy coastal regions of California, Washington, and Oregon. Elk are the second largest member of the deer family (moose are larger). Adult males, or bulls, range upwards of 700 pounds while females, or cows, average 500-525 pounds. Their coats are reddish brown with heavy, darker-colored manes and a distinct yellowish rump patch.

Bulls grow antlers annually from the time they are nearly one year old. When mature, a bull’s "rack" may have 6 to 8 points or tines on each side and weigh more than 30 pounds. The antlers are usually shed in March or April, and begin regrowing in May, when the bony growth is nourished by blood vessels and covered by furry-looking "velvet." Antler growth ceases each year by August, when the velvet dries up and bulls begin to scrape it off by rubbing against trees, in preparation for the autumn mating season or rut. A bull may gather 20-30 cows into his harem during the mating season, often clashing or locking antlers with another mature male for the privilege of dominating the herd group. By November, mating season ends and elk generally move to their winter ranges. Calves weighing 25-40 pounds are born in late May or early June.

Climate is the most important factor affecting the size and distribution of elk herds here. Nearly the whole park - approximately 2.2 million acres - provides summer range for elk. However, winter snowfalls force elk and other ungulates to leave the greater part of the park. Only the northern, lower-elevation portion of Yellowstone, where temperatures are more moderate and snowfall less than in the park interior, can support large numbers of wintering elk. Annual precipitation, which occurs mostly as snow, averages as high as 75" in the southern, high-mountain plateaus of the park; minimum temperatures there are often well below 0 F, and have been as low as -66 F. In contrast, most of the northern range averages less than 30" of precipitation annually, and winter temperatures are considerably warmer.

The Overgrazing Controversy

National attention has been focused on Yellowstone's northern elk winter range since the early 1930s. Scientists and managers then believed that grazing and drought in the early part of the century had reduced the range's carrying capacity, and that twice as many elk were on the range in 1932 as existed in 1914. From 1935 to 1968, elk, pronghorn, and bison numbers were artificially controlled by shooting or trapping and removal by park rangers. Then in the 1960s, based on new studies that suggested ungulate populations could possibly be self-regulating, elk reductions were discontinued in the park. The belief that elk grazing was damaging to northern range vegetation and that grazing accelerates erosion, although not supported by research data and analysis, has continued to the present. Studies of the northern elk winter range began in the 1960s and revealed no clear evidence of range overuse (Houston 1982). More recent studies conclude that sagebrush grasslands of Yellowstone's northern winter range are not overgrazed (Singer and Bishop 1990). In fact, plant production was enhanced by ungulate grazing in all but drought years. Protein content of grasses, yearly growth of big sagebrush, and seedling establishment of sagebrush were all enhanced by ungulate grazing. Neither reduction in root biomass nor an increase in dead bunchgrass clumps was observed. However, many questions remain concerning the condition of riparian zones and associated shrubby vegetation; the park hopes to conduct additional studies on aspen and willows and their relationship to ungulates on the northern range.

Two reports were made available in 1997, discussing at length the issue of grazing levels and other influences on Yellowstone's northern range. Yellowstone's Northern Range: Complexity and Change in a Wildland Ecosystem discusses the history of research and management in northern Yellowstone, home to one of the world's largest herds of elk and long the subject of controversy. Effects of Grazing by Wild Ungulates in Yellowstone National Park contains 22 technical publications summarizing recent research studies that have been peer-reviewed by scientists. Much of the research was completed by scientists from agencies other than the National Park Service, by independent contractors, and by scientists from universities located across the United States. For a copy of either report, contact the Yellowstone Center for Resources, Box 168, Yellowstone NP, Wyoming 82190, or call (307)344-2203.

Other Influences on Yellowstone's Elk Populations

Over-winter calf mortality, yearling mortality, and adult bull mortality all increase with higher elk population densities. Studies show that summer predation by grizzly bears, coyotes, black bears, and golden eagles takes an average of 32% of the northern range elk calves each year. Mountain lions prey upon elk, as do hunters north of the park (taking about 10% of the northern herd annually through the 1980s).

Gray wolves, eliminated from the park by the 1930s, are being restored, but not because park managers think the wolves will "control" the number of elk. Instead, 15 North American wolf experts predicted that 100 wolves in Yellowstone would reduce the elk by less than 20%, 10 years after reintroduction. Computer modeling of population dynamics on the northern winter range predicts that 75 wolves would kill 1,000 elk per winter, but that elk would be able to maintain their populations under this level of predation, and with only a slight decrease in hunter harvest. Since the restoration of wolves to Yellowstone began in January 1995, scientists have begun to document the effects of wolves on elk and other species. Wolves are preying predominantly on elk, as expected. They have also occasionally preyed upon moose, bison, deer, and even one pronghorn antelope.

The carrying capacity of the northern winter range increased in the 1980s because elk colonized new winter range in and north of the park, wet summers resulted in better plant production, winters were mild, and the fires of 1988 opened forests allowing more ground cover to grow. Since 1985, more than 11,000 acres of elk winter range have been purchased by the State of Montana and the U.S. Forest Service north of the park, increasing elk carrying capacity and reducing conflicts between native wildlife and agriculture.

The Madison-Firehole Herd

The Madison-Firehole elk herd has been the focus of research by Dr. Bob Garrott of Montana State University since November 1991. This herd numbers from 650-850, and is believed to winter almost entirely within Yellowstone Park. The population appears to be naturally regulated to a degree not found in other, human-hunted elk herds. The information resulting from this research is useful in comparing unhunted and hunted elk populations. Researchers examined the effects of environmental variability on ungulate reproduction and survival. Researchers also examined elk use of areas burned in the wildfires of 1988. Observations indicated that elk have made more than casual use of burned trees; tests showed that fires altered the chemical composition of lodgepole pine bark, making it more digestible and of higher protein content than live bark. While the burned bark was not the highest quality forage for elk, it is comparable to other low quality browse species. The researchers speculated that elk select burned bark because it is readily available above the snow cover in winter.

Lynx

Lynx (Felis lynx canadensis) were reported in the park in the early years of this century. Bailey (1927) reported that "there are said to be a very few Canada lynxes, but we saw no tracks or signs of them," during a July 1926 outing in Yellowstone backcountry by more than 200 Audubon Society members. Skinner (1927) estimated a lynx population of 10 with stationary status. By the mid-1940s, lynx were reported as extremely scarce. Annual reports of wildlife in the park list lynx as a "rare native" in the late 1960s, but in the early 1970s this animal was not listed as present.

Consolo Murphy and Meagher (in press) reported a total of 57 records of lynx on file in Yellowstone for the period 1883-1995, all but one of which were within park boundaries. Sightings were reported 34 times and tracks reported 17 times, both throughout the park, although more reports occurred in the southern half of Yellowstone. Lynx were reported more often in winter, although all months are represented in these records. Since 1995 there have been two reports of lynx, both in 1997, in the northern half of the park. The Smithsonian Museum has a skull of a female lynx reportedly collected from an unspecified location in Yellowstone in 1904. Museums at the Universities of Idaho and Wyoming have no specimens of lynx collected in Yellowstone. The park has no records of lynx having been killed or found dead here. Neither has research been conducted to determine whether transient or resident populations exist. Sightings by visitors or employees are the only evidence we have of the possible presence of these animals that so closely resemble bobcats (Felis rufus) that sightings are difficult to verify. Consolo Murphy and Meagher concluded that evidence is too scant to reliably state that a resident population of lynx exists in the park today, if it did historically.

As part of a proposed settlement over a lawsuit filed by the Defenders of Wildlife and 14 other organizations, the U.S. Fish and Wildlife Service (USFWS) recently proposed to take action to list the Canada lynx under the Endangered Species Act. A series of legal actions regarding the lynx have been pending since 1991. The USFWS determined that lynx were historically resident in 16 of the contiguous United States, and that they currently occur at low levels in Montana, Washington, and Maine. They are rare in Idaho, Wyoming, Oregon, Michigan, Minnesota, Wisconsin, Utah, Colorado, Vermont, and New Hampshire; the USFWS believes they have been extirpated from New York, Pennsylvania, and Massachusetts. Publication of a proposed rule in the Federal Register is planned for the summer of 1998, followed by a public comment period to actively solicit new information about the status of lynx, related threats, and ongoing conservation activities.

Adult lynx are about the size of a large domestic cat. Males can weigh upwards of 30 pounds, while females are smaller. Lynx have large legs and broad, well-furred paws, blunt tails, and prominent tufted ears. Lynx are generally grayish-brown with white, buff, or brown on the facial ruff and throat. Limited studies suggest that lynx breed in April or May, and give birth to three to five kittens in late May or June. Lynx are usually found in boreal forests and they tolerate deep snow quite well. They are commonly associated with snowshoe hares, but may also prey on squirrels, grouse and mice. The conifer forests, semi-open and rocky areas of the park seem to offer summer conditions suitable for both bobcats and lynx--adequate shelter, a variety of rodents, rabbits, hares, birds, and other small animals for food. Lynx survive similarly severe winter weather conditions in Canada. Research there has shown that bobcats, another native wildcat, and lynx are seldom found in the same area as bobcats are more aggressive and may dominate. Whether this behavioral factor may affect living conditions for lynx in Yellowstone is presently unknown.

The similarity between lynx and bobcats makes it difficult to determine their status in Yellowstone. A large adult bobcat may be larger than a small adult lynx, so size is not a good characteristic for positive identification. Both bobcats and lynx have ear "tufts" of black hair. Although lynx are more solidly gray and bobcats are often buffy and have many black spots, larger bobcats usually have fewer spots and some turn almost solidly gray in winter, so general coloration is also a difficult characteristic for distant identification. If you see one of these small wildcats and have time, good light, and binoculars, look at the inside of the cat’s forelegs. There are no black bars there on a lynx, although there may be some dark spots. Also, the tip of the tail of a lynx is solidly black. (The upper side of a bobcat's tail has several dark bands that become more distinct toward the tip but the underside of the tip itself is white.)

If you find only tracks, measure and photograph them carefully, then consult a track field guide for identification. Bobcat tracks seldom exceed 2 1/4 inches; lynx tracks usually are longer than 3 1/2 inches. And consider yourself lucky to see any of the three felids that may exist in Yellowstone (bobcat, mountain lion, lynx). These rare and elusive cats are most active at night, so even those who study them seldom have an opportunity to see one! If you think you see a lynx or lynx tracks, please report them promptly to a ranger or visitor center. For animals so rarely recorded, every observation is useful and important.

In recent years, the park has experimented with non-harmful methods to determine the presence of some rarely seen animals, by sampling for snow tracks and guard hairs. To date, the presence of lynx has not been confirmed by these methods.

Moose

Moose (Alces alces shirasi Nelson), the largest member of the deer family, were reportedly very rare in northwest Wyoming when Yellowstone National Park was established in 1872. Subsequent protection from hunting and wolf control programs may have contributed to increased numbers but suppression of forest fires probably was the most important factor, since moose here depend on mature fir forests for winter survival.

Moose breed from early September to November and one to three calves are born in May or June. Calves weigh 25 to 35 pounds at birth but grow rapidly; adult females (cows) weigh up to 800 pounds and males (bulls) up to 1300 pounds. Bulls are readily identified by their large, palmate antlers, which are shed annually, and their bells an apparently useless dewlap of skin and hair that dangles from the throat. Moose live mostly solitary lives, and die from disease, starvation, or predation by wolves and, occasionally, by grizzly bears.

Surveys in the late 1980s suggested a total park population of fewer than 1000 moose.

Research on radio-collared moose in northern Yellowstone has shown that when snow depth forces moose from low-elevation willow stands in November, they move up to as high as 8500 feet, to winter in mature stands of subalpine fir and Douglas-fir. They browse fir almost exclusively during the deep-snow winter months. Tyers (unpubl. data) found that moose ate 39.6 percent subalpine fir, 25.5 percent willows, 10.6 percent lodgepole pine, 4.6 percent gooseberry, and 4 percent buffaloberry. Snow is not as deep under a canopy of conifer branches since some snow remains on them, and a crust that may restrict moose movements is less likely to form on shaded snow. However, Tyers found that moose could winter in areas where snow considerably deeper than that which elk could withstand.

The moose calf crop has been declining since the fires of 1988. During that summer there was also high predation of moose by grizzly bears in small patches of surviving timber. The winter following the fires many old moose died, probably as a combined result of the loss of good moose forage and a harsh winter. The fires forced some moose into poorer habitats, with the result that some almost doubled their home range, using deeper snow areas than previously, and sometimes browsing burned lodgepole pines. Unlike moose habitat elsewhere, northern Yellowstone does not have woody browse species that will come in quickly after a fire and extend above the snowpack to provide winter food. Therefore, the overall effects of the fires were probably detrimental to moose populations. Park managers, in cooperation with staff from the adjacent Gallatin National Forest and the Montana Department of Fish, Wildlife and Parks continue to seek good methods to monitor the status of moose in northern Yellowstone. Aerial surveys of willow habitats in spring have shown some promise of providing an index of moose population trends in Yellowstone, although their current population and distribution remain largely unknown.

Moose are commonly observed in the park's southwestern corner along the Bechler and Falls rivers, in the riparian zones around Yellowstone Lake, in the Soda Butte Creek, Pelican Creek, Lewis River, and Gallatin river drainages, and in the Willow Park area between Mammoth and Norris. Summer moose migrations from south and west of the park into Yellowstone have been confirmed by radiotelemetry.

Mountain Lions

The mountain lion (Felis concolor), also called the cougar, is the largest member of the cat family living in Yellowstone.  Mountain lions can weigh up to 200 pounds, although lions in Yellowstone are thought to range between 140 and 160 pounds for males and around 100 pounds for females.  Two to three kittens may be born at any time of year, although most arrive in summer and fall.  For reasons that are not clear, only about 50 percent of kittens survive their first year.  The current population of lions in Yellowstone is estimated to be 18-24 animals and is thought to be increasing.

Mountain lions are rather secretive, consequently, most visitors are unaware of their existence in Yellowstone.  Lions probably live throughout the park in summer.  In winter, difficulty of movement and lack of available prey causes most lions to move to lower elevations.  Lions are territorial and will kill other lions.  The dominant animals reside in the northern range areas of the park where prey is available year-round.  Mountain lions prey chiefly upon elk and deer, although their diet probably varies based upon opportunity, porcupines provide an important supplement to the lion's diet.

Mountain lions were significantly reduced by predator control measures during the early 1900s.  It is reported that 121 lions were removed from the park between the years 1904 and 1925.  At that time, the remaining population was estimated  to be 12 individuals.  Mountain lions apparently existed at very low numbers between 1925 and 1940.  Reports of lions in Yellowstone have increased steadily from 1 each year between 1930 and 1939 to about 16 each year between 1980 and 1988.  However, increases in visitor travel in Yellowstone and improvements in record keeping during this period probably contributed to this trend.  

In 1987, the first study of mountain lion ecology was initiated in Yellowstone National Park.  The research documented population dynamics of mountain lions in the northern Yellowstone ecosystem inside and outside the park boundary, determined home ranges and habitat requirements, and assessed the role of lions as a predator in the ecosystem.  In recent years in other areas of the West, mountain lions have occasionally attacked humans.  No documented lion/human confrontations have occurred in Yellowstone.

Yellowstone's Reptiles

General

• Cool, dry conditions limit Yellowstone's reptile to six species.
• Population numbers for these species are not known.
• Reptiles: prairie rattlesnake, bull snake, valley garter snake, wandering garter snake, rubber boa, sagebrush lizard.

Yellowstone is home for a small variety of reptiles. Glacial activity and current cool and dry conditions are likely responsible for their relatively low numbers in Yellowstone.

In 1991 park staff began cooperating with researchers from Idaho State University to sample additional park habitats for reptiles and amphibians. This led to establishment of long-term monitoring sites in the park (map, page 119). The relatively undisturbed nature of the park and the baseline data may prove useful in testing hypotheses concerning the apparent declines of several species of toads and frogs in the western United States. Reptile and amphibian population declines may be caused by such factors as drought, pollution, disease, predation, habitat loss and fragmentation, introduced fish and other non-native species.

Although no Yellowstone reptile or amphibian species are currently listed as threatened or endangered, several-including the boreal toad-are thought to be declining in the West. Surveys and monitoring are underway to try to determine if amphibian populations are declining in Yellowstone National Park

VALLEY GARTER SNAKE

 

Identification

• Subspecies of the common garter snake.
• Medium sized snake reaching total length of up to 34 inches.
• Nearly black background color with three bright longitudinal stripes running the length of the body, underside is pale yellow or bluish gray.
• Most distinguishing characteristics of this subspecies in our region are the irregular red spots along the sides.

Habitat

• Thought to be common in the past, now in decline for no apparent reason.
• Closely associated with permanent surface water.
• In Yellowstone observed only in the Falls River drainage in the Bechler region and three miles south of the south entrance along the Snake River.

Behavior

• Generally active during the day.
• In the Yellowstone area it eats mostly toads, chorus frogs, fish remains, and earthworms; can eat relatively poisonous species.
• Predators include fish, birds, and
  carnivorous mammals.

WANDERING GARTER SNAKE

 

Identification

• Most common reptile in the park.
• 6 to 30 inches in length.
• Brown, brownish green, or gray with three light stripes-one running the length of the back and a stripe on each side.

Habitat

• Usually found near water in all areas of the park.
• Eats small rodents, fish, frogs, tadpoles, salamanders, earthworms, slugs, snails, and leeches.

Behavior

• May discharge musk from glands at the base of the tail when threatened.
• Gives birth to as many as 20 live young in late summer or fall.

BULLSNAKE

 

Identification

• A subspecies of the gopher snake, is Yellowstone's largest reptile, ranging from 50 to 72 inches long.
• Yellowish with a series of black, brown, or reddish-brown blotches down the back; the darkest, most contrasting colors are near the head and tail; blotches are shaped as rings around the tail.
• Head resembles a turtle's in shape, with a protruding scale at the tip of the snout and a dark band extending from the top of the head through the eye to the lower jaw.

Habitat

• In Yellowstone, found at lower elevations; drier, warmer climates; and open areas such as near Mammoth.
  Behavior
• Lives in burrows and eats small rodents-behavior that gave the gopher snake its name.
• Often mistaken for a rattlesnake because of its appearance and its defensive behavior: when disturbed, it will coil up, hiss loudly, and vibrate its tail against the ground,
  producing a rattling sound.

RUBBER BOA

 Identification

• Infrequently encountered in Yellowstone, perhaps due to its nocturnal and burrowing habits.
• One of two species of snakes in the United States related to tropical boa constrictors and pythons.
• Maximum length of 24 inches.
• Back is gray or greenish-brown, belly is lemon yellow; scales are small and smooth, making it almost velvety to the touch.

Habitat and Behavior

• Eats rodents.
• May spend great deal of time partially buried under leaves and soil, and in rodent burrows.
• Usually found in rocky areas near streams or rivers, with shrubs or trees nearby.
• Recent sightings have occurred in the Bechler region and Gibbon Meadows.

PRAIRIE RATTLESNAKE

 

Identification

• More than 48 inches in length.
• Greenish gray to olive green, greenish brown, light brown, or yellowish with dark brown splotches down its back that are bordered in white.

Habitat

• Only dangerously venomous snake in the park.
• Lives in the lower Yellowstone River areas of the park, including Reese Creek, Stephens Creek, and Rattlesnake Butte, where the habitat is drier and warmer than elsewhere in the park.

Behavior

• Usually defensive rather than aggressive.
• Only two snake bites are known during the history of the park.

SAGEBRUSH LIZARD

 

Identification

• Only lizard in Yellowstone.
• Maximum size of five inches from snout to tip of the tail; males have longer tails and may grow slightly larger than females.
• Gray or light brown with darker brown stripes on the back set inside lighter stripes on the sides, running the length of the body; stripes not always prominent and may appear as a pattern of checks down the back; underside usually cream or white.
• Males have bright blue patches on the belly and on each side, with blue mottling on the throat.

Habitat

• Usually found below 6,000 feet but in Yellowstone lives up to 8,300 feet.
• Populations living in thermally influenced areas are possibly isolated from others.
• Most common along the lower portions of the Yellowstone River near Gardiner, Montana and upstream to the mouth of Bear Creek; also occurs in Norris Geyser Basin, Shoshone and Heart Lake geyser basins, and other hydrothermal areas.

Behavior

• Come out of hibernation about mid May and active through mid September.
• Diurnal, generally observed during warm, sunny weather in dry rocky habitats.
• During the breeding season males do push-ups on elevated perches to display their bright blue side patches to warn off other males.
• Feed on various insects and arthropods.
• Eaten by bull snakes, wandering garter snakes, rattlesnakes and some birds.
• May shed tail when threatened or grabbed.