Animals of Yellowstone
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Summer Issue / August 2021 Written By: Wikipedia
Yellowstone ellowstone National ational Park ark U.S. Department of the Interior
National Park Service
Photo courtsey of Unsplash user Goutham Ganesh Sivanandam via Creative Common License Adult bison in the plains.
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B
Bison
ison are the largest grazing mammals in Yellowstone National Park. They are obligate herbivores, 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 1,300 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. Bison live an average lifespan of 20–25 years in the wild.[2]
Yellowstone is the only place in the lower 48 states where a population of wild American bison has persisted since prehistoric times, although fewer than 50 native bison remained there 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 Lamar Buffalo Ranch in Yellowstone’s Lamar Valley. Activities there included irrigation, hay-feeding, roundups, culling, and predator control, to artificially ensure
Photo courtsey of Unsplash user Bryce Olsen via Creative Common License Adult bison roaming through grasslands.
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 2003, the entire population numbered 1,477. Bison were trapped and herds periodically reduced until 1967, when only 397 bison were counted parkwide. All bison herd reduction activities were phased out after 1966, again allowing natural ecological processes to determine bison numbers and distribution. Presently, the park’s bison population is estimated at about 4,000. 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.[3]
E
lk or wapiti (Cervus canadensis) 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 United States Army was called in to protect the park and wildlife slaughter was brought under control, did the large animals increase in number.[12] In recent years, however, Yellowstone’s elk population has plummeted. The Northern Herd, the only herd that winters in the park, has declined from nearly 20,000 animals in 1994 to less than 4,000 in 2013. Ecologists have linked this decline to a declining population of cutthroat trout in Yellowstone Lake, caused by invasive lake trout. With less fish to eat, grizzly bears began to eat more elk calves, causing a steep decline in elk numbers.[13][14] 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
Page 47 but disappeared from the eastern United States in the early 19th century. 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 the largest). Adult males, or bulls, range upwards of 700 pounds (~320 kg) while females, or cows, average 500-525 pounds (~225–240 kg). Their coats are reddish brown with heavy, darker-colored manes and a distinct yellowish rump patch. Elk usually live about 15 years in the wild. 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. and elk generally move to their winter ranges.
Elk
Photo courtsey of Unsplash user Edward Taylor Two male elk in the forest during the day.
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A
Bears
s of 2017, the grizzly bear (Ursus arctos horribilis) population within the Greater Yellowstone Ecosystem (Yellowstone and surrounding areas) was estimated at about 718, with a minimum of 640 and a maximum of 796.[4] The black bear (Ursus americanus) population within the same ecosystem was estimated at about 575, with a minimum of 500 and a maximum of 650.[5] While in spawning streams, Yellowstone cutthroat trout are preyed upon by numerous predators including black bears and grizzly bears. Due to their high digestibility, and protein and lipid content, spawning cutthroat trout are one of the highest sources of net digestible energy for grizzly bears in the Yellowstone ecosystem. Cutthroat trout are an important late-spring and early-summer food source for bears, providing them the opportunity to regain body mass after den emergence, and assisting females with cubs meet the energetic demands of lactation. The average lifespan of a grizzly bear is about 22 years, and the average lifespan of a black bear is about 17 years.
Bears were once commonly observed along roadsides and within developed areas of Yellowstone National Park. Bears were attracted to these areas
Photo courtsey of Unsplash user Michael Scherback Two grizzly bears fishing at a waterfall.
ability 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 park visitors, an average of 48 bearcaused human injuries occurred each year from 1930 through 1969. Rocky Mountain grizzly bears have killed several people in the park since the 1970s.[6] Over the next several decades, the bears learned to hunt and forage for themselves from non-human food sources, and their population slowly grew.[7] On March 22, 2007, the grizzly bear was taken off the endangered species list. In the years since it was listed as a threatened species, the Yellowstone grizzly bear population has increased to at least 640 by 2017.[4] From 1980 to 2002, over 62 million people visited Yellowstone National Park. During the same period, 32 people were injured by bears. Grizzly bear-inflicted injuries to humans in developed areas averaged approximately one per year during the 1930s through the 1950s, and four per year during the 1960s.
T
he mountain lion (Puma concolor), also called the cougar, is the largest member of the cat family living in Yellowstone. Mountain lions can weigh up to 200 pounds (~90 kg), although lions in Yellowstone are thought to range between 140 and 160 pounds (~65 and ~70 kg) for males and around 100 pounds (45 kg) 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 live an average lifespan of about 12 years in the wild Mountain lions were significantly reduced by predator control measures during the early 20th century. 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
Page 49 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.
Visitors should be aware of these signs.
Warning!
Mountain Lion
Habitat
Mountain Lions
Photo courtsey of Unsplash user Priscilla Du Preez Adult cougar on a rock formation.