Ecology of the Rocky Mountains

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Bighorn sheep (such as this lamb) have declined dramatically since European-American settlement of the Rocky Mountains.

The ecology of the Rocky Mountains is diverse due to the effects of a variety of environmental factors. The

Yellowstone Plateau in Wyoming, the montane forests of Utah, and in the high Rockies of Colorado and New Mexico
, and finally the alpine tundra of the highest elevations.

These habitats are home to a great deal of wildlife from herbivores, such as

gray wolf, coyote, fox, and wolverine, along with a great variety of small mammals, fish, reptiles and amphibians, numerous bird species, and tens of thousands of species of terrestrial and aquatic invertebrates and soil organisms.[1]

Permanent human settlement of the Rocky Mountains has caused numerous species to decline in population, including species of trout, birds, and sheep.

Gray wolves
and grizzly bears were almost eliminated from the United States portion of the range, but are returning due to conservation measures.

The population of black bears in the Rocky Mountains is neither dramatically increasing nor decreasing.

Setting

Mount Elbert rises through multiple biotic zones, with alpine tundra at its peak.

The Rocky Mountains range in latitude between the Liard River in British Columbia (at 59° N) and the Rio Grande in New Mexico (at 35° N), and in height up to the highest peak, Mount Elbert at 14,440 feet (4,400 m), taking in great valleys such as the Rocky Mountain Trench and San Luis Valley. Precipitation ranges from 10 inches (250 mm) per year in the southern valleys[2] to 60 inches (1,500 mm) per year locally in the northern peaks.[3] Average January temperatures can range from 20 °F (−7 °C) in Prince George, British Columbia to 43 °F (6 °C) in Trinidad, Colorado.[4]

Biotic zones

Ecologists divide the Rocky Mountain into a number of

indicator species. Areas of the Rockies that do not support or have few trees include the prairie of the eastern foothills and the Alpine tundra. The foothill prairie grassland lies to the east of the Rockies where the mountains fall to meet the Great Plains at the Rocky Mountain Front (below roughly 1,800 feet (550 m)). Alpine tundra meanwhile occurs in regions above the treeline, which varies from 12,000 feet (3,700 m) in New Mexico to 2,500 feet (760 m) at the northern end (near the Yukon).[4]

Bison grazing in grassland, Montana

The

whitebark pine or bristlecone pine); or a mixture of white pine, fir, and spruce that appear as shrub-like krummholz. Finally, rivers and canyons are home to unique forest habitats even in the more arid parts of the mountain range.[1]

Biotic zones and vegetation types in the Rocky Mountains can be explained by

solar radiation, wind, soils, and hydrology could be described and modeled. Peet provided the most complete description of 10 major forest community types, which are summarized here.[6] Two nonforested vegetation types, plains and alpine tundra, described by Sims[7] and Billings,[8] are added. Because of the variations in latitude and precipitation along this huge mountain range, the elevations presented here are gross generalizations.[1]

Extensive investigations have been made of the forests of the Rocky Mountains.[6] Weber cautioned that the vegetation zones "overlap and telescope into each other considerably" in a landscape that is "always full of surprises."[9] The resulting patchwork mosaic of vegetation types and disturbance regimes leads to a complex of side-by-side communities, wildlife habitats, and species distributions.[1]

Plains

The eastern side of the Rocky Mountains is bordered by

species composition varies locally with changes in soil characteristics and topographic position—that is, from hilltops to valley bottoms.[1]

Riparian and canyon forests

Broad-leaved deciduous cottonwoods,

herbaceous layer in riparian communities is often more diverse than upslope areas and adjacent forests.[6] Riparian and canyon vegetation types are generally too thin or too small to be displayed on regional vegetation maps, but the habitat is extremely important in the arid West.[1]

Pinyon-juniper woodland

Colorado pinyons and Utah junipers growing near Grand Junction, Colorado

In the southern Rocky Mountains, a transition occurs between about 5,900 and 8,200 feet (1,800 and 2,500 m), where plains communities are accompanied by

Utah junipers grow to the north. Many shrubs and grasses of the plains occupy the gaps between tree outcrops. Heavy livestock grazing is associated with the spread of junipers (by reducing competition from grasses), and fire suppression is partly responsible for their continued dominance.[1][10]

Ponderosa pine woodland

Main article: Rocky Mountain ponderosa pine forest

The appearance of

bitterbrush), and herb layers (such as mountain muhly, sedges, and sagebrushes) can develop. Typical intervals between natural fires are less than 40 years in most ponderosa pine forests.[1] Fires that recur every 10–20 years suppresses the growth of Douglas-fir saplings and encourages the growth of ponderosa pine.[11]

Open ponderosa pine forest in Colorado

In geological time, ponderosa pine ecosystems are relatively new to the foothills of the central Rocky Mountains. An even newer addition to the ecosystem, European-American settlers, devastated the ponderosa pine forests through logging for houses, fencing, firewood, mine timbers, and railroad ties, and with fire. The ponderosa pine forests were close to the developing population centers at the forest-prairie edge. The scale of the loss of ponderosa pine habitat is demonstrated best in several hundred paired photographs from the early 20th century and 1980s. However, nearly all the paired photographs also reveal that the most important feature of the ponderosa pine ecosystem is its resilience. Ponderosa pine seedlings establish quickly in disturbed sites. Research in the Front Range of Colorado shows a tenfold increase in ponderosa pine biomass since 1890 in many stands. This regeneration has restored habitat for many wildlife species[1] but has also led to unnatural forest densities in many areas.[12]

Pine-oak woodland

In the southern Rocky Mountains, lower slopes of ponderosa pine communities can be accompanied by

mountain-mahoganies). In the absence of fire, the oak stands may be invaded by pines.[1][6]

Douglas-fir forest

Douglas-firs grow in a broad range from Mexico to British Columbia, generally from near lower treeline upward in elevation to spruce-fir forests. In Colorado, the species ranges from about 5,410 to 8,860 feet (1,650 to 2,700 m) and is often found in mixed stands with ponderosa pine,

lodgepole pine. Like ponderosa pine, Douglas-fir is tolerant of frequent, low-intensity surface fires. High-intensity fire intervals in Douglas-fir forests in Wyoming average 50–100 years.[1]

Cascadian forest

Several tree species commonly associated with the Cascade Mountains grow on the rain-swept western slopes of the northern Rocky Mountains. These include

mountain hemlock, and larches.[13] These forests are subject to infrequent, high-intensity fires.[1]

Montane seral forest

Durango Mountain Resort
, Colorado.

Lodgepole pine forests interspersed with stands of

black spruce also occurs in this biotic zone.[13]

Intervals between fires typically range from 100 to 300 years. As evidenced by the fires in the Yellowstone National Park in 1988, lodgepole pine forests are rejuvenated by crown fires that replace tree stands. Aspen stands are keystone communities for hundreds of birds and mammals and are especially important forage for deer and elk.[1]

Spruce-fir forest

Spruce-fir forest near Red Mountain Pass, Colorado

The

lodgepole pine and the occasional Douglas-fir. In the Black Hills of South Dakota, white spruce replaces Engelmann spruce. Further north are the lodgepole pine, Engelmann spruce, and alpine fir mix of the Alberta Mountain forests above 5,495 feet (1,675 m) of elevation.[13] Stand-replacing fires typically occur at 200- to 400-year intervals. Widespread insect outbreaks in spruce-fir forests occur more frequently.[1] Recently, spruce bark beetles have begun to impact more old-growth spruce trees in these forests.[14]

Subalpine white pine forest

A whitebark pine in Central Idaho.

On exposed, dry slopes at high elevations, subalpine white pine forests replace spruce-fir forests. Common species of the white pine forests include

limber pine in the central and north-central Rocky Mountains, and bristlecone pine in the southern Rocky Mountains. Typical intervals between fires range from 50 to 300 years. The white pines are tolerant of extreme environmental conditions and can be important postfire successional species.[1] The whitebark pine is a keystone species in upper subalpine forests of the northern Rocky Mountains.[15] However, the whitebark pine has been in decline due to white pine blister rust: whitebark pine mortality in some areas exceeds 90%. Entire forest vistas, like that at Avalanche Ridge near Yellowstone National Park’s east gate, are expanses of dead, gray whitebarks.[16]

Treeline vegetation

Treeline is the elevation above which trees cannot grow. It is controlled by a complex of environmental conditions, primarily soil temperatures and the length of the growing season—which becomes shorter with higher elevations. The elevation of treeline rises steadily at the rate of 330 feet (100 m) per degree of latitude from the northern to the southern Rocky Mountains. Dominant treeline species, including spruces, firs, and white pines, often have a shrublike form in response to the extreme conditions at the elevational limits of their physiological tolerance; such dwarfed trees are called krummholz. Krummholz islands may actually move about 3/4 inch per year (2 cm) in response to the wind; they reproduce by vegetative layering on their lee sides, while dying back from wind damage on their windward sides. Under favorable climatic conditions, krummholz can assume an upright treelike form or can increase their cone crops and seedling establishment.[1]

Alpine tundra

Flowers in an alpine meadow at Copper Mountain, Colorado

succulents, and hundreds of grasses and wildflower species.[1][8][13]

Fauna

See also: List of animals of Yellowstone

The Rocky Mountains are important habitat for a great deal of wildlife, such as

fungi
; and soil microorganisms.

European-American settlement of the mountains has adversely impacted native species. Examples of some species that are known to have declined include

mountain lion, many small mammals, and common bird and plant species are described as stable because, in most instances, the populations are persistent and not rapidly increasing or declining.[1]

Invertebrates

Although most of the animals in the Rocky Mountains are invertebrates, little is known about this component of the region's fauna. As one entomologist[

Front Range of Colorado in particular support high species richness of butterflies and moths. In Colorado, the diverse habitats—from prairie to tundra—support about 2,000 species of butterflies, moths, and skippers; more than 1,000 species are in the Front Range. Some species of grasshoppers are unique to individual mountaintops in Colorado, New Mexico, Arizona, Nevada, and Utah. The Rocky Mountain locust, a common pest to farmers in the 19th century, is now extinct. Heavy grazing along river valleys in Montana and Idaho is thought to have irreparably destroyed locust breeding areas.[1]

Amphibians

The western toad

Globally, populations of amphibians are declining in size as a result of

sport fishes, timber harvest, increased ultraviolet radiation, and disease. The widespread declines of amphibian populations throughout the Rocky Mountains mirror these global trends. Western toads, once common between altitudes of 7,500 and 13,800 feet (2,300 and 4,200 m) throughout the central and northern Rocky Mountains, now occupy less than 20% of their previous range, from southern Wyoming to northern New Mexico. Eleven populations of western toads disappeared from the West Elk Mountains of Colorado between 1974 and 1982 because of a bacterial infection and, perhaps, multiple sublethal environmental causes. The number of breeding sites in Rocky Mountain National Park has declined to only 3. In the past two decades, western toads disappeared from 83% of their historical range in Colorado and from 94% of Wyoming sites. Populations of northern leopard frogs are significantly declining throughout the Rocky Mountains.[1]

Fish

The Rocky Mountains are home to a number of coldwater fish in the trout and salmon families, including rainbow trout, bull trout, lake trout, cutthroat trout, brown trout, brook trout, golden trout, mountain whitefish, Arctic grayling, and Dolly Varden.[18] Many of these, however, are introduced, such as rainbow, brown, and brook trout.

Colorado River cutthroat trout

The Colorado River Cutthroat trout, a native of western Colorado, eastern Utah, northwestern New Mexico, and southwestern Wyoming

Colorado River cutthroat trout were once abundant in mountainous tributaries of the Green and Colorado rivers, but non-native brown, brook, and rainbow trout had displaced them by the 1930s. They still survived in some isolated pockets, however, and these populations have been used to restore the cutthroats to many areas in their historic range. One of the largest strongholds was, and is, Trappers Lake in Colorado's Flat Top Mountains. However, in 1984, brook trout invaded because a flood washed them downstream from nearby Crescent Lake. By 2003, brook trout comprised 40 percent of the lake's fish population. Brook trout have an advantage over cutthroat trout because they spawn in fall. By the time Colorado River cutthroats hatch in August, brook trout fingerlings may be able to eat them. Colorado Parks and Wildlife is controlling their population with large nets and selective removal.[19]

Rio Grande cutthroat trout

Rio Grande cutthroat trout currently live on 700 miles of stream in the Santa Fe National Forest, which is approximately 91% of their historical range. The Rio Grande cutthroat trout was a candidate for listing under the Endangered Species Act from 2008 to 2014. In 2014 it was removed from candidacy as it was determined that listing was not warranted for this species.[20][21] Rio Grande cutthroat have the distinction of being the southernmost subspecies of cutthroat trout. However, due to the loss of populations across their native range and reports of Rio Grande cutthroat in Mexico and Texas, it is unclear how far south this trout once occurred. In 1955, it was designated the state fish of New Mexico.

Greenback cutthroat trout

A greenback cutthroat trout

The

Colorado Division of Wildlife and several federal agencies introduced these fish to many areas in the trout's former range. In 1996, it was designated as Colorado's state fish. Then in 2012, researchers at the University of Colorado found that the only pure population of these fish was in a small stream in the Arkansas River basin, outside their native range. Since then they have been reintroduced to Zimmerman Lake on the edge of northern Colorado's Neota Wilderness and Sand Creek in Red Mountain Open Space north of Fort Collins.[22]

Yellowstone cutthroat trout

The Yellowstone cutthroat trout

whirling disease, brought from Europe by nonnative brown trout.[25]

Mountain whitefish

Mountain whitefish fry in Yellowstone National Park

Mountain whitefish, unlike cutthroat trout, have not declined significantly in their native range.

Poudre and Fryingpan
rivers in western Colorado.

White sturgeon

The largest freshwater fish in the Rocky Mountains (and North America) is also in trouble. The

Kootenai River upstream to Kootenai Falls, Montana. The Kootenai River population of the white sturgeon is unstable and declining in size; fewer than 1,000 remain, 80% are older than 20 years, and virtually no recruitment has occurred since 1974, soon after Libby Dam in Montana began regulating flows.[1]

Birds

The Rocky Mountains are home to over 300 species of birds. These include raptor species that migrate through the mountains, such as

treeline. Many songbirds, including wrens, warblers, and finches[27]

Bald eagles

A bald eagle

The coniferous and deciduous forests of North America have long been the home of bald eagles. Bald eagle populations are now recovering after years of hunting, habitat destruction, and pesticide-induced deaths. In the early 1970s, Colorado had just one breeding pair of bald eagles but by 1993 biologists counted 19 breeding pairs. In Wyoming nesting attempts increased from 20 in 1978 to 42 in 1988. The bald eagle has not yet fully recovered, however; pesticide residues continue to inhibit bald eagle reproduction, and

habitat loss and lead poisoning remain serious threats.[1]

Peregrine falcons

habitat loss, and pesticide poisoning on wintering grounds remain threats to peregrine falcon recovery.[1]

White-tailed ptarmigans

White-tailed ptarmigan in Alberta

White-tailed ptarmigans have been monitored in Rocky Mountain National Park, Colorado, since 1966. Short-term population cycles are well documented in populations that are not hunted but not in populations outside the park, which are hunted. Although detailed population size data are available from more than 28 years of monitoring, scant information is available on habitat change, predator populations, or other potential causes of change in ptarmigan populations. In the park, the population seems to be increasing. A 2-year study revealed lower ptarmigan densities where elk use was greater, although characteristics of willow, which is ptarmigan habitat, did not significantly differ in the high- and low-use elk sites. Furthermore, a 2-year study of ptarmigan habitat cannot explain 28-year trends in population size. Habitat loss and other factors partly responsible for ptarmigan deaths—such as predation and competition—were not studied during the 28-year period.[1]

Ducks and geese

A bufflehead, one of many duck species found in the Rockies' lakes and streams

Many species of

dabbling ducks such as mallards and wigeons. Some species migrate, while other species stay in the Rockies year-round. Canada geese are also commonly found here.[citation needed
] Many ducks provide food for raptors such as bald eagles and peregrine falcons as well as an occasional coyote or bobcat.

Trumpeter swans

habitat loss.[1]

Neotropical migrant songbirds

Many forest-dwelling songbirds breed in the Rocky Mountains and winter in Central and South America. Wildlife biologists suspect that population size declines in the songbirds may be partly the result of increased predation and brood parasitism. Brood parasitism by brown-headed cowbirds, for example, increases as a result of nearby logging. In conifer forests in west-central Idaho, common songbirds benefited from timber harvest, whereas the abundances declined of rare species that inhabit old-growth forests (hermit thrush, Swainson's thrush, and pileated woodpecker).[1]

Mammals

Black bears

serviceberry.[28] They can be seen feeding on berries, grasses, and small animals.[29] Colorado has a population of 19,000 of the bears, up from 12,000 in the early 2000s.[28]

Grizzly bears

Grizzly bear and cub in the Shoshone National Forest, Wyoming

Grizzly bears once roamed throughout the Rocky Mountains and the western Great Plains. They were hunted relentlessly by European settlers in the 19th century and early 20th century. The last known grizzly bear in Colorado was killed in 1979. The decline of the bears to just 2% of their original range tells of the human-caused extirpation of large predators in the Rocky Mountain region. Only 700-900 grizzly bears may be alive today in the conterminous United States, with 300 grizzlies alive in the Canadian Rockies.[29] During the last 20 years, about 88% of all grizzly bears studied in the northern Rocky Mountains were killed by humans.[1] The U.S. Fish and Wildlife Service is considering delisting the grizzly in Montana, Idaho, and Wyoming.[30]

Cougars

Cougars are one of the most important carnivores in the ecosystems of the Rockies. They prefer to prey on mule deer, but occasionally kill elk, white-tailed deer, and bighorn sheep, and in Alberta, moose kills have been documented. Recently, cougars have recolonized many areas where they were eliminated in the 1800s and early 1900s, and have greatly increased in number.[31]
The highest densities of cougars are in foothill and montane areas, which are more diverse and rich than subalpine or alpine environments.

Gray wolves

Gray wolves in Yellowstone National Park

Wolves once were common throughout the Rocky Mountains. They were shot, poisoned, and trapped into local extinction by early settlers and federal agents. The last Gray wolf in Colorado was killed in 1940, and the wolf was first listed as an endangered species in 1967. Wolves from southeastern British Columbia recolonized northwestern Montana in 1986; by 1994 the population had grown to 7 packs and about 70-75 wolves. Wolves from Glacier National Park have dispersed naturally as far away as northeastern Idaho and just south of Yellowstone National Park. A wolf was shot near Yellowstone National Park in 1992. From January to March 1995, 15 adult wolves from 7 different packs in Canada were introduced into central Idaho wilderness areas. Several pairs have bred and produced the first litters of wolf pups born in Idaho in more than 50 years. Fourteen wolves (three family groups) were released in the Yellowstone National Park in late March 1995.[1] A total of 66 wolves were released to the two areas in this manner in January 1995 and January 1996.[32] Several wolves from the Northern Rockies have dispersed to the Southern Rockies but have failed to establish a population there. Most have been killed.[33]

2013 estimates of wolf populations in the two recovery zones reflect the success the species has had in both areas:

  • Greater Yellowstone Area: 460
  • Central Idaho: 684

These numbers, added with the estimated number of wolves in northwestern Montana (500), puts the total number of wolves in the Northern U.S. Rocky Mountain recovery area at over 1500 individuals. This includes approximately 134 packs (two or more wolves traveling together) and 71 breeding pairs (male and female that successfully rear a litter of at least two until Dec. 31). The recovery goal for the area was 30 breeding pairs total, and this number has been surpassed for some time.[34] In addition, there are at least 120 grey wolves in the Canadian Rockies.[35]

The restoration of the gray wolf to the Yellowstone National Park not only restores an important ecosystem component (the wolf) and process (predation by wolves) to bring the park into better ecological balance, but it also is economically sound. After weighing the costs (including full reimbursement to ranchers for the loss of livestock) and benefits (increased revenues from hunting and tourism), economists estimated (before the actual restoration took place) a net $18 million return during the first year after the wolves were returned, and about $110 million in 20 years. More tourists are expected to visit the area of the Yellowstone National Park and to stay longer in hope of hearing or seeing wolves in the wild.[36] Compensatory payments to ranchers for the loss of cattle and sheep to wolves averaged about $1,800 per year in northwestern Montana.[1]

Mustelids

An American marten in Grand Teton National Park

Many types of mustelids inhabit the meadows, forests, and peaks of the Rocky Mountains. Types of weasels here include:

Mustelids are some of the most important predators of squirrels, mice, and voles, although wolverines can take down an animal as large as a caribou and the primary food of river otters is fish. Several species, including the river otter, black-footed ferret, and wolverine, have declined over much of their range because of

habitat loss
, poisoning, and trapping, as well as decline in prey species.

Cervidae

Elk at the Opal terrace at Mammoth Hot Springs, Yellowstone National Park

Members of the deer family (

North American elk, mule deer, white-tailed deer, woodland caribou, and moose
.

Population trends in North American elk and deer (mule deer and white-tailed deer combined) may be heading in opposite directions. The number of elk has increased steadily in Colorado and Wyoming, whereas the abundances of deer are showing signs of decline. Elk on

U.S. Forest Service lands in the Rocky Mountains increased from 268,000 in 1965 to 372,000 in 1984. Similarly, the number of elk on Bureau of Land Management lands rose from 35,000 in 1966 to 114,000 in 1985. Meanwhile, the number of deer on U.S. Forest Service lands declined from 1,742,000 in 1965 to 1,197,000 in 1984. Deer populations also declined on Bureau of Land Management lands. Thus, in some areas in the last 20 years, the abundances of elk have increased by about 40%, whereas deer have decreased by about 30%. Possible reasons for the increase in elk populations include mild winters, range extension into lowlands and highlands, increased adaptability to human-modified landscapes, and lack of predation in spite of increased hunting. The causes of the deer population declines remain unknown but may include excessive harvest in the 1970s and habitat overlap with elk, intensifying competition for similar resources.[1] Note, however, that deer population in the rest of the United States has increased fiftyfold between 1900 and 2005, as hunting has been limited and open space has been preserved.[37]

Woodland caribou were historically found in most of the northern Rocky Mountains, possibly ranging as far south as Wyoming. They have declined dramatically over most of their range and have been eliminated in the Lower 48. Currently, populations are found in the Canadian Rockies, Alaska, and several other ranges. The primary cause for their decline is the logging of old-growth forests. British Columbia is attempting to reverse their decline by culling the province's abundant wolves.

Moose populations have increased 50% since 1980 in Wyoming and have been rapidly increasing since the reintroduction into Colorado beginning in 1978 and 1979.[1] Colorado currently has a thriving population of approximately 2,500 moose.[38] However, in Yellowstone National Park, moose have declined from 1,000 animals in the 1970s to 200 in 1996.[39]

Pronghorn

A pronghorn in Montana

Many areas of the Rocky Mountains, notably Yellowstone and Grand Teton national parks, have significant populations of pronghorn. Many of these are migratory. Grand Teton's population migrates all the way from the Green River Basin each year, through many developed areas. Efforts have been made to preserve its migration route.

Bighorn sheep

Populations of

domestic sheep. In recent years, more than 115 translocations were made to restore bighorn sheep into the Rocky Mountains and into many national parks. Only 39% of the 115 bighorn sheep translocations are persisting in 6 Rocky Mountain states. Populations of 100 or more sheep now occur in 10 national park units, populations of 100-200 sheep in 5 units, and populations of more than 500 sheep in 5 units. Populations of fewer than 100 animals exist in 5 other park units.[1]

Bison

Further information: Conservation of American bison
Mud Volcano
area

In the 1800s,

Yellowstone's Pelican Valley. The U.S. Army protected the bison until the National Park Service was established. There are currently between 4,000 and 5,000 bison in the park. There are also herds in Grand Teton National Park, along Colorado's Front Range, in the San Luis Valley, and on Montana's CSKT Bison Range. Herds are being established near Glacier National Park and in Alberta's Banff National Park.[40] Bison are a keystone species because their grazing and wallowing patterns create more diverse grasslands and meadows.[41]

Beaver

Tower Junction area) in the early 1920s reported 232 beavers and extensive beaver dams. Repeated surveys in the same area in the early 1950s and in 1986 revealed no beavers or dams. Beavers need aspens or tall willows for food and building materials—resources that are made scarce by lack of both fires and floods and by herbivory by elk, moose, and domestic livestock. Beaver ponds are known to maintain fish and invertebrate populations and to create and maintain riparian zones that are critical to wildlife, yet the beaver is virtually absent in many areas.[1] By 2015, Yellowstone had an estimated 100 colonies. Causes for their increase include predation of elk by wolves, which allowed aspens and willows to grow taller.[42]

A least chipmunk in Glacier National Park

Squirrels

Many types of squirrel inhabit the forests of the Rocky Mountains, including several species of chipmunks such as the Uinta chipmunk and the least chipmunk. Overwinter chipmunk survival rates are less than a third.[43] Tree squirrels include the American red squirrel (also known as pine squirrel), and the Abert's squirrel, found only in ponderosa pine forests. There are also several types of ground squirrels, such as the Wyoming ground squirrel, the rock squirrel, and the golden-mantled ground squirrel.[44][45] Squirrels are important to the forest because they help spread the seeds of many plants. They are also a major food source for predators like martens, weasels, and hawks.[1]

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  32. ^ "Wolf Restoration". Yellowstone National Park. National Park Service.
  33. ^ Fixler, Kevin (July 24, 2016). "Colorado wolf advocates, wildlife managers again feud over reintroduction". Summit Daily.
  34. ^ "Rocky Mountain Wolf Recovery 2005 Interagency Annual Report" (PDF). USFWS. Archived from the original (PDF) on May 24, 2006. Retrieved May 3, 2006.
  35. ^ Hempstead, Andrew. "Wild Dogs and Cats". Canadian Rockies. Moon Travel Guides. Archived from the original on August 17, 2012. Retrieved August 13, 2012.
  36. ^ French, Brett (September 27, 2021). "Montana wolf hunt criticized by Yellowstone Park superintendent". Billings Gazette. Retrieved September 28, 2021.
  37. ^ "Deer eating away at forests nationwide". NBC News. January 18, 2005.
  38. ^ Wickstrom, Terry (August 13, 2016). "Moose populations are thriving in Colorado". Denver Post.
  39. ^ "Moose". Yellowstone National Park. National Park Service.
  40. ^ Goldfarb, Ben (March 24, 2015). "Bison to be Reintroduced in Banff". High Country News.
  41. ^ "Bison Ecology". Yellowstone National Park. National Park Service.
  42. ^ "Beavers". Yellowstone National Park. National Park Service.
  43. JSTOR 3672112
    .
  44. ^ "Squirrels and Chipmunks". Rocky Mountain National Park. National Park Service.
  45. ^ "Rock Squirrel - Spermophilus variegatus". Nature Works.

Further reading

  • Constantz, George. Ice, Fire, and Nutcrackers: A Rocky Mountain Ecology. Salt Lake City: University of Utah Press, 2014.
    ISBN 978-1-60781-362-0
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