American pika

Last updated

American pika [1]
Temporal range: Middle Pleistocene - Holocene, 1.8–0  Ma
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Ochotona princeps rockies.JPG
An American pika feeding on grass in the Canadian Rocky Mountains
Status TNC G5.svg
Secure  (NatureServe) [4]
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Lagomorpha
Family: Ochotonidae
Genus: Ochotona
Species:
O. princeps
Binomial name
Ochotona princeps
(Richardson, 1828)
Subspecies [5]

O. p. princeps
O. p. fenisex
O. p. saxatilis
O. p. schisticeps
O. p. uinta

Contents

American Pika range.png
American pika range
American pika carrying forget-me-not flowers and grass to store for winter food in Cawridge, Alberta, Canada American pika (ochotona princeps) with a mouthful of flowers.jpg
American pika carrying forget-me-not flowers and grass to store for winter food in Cawridge, Alberta, Canada

The American pika (Ochotona princeps), a diurnal species of pika, is found in the mountains of western North America, usually in boulder fields at or above the tree line. They are herbivorous, smaller relatives of rabbits and hares. [6] Pikas have two different ways of foraging; they either directly consume food or they cache food in piles for the winter (haying).

Pikas are vocal, using both calls and songs to warn when predators are nearby and during the breeding season. Predators of the pika include eagles, hawks, coyotes, bobcats, foxes, and weasels.

Recent studies suggest populations in the southwestern United States are declining due to habitat loss and global warming. [7] However, the American pika is overall considered a species of Least Concern, and is still common in the northwestern United States and Canada.

Description

American pikas, known in the 19th century as "little Chief hares", [8] have a small, round, ovate body. Their body lengths range from 16.2 to 21.6 cm (6.4 to 8.5 in). Their hind feet range from 2.5 to 3.5 cm (1.0 to 1.4 in). [9] They usually weigh about 170 g (6.0 oz). [10] Body size can vary among populations. In populations with sexual dimorphism, males are slightly larger than females. [11]

The American pika is intermediate in size among pikas. The hind legs of the pika do not seem to be much longer than its front legs and its hind feet are relatively short when compared to most other lagomorphs. [11] It has densely furred soles on its feet except for black pads at the ends of the toes. [11] The ears are moderately large and suborbicular, and are hairy on both surfaces, normally dark with white margins. The pika's "buried" tail is longer relative to body size compared to other lagomorphs. [11] It has a slightly rounded skull with a broad and flat preorbital region. The fur color of the pika is the same for both sexes, but varies by subspecies and season. [11] The dorsal fur of the pika ranges from grayish to cinnamon-brown, often colored with tawny or ochraceous hues, during the summer. During winter, the fur becomes grayer and longer. [11] The dense underfur is usually slate gray- or lead-colored. It also has whitish ventral fur. Males are called bucks and females are called does like rabbits.

This individual was at 603 m (1,978 ft) above sea level in Mount Baker-Snoqualmie National Forest. Ochotona princeps 9482.JPG
This individual was at 603 m (1,978 ft) above sea level in Mount Baker-Snoqualmie National Forest.

Distribution and habitat

The American pika can be found throughout the mountains of western North America, from central British Columbia and Alberta in Canada to the US states of Oregon, Washington, Idaho, Montana, Wyoming, Colorado, Utah, Nevada, California, and New Mexico. [10] Of the 30 existing species of pika, it is one of only two which inhabit North America, along with the collared pika (O. collaris). In relation to the distribution of the American pika, the collared pika is located farther north and is separated by a gap of about 800 km (500 mi) extending across British Columbia and Alberta. [12]

Pikas inhabit talus fields that are fringed by suitable vegetation in alpine areas. They also live in piles of broken rock. [11] [13] Sometimes, they live in man-made substrate such as mine tailings and piles of scrap lumber. Pikas usually have their den and nest sites below rock, around 20–100 cm (8–39 in) in diameter, but often sit on larger and more prominent rocks. They generally reside in scree near or above the tree line. Pikas are restricted to cool, moist microhabitats on high peaks or watercourses. [13] Intolerant of high diurnal temperatures, in the northern portion of their range, they may be found near sea level, but in the south they are rare below 2,500 m (8,200 ft). [11] American pikas rely on existing spaces in the talus for homes and do not dig burrows. However, they can enlarge their homes by digging. [11]

Diet

The American pika is a generalist herbivore. It eats a large variety of green plants, including different kinds of grasses, sedges, thistles, and fireweed. Although a pika can meet its water demand from the vegetation eaten, it does drink water if it is available in its environment. [14]

Pikas have two different ways of foraging; they directly consume food (feeding) or they cache food in haypiles to use for a food source in the winter (haying). [11] They feed throughout the year while haying is limited to the summer. Since they do not hibernate, pikas have greater energy demands than other montane mammals. They also make 13 trips per hour to collect vegetation when haying, up to a little over 100 trips per day. [15] The timing of haying seems to correlate to the amount of precipitation from the previous winter. [16] Pikas start and then quit haying earlier in years following little snow and an early spring. In areas at lower elevations, haying begins before the snow has melted at high altitudes; at higher elevations, haying continues after it ends in lower elevations. [16]

When haying, pikas harvest plants in a deliberate sequence, corresponding to their seasonal phenology. [11] They seem to assess the nutritional value of available food and harvest accordingly. Pikas select plants that have the higher caloric, protein, lipid, and water content. [11] Forbs and tall grass tend to be hayed more than eaten directly. Haypiles tend to be stored under the talus near the talus-meadow interface, although they may be constructed on the talus surface. Males generally store more vegetation than females and adults usually store more than juveniles. [11] Like all lagomorphs (rabbits, hares, pikas), the American pika creates, expels & eats cecotropes (cecotrophy) to get more nutrition from its food. Cecotropes have more energy value than stored plant food and the American pika may consume them directly or store them for later. [11]

Life history

The American pika's cryptic coloration helps it blend in with its environment in the Sierra Nevada. Ochotona princeps.jpg
The American pika's cryptic coloration helps it blend in with its environment in the Sierra Nevada.

The American pika is diurnal. The total area of land that a pika uses is known as a home range. About 55% of its home range is territory that the pika defends against intruders. Territory size can vary from 410 to 709 m2 (4,410 to 7,630 sq ft) and is dependent on configuration, distance to vegetation, and quality of vegetation. [11] The home ranges of pikas may overlap, with the distances of the home ranges of a mated pair being shorter than that of the nearest neighbors of the same sex. [11] Spatial distances between adults of a pair is greatest during early and midsummer and reduces during late summer and early autumn. Pikas defend their territories with aggression. Actual aggressive encounters are rare and usually occur between members of the same sex and those unfamiliar with each other. A pika may intrude on another's territory, but usually when the resident is not active. During haying, territorial behavior increases. [14]

Adult pikas of the opposite sex with territories adjacent form mated pairs. When more than one male is available, females exhibit mate choice. [11] Pikas are reflex ovulators; ovulation only occurs after copulation, and they are also seasonally polyestrous. A female has two litters per year and these litters average three young each. Breeding takes place one month before the snow melts and gestation lasts around 30 days. Parturition occurs as early as March in lower elevations, but occurs from April to June at higher elevations. Lactation significantly reduces a female's fat reserves and they only wean the second litter if the first does not survive, despite exhibiting postpartum estrus. [11] Pikas are born altricial, being blind, slightly haired, and having fully erupted teeth. They weigh between 10 and 12 g (0.35 and 0.42 oz) at birth. At around nine days old, they are able to open their eyes. [11] Mothers forage most of the day and return to the nest once every two hours to nurse the young. Young become independent after four weeks, around the same time they are weaned. [11] Young may remain in their natal or an adjoining home range. When in their home range, young occupy areas away from their relatives as much as possible. Dispersal appears to be caused by competition for territories. [17]

Pikas are vocal, using both calls and songs to communicate among themselves. A call is used to warn when a predator is lurking nearby, and a song is used during the breeding season (males only), and during autumn (both males and females). [10] Predators of the pika include eagles, hawks, coyotes, bobcats, mountain lions, foxes, and weasels.

Taxonomy

The American pika was described in the scientific literature by John Richardson in Fauna Boreali-Americana in 1828. The original scientific name was Lepus (Lagomys) princeps. [18]

Lepus (Lagomys) princeps print from original scientific text Ochotona princeps (syn. Lepus (Lagomys) Princeps).jpg
Lepus (Lagomys) princeps print from original scientific text

Conservation and decline

As they live in the high and cooler mountain regions, they are very sensitive to high temperatures, and are considered to be one of the best early warning systems for detecting global warming in the western United States. [19] Temperature increases are suspected to be one cause of American pikas moving higher in elevation [20] in an attempt to find suitable habitat, as well as cooler temperatures. American pikas, however, cannot easily migrate in response to climate change, as their habitat is currently restricted to small, disconnected habitat "islands" in numerous mountain ranges. [21] Pikas can die in six hours when exposed to temperatures above 25.5 °C (77.9 °F) if individuals cannot find refuge from heat. In warmer environments, such as during midday sun and at lower elevation limits, pikas typically become inactive and withdraw into cooler talus openings. [16] Because of behavioral adaptation, American pikas also persist in the hot climates of Craters of the Moon and Lava Beds National Monuments (Idaho and California, respectively). Average and extreme maximum surface temperatures in August at these sites are 32 and 38 °C (90 and 100 °F), respectively. [22]

Recent studies suggest some populations are declining due to various factors, most notably global warming. [20] A 2003 study, published in the Journal of Mammalogy, showed nine of 25 sampled populations of American pika had been extirpated in the Great Basin, leading biologists to conduct further investigations to determine if the species as a whole is vulnerable. [23]

In 2010, the US government considered, then decided not to add the American pika under the US Endangered Species Act. [24] In the IUCN Red List, it is still considered a species of Least Concern. [3]

The Pikas in Peril Project, [25] funded through the National Park Service Climate Change Response Program, began data collection in May 2010. A large team of academic researchers and National Park Service staff - from three universities and eight national parks - worked together to address questions regarding the vulnerability of the American pika to future climate change scenarios projected for the western United States. The project concluded in 2016. [26]

More recent studies have found widespread extirpations and range retractions at lower elevations which are typically warmer and drier, patterns that have been further attributed to varying aspects of climate change such as warmer summer and winter temperatures and changes in precipitation. [27] [28] [29] [30] For example, one study found upslope retractions in 44 of 64 watersheds surveyed in the Northern Rockies, with retractions averaging 281 m (922 ft). [31] Another study in North Cascades National Park in Washington found that a single winter of little to no snow caused drastic declines in pika abundance, highlighting how snowpack provides a necessary insulation against cold winter temperatures. [32]

Related Research Articles

<span class="mw-page-title-main">Lagomorpha</span> Order of mammals

The lagomorphs are the members of the taxonomic order Lagomorpha, of which there are two living families: the Leporidae and the Ochotonidae (pikas). There are 110 recent species of lagomorph of which 109 are extant, including 10 genera of rabbits, 1 genus of hare and 1 genus of pika. The name of the order is derived from the Ancient Greek lagos + morphē.

<span class="mw-page-title-main">Pika</span> Genus of mountain-dwelling mammal

A pika is a small, mountain-dwelling mammal native to Asia and North America. With short limbs, a very round body, an even coat of fur, and no external tail, they resemble their close relative, the rabbit, but with short, rounded ears. The large-eared pika of the Himalayas and nearby mountains lives at elevations of more than 6,000 m (20,000 ft).

<span class="mw-page-title-main">Collared pika</span> Species of mammal

The collared pika is a species of mammal in the pika family, Ochotonidae, and part of the order Lagomorpha, which comprises rabbits, hares, and pikas. It is a small alpine lagomorph that lives in boulder fields of central and southern Alaska (U.S.), and in parts of Canada, including northern British Columbia, Yukon, and western parts of the Northwest Territories. It is closely related to the American pika, but it is a monotypic form containing no recognized subspecies. The name comes from distinctive patches of grayish fur on its nape and shoulders that form a “collar.” It is asocial, does not hibernate, and spends a large part of its time in the summer collecting vegetation that is stored under rocks ("haypiles") as a supply of food for the winter. Some individuals have been observed collecting and consuming dead birds as sources of fat and protein. Thousands of trips are made during July and August to collect vegetation for winter.

<span class="mw-page-title-main">Northern pika</span> Species of mammal

The northern pika is a species of pika found across mountainous regions of northern Asia, from the Ural Mountains to northern Japan and south through Mongolia, Manchuria and northern Korea. An adult northern pika has a body length of 12.5–18.5 centimeters (4.9–7.3 in), and a tail of 0.5–1.2 centimeters (0.20–0.47 in). The pika sheds its fur twice annually, bearing a reddish-brown coat in the summer and grayish-brown coat in winter. It feeds on various plant material and makes "hay piles" for winter use.

<span class="mw-page-title-main">Alpine pika</span> Species of mammal

The alpine pika is a species of small mammal in the pika family, Ochotonidae. The summer pelage of different subspecies varies drastically but, in general, it is dark or cinnamon brown, turning to grey with a yellowish tinge during the winter. The alpine pika is found in western Mongolia, eastern Kazakhstan, and Russia, as well as in China, in very cold, mountainous regions. It is a generalist herbivore, and mainly forages on mosses, tree branches, pine nuts, and plant stems. It can emit three series of different vocalizations: a long call, a short call, and an alarm call. It is rated as a species of least concern on the IUCN Red List of Endangered Species.

<span class="mw-page-title-main">Helan Shan pika</span> Species of mammal

The Helan Shan pika or silver pika is a species of mammal in the pika family, Ochotonidae. It is endemic to China where it is found in a small region of the Helan Mountains. It is listed as "Endangered" in the IUCN Red List of Threatened Species as of 2016.

<span class="mw-page-title-main">Daurian pika</span> Species of mammal

The Daurian pika is a small relative of rabbits and hares in the order Lagomorpha. It is well known for its “barking” alarm call, and for its peculiar habit of making hay to help survive the winter. There are 4 recognized subspecies, Ochotona dauurica annectens, O.d. bedfordi, O.d. dauurica, and O.d. mursavi. Daurian pikas, like other lagomorphs, are characterized by a secondary set of incisor teeth. They are sexually monomorphic, with thick reddish coats. Pikas have no external tail, and their ears are large and rounded. The auditory bullae, a feature of the skull of daurian pikas are small in comparison to many other pikas. This is thought to be related to their fairly low altitude habitat preference. They are considered keystone species within their habitat.

<span class="mw-page-title-main">Gaoligong pika</span> Species of mammal

The Gaoligong pika is a species of mammal in the family Ochotonidae. It is endemic to China. Many of the general physical characteristics of the pika species are shared by Gaoligong pikas. However, the Gaoligong pika is specifically characterized by unique physical characteristics, including a red-brown colored crown around the neck and black behind the ears. They can produce one litter per year and can live up to three years. Their behavior is currently undetermined due to limited information available about the species. This is due to the inaccessibility of their habitat.

<span class="mw-page-title-main">Glover's pika</span> Species of mammal

Glover's pika is a species of mammal in the family Ochotonidae. It was first described in 1922, by Michael Rogers Oldfield Thomas. The summer dorsal pelage is grayish rufous, grayish brown, or tea brown in colour. The winter pelage is similar to the summer pelage, but is lighter in tone. Endemic to China, it is found in high altitudes of northeastern Tibet, southwestern Qinghai, western Sichuan, and northwestern Yunnan. It is a generalist herbivore, and is known to construct haypiles. It is rated as a species of least concern by the International Union for Conservation of Nature. It is also regionally red listed as least concern in China.

<span class="mw-page-title-main">Hoffmann's pika</span> Species of mammal

Hoffmann's pika is a species of mammal in the pika family, Ochotonidae, that is endemic to Mongolia. It is currently listed as endangered by the International Union for Conservation of Nature (IUCN).

<span class="mw-page-title-main">Ili pika</span> Species of mammal

The Ili pika is a species of mammal in the family Ochotonidae, endemic to northwest China. After its discovery in 1983, it was studied for a decade.

<span class="mw-page-title-main">Koslov's pika</span> Species of mammal

Koslov's pika or Kozlov's pika is a species of mammal in the family Ochotonidae. It is endemic to China. Its natural habitat is tundra. It is threatened by habitat loss. Kozlov's pika are herbivores, they are known as "ecosystem engineers" as they're known to promote diversity of different plants species. Specifically, this species of Pikas has been enlisted as "endangered" in China. Kozlov Pikas are estimated to be within the Northern edge of the Arkatag Range in China.

<span class="mw-page-title-main">Large-eared pika</span> Species of mammal

The large-eared pika is a species of small mammal in the family Ochotonidae. It is found in mountainous regions of Afghanistan, Tibet, Bhutan, India, Kazakhstan, Kyrgyzstan, Nepal, Pakistan and Tajikistan where it nests among boulders and scree.

<span class="mw-page-title-main">Afghan pika</span> Species of mammal

The Afghan pika is a species of small mammal in the pika family, Ochotonidae. It is found in Iranian Plateau or Afghanistan, Iran, Pakistan and Turkmenistan and the IUCN lists it as being of "least concern".

<span class="mw-page-title-main">Turkestan red pika</span> Species of mammal

The Turkestani red pika is a species of mammal in the family Ochotonidae. The summer fur at its back is bright rufous and the ventral fur is white or ochraceous. The winter dorsal fur is pale brown and the ventral fur is white or light ochraceous in colour. It is found in the mountains of western Xinjiang in China, and sporadically also in the central Asian mountains in Kazakhstan, Kyrgyzstan, Tajikistan, and Uzbekistan. The female has a low fertility rate, and gives birth to offspring during the breeding season from spring to summer. She generally produces two litters each year, with two to six young. It is rated as a species of least concern on the International Union for Conservation of Nature Red List of Endangered Species, but it is considered to be near-threatened within the China part of its range.

<span class="mw-page-title-main">Thomas's pika</span> Species of mammal

Thomas's pika, also known as the Thomas-pika, is a species of small mammal in the pika family, Ochotonidae. The fur on its upper body is reddish brown in summer, and mouse grey in winter. It is a generalist herbivore threatened by habitat loss, being found on isolated peaks of the eastern Qilian Mountains in Qinghai, Gansu, and northwestern Sichuan, in China. The International Union for Conservation of Nature Red List of Endangered Species assessed the animal as insufficiently known in 1994, as near threatened in 1996, and as a species of least concern in 2008.

<span class="mw-page-title-main">Pallas's pika</span> Species of mammal

Pallas's pika, also known as the Mongolian pika, is a species of small mammals in the pika family, Ochotonidae. It is found mainly in the mountains of western Mongolia.

<span class="mw-page-title-main">Turuchan pika</span> Species of mammal

The Turuchan pika is a species of pika found in isolated regions in the Central Siberian Plateau. It is a small (16–19 cm) rock dwelling species that is active during the day due to the low temperature at night. It was previously thought to be a subspecies of the Northern pika. Little is known about this species, but is known to be locally abundant.

Constance I. Millar is an American research ecologist working for the United States Forest Service at the Pacific Southwest Research Station in Berkeley, California. Her work focuses on the effects of climate change on high-elevation ecosystems in both the past and the present. She has also developed ways to evolve management techniques of forest ecosystems to improve the ability to protect them against climate change.

References

  1. ↑ Hoffman, R.S.; Smith, A.T. (2005). "Order Lagomorpha". In Wilson, D.E.; Reeder, D.M (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. pp. 191–192. ISBN   978-0-8018-8221-0. OCLC   62265494.
  2. ↑ Jopling, A.V (1981). "Stratigraphic, Sedimentological and Faunal Evidence for the Occurrence of Pre-Sangamonian Artefacts in Northern Yukon". Arctic. 34 (1). doi: 10.14430/arctic2499 .
  3. 1 2 Smith, A.T.; Beever, E. (2016). "Ochotona princeps". IUCN Red List of Threatened Species . 2016: e.T41267A45184315. doi: 10.2305/IUCN.UK.2016-3.RLTS.T41267A45184315.en . Retrieved 12 November 2021.
  4. ↑ "NatureServe Explorer 2.0". explorer.natureserve.org. Retrieved 4 November 2022.
  5. ↑ Hafner, David J.; Smith, Andrew T. (April 2010). "Revision of the subspecies of the American pika, Ochotona princeps (Lagomorpha: Ochotonidae)". Journal of Mammalogy. 91 (2): 401–417. doi: 10.1644/09-MAMM-A-277.1 .
  6. ↑ "Pikas". World Wildlife Fund. Archived from the original on 9 May 2007. Retrieved 2007-05-15.
  7. ↑ "Pikas Disappearing from Parts of the West Due to Climate Change | U.S. Geological Survey". www.usgs.gov. Retrieved 2023-04-15.
  8. ↑ Mearns, B & R. John Kirk Townsend: Collector of Audubon's Western Birds and Mammals (PDF). p. 108. Retrieved 2009-10-06.
  9. ↑ "Ochotona princeps". public.srce.hr. Archived from the original on 2005-03-18. Retrieved 2007-05-15.
  10. 1 2 3 "American Pika". NatureWorks. Archived from the original on 1 May 2007. Retrieved 2007-05-15.
  11. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Smith, Andrew T.; Weston, Marla L. (1990-04-26). "Ochotona princeps" (PDF). Mammalian Species (352). The American Society of Mammalogists: 1–8. doi: 10.2307/3504319 . JSTOR   3504319 . Retrieved 2009-10-02.
  12. ↑ MacDonald, Stephen O.; Jones, Clyde (1987). "Ochotona collaris". Mammalian Species (281): 1–4. doi:10.2307/3503971. JSTOR   3503971.
  13. 1 2 Hafner, D.J. (1993). "North American pika (Ochotona princeps) as a late Quaternary biogeographic indicator species". Quaternary Research. 39 (3): 373–380. Bibcode:1993QuRes..39..373H. doi:10.1006/qres.1993.1044. S2CID   83513667.
  14. 1 2 Martin, J. W. 1982. Southern pika (Ochotona princeps) biology and ecology: a literature review.
  15. ↑ Erik A. Beever; Peter F. Brussard & Joel Berger (January 2003). "Patterns of apparent extirpation among isolated populations of pikas (Ochotona princeps) in the Great Basin". Journal of Mammalogy. 84 (1): 37–54. doi: 10.1644/1545-1542(2003)084<0037:POAEAI>2.0.CO;2 .
  16. 1 2 3 Smith, A.T. (November 1974). "The distribution and dispersal of pikas: influences of behavior and climate". Ecology. 55 (6): 1368–1376. Bibcode:1974Ecol...55.1368S. doi:10.2307/1935464. JSTOR   1935464.
  17. ↑ Peacock, MM (1997). "Determining natal dispersal patterns in a population of North American pikas (Ochotona princeps) using direct mark-resight and indirect genetic methods". Behavioral Ecology. 8 (3): 340–350. doi: 10.1093/beheco/8.3.340 .
  18. ↑ Richardson, John (1829). Fauna boreali-americana. London: J. Murray. Retrieved 20 December 2014.
  19. ↑ Brown, Paul (August 21, 2003). "American pika doomed as 'first mammal victim of climate change'". The Guardian . London. Retrieved 2007-05-15.
  20. 1 2 Blakemore, Bill (May 9, 2007). "Route to Extinction Goes up Mountains, Scientists Say". World News with Charles Gibson . Retrieved 2007-05-15.
  21. ↑ "Species | Protecting Wildlife".
  22. ↑ Dept. of Interior, Fish and Wildlife Service, 12-month Finding on a Petition to List the American Pika as Threatened or Endangered
  23. ↑ van Noordennen, Pieter (May 9, 2007). "American Pika". GORP. Archived from the original on May 13, 2010. Retrieved May 15, 2007.
  24. ↑ Reis, Patrick (2010-02-05). "Obama Admin Denies Endangered Species Listing for American Pika". The New York Times . Archived from the original on 9 February 2010. Retrieved 2010-02-07.
  25. ↑ "Pika Monitoring in the Upper Columbia Network". Archived from the original on 2017-01-25. Retrieved 2014-03-27.
  26. ↑ Thomas J Rodhouse; et al. "Pikas in Peril". ResearchGate .
  27. ↑ Billman, Peter D.; Beever, Erik A.; McWethy, David B.; Thurman, Lindsey L.; Wilson, Kenneth C. (2021). "Factors influencing distributional shifts and abundance at the range core of a climate-sensitive mammal". Global Change Biology. 27 (19): 4498–4515. doi: 10.1111/gcb.15793 . ISSN   1365-2486. PMID   34236759. S2CID   235767277.
  28. ↑ Stewart, Joseph A. E.; Wright, David H.; Heckman, Katherine A. (2017-08-30). "Apparent climate-mediated loss and fragmentation of core habitat of the American pika in the Northern Sierra Nevada, California, USA". PLOS ONE. 12 (8): e0181834. Bibcode:2017PLoSO..1281834S. doi: 10.1371/journal.pone.0181834 . ISSN   1932-6203. PMC   5576638 . PMID   28854268.
  29. ↑ Stewart, Joseph A. E.; Perrine, John D.; Nichols, Lyle B.; Thorne, James H.; Millar, Constance I.; Goehring, Kenneth E.; Massing, Cody P.; Wright, David H. (May 2015). Riddle, Brett (ed.). "Revisiting the past to foretell the future: summer temperature and habitat area predict pika extirpations in California". Journal of Biogeography. 42 (5): 880–890. Bibcode:2015JBiog..42..880S. doi:10.1111/jbi.12466. S2CID   84793755.
  30. ↑ Beever, Erik A.; Ray, Chris; Wilkening, Jenifer L.; Brussard, Peter F.; Mote, Philip W. (2011). "Contemporary climate change alters the pace and drivers of extinction". Global Change Biology. 17 (6): 2054–2070. Bibcode:2011GCBio..17.2054B. doi:10.1111/j.1365-2486.2010.02389.x. ISSN   1365-2486. S2CID   86079175.
  31. ↑ Billman, Peter D.; Beever, Erik A.; McWethy, David B.; Thurman, Lindsey L.; Wilson, Kenneth C. (October 2021). "Factors influencing distributional shifts and abundance at the range core of a climate‐sensitive mammal". Global Change Biology. 27 (19): 4498–4515. doi: 10.1111/gcb.15793 . ISSN   1354-1013. PMID   34236759. S2CID   235767277.
  32. ↑ Johnston, Aaron N.; Christophersen, Roger G.; Beever, Erik A.; Ransom, Jason I. (2021). "Freezing in a warming climate: Marked declines of a subnivean hibernator after a snow drought". Ecology and Evolution. 11 (3): 1264–1279. Bibcode:2021EcoEv..11.1264J. doi:10.1002/ece3.7126. ISSN   2045-7758. PMC   7863385 . PMID   33598129.
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