American pika
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.
Distribution and habitat[edit]
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[edit]
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]
Conservation and decline[edit]
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]