Physical Description American pikas are intermediate in size when compared to other ochotonids. Their body mass exhibits a great deal of variation and ranges from 121 to 176 grams. In certain parts of their range, males are larger than females, but only slightly. Their body is ovoid, with short ears, long vibrissae (40-77 mm), short limbs, and no visible tail. Their back paws are digitigrade, have four toes (compared to five on the front), and range from 25 to 35 mm in length. Both sexes have a pseudocloacal openings, which must be everted to expose the penis or clitoris. Females have six mammae which do not enlarge during lactation. American pikas have a high body temperature (average of 40.1°C) and relatively low upper lethal temperature (average of 43.1°C). They have a high metabolic rate (1.53 cm^3 oxygen/hour), and thermoregulation is behavioral rather than physiological. (Chapman and Flux, 1991; Smith and Weston, 1990; Wolf, et al., 2007) Pelage color of American pikas changes seasonally but maintains an off-white hue on its ventral surface (as opposed to white in Ochotona collaris). On its dorsal surface, pelage ranges from grayish to cinnamon-brown in the summer. In the winter, their dorsal pelage is gray and is twice as long as summer pelage. Their ears are round, covered with dark hair on their internal and external surfaces, and edged in white. Their paws are densely furred, including the soles, with the exception of small black naked pads at the ends of the toes. Their skull is slightly round with a flat, broad interorbital region. Other distinguishing characteristics of the American pika's skull include a slender rostrum, nasals that are widest anteriorly, maxillae with one large fenestration (rather than numerous small fenestrae of Leporidae), an elongated jugal, which forms a prominent projection from the posterior zygomatic arch, and a dental formula of 2/1, 0/0, 3/2, 2/3 totaling 26 teeth. (Chapman and Flux, 1991; Smith and Weston, 1990; Wolf, et al., 2007) Other Physical Features

endothermic

homoiothermic

bilateral symmetry Sexual Dimorphism

sexes alike

male larger Range mass 121 to 176 g 4.26 to 6.20 oz

Range length 162 to 216 mm 6.38 to 8.50 in

Average basal metabolic rate 1.53 cm3.O2/g/hr

Average basal metabolic rate 0.932 W AnAge

Reproduction American pikas are monogamous, and mate pairs are formed with adults from adjacent territories. When more than one potential mate is available, females may exhibit mate choice. (Smith and Weston, 1990) Mating System

monogamous American pikas typically mate as yearlings. Males are considered sexually active when their testes are 11 mm in length or greater (Smith and Weston, 1990). American pikas are reflex ovulators (i.e., ovulation only occurs after breeding) and are seasonally polyestrus. Each female has 2 litters per year, with an average of 3 young per litter. Breeding commences 1 month before snow-melt and gestation last approximately 30 days. At low elevations, parturition occurs as early as March but occurs from April to June at higher elevations. Pups weigh between 10 and 12 g at birth and are weaned by 28 days old. Lactation significantly reduces a female's fat reserves, and although females exhibit postpartum estrus, they only nurse the second litter if the first does not survive. (Smith and Weston, 1990; Wolf, et al., 2007) Key Reproductive Features

iteroparous

seasonal breeding

gonochoric/gonochoristic/dioecious (sexes separate)

sexual

induced ovulation

fertilization

viviparous

post-partum estrous Breeding interval American pikas breed twice yearly, during the same breeding season.

Breeding season American pikas breed one month before snow-melt and once again following the birth of their first litter.

Range number of offspring 1 to 6

Average number of offspring 3

Average number of offspring 3 AnAge

Average gestation period 30 days

Average gestation period 30 days AnAge

Range weaning age 18 to 35 days

Average weaning age 28 days

Average time to independence 4 weeks

Average age at sexual or reproductive maturity (female) 347 days

Average age at sexual or reproductive maturity (female)

Sex: female 347 days AnAge

Average age at sexual or reproductive maturity (male) 1 years American pikas are born slightly altrical; they are blind, slightly haired, have fully erupted teeth, and weigh between 10 and 12 grams at birth. For the first 18 days, young are completely dependent on their mothers. Pups open their eyes at 9 days of age. Mothers spend most of their time foraging, but visit the nest once every 2 hours to nurse for an average of 10 minutes. Pups become independent by about 4 weeks old (soon after weening). American pikas exhibit a remarkable growth rates compared to other members of Lagomorpha, and can reach adult size after only 3 months. (Smith and Weston, 1990; Wolf, et al., 2007) Parental Investment

altricial

female parental care

pre-fertilization provisioning protecting female

pre-hatching/birth provisioning female protecting female

pre-weaning/fledging provisioning female protecting female

pre-independence provisioning female protecting female



Lifespan/Longevity Average annual mortality of American pikas is 37 to 53%, and age-specific mortality is highest for 0 to 1-year-olds and 5 to 7-year-olds. The maximum age of American pikas in the wild and in captivity is 7 years, with an average life expectancy of 3 years in the wild. (Chapman and Flux, 1991; Fitzgerald, et al., 1994) Range lifespan

Status: wild 7 (high) years

Range lifespan

Status: captivity 7 (high) years

Average lifespan

Status: wild 3 years

Average lifespan

Status: wild 6.0 years Max Planck Institute for Demographic Research

Average lifespan

Status: wild 7.0 years Max Planck Institute for Demographic Research

Ecosystem Roles American pikas are considered allogenic engineers (i.e., altering the environment through their activities). Their large haypiles, containing both plant and fecal matter, are not entirely consumed during the winter, leaving large accumulations of decomposing biomass to act as fertilizer and a potential food source for other animals. As fertilizer, haypiles ultimately increase soil nitrogen, a limiting resource for vegetation at high altitude. Also, American pikas are host to many species of intestinal parasites (Coccidia) and parasitic fleas (Siphonaptera). (Aho, et al., 1998; Bossard, 2006; Lynch, et al., 2007) Ecosystem Impact

keystone species Commensal/Parasitic Species

Eimeria cryptobarretti

Eimeria banffensis

Eimeria calentinei

Eimeria klondikensis

Isospora marquardti

Eimeria barretti

Eimeria princeps

Eimeria worleyi

fleas (Siphonaptera)

Economic Importance for Humans: Positive There are no known positive effects of American pikas on humans.

Economic Importance for Humans: Negative There are no known negative effects of American pikas on humans.

Contributors Alexandra Peri (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), University of Michigan-Ann Arbor, John Berini (editor), Animal Diversity Web Staff, Catherine Kent (editor), Special Projects.

Glossary Nearctic living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico. acoustic uses sound to communicate altricial young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching. bilateral symmetry having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria. chemical uses smells or other chemicals to communicate coprophage an animal that mainly eats the dung of other animals cryptic having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect. diurnal active during the day, 2. lasting for one day. duets to jointly display, usually with sounds in a highly coordinated fashion, at the same time as one other individual of the same species, often a mate endothermic animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds. female parental care parental care is carried out by females fertilization union of egg and spermatozoan folivore an animal that mainly eats leaves. herbivore An animal that eats mainly plants or parts of plants. induced ovulation ovulation is stimulated by the act of copulation (does not occur spontaneously) iteroparous offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes). keystone species a species whose presence or absence strongly affects populations of other species in that area such that the extirpation of the keystone species in an area will result in the ultimate extirpation of many more species in that area (Example: sea otter). monogamous Having one mate at a time. motile having the capacity to move from one place to another. mountains This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation. native range the area in which the animal is naturally found, the region in which it is endemic. scent marks communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them seasonal breeding breeding is confined to a particular season sexual reproduction that includes combining the genetic contribution of two individuals, a male and a female solitary lives alone stores or caches food places a food item in a special place to be eaten later. Also called "hoarding" tactile uses touch to communicate taiga Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present. temperate that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle). terrestrial Living on the ground. territorial defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement tundra A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short. visual uses sight to communicate viviparous reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.