Ochotonidae

Diversity

The family Ochotonidae comprises the pikas, including one extant genus Ochotona and 30 currently recognized species (Hoffman and Smith, 2005). There are more than 30 extinct genera that have been identified as far back as the Eocene, one of which, Prolagus , went extinct in the late 18th century (Dawson, 1969; Ge et al., 2012). Today, Ochotonidae represents approximately 1/3 of lagomorph diversity (Smith, 2008). Their range is primarily in Asia although there are two North American species, American pikas and collared pikas (Smith et al., 1990). They range in weight from 70 to 300 g and are usually less than 285 mm in length (Smith, 2008). There is no known sexual dimorphism (Vaughan et al., 2011). The main differences from leporids are their (i) small size, (ii) small, rounded ears, (iii) concealed tails, (iv) lack of supraorbital processes, and (v) 2, rather than 3, upper molars (Smith, 2008). There are two main ecotypes, one of which is associated with rocky habitats and the other with meadow, steppe, forest, and shrub habitats. Each ecotype is associated with specific life history traits as well as behavior. Most species fall within one of these ecotypes, although there are some species which exhibit intermediate characteristics (Smith, 2008).

Geographic Range

Although the historic range of ochotonids included Asia, Europe, northern Africa, and North America, today ochotonids are found only in Asia and the high mountains of western North America. Their center of diversity is China, where 24 species are found (Smith, 2008). In Asia, pikas are found as far west as Iran, south into India and Myanmar, and into northern Russia. The two Nearctic species are found in the central Alaskan Range, the Canadian Rockies, and the Rockies, Sierra Nevadas, and Great Basin in the continental United States (IUCN, 2011).

• Biogeographic Regions
• nearctic nearctic
  • native native
• palearctic palearctic
  • native native

Habitat

Ochotonids are found in two distinct habitats: talus habitat or in meadow, steppe, forest, and shrub habitats. Talus-dwellers inhabit the crevices between rocks on mountain slopes. These species forage in the alpine meadows that abut the rocks or from the vegetation that grows between the rocks. They are found across a wide altitudinal gradient from below 90 to above 6000 m (Nowak and Wilson, 1991). Species that are typically found in talus habitats are alpine pikas , silver pikas , collared pikas , Chinese red pikas , Glover’s pikas , Himalayan pikas , northern pikas , Ili pikas , large-eared pikas , American pikas , Royle’s pikas , and Turkestan red pikas (Smith, 2008).

Non-talus dwelling pikas are found in a variety of vegetated habitats where they forage and produce burrows. The meadows they occupy are also typically at high elevation. The meadow-burrowing pikas are all found in Asia and include Gansu pikas , black-lipped pikas , Daurian pikas , Kozlov’s pikas , Ladak pikas , Muli pikas , Nubra pikas , steppe pikas , Moupin pikas , and Thomas’s pikas (Smith, 2008).

Some species, including Pallas's pikas and Afghan pikas are known to occur in both habitat types and are referred to as intermediate species (Smith, 2008). Although intermediate in habitat, these species exhibit the life-history traits and behavior of meadow-dwelling pikas.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• savanna or grassland savanna or grassland
• forest forest
• mountains mountains

Systematic and Taxonomic History

Ochotonidae is one of two families in the order Lagomorpha (Huchon et al., 2002; Meredith et al. 2011). The other is Leporidae (rabbits and hares). Lagomorpha and Rodentia make up the clade Glires (Meng et al., 2003). Glires and Archonta make up the clade Euarchontaglires (Murphy et al. 2001). Ochotonidae was first described in 1897 by Oldfield Thomas. Synonyms include Lagomina Gray, 1825; Lagomyidae Lillijeborg, 1866; and Prolaginae Gureev, 1960 (Hoffman and Smith, 2005).

The relationships within the family and within the genus Ochotona are less well understood. Recent molecular phylogenies include Yu et al. (2000), Niu et al. (2004), Lissovsky et al. (2007), and Lanier and Olson (2009). Current understanding is that there are three subgenera within Ochotona based on both morphological and molecular evidence (Yu et al., 2000). The relationships between these and the independence of some species is still highly debated (Hoffman and Smith, 2005).

Physical Description

Ochotonids exhibit little physical variation. They are generally small, ranging in body length from 125 to 300 mm and weighing 70 to 300 g (Nowak and Wilson, 1991; Smith, 2008). Unlike leporids , pikas lack a visible tail and have short rounded ears with large, valvular flaps and openings at the level of the skull (Vaughan et al. 2011). The ears are only weakly movable (Diersing, 1984) and their nostrils can be completely closed (Nowak and Wilson, 1991). They have short limbs with the hind limbs barely longer than the forelimbs (Nowak and Wilson, 1991). They have 5 front digits and 4 hind digits all with curved claws (Vaughan et al., 2011). The soles of the feet are covered by long hair but the distal pads are exposed (Diersing, 1984). They are digitigrade while running but plantigrade during slow movement (Vaughan et al., 2011). Ochotonids have 22 thoracolumbar vertebrae and lack a pubic symphysis (Diersing, 1984).

The skull is generally similar to that of leporids . It is flattened, exhibits fenestration, and is constricted between the orbits (Vaughan et al., 2011). The ochotonid tooth formula is 2/1 0/0 3/2 2/3=26. The first incisors are ever-growing and completely enameled, while the second are small, peg-like, and directly behind the first. The cutting edge of the first incisor is v-shaped (Nowak and Wilson, 1991). They have a long post-incisor diastema and hypsodont, rootless cheek teeth. Occlusion is limited to one side at a time, with associated large masseter and pterygoideus muscles allowing for transverse movement while the cheekteeth have transverse ridges and basins (Vaughan et al., 2011). The zygomatic arch is slender and not vertically expanded. The jugal is long and projects more than halfway from the zygomatic root of the squamosal to the external auditory meatus (Diersing, 1984). Unlike leporids, pikas lack a supraorbital process. Their rostrum is short and narrow and the maxilla has a single large fenestra (Vaughan et al., 2011). The auditory bulla, which is fused with the petrosal, are spongiose and porous. The bony auditory meatus is laterally directed and not strongly tubular (Diersing, 1984).

Pikas exhibit no sexual dimorphism (Nowak and Wilson, 1991). Males lack a scrotum and both sexes have a cloaca, which opens on a mobile apex supported by a rod of tail vertebrae (Diersing, 1984; Vaughan et al., 2011). Females have between 4 and 6 mammae, with one pair inguinal and one to two pairs pectoral (Nowak and Wilson, 1991). Ochotonid coats consist of long, dense, fine fur and are usually grayish brown, although they vary inter- and intra-specifically depending on habitat. Some ochotonids go through two molts, with darker fur during the summer and grayer pelage in the winter (Diersing, 1984).

Physiologically, pikas have a high metabolic rate. They also have low thermal conductance and, even at moderately high temperatures, low ability to dissipate heat (MacArthur and Wang, 1973).

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

Reproduction

Most talus-dwelling pika species are monogamous or polygynous (Gliwicz, Witczuk, and Pagacz, 2005; Smith, 2008). There are some notable exceptions, including documented cases of polygynandry in collared pikas (Zgurski and Hik, 2012). In contrast, meadow-dwelling pikas exhibit monogamous, polygynous, polyandrous, or polygynandrous mating systems, depending on the sex ratio at the beginning of the breeding season (Smith and Dobson, 2004).

• Mating System
• monogamous monogamous
• polyandrous polyandrous
• polygynous polygynous
• polygynandrous (promiscuous) polygynandrous (promiscuous)

The talus-dwelling species, such as American pikas , exhibit low annual production of offspring (Smith 1988). Typically, talus-dwelling pikas produce only one successfully weaned litter of 1 to 5 young a year. On average, approximately 2 young per mother are successfully weaned per year (Smith, 2008). Juveniles reach sexual maturity as yearlings (Smith et al., 1990). Some talus-dwelling species exhibit absentee maternal care typical of lagomorphs (Whitworth 1984). The gestation period of American pikas , for example, is 30.5 days (Smith, 1988) and their breeding season lasts between late April and the end of July (Markham and Whicker, 1973). In contrast, meadow-dwelling species have much higher potential reproductive output, but it varies depending on environmental conditions. They can produce litters that are twice as large as those of talus-dwellers up to every three weeks during the reproductive season. The reproductive season of O. curzoniae , a meadow-dwelling species, generally lasts from March to late August but can vary between years and sites (Yang et al., 2007). On average, multiple litters are produced each year and most young are successfully weaned (Smith, 2008). Further increasing their reproductive output, juveniles born early in the breeding season will reach sexual maturity and breed during the summer of their birth (Smith et al., 1990).

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual

Some talus-dwelling species exhibit absentee maternal care typical of lagomorphs (Whitworth 1984). Males and females of some meadow-dwelling species participate in affiliative behavior with juveniles as well as mate guarding and defending territories (e.g. Smith and Gao, 1991). Juveniles of meadow-dwelling species also continue to live on the parental territory through at least their first year (Smith, 2008).

• Parental Investment
• altricial altricial
• male parental care male parental care
• female parental care female parental care
• pre-fertilization
  • protecting
    • male
• pre-hatching/birth
  • protecting
    • male
• pre-independence
• post-independence association with parents
• inherits maternal/paternal territory

Lifespan/Longevity

The average mortality of talus-dwelling species is low and many are long lived compared to most small mammals (Smith et al., 1990). American pikas live on average 3 to 4 years but have been known to live up to 7 years (Forsyth et al, 2005). Meadow-dwelling species experience high annual mortality and few individuals live more than two years (Smith, 1988).

Behavior

North American talus-dwelling pikas occupy and defend territories individually, particularly against members of the same sex. Except for when they come together to mate, these talus-dwelling pikas are relatively asocial (Smith et al., 1990). Dominance does not extend beyond an individual’s territory. Most social interactions are aggressive and chases and fights result from conspecific intrusion, and the theft of vegetation from the haypiles of conspecifics. Talus-dwelling ochotonids use vocalizations and scent-marking to demarcate their territories, which are relatively large and make up about ½ of their home range (Svendsen 1979; Smith, 2008). Territories are usually established near the edge of the talus/vegetation border and vary in size depending on species and the productivity of the adjoining vegetation (Smith, 2008). They are typically between 450 and 525 m^2 (Gliwicz, Witczuk, and Pagacz, 2005).

Some Asian talus-dwelling pika species defend territories as pairs. The pair uses the same main shelter and spend most of their time in the same area. They cooperate in hay-storage and communicate using vocalizations, but are asocial outside of the pair. Primarily the males demarcate the territory and defend it against intruders. These territories are typically larger than those of individual pikas, around 900 m^2 per pair, and these pikas live at much higher densities. (For a more complete discussion see Gliwicz, Witczuk, and Pagacz (2005).)

In contrast, the Asian meadow-dwelling species are considered to exhibit highly social family groups, consisting of adults as well as young of the year in communal burrows (Smith, 2008). These species live at much higher densities (more than 300/ha) than the talus-dwelling species and experience more variation in population density over seasons and between years (Nowak and Wilson, 1991). Meadow-dwelling pika exhibit both affiliative behaviors, such as allogrooming, nose rubbing, and various forms of contact, within family groups, as well as aggressive territorial behaviors toward non-family members. In addition, family members communicate with vocalizations, which can elicit affiliative contact (Smith, 2008). They also defend territories as a family unit and share communal hay piles (Smith et al., 1990). Their territories are also demarcated by scent-marking and vocalizations.

Both ecotypes are poor dispersers and typically do not range far from their natal territory. In talus-dwellers, an individual with control of a territory typically maintains it for life, and upon it’s death will be replaced by a juvenile born in a nearby territory and usually of the same sex (Smith, 1974; Smith, 2008). In meadow-dwellers, juveniles will stay in their home burrow for the first year and then less than half will disperse to nearby territories. Males are more likely to disperse, but even then typically move only a few territories away (Smith, 2008).

Pikas do not hibernate during the winter, but instead stay active in their burrows or rocky crevices. During this time they consume the food caches that they collected during the summer (Smith et al., 1990). Ochotonids are primarily diurnal, but can be active at all times of day as well as throughout the year (Nowak, 1991). They are frequently observed sunning themselves on rocks during warmer months (Diersing, 1984; Nowak, 1991).

• Key Behaviors
• terricolous
• motile motile
• territorial territorial
• social social

Communication and Perception

Most pika species vocalize both for predator alarms and territory defense (Smith et al., 1990; Nowak, 1991; Trefry and Hik, 2009). They produce a high-pitched 'eek' or 'kie' that is ventriloquial in character (Diersing, 1984). They have also been demonstrated to eavesdrop on the alarm calls of heterospecifics, such as marmots and ground squirrels (Trefry and Hik, 2009). Ochotonids can also communicate danger by drumming on the ground with their hind feet (Diersing, 1984). Meadow-dwelling, burrowing species produce multiple types of vocalizations, many of which are used in socializing with conspecifics (Smith, 2008). Low chattering and mewing noises have also been reported (Diersing, 1984). Both ecotypes also use scent-marking (Smith, 2008).

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

• Other Communication Modes
• scent marks scent marks
• vibrations vibrations

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Pikas are generalist herbivores and typically collect caches of vegetation, which they live off of during the winter. They consume leaves and stems of forbs and shrubs as well as seeds and leaves of grasses; sometimes they also consume small amounts of animal matter (Diersing, 1984). Like most leporids, they produce two types of feces: soft caecotroph and hard pellets (Smith, 2008). During the summer, after the breeding season, pikas accumulate large stores of many different plants in their haypiles, which they then store for winter consumption. Their foraging patterns varies throughout the season in accordance with which plants are available, preferred, and/or have the highest nutritional content, selecting for higher caloric, lipid, water, and protein content (Smith and Weston, 1990). The foraging habits of pikas affect plant communities. Pikas alter which plants are collected while foraging as well as how far they go to forage, depending on whether they are being immediately consumed or are being added to a haypile. This variation results in a mosaic of plant community composition (Huntly, Smith and Ivins, 1986). This selective foraging has been demonstrated to stabilize plant community composition and slow the process of succession, as well as reduce the number of seeds in the soil (Huntly, Smith and Ivins, 1986; Khlebnikov and Shtilmark, 1965).

• Primary Diet
• herbivore herbivore
  • folivore folivore

• Foraging Behavior
• stores or caches food stores or caches food

Predation

Pikas serve as an important food source to both birds and mammals in all of the habitats they occupy. Meadow-dwelling pikas, in particular, can be a preferred food or buffer species throughout the year, but are especially important prey in the winter as they are still active while similarly sized rodents hibernate (Smith et al., 1990). During high-density years, burrowing pikas can be the most important food source for Asian steppe predators, sometimes making up more than 80% of a predator’s diet (Sokolov, 1965). In addition to being prey for small to medium-sized carnivores, pikas are also often consumed by larger carnivores, including wolves and brown bears (Smith et al., 1990).

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

In addition to the important ecosystem roles that ochotonids serve as consumers and as prey, they also alter their environments through bioturbative ecosystem engineering. The burrowing of meadow-dwelling pikas improves soil quality and reduces erosion (Smith and Foggin, 1999). The accumulation and decomposition of leftover caches and the feces in burrow systems also helps increase the organic content of soil (Smith et al., 1990). In addition to their abiotic benefits, pika burrows are used by other mammals and birds and their caches are often consumed by other herbivores (Smith et al., 1990). The haypiles of talus-dwelling pikas also improve soil quality upon decomposition, thereby facilitating plant colonization of the talus (Smith et al., 1990).

• Ecosystem Impact
• soil aeration soil aeration
• keystone species keystone species

Economic Importance for Humans: Positive

Traditionally, pikas were a valuable source of fur throughout Asia and in particular the Soviet Union (Smith et al., 1990). Additionally, some traditional herdsmen selectively graze their livestock in the winter on pika meadows where haypiles are exposed above the snow (Loukashkin, 1940).

• Positive Impacts
• body parts are source of valuable material

Economic Importance for Humans: Negative

Some ochotonid species are considered pests in Asian countries, where they are believed to compete with livestock for forage, erode soil, and negatively affect agricultural crops such as apple trees and wheat (Smith et al., 1990). It has been demonstrated that pikas can harm agricultural crops (Smith et al., 1990) but no control studies have been conducted that support other claims. Pika foraging has been implicated in accelerating range deterioration but only in areas that were already overgrazed (Shi, 1983; Zhong, Zhou and Sun, 1985). Millions of hectares have been subject to poisoning in an effort to control pika numbers with mixed results, including extermination of non-target species (Smith et al., 1990).

• Negative Impacts
• crop pest

Conservation Status

Today, four ochotonid species ( silver pikas , Hoffmann's pikas , Ili pikas , Kozlov's pikas ) are classified as endangered or critically endangered due to habitat loss, poisoning, or climate change (Smith, 2008; IUCN, 2011). Additionally, many subspecies are threatened due to low vagility and its effects on stochastic metapopulation dynamics (Smith, 2008). Not enough is known about many species (10% are still considered data deficient by the IUCN) to truly assess their conservation status. Until the systematics of the family is better understood it will be hard to determine the outlook for many populations. Due to their low tolerance for high temperatures and low vagility, ochotonids are considered especially vulnerable to warming so the need for conservation efforts is expected to increase with climate change (Holtcamp, 2010).

Additional Links

Encyclopedia of Life

Contributors

Aspen Reese (author), Yale University, Eric Sargis (editor), Yale University, Hayley Lanier (editor), University of Wyoming - Casper, Tanya Dewey (editor), University of Michigan-Ann Arbor.

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