Pikas (Ochotonidae)

(vertebrate zoology) A family of the mammalian order Lagomorpha; members are relatively small, and all four legs are about equally long.

(Ochotonidae)

Class: Mammalia

Order: Lagomorpha

Family: Ochotonidae

Thumbnail description
Small, egg-shaped herbivores with prominent round ears, small eyes, and no visible tail

Size
5–8 in (13–20 cm); 3–10 oz (80–300 g)

Number of genera, species
1 genus; 30 species

Habitat
Talus, meadow, and steppe

Conservation status
Extinct: 1 species; Endangered: 1 species; Vulnerable: 3 species; Lower Risk/Near Threatened: 2 species; Data Deficient: 2 species

Distribution
Mountains of western North America; primarily high mountains and steppe of central Asia

Evolution and systematics

Molecular evidence indicates that the family Ochotonidae (pikas) separated from the family Leporidae (the other family in the order Lagomorpha) 37 million years ago. Paleontological evidence closely matches this date, suggesting that the two families separated in the early Oligocene. All evidence points to an Asian origin for the family. Pikas spread to North America by the late Oligocene. Pikas quickly differentiated into many forms and became particularly diverse during the Miocene. During this time, representative genera were found in North America, Asia, and Africa. The first Ochotona appeared in the early Pliocene of Asia, and Ochotona first entered North America in the mid-Pliocene. Ochotona and Prolagus, the only other pika genus to reach historical times, are first found in Europe during the late Pliocene. Prolagus subsequently went extinct, leaving Ochotona as the only living representative of the family from a record of 25 fossil genera.

The close resemblance of all pika species makes it difficult to find external characters to tell them apart. Even using traditional morphological measurements on skull bones and dentition has not been sufficient to stem controversy over the systematic alignment of pika species; no two revisions of the genus are the same. Some subspecies have landed in as many as four different species. Molecular techniques have begun to clarify pika systematics, and a consensus is nearing, although the task is far from completed. Currently, 30 species of Ochotona are recognized.

Physical characteristics

All living pikas are very similar in appearance. They are small egg-shaped balls of fluff sporting thin, relatively large round ears and without a visible tail. Pikas range in size from the Gansu pika (Ochotona cansus), which weighs in at approximately 3 oz (80 g), to Glover's pika (O. gloveri), which can reach 10 oz (300 g). Most pikas are a brownish gray, and accents are most often in the red spectrum.

Distribution

Ochotona has a northern, Holarctic, distribution. In North America, they are found primarily at high elevations throughout the inter-montane west (American pika, O. princeps) or in the mountains of Alaska and the Yukon (collared pika, O. collaris). The remainder of the genus is found throughout central Asia, in the Himalayan massif and associated ranges, and across eastern Siberia to Sakhalin Island and onto Hokkaido Island, Japan. The steppe pika (O. pusilla) reaches west to the Ural Mountains, and one small population found to the west of this chain can be classified as European.

Habitat

There are two types of pikas: those that occupy rocks or piles of talus and those that live in meadow or steppe environments and construct burrows. This contrast in habitat type determines all aspects of behavior and reproduction in pikas, such that these traits are best treated together for each ecological type of pika.

Behavior

In general, rock-dwelling pikas are territorial as individuals or in pairs, relatively asocial (most are quite pugnacious), have a restricted recorded vocal repertoire of two calls, are long-lived (some reaching six years of age), and have relatively stable low-density populations over time. In contrast, burrowing pikas that occupy meadow or steppe habitats live in family burrow system territories, are extremely social, communicate by uttering a number of different vocalizations, have short adult life spans, and their populations undergo extreme annual fluctuations in size and may reach densities of up to 120 animals per acre (300/ha).

One similarity between the two types of pikas is the long-call, or song, given by adult males during the breeding season. The long-call consists of many repeated elements in a distinctive pattern for each species. There are, however, clear similarities between these calls in the rock-dwelling American pika (Ochotona princeps) and the burrowing plateau pika (O. curzoniae).

Throughout the day, most pikas are active about one-third of the time, and much of this is spent in quiet repose sitting atop a prominent rock surveying their surroundings. When they do patrol their territory, pikas often rub their cheek gland on rocks to advertise their presence. A quick vigorous chase normally ensues when another pika is encountered on their territory. Sometimes combatants actually make contact, with fur flying from the rump of the interloper. These chases are predictable when the interloper is an animal of the same gender or a non-neighbor of the opposite gender. However, chases are initiated only about half of the time when the animal encountered is a neighbor of the opposite gender. Otherwise, these opposite-sexed neighbors sit in a limbo of social tolerance, neither chasing nor engaging in any overt affiliative behavior that most likely defines a breeding pair.

Interestingly, these territories are not randomly spaced by gender across the talus. Instead, adjacent territories are generally occupied by a pika of the opposite sex. Pikas can live for up to six years of age and thus territory vacancies are uncommon. When they do occur, replacement is an animal of the same gender as the animal that died. Males will not allow settlement next door by another male, and similarly females chase off all available females. Female-female aggression ensures that their spacing is too far apart and the territories on talus are too large for any one male to control access to many females. Pika behavior controls the spacing of animals on the talus, and ultimately leads to a monogamous mating system. These dynamics ensure that the population structure of the pika is relatively stable over time.

Common predators of pikas are weasels and pine martens (genus Mustela). When a pika sees a predator, it utters an alarm call, a repetitive variant of the short call. Martens must capture pikas on the surface of the talus, as they are too big to fit in the cracks and crannies of the talus. When pikas first see a marten, they burst into an alarm call designed to warn neighbors (most of whom are close relatives) of the looming threat. If the predator is a weasel, then the pika often waits a few minutes before first giving the call. Weasels can follow pikas into their lairs in the rocks and, apparently, this latency to call allows the weasel time to clear out of the pika's territory before the pika alerts its neighbors of the threat.

The climate on the Tibetan plateau is frigid during winter and there is usually no snowpack (most precipitation occurs during summer) to insulate animals from these extreme colds. The high degree of socialization, coupled with the philopatry of juveniles, has led to the conclusion that these family groups are selected to stay together during winter, when huddling may increase their average survivorship.

Nearly all mammalian carnivores and predacious birds on the Tibetan Plateau specialize on eating pikas. In response, plateau pikas utter an alarm call when predators are sighted. But, there are some unusual twists to this behavior. First, the call is very faint and barely audible from a short distance away. Apparently, it is designed only to warn immediate family members and not those from neighboring families. Second, the call is only given during the period of the first three days any new litter of juveniles is surface active. Giving the call may bring the predator's attention to the caller, and thus may be costly. After three days on the meadow, the young may be sufficiently experienced and no longer benefits sufficiently from an anti-predator alarm call. At this point, all the animals remain silent until the next litter surfaces.

Feeding ecology and diet

Like all lagomorphs, pikas are generalized herbivores. Their most characteristic feeding behavior is the gathering of vegetation during summer that is stored in a centralized cache, or haypile, to serve as food during winter. Again like all lagomorphs, pikas excrete two types of feces and commonly reingest the soft viscous feces.

Pikas are most active during the mid- to late summer when they begin to gather vegetation with which to construct their haypile. At this time, a flurry of activity ensues with animals sometimes making one round-trip per minute to the adjoining meadow to pluck a long stem of a succulent herb. Commonly, a pika will sit on a rock briefly, utter a short call to proclaim its territory, rush to the meadow for a mouthful of vegetation, rush back, deposit the load, quickly give another call, and rush off again. The haypiles constructed by members of a pair are normally located on their territory closer to the territory of their pair mate rather than centered on their territory. Pikas forage for vegetation off of the talus, generally close to the talus-meadow interface. Their behavior when feeding contrasts sharply with that of when they are gathering hay. Feeding pikas pluck individual small stems, generally of grass, which they eat while maintaining an alert posture; they appear to be extremely wary of predators while feeding. Pikas gather vegetation for their haypiles at far greater distances from the talus and, in contrast to their alert posture while feeding, appear foolhardy and unaware of predators while gathering hay. They try to get the largest mouthful of vegetation that they can, often diving at the base of a forb to clip it off.

Reproductive biology

Rock-dwelling pikas produce few young each year, whereas burrowing forms produce many large litters each season.

Most pikas originate from first litters as there is strong selection pressure for young to become active as early in the short summer season as possible. Juvenile pikas must grow up fast, claim a vacant territory (if one exists), and construct a haypile before the next winter's snow descends on the talus. Young normally remain close to their site of birth, and dispersal to a territory far away on their home talus, or movement to another talus patch, is rare.

Young become independent approximately three weeks after parturition, and they remain on their family burrow system territory throughout the summer and the following winter. Thus, as litter after litter appear on the meadow, the number of animals in each family grows and the overall population density skyrockets. Some populations reach densities of more than 120 animals per acre (300 per ha). Mortality is high during the harsh Tibetan winters and most animals perish; it is rare for any pika to live into its second year. The breeding season begins in early spring, and this is also the time that the composition of families is determined. There is a modest reshuffling of pikas before mating occurs. Nearly all pikas born the preceding summer remain on their home territory, but some, in particular males, disperse short distances and join neighboring families. The most common movements are to an immediately adjoining neighbor, but some pikas move as far as five territories away. The result of most of these movements is an equalizing of density across the meadow. Males do not move to families with more females. Instead, they move to families with more males.

The mating system expressed by plateau pikas results from the combination of the random nature of over-winter mortality and the few dispersal movements of animals alive just before the mating season. Most family burrow systems are occupied by a single adult male and female, which results in monogamy. However, when the number of surviving males and females is higher than can be accommodated on the restricted number of territories by only pairs, more complex situations arise. Some families are composed of one male and many females (polygyny), others with multiple males and one or more females (polyandry). These three different mating systems can occur in neighboring family burrow systems, a situation unique in mammals. In addition, the formation of these mating systems does not appear to result from variance in habitat quality on the meadow; there is no correlation between the type of mating system on a burrow system in one year with what will appear there the following year.

Conservation status

Twenty-six of the 30 pika species have been fully assessed for their IUCN Red List conservation status, and of these, six (23%) have been classified as Threatened (O. argentata, O. hoffmanni, O. huangensis, O. iliensis, O. koslowi, and O. pusilla). The first five on this list live in remote areas and are poorly known. The steppe pika (O. pusilla) has retreated as its habitat has been plowed under. An additional four species have one or more threatened subspecies. In nearly all cases, these forms are threatened because of habitat loss or inadvertent poisoning (control efforts directed at other, more common, pika species).

Significance to humans

Direct economic benefits from pikas are few; they are too small to serve as a source of country food. In central Asia, their pelts were once used to make felt. A distillate of the soft feces of pikas ("mumio") is used as a folk medicine in central Asia to speed up the healing of broken bones or to remedy rheumatism. Some species are believed to be agricultural pests or to damage rangelands and are subject to widespread poisoning efforts. A contrasting view is that these species are important in their respective ecosystems and should be preserved to maintain local biodiversity rather than to be subject to control.

Species accounts

Resources

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IUCN Species Survival Commission, Lagomorph Specialist Group. Department of Biology, Box 871501, Arizona State University, Tempe, AZ 85287-1501 USA. E-mail: a.smith@ asu.edu Web site:

IUCN—The World Conservation Union, Species Survival Commission, Red List Programme Office. Official IUCN Red List of Threatened Species. .

[Article by: Andrew T. Smith, PhD]