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Pika
Genus of mammals in the family Ochotonidae of the order Lagomorpha

The pika is a small mountain mammal native to Asia and North America, closely related to the rabbit but distinguished by short, rounded ears. The large-eared pika inhabits the Himalayas at elevations above 6,000 m. Belonging to the family Ochotonidae within the order of lagomorphs, pikas are the smallest lagomorphs, with one extant genus, Ochotona, comprising 37 species. They prefer rocky slopes and gather hay for winter and are known for their high-pitched alarm call. Notably, the American pika and collared pika inhabit western North America including British Columbia and Alaska.

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Habitat

Pikas are native to cold climates in Asia and North America. Most species live on rocky mountainsides, where numerous crevices are available for their shelter, although some pikas also construct crude burrows. A few burrowing species are native to open steppe land. In the mountains of Eurasia, pikas often share their burrows with snowfinches, which build their nests there.10 Changing temperatures have forced some pika populations to restrict their ranges to even higher elevations.11

Characteristics

Further information: Cecotrope

Pikas are small mammals, with short limbs and rounded ears. They are about 15 to 23 cm (5.9 to 9.1 in) in body length and weigh between 120 and 350 g (4.2 and 12.3 oz), depending on species.

These animals are herbivores and feed on a wide variety of plant matter, including forbs, grasses, sedges, shrub twigs, moss and lichens. Easily digestible food is processed in the gastrointestinal tract and expelled as regular feces. But in order to get nutrients out of hard to digest fiber, pika ferment fiber in the cecum (in the GI tract) and then expel the contents as cecotropes, which are reingested (cecotrophy). The cecotropes are then absorbed in the small intestine to utilize the nutrients.

Collared pikas have been known to store dead birds in their burrows for food during winter and eat the feces of other animals.12

As with other lagomorphs, pikas have gnawing incisors and no canines, although they have fewer molars than rabbits. They have a dental formula of 2.0.3.21.0.2.3 = 26.13 Another similarity that pikas share with other lagomorphs is that the bottom of their paws are covered with fur and lack paw pads.14

Rock-dwelling pikas have small litters of fewer than five young, whilst the burrowing species tend to give birth to more young and to breed more frequently, possibly owing to a greater availability of resources in their native habitats. The young are born altricial (eyes and ears closed, no fur) after a gestation period of between 25 and 30 days.15

Activity

Pikas are active during daylight (diurnal) or twilight hours (crepuscular), with higher-elevation species generally being more active during the daytime. They show their peak activity just before the winter season. Pikas do not hibernate and remain active throughout the winter by traveling in tunnels under rocks and snow and eating dried plants that they have stored.16 Rock-dwelling pikas exhibit two methods of foraging: the first involves direct consumption of food, and the second is characterized by the gathering of plants to store in a "haypile" of cached plants.17

The impact of human activity on the tundra ecosystems where pikas live has been recorded dating back to the 1970s.18 Rather than hibernate during winter, pikas forage for grasses and other forms of plant matter and stash these findings in protected dens in a process called "haying". They eat the dried plants during the winter.19 When pikas mistake humans as predators, they may respond to humans as they do to other species that do prey on pikas. Such interactions with humans have been linked to pikas having reduced amounts of foraging time, consequentially limiting the amount of food they can stockpile for winter months.20 Pikas prefer foraging in temperatures below 25 °C (77 °F), so they generally spend their time in shaded regions and out of direct sunlight when temperatures are high.21 A link has also been found between temperature increases and lost foraging time, where for every increase of 1 °C (1.8 °F) to the ambient temperature in alpine landscapes home to pikas, those pikas lose 3% of their foraging time.22

Eurasian pikas commonly live in family groups and share duties of gathering food and keeping watch. Some species are territorial. North American pikas (O. princeps and O. collaris) are asocial, leading solitary lives outside the breeding season.23

Vocalization

Pikas have distinct calls, which vary in duration. The call can be short and quick, a little longer and more drawn out or long songs. The short calls are an example of geographic variation. The pikas determine the appropriate time to make short calls by listening for cues for sound localization.24 The calls are used for individual recognition, predator warning signals, territory defense, or as a way to attract potential mates.25 There are also different calls depending on the season. In the spring the songs become more frequent during the breeding season. In late summer the vocalizations become short calls. Through various studies, the acoustic characteristics of the vocalizations can be a useful taxonomic tool.26

Lifespan

The average lifespan of pikas in the wild is roughly seven years. A pika's age may be determined by the number of adhesion lines on the periosteal bone on the lower jaw. The lifespan does not differ between the sexes.27

Species

Main article: List of ochotonids

The 29 extant species currently recognized are:

Extinct species

Many fossil forms of Ochotona are described in the literature, from the Miocene epoch to the early Holocene (extinct species) and present (16.4-0 Ma29). They lived in Europe, Asia, and North America.Some species listed below are common for Eurasia and North America (O. gromovi, O. tologoica, O. zazhigini, and probably O. whartoni).

  • Eurasia
    • large forms
    • medium-sized forms
      • Ochotona agadjianiani (Asia, Pliocene)63
      • Ochotona antiqua (Moldavia, Ukraine, and the Russian Plain, Caucasus, and probably Rhodes, late Miocene to Pliocene)646566
      • Ochotona azerica (Transcaucasia: Azerbaijan,67 middle Pliocene)6869
      • Ochotona lingtaica (Asia, Pliocene)7071
      • Ochotona dodogolica (Asia: western Transbaikalia, Pleistocene)7273
      • Ochotona nihewanica (China: Hebei, early Pleistocene)74757677
      • Ochotona plicodenta (Asia, Pliocene)7879
      • Ochotona polonica (Europe: Poland, Germany, France, Pliocene)808182
    • small-sized forms
      • Ochotona bazarovi (Asia, upper Pliocene)838485
      • Ochotona dehmi (Germany: Schernfeld, Pleistocene)8687
      • Ochotona filippovi (Siberia, Pleistocene)8889
      • Ochotona gracilis (Asia, Pliocene)9091
      • Ochotona horaceki (Slovakia: Honce, Pleistocene)9293
      • Ochotona minor (China, late Miocene)949596
      • Ochotona sibirica (Asia, Pliocene)9798
      • Ochotona valerotae (France: Valerots site, Pleistocene)99100
      • Ochotona youngi (Asia, Pliocene)101and others.102103
    • other examples
      • Ochotona agadzhaniani (Transcaucasia: Armenia, Pliocene)104
      • Ochotona alaica (Asia: Kyrgyzstan, Pleistocene)105
      • †Ochotona(Proochotona) eximia (Moldova, Ukraine, Russia, Kazakhstan, Miocene to Pliocene)106
      • †Ochotona(Proochotona) gigas (Ukraine, Pliocene)107
      • Ochotona gureevi (Transbaikalia, middle Pliocene)108109
      • Ochotona hengduanshanensis (China, Pleistocene)110
      • Ochotona intermedia (Asia, Pliocene)111112
      • †Ochotona(Proochotona) kalfaense (Europe: Moldova, Miocene)113
      • †Ochotona(Proochotona) kirgisica (Asia: Kyrgyzstan, Pliocene)114
      • Ochotona kormosi (Hungary, Pleistocene)115116
      • †Ochotona(Proochotona) kurdjukovi (Asia: Kyrgyzstan, Pliocene)117
      • Ochotona largerli (Georgia, Pleistocene)118
      • Ochotona lazari (Ukraine, Pleistocene)119
      • Ochotona mediterranensis (Turkey, Pliocene)120
      • Ochotona ozansoyi (Turkey, Miocene)121
      • Ochotona pseudopusilla (Ukraine and Russian Plain, Pleistocene)122123
      • Ochotona spelaeus (Ukraine, late Pleistocene)124125
      • Ochotona tedfordi (China: Yushe Basin, late Miocene)126127
      • Ochotona cf. whartoni (Irkutsk Oblast and Yakutia, Pleistocene, see also North America)128
      • Ochotona zabiensis (southern Poland, early Pleistocene)129130
      • Ochotona sp. (Greece: Maritsa, Pliocene)131
      • Ochotona sp. (Hungary: Ostramos, Pleistocene)132
      • Ochotona sp. (Siberia, Pleistocene)133
      • Ochotona sp. (Yakutia, Pleistocene)134
  • North America

Paleontologists have also described multiple forms of pika not referred to specific species (Ochotona indet.) or not certainly identified (O. cf. antiqua, O. cf. cansus, O. cf. daurica, O. cf. eximia, O. cf. gromovi, O. cf. intermedia, O. cf. koslowi, O. cf. lagrelii, O. cf. nihewanica). The statuses of Ochotona (Proochotona) kirgisica and O. spelaeus are uncertain.153

The "pusilla" group of pikas is characterized by archaic (plesiomorphic) cheek teeth and small size.154

The North American species migrated from Eurasia. They invaded the New World twice:

  • O. spanglei during the latest Miocene or early Pliocene, followed by a roughly three-million-year-long gap in the known North American pika record155
  • O. whartoni (giant pika) and small pikas via the Bering Land Bridge during the earliest Pleistocene156

Ochotona cf. whartoni and small pikas of the O. pusilla group are also known from Siberia. The extant, endemic North American species appeared in the Pleistocene. The North American collared pika (O. collaris) and American pika (O. princeps) have been suggested to have descended from the same ancestor as the steppe pika (O. pusilla).157

The range of Ochotona was larger in the past, with both extinct and extant species inhabiting Western Europe and Eastern North America, areas that are currently free of pikas. Pleistocene fossils of the extant steppe pika O. pusilla currently native to Asia have been found also in many countries of Europe from the United Kingdom to Russia and from Italy to Poland, and the Asiatic extant northern pika O. hyperborea in one location in the middle Pleistocene United States.158

While Ochotona is the only currently living genus of Ochotonidae, extinct genera of ochotonids include †Albertona, †Alloptox, †Amphilagus, †Australagomys, †Austrolagomys, †Bellatona, †Bellatonoides, †Bohlinotona, †Cuyamalagus, †Desmatolagus, †Eurolagus, †Gripholagomys, †Gymnesicolagus, †Hesperolagomys, †Heterolagus, †Kenyalagomys, †Lagopsis, †Marcuinomys, †Ochotonoides, †Ochotonoma, †Oklahomalagus, †Oreolagus, †Paludotona, †Piezodus, †Plicalagus, †Pliolagomys, †Prolagus, †Proochotona (syn. Ochotona), †Pseudobellatona, †Ptychoprolagus, †Russellagus, †Sinolagomys, †Titanomys and †Tonomochota.159160 The earliest one is Desmatolagus (middle Eocene to Miocene, 42.5–14.8 Ma161), usually included in the Ochotonidae, sometimes in Leporidae or in neither ochotonid nor leporid stem-lagomorphs.162

Ochotonids appeared in Asia between the late Eocene and the early Oligocene, and continued to develop along with increased distribution of C3 grasses in previously forest dominated areas under the "climatic optimum" from the late Oligocene to middle Miocene. They thrived in Eurasia, North America, and even Africa. The peak of their diversity occurred during the period from the early Miocene to middle Miocene. Most of them became extinct during the transition from the Miocene to Pliocene, which was accompanied by an increase in diversity of the leporids. It has been proposed that this switch between ochotonids and larger leporids was caused by expansion of C4 plants (particularly the Poaceae) related to global cooling in the late Miocene, since extant pikas reveal a strong preference for C3 plants (Asteraceae, Rosaceae, and Fabaceae, many of them C3). Replacement of large areas of forests by open grassland first started probably in North America and is called sometimes "nature's green revolution".163

Notes

Additional references of the Paleobiology Database

Further reading

  • Orr, Robert Thomas (1977). The Little-known Pika (illustrated ed.). New York: Macmillan. ISBN 9780025939608.
Wikimedia Commons has media related to Ochotona. Wikispecies has information related to Ochotona.
  • The trek of the pika, by Michael Morris, Parks Canada, Mount Revelstoke and Glacier National Parks. (includes sound file)

References

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