Sandra L Swift

Northern Arizona University

The lagomorph family Ochotonidae, represented today by a single living genus (Ochotona [pika]), originated in the middle Oligocene of Asia. During the late Miocene and into the Pliocene, the family flourished throughout Eurasia and migrated into North America. Beginning in the late Pliocene and throughout the Pleistocene, the group has declined, survived only by the genus Ochotona (Erbajeva, 1988, 1994, 1996; Er-bajeva and Tyutkova, 1997).

Today more than 23 species of Ochotona live in Asia, and only 2 live in North America (Hoffmann, 1993). Smith et al. (1990:14) rightly pointed out that the "Pikas are ... a very poorly known group of mammals"; researchers are still uncertain of the alignment of many of the species and related forms. Corbet (1978) synonymized the two North American forms (O. princeps [American pika] and O. collaris [collared pika]) along with the northern Asian pika (O. hyperborea) with O. alpina (alpine pika) that lives in the mountainous Altai region of southern Siberia and northern Xinjian (China) and in Mongolia (Smith et al., 1990). Weston (1981) determined that O. alpina is distinct from the American forms, and that the American species are more closely similar to O. hyperborea, which is distributed through eastern to northeastern Siberia (Smith et al., 1990).

Gureev (1964) divided the living Ochotona of Asia into four morphological groups, all considered to be small forms of pikas (as are the American species). Large forms of Ochotona known from northern Eurasia (O. tologoica, O. gromovi, O. zazhigini, and O. zasuchini) were extinct by the end of the Pliocene (Erbajeva, 1985, 1988). The extinct O. whartoni (Guthrie and Matthews, 1971) is the only large species of Ochotona known from North America. It seems to have persisted in more northern latitudes, occurring as far east and south as southern Ontario until the earliest Holocene (Mead and Grady, 1996). This large form in North America persisted long after the large morphs lived in Eurasia.

The modern habitat requirements of the various species are described in Smith et al. (1990) and are seemingly well defined and understood for the North American O. princeps (Hafner, 1993, 1994; Hafner and Sullivan, 1995). Although it is assumed that the habitat requirements ascribed for O. princeps in the interglacial climate of today are relevant ecological templates for the form during the most recent Wisconsinan Glaciation, fossil data from dry cave deposits in the intermountain West might suggest a different paradigm (Mead and Spaulding, 1995).

The European and Asian Neogene stratigraphic record of all ochotonids, including Ochotona, is fairly detailed, with many localities of varying levels of chronological certainty (Sych, 1980; Bishop, 1982; Erbajeva, 1985, 1988, 1994). The North American Neogene record is far less complete (figure 14.1; table 14.1).

Shotwell (1956) described the earliest record of Ochotona (O. spanglei) for North America, with remains from Oregon of latest Hemphillian (early Pliocene) age. No other fossil ocho-tonids are described from Pliocene deposits (Hemphillian or Blancan), so one can only assume that pikas were exceedingly rare in North America throughout the Pliocene. Philip Bjork (pers. comm.; Bjork, 1997) has indicated that he has an apparent Blancan record of a small morph of Ochotona from the Black Hills, South Dakota (figure 14.1 at Unwily Coyote).

The North American record of Ochotona is sparse until the early Pleistocene Irvingtonian, when a more widespread occurrence is indicated (table 14.1; figure 14.1). At least two morphological forms of Ochotona lived in North America during the Irvingtonian, one large and one small. Guilday (1979), Mead (1987), and Mead and Grady (1996) provided an overview of the Irvingtonian record of Ochotona of North America, with emphasis on the eastern region. Irvingtonian-age Ochotona are known from Cumberland, Hamilton, and Trout caves in eastern North America (figure 14.1). Ochotona (large and small morphs) of purported Irvingtonian age are known

Alaska Irvingtonian

FIGURE 14.1 Map of North America showing fossil localities containing Ochotona of Hemphillian, Blancan, and definite Irvingtonian age (from table 14.1). Rancholabrean-age localities are numerous, and descriptions of them can be found in Mead (1987) and Mead and Spaulding (1995). A number of localities at high latitudes in Canada and Alaska are of equivocal age assignment and lack precision, and therefore are omitted here (see Mead, 1987; Morlan, 1996). The approximate Recent distributions of O. princeps and O. collaris are shown.

FIGURE 14.1 Map of North America showing fossil localities containing Ochotona of Hemphillian, Blancan, and definite Irvingtonian age (from table 14.1). Rancholabrean-age localities are numerous, and descriptions of them can be found in Mead (1987) and Mead and Spaulding (1995). A number of localities at high latitudes in Canada and Alaska are of equivocal age assignment and lack precision, and therefore are omitted here (see Mead, 1987; Morlan, 1996). The approximate Recent distributions of O. princeps and O. collaris are shown.

from a number of localities in the Arctic high latitudes in the West (Mead, 1987; Morlan, 1996). The small form (similar to O. princeps) occurred in the East to more southern latitudes. An unpublished account occurs from Cathedral Cave, Great Basin, Nevada (J. I. Mead and C. J. Bell, unpublished). Here we present the first record of Irvingtonian Ochotona from the intermountain West, a record from high-elevation Porcupine Cave, Colorado.

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