Ochotona (Lagomorpha) from Late Quaternary Cave ...

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45, 93–101 (1996)

Ochotona (Lagomorpha) from Late Quaternary Cave Deposits in Eastern North America JIM I. MEAD Department of Geology, P.O. Box 4099, and Quaternary Studies Program, P.O. Box 5644, Northern Arizona University, Flagstaff, Arizona 86011; and The Mammoth Site, P.O. Box 606, Hot Springs, South Dakota 57747 AND

FREDERICK GRADY Department of Paleobiology, Smithsonian Institution, Natural History, Washington, District of Columbia 20560 February 22, 1995

leontological remains can be difficult if not impossible. Paleontological remains illustrate that there are two major size differences, which are assumed to be species differences. Size alone does not determine a species, and there is no way of knowing at present whether or not pikas of similar size are all of one biological species. For these reasons we discuss the fossils in terms of morphological forms, realizing that each may in fact be multiple biological species of the same size. To help clarify the problems surrounding pikas, we provide a brief review of the paleontological history of the pika family. We discuss the paleontological remains from northeastern North America in terms of: (1) the morphological forms, (2) their chronology, and (3) the assumed associated environmental community in which they lived.

Pikas (Ochtona)—small gnawing mammals, related to rabbits—range today throughout parts of the Northern Hemisphere, but had a wider distribution during the Pleistocene. Nine caves from northeastern North America (a region not occupied by pikas today) have Pleistocene deposits containing remains of Ochotona. We examine 526 fossil specimens (ranging in age from approximately 850,000 to 8670 yr B.P.) from five of these caves. Two morphological forms of Ochotona lived in northeastern North America during the late Pleistocene—a large species (probably O. whartoni) and a small species (probably O. princeps). Ochotona of glacial age are not necessarily indicative of talus slopes and mesic communities. O. princeps-like of the Irvingtonian of West Virginia were living with an amphibian-reptilian assemblage found in the area today, implying winters not much, if at all, colder than at present. Late glacial and postglacial change in climate south of the ice sheets in effect would have isolated Ochotona in eastern North America, where they were unable to retreat to the west or north. Whereas western pika had the option of moving up in elevation, into boreal islands, eastern forms became restricted to everdiminishing habitats, culminating in extinction and extirpation. Radiocarbon ages imply that Ochotona lived in eastern North America during the late Pleistocene (late Rancholabrean) and into the earliest Holocene. We describe the youngest remains of Ochotona in eastern North America and the youngest for the extinct large form, O. whartoni. © 1996 University of Washington.

TAXONOMY AND DISTRIBUTION OF QUATERNARY PIKA

Pikas are small lagomorphs (rabbits and relatives; Order Lagomorpha) belonging to the family Ochotonidae. Many species live throughout the Holarctic region today (Northern Hemisphere north of the Tropic of Cancer and the Himalaya Mountains). Unfortunately there are few osteological and dental criteria for adequately recognizing subgenera (Corbet, 1978; Mitchell, 1981; Hoffmann, 1993). Because of the considerable geographical differences within forms of pika, there is wide debate on the actual number of living species. Most authorities agree that at least 14 species live in Asia (Corbet, 1978); Mitchell (1981) recognizes 18 species. Hoffman (1993) and Smith et al. (1990) indicate that there are at least 23 species and that most are restricted today to Asia. Only two small forms, O. princeps (American pika) and O. collaris (collared pika) presently live in North America (Hall, 1981) (Fig. 1). Corbet (1978) has synomynized the two North American forms with O. alpina (alpine pika) that lives in the Altai Mountains of southern Siberia and northern China through Mongolia to the tundra of the Bering Strait of eastern Siberia. Weston (1981) determined that O. alpina is distinct from O. princeps and O.

INTRODUCTION

This paper describes what appear to be unusually recent (early Holocene) occurrences of pikas (Ochotona) in eastern North America, a region where no pikas live today. Such records of pikas in eastern North America are significant for paleontology, zoogeography, and paleoclimatology. We discuss the record of two morphological forms: a small form that exists today in western North America and a large form that perhaps went extinct by the Illinoian Glaciation (see discussion below). Although pikas are easily identified to the generic level using dental and osteological criteria, species identification using pa93

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MEAD AND GRADY

FIG. 1. Map of North America showing the modern distribution of Ochotona (stippled) and the disjunct Rancholabrean (late Quaternary) localities (Mead, 1987).

collaris, and that these are independent of, but closely similar to, O. hyperborea (northern pika) (Smith et al., 1990). Gureev (1964) divided the living pikas of Asia into four morphological groups (“roylei,” “dauurica,” “alpina,” and “thibetana”). All species within the groups are considered small forms of pika, with some, especially in the “thibetana” group, being the smallest. Other useful discussions of Ochotona include Erbajeva (1988) and Smith et al. (1990). Two genera (Sinolagomys and Desmatolagus) make up the earliest record of Ochotonidae, from the Oligocene of Asia (probably the area of origin; Dawson, 1967; Erbajeva, 1985). Fossil ochotonids of Asia are reviewed in Erbajeva (1988). The oldest known fossil of Ochotona in the Nearctic (temperate and Arctic North America) is O. spanglei of the early Pliocene (late Hemphillian land mammal age) of Oregon (Shotwell, 1956). Although pikas were surely in North America south of the

Arctic during the Blancan land mammal age (the majority of the Pliocene), no remains are reported in the literature. Mead (1987) and Hafner (1993) have reviewed the Quaternary records of pikas of North America (Irvingtonian [1.95 to approximately 0.3 myr, millions of years ago] and Rancholabrean [0.3 to 0.01 myr] land mammal ages). Ochotona of the North American Quaternary is predominantly a western taxon, with Irvingtonian material being found principally along the higher latitudes (Mead, 1987). Nine localities containing Ochotona from eastern North America are atypical for the known Nearctic distribution of the genus (Table 1; Fig. 1). Large species of Ochotona are known from northern Eurasia (O. tologoica, O. gromovi, and O. complicidens, to name a few), but all were extinct by the end of the upper Pliocene (Erbajeva, 1985; approximate to the North American Blancan). A species of extinct, large pika (O. whartoni) is known from

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TABLE 1 Cave Localities in Eastern North America Containing Remains of the Pika, Ochotona Cave locality 1. Cave Mountain, West Virginia 38°369N;79°179W 2. Cumberland, Maryland 39°419N;78°479W 3. Elba, Ontario 44°019N;80°109W 4. Hamilton, West Virginia 38°369N; 79°229W 5. Jasper Saltpeter, Virginia 36°469N;82°489W 6. Kelso, Ontario 43°309N;79°559W 7. New Trout, West Virginia 38°369N;79°229W 8. Rapp’s, West Virginia 37°589N;80°239W 9. Trout, West Virginia 38°369N; 79°229W

Age*

Species form

Primary reference

?Rancholabrean

Smalla

This report

Irvingtonian; 700,000 or 500,000 yr B.P. 8670 ± 220 yr B.P. AMS age on Ochotonaa Irvingtonian; 850,000 to 820,000 yr B.P. ?Illinoian Glaciation

Smalla

Guilday (1979); this report

Largea

Smalla

H. Savage, 1992, written communication; this report This report

Small

Guilday (1979)

Late Wisconsinan Glaciation

Large

Churcher and Dods (1979)

Rancholabrean

Smalla

This report

?Illinoian Glaciation

Small

Guilday (1979)

Irvingtonian

Small

Guilday (1979)

Note. ? 4 uncertain age assignment. Illinoian Glaciation should be read as pre-Wisconsinan Glaciation, pre-late Rancholabrean, maybe early Rancholabrean. a See text for discussion.

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remains of pikas recovered from the eastern North American localities of Cave Mountain, Cumberland, Hamilton, New Trout, and Elba caves. CAVE LOCALITIES, EASTERN NORTH AMERICA

Data about Ochotona from previously discussed localities in eastern North America are presented in Guilday (1979) and Churcher and Dods (1979). Below are discussions of the previously undescribed localities. Not all data from these localities are presented in the published literature. We provide a review of each site that contains Ochotona and as much pertinent background data as possible. Cave Mountain Cave, Pendleton County, West Virginia Fossil material was recovered approximately 100 m from the main entrance in Cave Mountain Cave in the left passage. Sediments and fossils were collected in 10-cm intervals down to a depth of 140 cm. Historic miners’ paraphernalia were also recovered in the lower levels of this profile, indicating that the sediments are a redeposited unit from nitrate mining during the 1860s. Fossils of multiple ages could have been mixed in the redeposition. The majority of the recovered fauna of about 45 mammalian species imply a late Rancholabrean age. The recovery of the rodents, Atopomys salvelinus and Peromyscus cumberlandensis, suggest that some Irvingtonian age material is also intermixed into the deposit. A single jaw of Ochotona was recovered (number of identified specimens, NISP 4 1) containing the p3-m3 (“p” and “m” refer to mandibular premolars and molars [respectively]; “P” and “M” refer to similar maxillary teeth). It is not known whether this specimen represents a late Rancholabrean or an Irvingtonian record. Cumberland Cave, Allegany County, Maryland

the Cape Deceit local fauna (type locality), Alaska (Guthrie and Matthews, 1971) where it is assessed to be of Irvingtonian I age, z1.9 to 0.9 myr (Repenning, 1987) (Fig. 1). This large species is also known from Gold Hill, Alaska, where its age is estimated to be of the Illinoian Glaciation (early Rancholabrean; >z125,000 yr B.P.; Guthrie, 1973; Pewe, 1975), and from at least 10 locations in the Old Crow Basin, Yukon, where the age estimates seem questionable, but are stated to be of the Illinoian Glaciation, Sangamonian Interglaciation (z125,000– 80,000 yr B.P.), and the mid-Wisconsinan Glaciation (reviewed by Mead, 1987). Although poorly dated, O. whartoni probably lived in the high Arctic into the Wisconsinan. A distal fragment of a femur of Ochotona indicates that a large pika lived in eastern North America (Kelso Cave, Halton County, Ontario) possibly in the Illinoian Glaciation period, but this age is speculative (Churcher and Dods, 1979; see later discussions). Although Guilday (1979) described the pika remains from Cumberland, Jasper Saltpeter, Rapp’s, and Trout caves (eastern North America), he identified the material only as a small species of Ochotona. Herein we discuss additional

Cumberland Cave, first excavated in 1912, is considered the best documented Irvingtonian age locality in eastern North America (Kurten and Anderson, 1980). Early excavations used heavy equipment and explosives to remove fossil material; no map exists locating the position of these recovered fossils. Bulk sediments containing fossils remain to be identified, although many specimens have been described (Gidley and Gazin, 1938; Guilday, 1971; Holman, 1977; Zakrzweski, 1975; Van der Meulen, 1978). Rodent teeth recovered in association with the pika specimens date to approximately 500,000 yr B.P., based on Repenning’s (1987) interpretation of microtine evolution (Irvingtonian II event; 900,000 to 400,000 ± 25,000 yr ago). Van der Meulen (1978) prescribes an age closer to about 700,000 yr B.P. for the deposit. There are two specimens of Ochotona from this locality. Hamilton Cave, Pendleton County, West Virginia Initial discoveries of fossils in Hamilton Cave were made as early as the late 1940s, but significant discoveries and system-


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atic excavations were not made until the early 1980s. Three localities in Hamilton Cave have produced fossil remains of the pika: Cheetah Room, Smilodon 2, and Tite Hole. The Cheetah Room was excavated in 25-cm levels from 0 to 125 cm depth, with one additional sediment sample from 0 to 50 cm depth. Total number of specimens from this locality is 516, with the following NISP from the various levels: 0–25 cm 4 330; 25–50 cm 4 63; 50–75 cm 4 10; and bulk 0–50 cm 4 113. The Tite Hole and Smilodon 2 localities were excavated in one 25-cm level each, from 0–25 cm in depth, and contained an NISP of 6 and 42, respectively. Pika remains were not the only faunal material recovered from these deposits. Ochotona accounts for about 8% of the total terrestrial mammal faunal remains from the test excavations in the Cheetah Room and Smilodon 2 sites. Pika remains were associated with a middle Pleistocene microfauna estimated to be approximately 820,000 to 850,000 yr B.P. (Repenning and Grady, 1988), within Repenning’s (1987) Irvingtonian II event. Microtine rodents, a cheetah-like cat, and the herpetofauna (amphibians and reptiles) recovered from these deposits have been discussed in Repenning and Grady (1988), Van Valkenburgh et al. (1990), Winkler and Grady (1990), and Holman and Grady (1989). New Trout Cave, Pendleton County, West Virginia New Trout Cave has been investigated only recently. The cave is developed in the Conemans and New Scotland limestones (Grady, 1982). Material presented here is from the Main Bone Site in the cave, about 280 m into the cave from the entrance at the far end of the second room (Grady and Garton, 1981, 1982; Grady, 1984). Bone-bearing cave sediments were collected from an area approximately 3 by 1 m. Excavation of the sediments was done in 30-cm levels [labeled A (top) to H (lowest)] to a depth of about 220 cm (see profile in Holman and Grady, 1987). Pika remains with an NISP of 7 from Level E account for approximately 1 to 2% of the total identified terrestrial mammals recovered from that level. The top of the unit (A; 0–30 cm depth) was radiocarbon dated (on bone collagen from skeletal remains of a variety of species) to 17,060 ± 220 yr B.P. (Sl-4102). Level B (30–60 cm depth) was bone dated to 28,250 ± 850 yr B.P. (Sl-4103) and level C (60–90 cm depth) to 29,400 ± 1700 yr B.P. (SI-4104). No ochotona remains were recovered from these late Rancholabrean-age (Wisconsinan Glaciation) upper units. However, pika remains were recovered from approximately 150-cm depth (level E; ± 60 cm below the level C radiocarbon date) and therefore date $30,000 yr B.P. (Grady and Garton, 1981, 1982). We assume that level E and its fauna date to within the Wisconsinan Glaciation (#80,000 yr B.P.), but a Sangamonian or older age is also possible. Some of the species recovered in the fauna (all levels) have been described by Grady (1984) and Holman and Grady (1987). Although redeposition of the Ochotona into level E from an early deposit (Rancholabrean or Irvingtonian) cannot be totally ruled out, there are no mammals

from that unit containing Ochotona that are extinct or typical of the Irvingtonian that would indicate or support this possibility (Grady and Garton, 1981, 1982). Other than the pika remains, the entire fauna is consistent with others of the Wisconsinan Glaciation. Elba Cave, Dufferin County, Ontario Elba Cave is a fissure deposit in the Mono Cliffs Provincial Park, Dufferin County, Niagara Escarpment, south-central Ontario. Entrance into the limestone cavern is vertical. Six hundred twenty-five bones of various animals were recovered loose by Howard Savage and crew on various ledges. A single Ochotona femur was recovered on such an exposed ledge at a depth of 25 m below surface (Howard Savage, 1992; written communication, April, 1994). The single pika element was measured then radiocarbon dated by Savage. An accelerator mass spectrometry analysis of the purified collagen fraction from the femur yielded an age of 8670 ± 220 yr B.P. (TO-2566; 13 C 4 −25 pm). PROBLEMATIC AGE ASSIGNMENTS FOR KELSO AND ELBA CAVES

Ochotona from deposits of the Kelso and Elba caves, Ontario (Fig. 1), have seemingly erroneous Holocene ages. What makes the ages suspect is that the species of Ochotona in association with the ages is the large species, O. whartoni, believed extinct since the Illinoian Glaciation (middle Pleistocene; early Rancholabrean). The Elba Cave single femur dated to 8670 yr B.P. presents an enigma; it is the youngest dated specimen of Ochotona in eastern North American and it appears to belong to an extinct, large species. Part of the problem of accepting that a large species of Ochotona persisted in eastern North America into the Wisconsinan or early Holocene comes from the paleontologic dating of Kelso Cave deposit (Churcher and Dods, 1979). The Kelso Cave deposit was assigned to the Illinoian Glaciation [“the presence of Ochotona sp. suggests a possible Illinoian age for the deposit . . .” (Churcher and Dods, 1979, p. 1613)] on the basis of Illinoian ages assigned to Ochotona at other eastern caves (Guilday, 1979) and in Alaska and the Yukon (see review of deposits and assigned age in Mead, 1987). We now understand that these chronologies (see references in Mead, 1987) are in part equivocal and certainly not precise. An alternative age assignment was first proposed by Churcher and Dods (1979) at the same time they decided to go with an assumed Illinoian age. “It is possible that the Kelso Cave fauna is a late Wisconsin[an] or early postglacial fauna in which Ochotona had survived as a relict population in the rocky areas of Ontario along the Niagara Escarpment” (Churcher and Dods, 1979, p. 1619). Pollen was obtained by Churcher and Dods from a small sample of the matrix containing the Ochotona remains at Kelso Cave. Although the pollen remains from the Kelso Cave matrix


have not been directly radiometrically dated, the recovered pollen indicates a climate similar to the boundary between the spruce zone (zone 1) and the pine zone (zone 2) in the Crawford Bog pollen sequence obtained from a locality 6 km south– southwest of Kelso Cave. That boundary has an average age of about 10,500 yr B.P. (McAndrews, 1972; Karrow et al., 1975). The reconstructed climate for both the boundary in the Crawford Bog sequence and the deposition of the Kelso Cave pika is one of a typical temperate northern forest in which summer temperatures are hot and winter temperatures are well below freezing over several months, and in which moisture was adequate for sustained tree growth. Such a plant community would not be expected of such a northern locality during the Illinoian Glaciation. Associated fauna with the Ochotona and pollen remains in the Kelso Cave sample are not typical of glacial-age faunas and do not contain any extinct or extralimital forms, except for the pika. All faunal elements, except Ochotona, are part of the modern fauna of southern Ontario (Churcher and Dods, 1979). Ochotona as has been used as an indicator of glacial age environments (Guilday, 1979; Churcher and Dods, 1979). Alternatively, Ochotona remains from Kelso Cave have been incorrectly interpreted to be of Illinoian Glaciation (early Rancholabrean) and are truly late Wisconsinan or earliest Holocene in age. Faunal remains from Elba Cave are not cemented into a matrix unit as was the case with the Kelso Cave remains. Twenty mammalian species were recovered by Savage in the various parts of Elba Cave, some in an indirect association with the Ochotona. Eighteen of the 20 taxa are typical of the present-day local fauna of Dufferin County, Ontario. Only two species were found not to be of the local modern faunal community: pika and pine marten (Martes americana). The pine marten is known to have been exterminated from southern Ontario by the early 1900s, leaving just the pika as the only extinct or extirpated species recovered from the cave (H. Savage, written communication, April 1994); essentially the same scenario as from Kelso Cave. The use of Ochotona as an indicator of Illinoian age seems at best suspect for eastern North America. SPECIES IDENTIFICATION

Methods We examined 526 specimens of Ochotona from Cave Mountain, Cumberland, Hamilton, and New Trout caves. All fossil specimens are curated in the Department of Paleobiology, Smithsonian Institution. Larger material represents fragmented mandibles and maxilla, many including teeth; isolated molars and premolars predominate. A few postcranial remains were recovered, including humeri, femora, astragali, and calcanea. Initially we completed 34 measurements on the following: p3m3, p3, p4, m1, m2, m3, P2, P3, P4, M1, and M2, humeri, femora, astragali, and calcanea.

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We measured modern comparative specimens from six species [from Gureev’s (1964) morphological groups]: O. alpina, O. collaris, O. dauurica (Dauurian pika), O. princeps, O. roylei (Royle’s pika), and O. thibetana (Moupin pika) and included measurements from the literature for O. hyperborea, O. pusilla (steppe pika), and O. whartoni (Guthrie and Matthews, 1971; Sych, 1980). These specimens allowed us to examine the size of “large” pika and variation within the four groups of “small” pika species. The Elba Cave specimen has been destroyed by the radiocarbon analysis. Only descriptive information (from H. Savage) about its femur is presented below. Elba Cave According to H. Savage (written communication, April 1994), “Osteometrically, comparison of the Elba Cave femur with present day Ochotona princeps femora from Montana Mountain of the southern Yukon showed the Elba specimen to be between one-quarter and one-third larger than adult southern Yukon specimens, and to approximate closely the size of the Kelso Cave pika femur.” According to Churcher and Dods (1979, p. 1616–1617), the femur fragment from Kelso Cave is “. . . larger than modern species of Ochotona, [and] is considered to represent a large species of that genus. It is larger than recent O. princeps or O. collaris specimens available for comparison but similar in size to a large pika from Beringia. The Kelso Cave specimen is as large or larger than the Pleistocene Old Crow specimen and thus could also represent O. whartoni.” From the above statements, we infer that a large species, O. whartoni-like (if not O. whartoni), has been recovered from both Kelso and Elba caves. Cave Mountain, Cumberland, Hamilton, and New Trout Caves Because fossil specimens were so few for any single group of teeth, or specimens were fragmented, we did not complete a statistical analysis of the measurements described above. Measurements that were taken on the modern and fossil material cluster within the realm of the living small species group. Figure 2 illustrates that the fossil material from these caves belong to a small form of pika, similar in size to a number of Asian Ochotona and to the two species found presently in North America. Measurements of the alveolar length of the mandible from the living small species cluster, with a single specimen of O. pusilla being the largest and O. thibetana being the smallest (Fig. 2a). Pleistocene specimens from Hamilton Cave and the Cumberland Cave material described here are all in the middle to the small end of the range of the alveolar tooth row length for the small species of pika (Fig. 2a). The alveolar length of the type specimen of O. whartoni is over 2 mm longer then any of the small species measured (Fig. 2a). Cumberland Cave specimens presented by Guilday (1979; NISP 4 13) are also within a clustering of the small species.


MEAD AND GRADY

FIG. 2. Diagrams of measurements from modern and fossil species of Ochotona. (A) Alveolar tooth row of mandibular elements. (B) Length and width measurements of the m1 (lower first molar). (C) Length and width measurements of the P3 (upper third premolar). CC, Cumberland Cave; CMC, Cave Mountain Cave; HCCR, Hamilton Cave Cheetah Room; HCTH, Hamilton Cave Tite Hole; HCS, Hamilton Cave Smilodon, and NTC, New Trout Cave, (*) O. alpina, (V) O. collaris, (■) O. dauurica, (h) O. hyperborea, (+) O. princeps, (n) O. pusilla, (u) O. roylei, (m) O. thibetana, and (W) O. whartoni.

The m1 (Fig. 2b) from Hamilton Cave (Cheetah Room and Tite Hole) fit well within the clustering of measurements for the living species of O. alpina, O. collaris, O. dauurica, O. princeps, O. roylei, and O. thibetana, with the last species being the smallest in the grouping. Some of the Hamilton Cave (Cheetah Room) specimens are fairly small, close to the size of O. thibetana. The single specimen from New Trout Cave is as long but somewhat wider than those typical of the living species used in this study. Modern species examined for measurements of upper dentition indicate fairly tight clustering of sizes, again with O. thibetana consistently being the smallest. Figure 2c illustrates the length and width measurement of the P3 of living and fossil specimens. Most of the P3 cluster with a length of approximately 0.9 to 1.0 mm. Although some of the Hamilton Cave material are of this size, a number are as small as those typical of O. thibetana (0.6–0.8 mm). Although some of the measurements are not illustrated, those presented in Figure 2 show that the specimens from Cave Mountain, Cumberland, Hamilton, and New Trout caves are consistently within the size of small species from presumably either O. princeps or O. collaris. A small species was also recovered from Cumberland, Jasper Saltpeter, Rapp’s, and Trout caves (Guilday, 1979). There does not appear to be any evidence to indicate that the eastern North American Ochotona small species is distinctly different than the two living forms now restricted to the western portion of the continent. Perhaps small species of Ochotona living in eastern North America during the Irvingtonian and Rancholabrean was O. princeps, being just an eastern extension of the now western-restricted from located south of the continental glaciers of the Wisconsinan. Alternatively, the eastern small species was O. collaris, now restricted to northwest-

ern-most North America, where it migrated from along with O. whartoni. Additional data are needed, including statistically valid quantities of postcranial elements, from eastern caves and from midcontinent ecotonal regions such as the Black Hills of the Northern Great Plains. DISCUSSION AND CONCLUSIONS

Nine caves from northeastern North America have Pleistocene deposits containing remains of Ochotona; four are reported here for the first time. Two morphological forms of Ochotona lived in northeastern North America during the Pleistocene. Irvingtonian Ochotona Pika of Irvingtonian age (approximately 1.95 to 0.30 myr; up to the lllinoian Glaciation) are known from Cumberland, Hamilton, and Trout caves in eastern North America and in the Arctic. At least two morphological forms of Ochotona lived in North America during the Irvingtonian: large and small. The large O. whartoni lived in western Arctic regions and is known at this time only from Cape Deceit, Alaska. This large form seems to be restricted to the western Arctic region, although this presumed limited distribution may be due to a collection bias. Eastern North America during the Irvingtonian is inhabited by only the small morphological form, one that is indistinguishable from O. princeps and O. collaris. Irvingtonian deposits with this small species include Cumberland, Hamilton, and Trout caves. Rancholabrean Ochotona The Rancholabrean as used here dates approximately 300,000 to 10,000 yr B.P., and includes at a minimum deposits


stated to be of the Illinoian Glaciation, Sangamonian Interglaciation, and the Wisconsinan Glaciation (Lundelius et al., 1987). Pika are recorded in eastern localities during the Rancholabrean at Cave Mountain, Elba, Jasper Saltpeter, Kelso, New Trout, and Rapp’s caves, and from the western Arctic and western U.S. states. The large O. whartoni lived in the western Arctic and is recorded at Gold Hill (Alaska) and the Yukon localities, where it is known from assumed Illinoian, Sangamonian, and Wisconsinan deposits. O. whartoni specimens first, and only, show up in eastern North America in Ontario in late Wisconsinan to early Holocene deposits. Based on our interpretation, O. whartoni lived, possibly relictually, in the Ontario region at Kelso and Elba caves into the early Holocene (approximately 9000 yr B.P.), when it seems to have become extinct. Speculation would imply that O. whartoni migrated from Beringia south and east to Ontario sometime during the early Rancholabrean, possibly during the interglaciation or interstades. O. whartoni apparently did not live farther south into the Appalachia region, its southernmost extent in North America being the two localities in Ontario. The small species form (O. princeps-like) also lived in eastern North America during the Rancholabrean, but only south of Ontario. As with the large species, the O. princeps-like form seems to have persisted in northeastern North America as a relictual population into the Wisconsinan Glaciation (if the material from Cave Mountain and New Trout caves are dated correctly). Of the four localities known for this age, two are evidently of Illinoian age and two of assumed Wisconsinan age. Based on the fossil record, the pika was never very common or very widespread in the region during the Rancholabrean. The youngest age for the existence of O. princeps-like in the eastern region is $30,000 yr B.P. With only one dated locality available (New Trout Cave), it is equivocal to state that it became extirpated at that time. O. princeps was common and widespread in western North America during the Wisconsinan Glaciation (Mead, 1987; Hafner 1993; Grayson, 1993). The Rancholabrean record for O. collaris is less well known; however, it is recorded from deposits in Alaska (Guthrie, 1973). Ecology Today O. princeps and O. collaris generally are restricted to more boreal plant communities and habitats with rocky talus, those which permit burrowing/living in and around the opennetwork boulder deposits (MacDonald and Jones, 1987; Smith and Weston, 1990). Although Ochotona are typically thought of as “rocky/talus obligates,” this interpretation may not be totally accurate and possibly not true for all Pleistocene-age forms. Youngman (1975) pointed out that O. collaris, although typically found in talus regions, has been located in terrain of fractured rock. He also noted that O. collaris has been found living “near the shore of Cultus Bay, Kluane Lake [Yukon], and had a burrow just above water level under six-inch willows in grass and horsetail” (Youngman, 1975, p.56). Like a number

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of the Asian pikas, North American forms during the different environmental parameters of the glaciations probably could have ventured out and away from the “rocky-talus obligate” niche that they often fill today. Warm summer temperatures restrict western populations of O. princeps to boreal mountain “islands.” Smith (1974) found that O. princeps cannot tolerate high diurnal temperatures found at lower elevations; near the southern limits of its distributional range, pikas are uncommon at elevations lower than 2500 m. Kosaka et al. (1985) found the Asian Ochotona rufescens (Afghan pika) to be intolerant of high diurnal temperatures. The disadvantages in the Ochotona thermoregulatory mechanism is probably one of the reasons why its distribution has shrunk during the present interglacial and has been confined to high latitudes and to high elevations at lower latitudes. The present ecology of O. princeps is discussed further in Hafner (1994; Hafner and Sullivan, 1995). Much remains to be understood about late Quaternary ecology of Ochotona of western North America. Mead (1987) indicated that what appear to be the distribution-limiting requirements for the living pikas of western North America are not necessarily the same for Wisconsinan-age Ochotona for the same region. Mead (1987) felt that Ochotona of glacial age are not indicative of strict talus habitat and mesic communities. Hafner (1993) disagreed, indicating Ochotona are always indicative of mesic and rocky environments. Mead and Spaulding (1995) present ecological data supporting Mead’s (1987) earlier hypothesis indicating that Ochotona of the glacial episodes did not necessarily live in mesic or talus-restricted habitats. Environmental Interpretations During the Irvingtonian at Hamilton Cave (approximately 850,000 to 820,000 yr B.P.), a small morphological form of Ochotona was living in a community also containing a rich herpetofauna including 11 salamanders, 8 anurans, 1 turtle, 3 lizards, and 9 snakes. The herpetofauna of the Irvingtonian deposit is similar to that which lives in West Virginia area today, implying that winters may not have been much colder than they are today (Holman and Grady, 1989). Evidently this was not a glacial hiatus or boreal environment, or if so, it represents one with an equable climate. The deposit from New Trout Cave dating to the Wisconsinan Glaciation ($30,000 yr B.P.) appears to be an example of a disharmonious community. Select mammalian species recovered in sediments containing O. princeps-like fossils imply a boreal or tundra-like local environment (e.g., Dicrostonyx torquatus, collared lemming; although see alternative reconstructions in Mead and Mead, 1989). However reptilian species such as Sceloporus undulatus (eastern fence lizard), Eumeces laticeps (broadhead skink), Carphophis amoenus (eastern worm snake), Diadophis punctatus (ringneck snake), Heterodon platyrhinos (eastern hognose snake), and Lampropeltis triangulum (milk snake) denote a pinelands to temperate decidu-


MEAD AND GRADY

ous forest environment. Mammalian species in conjunction with the herpetofauna indicate a more equable climate occurred at $30,000 yr B.P. during the Wisconsinan Glaciation (Holman and Grady, 1987). Cooler summers probably occurred to support the more northern mammalian fauna, but not so cold as to evict the egg-laying reptiles. A mosaic vegetational structure may have contributed to the joint occurrence of northern mammals and temperate mammal and herp species during the midWisconsinan Glaciation. This may be the same reason why Wisconsinan-age Ochotona is found at the Smith Falls locality in Nebraska, an atypical setting for the pika, far east of its present distribution (Voorhies, 1986). O. whartoni-like forms were living in Ontario where pollen remains imply an age estimate of 10,500 yr B.P. and a climate typical of temperate northern forests in which summer temperatures are warm-hot and winter temperatures are well below freezing over several months. During the Wisconsinan Glaciation, when most of Canada and the northern fringe of eastern United States was covered by the Laurentide continental ice sheet, glacial ice effectively separated the Beringian O. collaris and at least ancestral forms of O. whartoni from the morphological forms living in eastern North America. There may have been suitable habitat for Ochotona (assumed to be O. princeps, and not the O. collaris isolated in Alaska) from east to west along the southern border of the continental ice sheets during the Wisconsinan Glaciation. Among the changes in climate of eastern North America since 18,000 yr B.P. (Webb et al., 1993, p.448), one of the most obvious was the northward movement of many taxa in a manner suggestive of a general warming. The movement was apparently gradual between 18,000 and 12,000 yr B.P. The period from 12,000 to 9000 yr B.P. was marked by rapid changes. During the changes from 18,000 to 12,000 yr B.P, there was a switch in alignment of the gradient in herb pollen taxa from its original north–south orientation to an east–west orientation with the formation of the modern prairie after 12,000 yr B.P. During the latest late glacial and early postglacial, the western Midwest dried out and the prairie formed. Winter temperatures effectively rose after 9000 yr B.P. Maps of mean January and July temperatures indicate a general warming as the ice sheets retreated, as well as the delay in peak warmth until after 9000 yr B.P. Maps of inferred precipitation estimates illustrate a development of the modern east–west precipitation decrease in the midcontinent beginning at 9000 yr B.P. The inferred estimate for 18,000 to 12,000 yr B.P. indicate that most of the region south of the continental ice sheets received less precipitation than they do today; however, the lower temperatures during that time made at least the eastern conditions moister—a time of more available moisture (Webb et al., 1993). Such changes in climate south of the ice sheets in effect would have isolated any Ochotona in eastern North America, which would have been unable to retreat to the west. Whereas western pikas had the option, in some areas, of moving up in

elevation into boreal islands, eastern forms became restricted to ever-diminishing habitats. It may be this change in climate culminating by approximately 9000 yr B.P. that finally decimated two eastern morphological forms of pikas, one small and one large. Although the small species may well be alive in the west as O. princeps (or O. collaris in the Arctic), the large form is extinct. MODERN SPECIMENS EXAMINED

O. alpina: USNM (US National Museum): 175395, 175397, 175400, 175405, 175414. AMNH (American Museum of Natural History): 178808; O. collaris; USNM: 131287, 131292. AMNH: 121392, 121389, 125717, 125719, 13726; O. dauurica; USNM: 172601, 176272, 176274, 176273. AMNH: 56859, 58876, 59793, 59790; O. princeps; USNM: 74015, 169156. AMNH: 120690, 120696, 120697, 122660, 125336; O. roylei; USNM: 353174, 353183, 353169. AMNH: 28609, 87075, 87076, 171155, 290121; O. thibetana; USNM: 144029, 144032, 144036, 200881, 255949. AMNH: 56855, 56856, 60407, 60408, 60412, 113523, 113522, 113528. ACKNOWLEDGMENTS We appreciate assistance from Charles Repenning, Tony Barnosky, M. Erbajeva, A. Smith, the curators at the U.S. National Museum and the American Museum of Natural History, and numerous cavers. Appreciation is extended to Howard Savage (University of Toronto, Department of Anthropology) for providing us total access and usage of his unpublished data about Elba Cave. Roelf P. Beukens (IsoTrace Radiocarbon Laboratory, University of Toronto, Ontario) produced the radiocarbon analysis of the Elba Cave pika. A preliminary form of this paper was presented at the International Theriological Congress, Rome, Italy in 1989; we appreciate travel assistance from Northern Arizona University. We thank Russell Graham and an anomynous referee for helpful suggestions.

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