Chapter 4: Short-faced Bear 1

Lisa W. Nelson is at the Mammoth Graveyard, The Mammoth Site of Hot Springs, South Dakota, 1994. She writes about the Giant Short-Faced Bear in Mammoth Graveyard (1994):

“The giant short-faced bear, Arctodus simus, is identified as the most powerful predator of the Ice Ages by authorities Björn Kurtén and Elaine Anderson. Originally described as strictly a meat-eating carnivore, researchers have since suggested Arctodus simus was omnivorous, eating both meant and vegetation as do modern bears. Research conducted in 1992 indicates Arctodus simus was a scavenging predator.

The giant short-faced bear got its name because its snout appears short in relation to the overall length of its head. And he was a giant. Standing on all four feet, it was a little taller than five feet at the shoulder, the bear weighed close to 1,400 pounds – at least twenty-five to thirty percent bigger than the grizzly bear of today.

With its unusually long legs, the short-faced bear was swift-running and lean in appearance. Arctodus simus actually was built more like a cat than a bear. Even its face more closely resembled the feline family.” (1994:11)

Giant Short-Faced Bear Arctodus Simus. From: Lisa W. Nelson, Mammoth Graveyard (1994:11)

Short-faced bear attacking a steppe-bison in the Yukon Territory. After: John Storer Discover Beringia

Short-faced bear in the Yukon Territory. After: John Storer, Discover Beringia

Beringian Research Notes 1996 No. 4. North American Short-Faced Bear by C. R. Harington, Canadian Museum of Nature, Ottawa, Canada:

“North American short-faced bears (Arctodus simus and Arctodus pristinus), sometimes picturesquely called ‘Bulldog Bears,’ were the largest land carnivores in North America during the ice age (Quaternary the last two million years). They were unusually tall, and highly carnivorous. They ranged from Alaska and the Yukon to Mexico, and from Pacific to Atlantic coasts.

Of the two North American short-faced bears, the giant short-faced bear (Arctodus simus) was the largest (Figure 1) the biggest known skull being from the Yukon. This bear is distinguished from the lesser short-faced bear (Arctodus pristinus) by larger size; bigger, broader, more crowded teeth; a shorter face and relatively longer legs. The largest animals were nearly 1.5 m high when walking normally, but stood about 3.4 m when up on their hind legs. They could have had a vertical reach of more than 4.3 m.

Although much taller than brown bears (Ursus arctos), giant short-faced bears were not so heavily built (Figure 2). Their limbs, particularly the hindlimbs, were longer and more slender. A calculation of the autumn weight of a giant short-faced bear (with its full component of fat), based on diameter of the upper hind leg (femur) shaft, is approximately 700 kg. The largest known polar bear (Ursus maritimus) recorded in Canada, weighed 660 kg.

The face of Arctodus simus was unusual in its lack of a well-marked forehead and the presence of a short broad muzzle in this respect resembling a lion rather than any of the living North American bears. A striking features of the largest skull, from Gold Run Creek, Yukon, is its great width relative to length (nearly 80% compared to recent brown, black and Pleistocene cave bears [Ursus spelaeus], which are all less than 70%. Certainly the muscles which passed between the broad cheek bones to power the lower jaws were extremely well-developed, as would be expected in a highly carnivorous bear, and perhaps one adapted for bone brushing in order to obtain the rich marrow.

Bears display as much, or more, individual and sexual variation than any other mammalian group. Most living North American adult male bears are about 20% bigger than the females, and Arctodus shows the same kind of variation. However, specimens from Alaska, Yukon, Nebraska, California (Irvington) and perhaps Utah, probably mostly males, are much larger than the largest males from Rancho La Brea (Los Angeles, California) and other sites. Therefore, they are recognized as a different subspecies Arctosus simus yukonensis) than the smaller form (Arcodus simus simus).

The giant short-faced bear evidently occupied higher, well-drained grasslands mainly west of the Mississippi River, whereas the lesser short-faced bear preferred moister, more heavily-wooded eastern coastal regions. The former species had reached its northernmost range (as well as reaching maximum size) in the Yukon and Alaska by the mid-Wisconsinan interstadial. This is indicated by a series of radiocarbon dates on bone focusing on that period.

For example, approximate radiocarbon dates on Yukon Arctodus specimens are: 44,000 B.P. on an upper footbone from Sixtymile, 29,600 B.P. on a humerus excavated from frozen silt on Hunker Creek; 26,000 B.P. on the massive adult male cranium [skull] from Gold Run Creek; 25,000 B.P. on the facial region of an adult male from Hunker Creek; and 20,000 B.P. on an excellently-preserved cranium of an adult female from Ophir Creek (Figure. 3), which shows that this bear survived at least until the cold peak of the last glaciation in Eastern Beringia (unglaciated part of Alaska, Yukon and adjacent Northwest Territories). The only other recorded Canadian specimens are from mid-Wisconsinan deposits at Edmonton, Alberta and possibly last interglacial deposits at Lebret, Saskatchewan.

Presumably the giant short-faced bear was a rather solitary scavenger or predator except for mothers with cubs and during the mating period. The light, long-legged, short-necked body; the skull with its vise-like jaws, stout fangs and short, broad muzzle (like lions) all indicate that this animal was capable of bursts of speed when necessary and covering large areas for prey or for carcasses on which to scavenge. Further, it was the largest, most powerful carnivore among the Pleistocene land animals of North America. Isotopic analysis of Alaskan and Yukon short-faced bear bones supports the idea that they were highly carnivorous. The great width between the canine teeth may have allowed a more secure grip on prey and/or the wide snout might be related to a keenly developed sense of smell. The situation is similar to the polar bear the most carnivorous of living bears. Arctodus may have scavenged and preyed on large herbivores, such as bison (Figure 1), muskoxen, caribou, deer, horses and ground sloths.

Arctodudus simus died out toward the close of the last glaciation, perhaps partly because of the early extinction of some of the large herbivores that it may have preyed upon or scavenged, and partly because of increased competition with brown bears, which apparently entered North America during the Illinoian glaciation (some 200,000 to 130,000 years ago). The last view has been challenged by a 1995 study of paleodiet and ecology of short-faced and brown bears. Two radiocarbon dates on Arctodus bone from Texas and Utah of about 12,650 B.P., and a third of 11,500 B.P. from Little Box Elder Cave, Wyoming, are the most recent ones recorded. The latter cave contains the only known association of Ursus arctos and Arctodus simus in southern North America. Farther north, in the western Yukon, the species lived together during the mid-Wisconsin interstadial, according to radiocarbon dates on brown bear bones of about 41,000 B.P. and 36,500 B.P.

Tremarctos ornatus, the spectacled bear of South America, is the closest living relative of the extinct North American short-faced bears.“

C. R. Harington, Beringian Research Notes No. 4. North American Short-Faced Bear (1996-1-49)

North American short-faced bear killing a bison bull. From: C. R. Harington, Beringian Research Notes No. 4, North American Short-Faced Bear (1996). Figure 1. Ink sketch by Bonni Dalzell.

Relative size comparisons of grizzly, brown, and giant short-faced bears. Ruth Anne Border, 1988. From: C. R. Harington Beringian Research Notes No. 4, North American Short-Faced Bear (1996). Figure 2.

Right side view of Arctodus simus, female in early adulthood. Note the curving upper profile of the cranium and short snout. (CNM photo). From: C. R. Harington Beringian Research Notes No. 4, North American Short-Faced Bear (1996). Figure 3.

From: C. R. Harington Beringian Research Notes No. 4, North American Short-Faced Bear (1996).

Short-faced bear: where it lived

Palaeoecology and Palaeoenvironments of Late Cenozoic Mammals, edited by Kathlyn M. Stewart and Kevin L. Seymour (1996) University of Toronto Press, Toronto. “Distribution and size variation in North American Short-faced bears, Arctodus simus”. By Ronald L. Richards, C.S. Churcher, William D. Turnbull.

“Remains of A. simus are found throughout North America (except in the southeast) and also date from middle Irvingtonian through Rancholabrean time. Kurtén recognized two subspecies of A. simus: the larger A. s. yukonensis from Yukon Territory, Alaska, and Nebraska and the smaller A. s. simus recovered throughout the rest of North America. 1996:192)

Remains of the short-faced bear A. s. yukonensis they have found also in Alaska (in the Fairbanks area, and at the Ikpikpuk River), on Alaska’s North Slope, Brooks Range, near the Arctic Coast, and in the Yukon Territory (Dawson area, and in the Old Crow basin, in the northern part of the Yukon Territory, close to the Arctic Coast).” (1996:211)

“Geographic and temporal variation of size in A. simus suggests that A. s. yukonensis occurred in western North America during the Irvingtonian and was apparently absent in the east. By Rancholabrean times, A. s. yukonensis had differentiated into measurably smaller individuals (A. s. simus) generally south of the region covered by Wisconsinan ice, but populations of larger individuals (A. s. yukonensis) persisted in northern latitudes.

The short-faced bear A. s. yukonensis maintained large size throughout the Irvingtonian, with southern populations declining in size in the Ranchelobrean. It may have maintained its large size in Alaska in part because of competition with the grizzly bear (U. arctos), which filled an adjacent but smaller size in the hunting set. A. s. yukonensis populations in unglaciated Alaska may have had contact with those south of the ice for much of the Wisconsinan time through an ‘ice-free corridor’ (Catto and Mandryk, 1990; Bobrowsky et al, 1993). Burns suggested that migration through the corridor was restricted during the period from 20,000-14,000 BP by the coalesced Cordilleran and Laurentide ice sheets.

With the extinction of much of the late Pleistocene megafauna, opportunities for large predators declined and some niches were apparently untenable. This, coupled with direct competition from U. arctos, may have facilitated the extinction of A. simus.” (1996:212, 213)

From: Ronald L. Richards, C.S. Churcher, William D. Turnbull (1996:193) Fig. 1. Note, please, where the large short-faced bear has lived in Alaska and the Yukon Territory, when the mammoth was grazing up there. It has lived there not only in the southern central parts (Fairbanks area, Dawson City, Klondike) but also much further north, near the present Arctic Coast: On Alaska’s North Slope, Brooks Range) (No. 101) and in the Old Crow Basin.(No. 81-88). In the Far North they were then just as large as in the southern parts of Alaska und the Yukon Territory.

Northernmost Short-faced Bear

Where have they found the northernmost remains of the short-faced bear? Which other kinds of animals have lived up there with this large bear? When has it lived up there, in what kind of a climate, and on what kind of a plant-cover? Was this bear adapted to an arctic climate? How large was it?

The research report, Arctodus simus from the Alaskan Arctic Slope informs us about this. The following scientists have published it: By C.S. Churcher, Department of Zoology, University of Toronto, Ont., Canada. A.V. Morgan, Department of Earth Sciences, University of Waterloo, Ont., Canada. L. D. Carter, United States Geological Survey, Anchorage, Alaska. In: Canadian Journal of Earth Sciences 30:1007-1013 (1993):

“Arctodus simus yukonensis, the extinct northern North American short-faced bear, is represented by an immature left humerus lacking its unfused proximal epiphysia, which was recovered from a point bar on the Ikpikpuk River, Alaska (69°41´N, 14°54´W). This is the northernmost record of this bear. The specimen is dated at 27,190 ± 280 BP (Iso Trace TO-2539) on ¹⁴C analysis, which lies within the observed age distribution of Arctodus. The individual is larger than average for the species based on the dimensions of the distal articulation, despite its immaturity, and may have been a male.” C.S. Churcher et al. (1993:1007)

Introduction

“A left humerus [upper arm bone] from an extinct giant short-faced running bear (Arctodus simus yukonensis) was collected from a point bar of the Ikpikpuk River, 150 km north of the Brooks Range on the Arctic Slope of Alaska (Fig. 2). This is the most northerly record of this species, which is the largest known North American Pleistocene terrestrial carnivore. Remains of other Pleistocene mammals, such as mammoth (Mammuthus primigenius), bison (Bison sp.) and especially horse (Equus cf. przewalski (= lambei); Forsten 1986), are locally common on point bars in the Ikpikpuk and other rivers of the northern Arctic foothills and southern Arctic Coastal Plain (Guthrie and Stoker 1990).

The stretch of the Ikpikpuk River that yielded the Arctodus humerus also yields bones of extinct mammals from a complex sequence of Pleistocene fluvial valley-fill deposits and latest Pleistocene to early Holocene fillstrath terrace deposits exposed in modern cutbanks (Carter and Galloway 1988, Nelson et al. 1988). Radiocarbon ages are not available for the cutbank deposits adjacent to the point bar that produced the Arctodus humerus. However, a similar cutbank about 2.5 km north of the Arctodus collection site exposes valley-fill sediments that is beyond the range of radiocarbon dating at its base (>49.000 BP) and contains wood in its upper part dated by radiocarbon at 13.570 ± 120 BP (Nelson et al. 1988). This deposit may represent much Middle to Late Wisconsin time, and possibly older intervals. … Numerous bones of mammoth, horse, and bison have been collected along the bases of these cutbanks. Many are well preserved because of the permafrost that underlies the entire Arctic Slope, while others deteriorated prior to entombment.

Taxa recognized from the Ikpikpuk River deposits include Mammoth sp., Equus cf. przewalski, Bison sp., Smilodon neogaeu [saber-tooth cat], Ursus arctos [brown bear], Ovibos moschatus [muskox], Alces sp.[moose], Rangifer tarandus [caribou, tundra reindeer], and Artiodactyla indet (?Saiga tatarica). A juvenile Smilodon ulna … was identified by C.S. Churcher.” - C.S. Churcher et al. (1993:1007)

Location of site 79 Acr 042 on the Ikpikpuk River, which yielded the radiocarbon dates reported by Nelson et al. (1988) and is close to the point bar where the Arctodus left humerus (ROM.VP 43646) was found. The Arctic Slope is the area between the two broken lines. From: C.S. Churcher et al. (1993:10) Fig. 2.

Discussion

“Taxonomy. Two species of Arctodus are recognized, Arctodus simus and Arctodus pristinus, the western and eastern short-faced bears, respectively (Harington 1973). Arctodus simus is recorded from the northwest and usually west of the Mississippi on the interior plains (Kurtén and Anderson 1980). It contains two subspecies, A. simus simus for the southern or Californian population and A. simus yukonensis for the Alaskan, Canadian, and northern Great Plains population. Arctodus pristinus comes  from southeastern North America and is usually pre-Sangamon, while A. simus is Sangamon or Wisconsin.” C.S. Churcher et al. (1993:10)

Size and conformation

“Arctodus simus represents the largest Quaternary North American land carnivore, and ranged from Alaska to Mexico and from the Atlantic to the Pacific Ocean (Harington 1990; Kurtén and Anderson 1980). Arctodus simus is larger, more robust, and has a shorter muzzle than A. pristimus. It was nearly 1.5 m high at the shoulders when walking or 3.4 m to the top of its head when reared on its hind legs (Harington 1991). It may have weighed 590-650 kg (Kurtén 1967) or 620-660 kg (Nelson and Madsen 1983). The preserved length of the humerus (460 mm without epiphysis) and the anteroposterior (parasagittal) diameter of the shaft (59.5 mm) give an estimated body weight of 493 kg. If a conservative additional 10 mm is allowed for the missing epiphysis, a 470 mm length gives a weight of 507 kg. Both these weights lie within the ranges suggested above. Males appear to be about 15% larger than females.

Arctodus’ legs were probably straighter and its feet planted more nearly parallel in contrast with the bowed legs and toed-in stance of Ursus (Harington 1991). ‘The humerus is a very large bone, rivalling or exceeding in length the greatest humerus of U. spalaecus [European cave-bear], but distinctly more slender in proportion.” C.S. Churcher et al. (1993:1010)

Distribution

“Arctodus simus appears to have been an open country predator, mainly of the northern and western North American plains. Because the Alaskan, Yukon, and northern plains Arctodus simus yukonnensis is larger than A. simus simus from the south and southwest, there is a cline from larger in the northwest to smaller in the south and south-central mid-continent… The still smaller, earlier, and probably antecedent Arctodus pristinus occupied the southeast.” C.S. Churcher et al. (1993:1010).

Temporal range

“A humerus from frozen silt in Lower Hunker Creek, near Dawson City, Yukon Territory, yielded the oldest finite radiocarbon date for Arctodus of 29,600 ± 1200 BP (I-11037) Harington (1980). No date for Arctodus from Alaska is available, although Pleistocene specimens are known from gravels near Fairbanks and along the Tanana River and elsewhere. Other northern records include Gold Run Creek (Harington 1977; Lambe 1911) and Old Crow Basin, Yukon Territory (Harington 1977), and Lebret, Saskatchewan (Harington 1973, 1990) (possibly 130,000 to 80,000 BP, or Sangamon).

The known dates cluster in two time intervals, one at 32,000 – 26,000 BP (4 finite dates) and the other at 13,500 – 10,000 BP (8 finite dates, with the hiatus [gap] seemingly reflecting the Late Wisconsin glacial episode. The Ikpikpuk River date of 27,190 ± 280 BP falls within this group.” C.S. Churcher et al. (1993:1011, 1012)

Summary

“A left humerus of the extinct North American giant short-faced bear Arctodus simus yukonensis has been recovered from the North Slope of Alaska from a point bar on the Ikpikpuk River and is the most northerly recorded. The individual was subadult, as the proximal epiphysis was unfused and is missing. Its size is above average for the species, as, despite its immaturity, the distal articulations are larger than average: thus it may be male. The individual is radiocarbon dated at 27,190 ± 280 BP and lived during the Mid-Wisconsin interstadial. Radiocarbon dated specimens of A. simus are known from two periods, 32,000 – 26,000 and 15,000 – 10,000 BP.” C.S. Churcher et al. (1993:1012)

The saber-tooth cat Homotherium serum with a Dall sheep ram in the upper Pleistocene in Alaska. After:  Mauricio Antón and Alan Turner The Big Cats 1997 Plate 10.