Frozen Fauna of the Mammoth Steppe: The Story of Blue Babe

by Guthrie, R. Dale

  The hypothesis changed: Blue Babe was attacked by a large cat or cats, from which he successfully escaped; however, the bison eventually died from wounds sustained in the encounter. I thought Blue Babe must have escaped because a large pride of lions would certainly have stayed with the carcass until it was totally eaten. The successful escape explained incomplete use of the carcass and signs of small animal scavenging.

  Fig. 3.8. Muzzle bite. In this drawing from a photograph, a lioness strangles a blue wildebeest by seizing the wildebeest’s mouth and nares. Blue Babe’s nose had a canine puncture on the side, suggesting a kill of this nature.

  Fig 3.9. Throat bite. Lions also strangle large prey by biting the animal’s trachea. The male in this picture has a firm clamp on the trachea, even though the zebra is still on its feet. The female claws at the rear end, attempting to throw the animal off its feet. Note the female has her claws in the same place as the scratch marks on Blue Babe’s legs. (Drawn from photo)

  While thinking over my new hypothesis involving Alaskan lions (Panthera leo), I found indications that northern lions may have been more solitary in their social behavior than are most lions today In winter, even two hungry lions could not have eaten an entire bison before it froze; they would have left a carcass just like Blue Babe’s.

  There is some evidence that lion prides in the far north were small. First, European cave paintings of the same Pleistocene lion species show males without a large, contrastingly colored mane (fig. 3.10). Clutton-Brock, Guinness, and Albon (1982) have observed that a male lion’s social paraphernalia is most extreme in situations where males compete for large numbers of females. In African lion populations where prides are quite small (Tsavo Flats), males normally are maneless (Schaller 1972). Thus the lack of a contrastingly colored mane in Pleistocene lions suggests that prides were smaller. Second, in the several instances where multiple lions are pictured in Paleolithic art, the group is never large.

  Fig. 3.10. Reconstructing northern lions from Paleolithic Art. Northern Pleistocene steppe lions, or “cave lions” as they are called in Europe, are almost identical to living lions in skeletal structure, but Paleolithic art indicates cave lions had a slightly different appearance. Male European lions probably did not have an enlarged, contrastingly colored mane; instead, they wore discrete dorsal and ventral manes, including a throat indentation at the hinge point of the jaw. Tails had the familiar dark-tufted tip, and some sort of side stripe or break in color pattern can be seen in the drawings. No large prides are pictured, but several drawings (a, d, and e) show more than one animal. Apparently these northern lions were social, like living lions.

  My working hypothesis that the bison was attacked by lions, had escaped, but later died and froze, and was subsequently scavenged began to seem contorted. Perhaps the bison was simply killed by felids who, for some reason, did not eat all of the meat. Two more pieces in the puzzle supported this later conclusion. When the mummy’s skin was split and stretched for mounting by the conservator, Eirik Granqvist, we found canine tooth punctures in the flank skin. These probably were not from bites intended to kill the bison but were punctures made in pulling the hide from the carcass to gain access to the meat, a characteristic method lions use (Schaller 1972). The puncture marks occurred in pairs, averaging 8.5 cm apart (fig. 3.11), almost exactly the width of the upper canine teeth measured on a Pleistocene lion in collections at the University of Alaska Museum. The width of the upper canines of the two short-faced bear (Arctodus) skulls available for measurement was under 7 cm. Both of these skulls were from very large bears. Wolves, wolverines, coyotes, and foxes all have much narrower distances between their canines and could thus be excluded.

  Fig. 3.11. Clues to the killer’s identity. Distance between punctures is shown in the enlarged square. Width between canines of Alaskan predator species contemporaneous with Blue Babe are shown in the upper left corner.

  Evidence pointed to a large cat as Blue Babe’s most likely predator, but was it really a lion? Lion fossils in Beringia are comparatively common (Harington 1969; Vereshchagin 1971; and Kurtén 1985). What about another large species of cat? There is no evidence that American jaguars colonized the Old World via Alaska during the Pleistocene. There is circumstantial evidence that the cheetah reached very far north at this time, and its bones are found in northern Europe and Asia. But cheetah fossils have not been found in Alaska. Additionally, cheetah canines are not widely spaced and could not have made paired holes over 8 cm apart. Cheetahs do not prey on large bovines, nor do they scavenge much. Thus, I think it most likely that Blue Babe was killed by a lion.

  The saber-toothed cat (Homotherium), or dirk-toothed cat as it is sometimes called, was in Alaska during the late Pleistocene (no precise dates). But those aptly named teeth would most likely have left cuts instead of punctures on Blue Babe’s hide. Saber-toothed canines are perfectly shaped for slicing; they are knife like in cross section and serrated on both anterior-posterior edges (fig. 3.12). The more conical canines of lions often do not break the skin, but rather secure the strangulation hold described earlier. Saber-toothed cats seem to have taken a different evolutionary route, relying on a penetrating neck bite, as do smaller felids today. I suspect the “saber” shape of the saber-tooth’s canine enabled the animal to penetrate the thick neck skin of a large ungulate.

  To appreciate the different ways cat canines function, we must look at the physics of skin penetration. The epidermis, or outer cornified skin layer, can be penetrated without great force. Blood vessels lie immediately under the epidermis, so even shallow wounds bleed. By contrast, the leathery collagen fibers of the dermis can only be penetrated by sharp, pointed objects (such as a hypodermic needle). A cone-shaped tooth has limited penetration because these collagen fibers interlace. As a conical tooth continues to penetrate, dermis fibers around the puncture are stretched, increasing friction on the tooth. The thicker the skin, the more difficult it is for the fibers to expand around the puncture; as a result, the depth of penetration is limited. Early hunters were aware of skin’s resistance to puncture and used a sharp projectile point larger than the shaft of the spear itself. In some cases they inserted stone microblades in a bone shaft to function in the same manner. Stone points are designed to cut an opening rather than punch a hole, allowing the shaft to penetrate much more deeply. Again, I think the long canines of saber-toothed cats worked this same way, slicing deeply into the neck of their prey.

  Fig. 3.12. Lion versus saber-toothed tiger canines. The serrated edge on the saber-tooth’s canine sliced through thick skin and allowed deep penetration. The more conical lion canine can only puncture. The uncut collagen fibers restrict penetration.

  Fig. 3.13. It is unlikely a single lion killed Blue Babe. Judging from African analogues, it takes at least two lions to bring down a large bovine. Large scratch marks on the rump and hind legs suggest that after several tries, lions threw Blue Babe off his feet from the rear.

  The saber-toothed cat’s canines (1) puncture the skin with a sharp tip, and (2) having a sharp posterior edge, they cut a wider opening instead of stretching a hole. This edge is not only sharp but (3) serrated. Serration concentrates the force alternately on a small surface, repeatedly severing collagen fibers as the canine penetrates. In addition, (4) the canine is flattened in cross section, to reduce friction and to penetrate deeply yet keep its strength. Together, these features allow deep penetration of a thick hide, and (5) once through the skin they sever critical tissue. A saber-toothed tiger’s teeth would thus leave characteristic cut marks on the carcass. This was not the case with Blue Babe; instead, we found puncture marks.

  Working with evidence from the necropsy and sorting through these various considerations, I felt more certain—although still amazed—that a lion or lions (fig. 3.13) had killed Blue Babe. Lions were once found across the far north of Eurasia and North America (fig. 3.14), and lion fossils have been found in Alaska that date from the same time as Blue Babe.

  Blue Babe’s
carcass later provided another bit of information to confirm that lions were involved in his death. When his skin was split in preparation for mounting, the taxidermist found a large tooth fragment embedded in the neck. Microscopic examination showed that this was a 1.01 mm thick fragment of enamel. I suspected this fragment was part of a tooth broken by a scavenger, but the enamel was too thick to belong to a wolverine or to any canid or ursid. The only Beringian late Pleistocene carnivore tooth that was of similar enamel thickness (0.92 mm) was a lion’s cheek tooth (canine teeth have thin enamel). An African lion skull in our collections had a carnassial enamel thickness of 1.15 mm. Size and surface texture of the fragment corresponded to that of a lion’s carnassial (fig 3.15). Lions use their carnassial teeth to shear through skin of ungulates and gain access to the meat (Ewer 1973), so it seems unlikely that a carnassial would have broken so dramatically on a soft hide. More likely, the lion broke its tooth while working on the bison after it had frozen. If this interpretation is correct, either soon after the kill or in a later scavenging episode, a lion broke its carnassial trying to get more meat from the carcass. Judging from the tooth fragment and the amount of meat remaining on the carcass (I estimate about 20 kg, fresh weight), the lion was not completely successful.

  This information explains why the bison carcass was apparently abandoned while still incompletely eaten. Schaller (1972) found that African lions finished every carcass (unless chased away by hyenas), usually eating all but the long bones. Let us assume it would take, at most, two to five days for a skinned and partially eaten bison carcass to freeze solid. (I have watched carcasses freeze in a wide range of winter temperatures, and this seems a reasonable rate.) Now we must take into account how much lions can eat. A fat bison bull provides considerable calories. Normally an animal will yield about 50% of its live weight in meat (Spiess 1979). Although there is no way of knowing exactly how much Blue Babe weighed, comparing his size with living bison I would guess his weight at about 700–800 kg. Schaller (1972) found that two male lions and one female lion ate a total of 150 kg of meat in a little less than two days. From other observations he calculated that a male lion required 35 kg and a female 22 kg of meat to gorge. A thin lion would gorge itself regularly over the first day or two, but satiety would slow consumption after that. Schaller estimated that over the long term, male lions require 7 kg and females 5 kg of meat daily in the Serengeti. Using these figures we can see that it would take a minimum of four or five adult Alaskan lions to consume Blue Babe before his carcass became completely frozen.

  Fig. 3.14. Late Pleistocene lion localities. Lions were one of the most widespread Pleistocene large mammal species. The relative abundance of lion bones found in Alaska suggests they were a dominant large predator. Lions seem to have lived throughout the steppes of northern Asia during most of the late Pleistocene. Though seemingly exotic, the association of lions with Blue Babe’s death is not unlikely when Pleistocene distributions of lion and bison are overlaid.

  Fig. 3.15. Comparisons of enamel thickness in northern carnivores. The thickness of the tooth enamel in the chip embedded in Blue Babe’s skin corresponds most closely to the enamel thickness of a lion’s carnassial. The enamel of lions’ large carnassial cheek teeth is quite thick because the wear pattern of its scissorlike action produces a self-sharpening, fragile edge.

  Fig. 3.16. Blue Babe’s carcass was incompletely eaten before it froze. Quite a bit of fat and red muscle remained frozen beneath the hide. Three or more lions could have finished the carcass before it froze, so it is likely that three or, more probably, less than three lions fed on Blue Babe. He was opened from the top while laying propped on his legs in an upright position. Bison often go down in this way when they are killed by wolves (Haynes, pers. comm.).

  Fig. 3.17. A lion or lions fed on Blue Babe after the carcass froze. Perhaps a lion returned to the kill site and tried to scavenge more meat. A lion did break the tip of its carnassial tooth in the bison’s hide, which would not have occurred in a soft, fresh hide, but could have easily happened in frozen skin.

  These calculations cannot, of course, determine how many lions were actually there when Blue Babe died, but they suggest that it was around two or three (fig. 3.16). Lions normally occur in adult sex ratios of one male to two females (Bertram 1975; Smuts 1976). Lions could and, as we see from the tooth fragment, probably did continue to feed after the bison was frozen (fig. 3.17). And judging from the scatter of fragmentary remains, other scavengers also used the carcass.

  Paleobehavior of the Alaskan Lions That Killed Blue Babe

  An obvious question that arises at this point is why Blue Babe—a mature male, 8 to 9 years old, in good condition—was susceptible to predation. Today, predators in the north usually take more vulnerable ungulates: individuals that are old, very young, diseased, injured, or in poor condition (e.g., Mech 1966). Studies of prey selection by African lions can help us resolve this puzzle. Sinclair (1977) showed that interaction between lions and large African bovines results in a nonrandom selection of prey related to sex and age, but it is a pattern different from the one we see between wolves and moose. Social defense is important among African buffalo. Thus the buffalo females and young which make up most of the herds are less likely to be preyed upon than are solitary old bulls. Sinclair found that bulls 8 years old or older were twice as likely as females to be taken by lions. Lion predation in the Serengeti accounts for 23% to 28% of total buffalo mortality, which means that almost half the males are ultimately killed by lions. Much of this vulnerability is due to the behavior of bull buffalo. Old bulls are normally solitary because younger bulls oust them from year-around herds (Sinclair 1977). Additionally, perhaps because of their social aggressiveness, old bulls are not tolerated by females or often by younger males. Such aggressiveness, however, has reproductive rewards in acquiring dominance for mating privileges, so it appears to be selected for, despite costs that later increase exposure to predation.

  When not confined to restricted enclosures, mature plains bison bulls are also likely to lead a solitary existence outside the rut season (Petersburg 1973; Shult 1972). Geist and Karsten (1977) proposed that, like African buffalo, female bison cluster together as an antipredator strategy because their smaller size makes them more vulnerable to predation than the bulls. Geist and Karsten further contended that bulls remain solitary or in small groups to avoid competition for forage from a large group. This allows them to stay longer in a single locality and still enjoy relatively high-quality forage.

  Although African buffalo bulls are formidable opponents, with sharp horns and massive build, they can only defend their anterior end. This defense is almost impenetrable by a lone predator (fig. 3.18), but its effectiveness declines against several lions (Schaller 1972; Sinclair 1977). Judging from both Schaller’s and Sinclair’s observations of ineffective attempts by lion prides to kill male buffalo and the numbers of living buffalo bulls carrying healed scars from lion attacks, killing success is far from certain even if several lions are involved in an attack.

  Again from Schaller’s observations, it seems unlikely that female lions regularly take healthy buffalo bulls. Schaller (1972) proposed that one advantage of including male lions in a pride was the group’s ability to take larger-bodied prey, due to the male lions’ greater size and strength. Also, the larger and more pugnacious males play an important role in protecting carcasses against spotted hyena packs.

  The implications of these African analogies for Blue Babe’s death are many. First, Blue Babe was of similar body and horn size as African buffalo bulls, and Alaskan lions were in the same size range as African lions. Thus the Pleistocene Alaskan predator-prey relationship may have been similar to the situation we can now observe in Africa. It seems unlikely, therefore, that single Alaskan lions regularly killed adult bison bulls. I have argued elsewhere (Guthrie 1980) that the sharp tips and long horns of Pleistocene Beringian bison were probably antipredator devices. Thus equipped, bison, with the weaponry and power t
o defend themselves, could whirl and face a single lion.

  Fig. 3.18. Lioness turns to run from a buffalo bull. Although lions are formidable predators, a single lion, especially a female, does not commonly tackle an African buffalo. Several lions are required, and normally a mature male lion assists the females in hunting large bull buffalo. (Drawn from photo)

  On the other hand, a pair of lions, one fore and one aft, poses a much greater defense problem. This is how African lions manage to kill buffalo. If the African-Alaskan analogy is appropriate, we can say that Blue Babe most likely was killed by several lions. As stated earlier, morphological evidence from cave drawings suggests that these northern lions did not form large prides. Perhaps two females hunted together, or maybe a lioness hunted with her almost-grown offspring. A male and a female could hunt in mated pairs, possibly in concert with several additional females. Also, two unmated males could form a team and attack larger prey not regularly taken by single lions. In fact, lions portrayed in Paleolithic art are usually shown in pairs, and in one instance the pair is clearly a short-maned male and a maneless female.

  Taking the African analogy even further, I would argue that one of Blue Babe’s attackers was probably a male, since African male lions are normally involved in killing large bovines. I think not less than two lions, including at least one male, killed Blue Babe on Pearl Creek.

  If this chain of logic is correct, it allows us to say something about the social structure of Pleistocene lions (fig. 3.19). Information from Blue Babe and European cave paintings can help us place Beringian lions on a continuum of social cooperation. Tigers are at one end of that continuum: adult tigers (Panthera tigris) seldom hunt together. Female and male tigers have separate territories (Schaller 1967), and their social paraphernalia is almost identical. Tigers hunt by stealth in deep woodland or woodland clearings, where a pair of animals would often be more of a detriment than a help. At the other end of this social spectrum is a large lion pride, composed of two or even more males and a number of females. African lions are dimorphic in their social paraphernalia. Male lions are readily identified by large contrastingly colored manes. Large lion prides hunt socially and in more open areas than do tigers. Lionesses do most of the hunting; males help in hunting larger species.