The mammoth steppe was a vast continuous environment that stretched from western Europe to Alaska during the coldest phase of the most recent Ice Age. Glacial ice locked up so much of earth’s atmospheric moisture that sea level fell, creating land bridges connecting the British Isles and Alaska with Eurasia. The mammoth steppe consisted of desert grassland, cold and windy but without much snow cover. This environment supported a wealth of megaherbivores including woolly mammoth, bison, yak, musk-ox, woolly rhino, horse, megaloceros (a giant deer), caribou, camel, and saiga antelope. Such a wide prey selection attracted several species of large predators. Scientists long speculated about the relationships between predator and prey on the mammoth steppe, but now it’s possible to determine which prey species each individual species of predator favored. In an ingenious study, Herve Bocheren, a German professor, used stable isotope tracking in combination with mathematical models to learn about the diet of late Pleistocene carnivores on the mammoth steppe. Some of his findings are quite surprising.
Map of the vast mammoth steppe ecosystem that existed between ~28,000 BP-~15,000 BP.
Various species of plants have distinct ratios of carbon and nitrogen isotopes, and therefore herbivores that eat these plants have similar ratios in their bone chemistry. Carnivores that then eat these herbivores also attain these distinct ratios of carbon and nitrogen isotopes. By analyzing the chemistry of ancient bones found in caves, the diets of these animals can be pieced together.
Stable isotope tracking suggests the spotted hyena (Crocuta crocuta) was the dominant predator in Europe until about 25,000 BP–before climatic conditions caused the expansion of the mammoth steppe grassland. Between 60,000 BP-28,000 BP forests and open woodlands still grew amidst the grasslands, and climate remained temperate though there were rapid fluctuations. The spotted hyena, the same species found in Africa today, thrived in temperate climates, and they outcompeted wolves, lions, and even Neanderthals here during this time period. Isotopic evidence shows hyenas ate a wide range of prey including mammoth, horse, and rhino; relegating wolves to prey such as elk, giant deer, and chamois. But hyenas were unable to survive in Eurasia during the following colder climate phase, and they became extirpated from the mammoth steppe. Hyenas must have a limiting minimum temperature limit that they can endure.
The most surprising result of Dr. Bocheren’s study was the discovery that cave lions (Panthera spelaea) relied on caribou for at least 25% of their diet. The lion of the mammoth steppe was not the same species as the African lion (Panthera leo). It was 10% larger but males had smaller manes. The evidence from this study supports conjecture that it was a solitary predator, unlike its extant cousin. Packs of hyenas and wolves were able to restrict access of this solitary predator from more desirable prey such as bison and horse, forcing cave lions to rely more on caribou. There is also a great variation in each individual lion’s choice of prey. One individual favored caribou and deer. Another specialized in cave bear but also took mammoth, deer, and rhino. A 3rd individual fed upon cave bear and deer. And a 4th ate the same mix of desirable prey that hyenas ate. Each individual learned to hunt certain prey animals, whereas a social predator would’ve likely taken a wider mix of prey. An individual lion killing an huge cave bear must have been an impressive sight. There is also fossil evidence of lion bite marks on bear bones. Today, certain Siberian tigers are known to specialize in hunting brown bears (Ursus arctos).
Dr. Bocheren studied the bone chemistry of scimitar-toothed cats (Dinobastis serum or Homotherium serum depending on whose nomenclature one chooses) as well. Unlike saber-tooths (Smilodon fatalis) this fanged cat was not an ambush predator but chased down its prey instead. Complete skeletons of scimitar-toothed cats have been found in Friesenhan Cave, Texas associated with many bones of juvenile mammoths. Because of this single site, scimitar-toothed cats were thought to be specialists in hunting juvenile mammoths. This study casts doubt on that assumption. Instead, the favorite prey of scimitar-toothed cats in Eurasia was the yak (Bos grunniens), along with bison and caribou. Less commonly, they did eat musk-ox, mammoth, and horse. They were a generalized predator, not a specialist. Scimitar-toothed cats are rare in the fossil record compared to other large carnivores and probably were extirpated from the mammoth steppe along with hyenas and leopards when the climate deteriorated about 25,000 BP.
Painting of lions on a wall in Chauvet Cave, France. Looks like the representation of a pride of lions. I’m not convinced the extinct European cave lion was a solitary animal as suggested by this study.
The yak (Bos grunniens). Isotopic tracking studies suggest this was the favored prey of the extinct scimitar-toothed cat.
Wolves (Canis lupus) replaced hyenas as the dominant predator in Eurasia after 25,000 BP. There was a wide genetic and morphological diversity among Pleistocene wolves on the mammoth steppe. The large extinct Pleistocene wolf ecomorph that lived in Alaska ate mostly horse, bison, and caribou but not mammoth. This line of wolves became extinct.
Isotopic evidence shows Paleolithic humans living about 28,000 years ago ate mammoth but did not allow their primitive dogs to consume the mammoth meat. Instead, humans fed their dogs caribou and musk-ox. However scavenging predators such as wolf, brown bear, wolverine, and fox did take advantage of anthropogenic mammoth hunting.
Dr. Bocheren’s isotopic study confirms the cave bear (Ursus speleus) was almost entirely herbivorous. Brown bear diet varied. Brown bears were more carnivorous in regions where they overlapped with cave bears but were more herbivorous in regions where they overlapped with highly carnivorous giant short-faced bears (Arctodus simus). Brown bears apparently avoided completion with larger bear species. In Alaska giant short-faced bears ate caribou, musk-ox, and other predators but plant foods may have made up to 50% of their diet. Surprisingly, they didn’t eat much horse or mammoth–2 common prey species here. The diet of this North American species south of the ice sheet has not yet been studied.
Note 1: I think the common names of cave lion, cave bear, and cave hyena are misnomers. 99.9% of the individuals of these species that ever lived never stepped inside a cave. There bones were more likely to be preserved in caves, hence the cave appellation. Nevertheless, it’s misleading to think of them as cave dwellers. This is just a pet peeve of mine, but I wish they would be given different common names.
Note 2: I’m not entirely convinced that Panthera spelaea was a solitary species, nor am I convinced this species played second fiddle to wolves and hyenas. I’ll think more on this and perhaps comment at a later date.
“Isotopic Tracking of Large Carnivore Paleoecology in the Mammoth Steppe”
Quaternary Science Reviews March 2015