during the late pleistocene, a
1 diverse assemblage of large-bodied mammals inhabited the "
2 steppe," a cold and dry yet productive environment that extended from western europe through northern asia and across the bering land bridge to the yukon. of the large
4--wolves, bears, and big cats--only the wolves and bears were able to maintain their ranges well after the end of the last ice age. a new study led by researchers at the university of california, santa cruz, suggests that dietary
5 may have been an important factor giving wolves and bears an edge over saber-toothed cats and cave lions.
"we found that dietary flexibility was strongly species-specific, and that large cats were
6 7 predators compared to wolves and bears. this is a key observation, as large cats have suffered severe range
8 since the last glacial maximum, whereas wolves and bears have ranges that remain similar to their pleistocene ranges," said justin yeakel, first author of a paper on the new findings published in the
9 of the royal society b.
yeakel, now a postdoctoral researcher at simon fraser university in british columbia, worked on the study as a graduate student at uc santa cruz with coauthor paul koch, professor of earth and planetary sciences at ucsc. the other coauthors are paulo guimarães of the university of são paolo, brazil, and hervé bocherens of the university of tübingen, germany.
the researchers based their findings on an analysis of stable
10 ratios, chemical traces in fossil bones that can be used to reconstruct an animal's diet. they used
11 published stable isotope datasets to reconstruct
3-
12 interactions at six sites located from alaska to western europe. the sites covered a range of time periods before, during and after the last glacial maximum, the period around 20 to 25 thousand years ago when the ice sheets reached their greatest extent.
the study found that the diets of the large cats were similar in different locations, especially in the post-glacial period. wolves and bears, in contrast, ate different things in different locations. prey species on the mammoth steppes included
bison（北美野牛）, horses,
13（牦牛）,
14 oxen（麝香牛）,
15（北美驯鹿）, and mammoths. the researchers noticed changes in predator diets coinciding with an increase in caribou abundance starting around 20,000 years ago.
"during and after the last glacial maximum, many predators focused their attention on caribou, which had been a marginally important prey resource before then," yeakel said. "large cats began concentrating almost
16 on caribou in both alaska and europe. wolves and bears also began consuming more caribou in alaska, but not in europe."
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