ScienceShot: Why the Coyote Got Small

Coyotes used to be a much more fearsome bunch, with thicker skulls, broader snouts, wider teeth, and 1.5 times the heft. When they did become more diminutive, the change happened relatively rapidly, according to a new study. An analysis of fossils from several sites in California and Idaho reveals that from 26,000 years ago until the end of the last ice age, about 11,000 years ago, coyotes retained consistently burly characteristics. But coyotes living less than 1000 years after the end of the ice age, when many large creatures such as camels, horses, and mammoths disappeared from North America, were indistinguishable from those roaming North America now (above, artist's concept of a modern-day coyote investigating the skull of an ice-age ancestor), according to a paper published online today in the Proceedings of the National Academy of Sciences. The sudden absence of large prey—as well as the extinction of the dire wolf, one of the coyotes' main competitors for food—most likely triggered the relatively rapid shrinkage, the researchers speculate.

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