HOW DID COUGARS AND BOBCATS RESPOND TO THE CHANGES AT THE END OF THE PLEISTOCENE?

At the end of the Pleistocene, most of the large mammals vanished from North America, including the predators (such as saber-toothed cats, dire wolves, Ice Age lions, and short-faced bears). Previous studies have shown that the coyotes of the late Pleistocene were bigger and more robustly built to compete for larger prey and then grew smaller and more gracile in the Holocene when their predator competition and large prey both disappeared. How did the surviving large cats respond to this event? We compared cougars (Puma concolor) and bobcats (Lynx rufus) from the late Pleistocene Rancho La Brea asphalt deposits (35-9 ka) to their recent counterparts. The most commonly fossilized bones of these rarely fossilized cats— lower first molar in the jaw, the third metacarpal in the front paw, and the third metatarsal in the hind foot—were measured with dial calipers. Even though the size range of Pleistocene La Brea specimens were completely contained within the modern range in every dimension, the Pleistocene cougars were significantly larger in the first molar and metatarsals, although not in the metacarpals. The bobcats, on the other hand, were not statistically different in any element. We also compared the fossil specimens by pit age to see if climate change during the glacial-interglacial transition about 20,000 years ago might have made a difference. Although most sample sizes were too small for robust statistical analysis, there were no evident changes through time. We conclude that Pleistocene cougars were like coyotes in competing with larger predators for larger prey during the Pleistocene, while bobcats have always specialized on smaller prey and therefore were not affected by the megafaunal extinction.