THEN AND NOW AGAIN – A BOBCAT’S TAIL

Bobcats (Lynx rufus) have lived in North America since at least the Pleistocene epoch. Our research focused on whether the bobcats living in Los Angeles today differ ecomorphologically from those that lived here from 55,000 to 11,000 years ago, potentially reflecting their response to the large-scale disturbances (climate change, megafaunal extinction) that impacted this time interval. Using specimens at the La Brea Tar Pits and Museum and the Natural History Museum of Los Angeles County, we collected linear dimensions and biomechanical indices for adult-aged cranial and limb elements of both modern (crania n=42 individuals, limb n=15) and fossil (crania n=6 to 12, limb n=6 to 10) bobcats from southern California. We used Mann-Whitney and Kruskal-Wallis tests to quantify sexual and geographic differences in the modern sample, chronological differences in the fossil sample, and any differences between fossil and modern samples. Consistent with the literature, we found sexual dimorphism in modern bobcats, with males generally having longer and wider teeth than females. Males also are larger in some limb bones, such as radial length, epicondylar breadth of the humerus, and olecranon process length. Fossil bobcats’ teeth were significantly larger than those of modern bobcats, except for the upper canine. Fossil bobcats also had longer and wider tibiae and longer femora. However, modern bobcats had more robust dentaries and larger muscle attachment areas in the proximal femur. These results show that bobcats have decreased in body size since the late Pleistocene. A possible explanation is Bergmann’s rule, which posits that body size decreases as temperature increases, as happened during the transition from Pleistocene to Holocene. Increasing jaw robustness enables bobcats to process larger prey, while greater hindlimb muscle attachment improves pounce behavior; these ecomorphological shifts may represent response to an increase in prey size or the disappearance of larger predators. These ecomorphological differences between bobcats living in southern California now and those living in the region over 10,000 years ago show the adaptability of mesocarnivores in a rapidly changing environment—and their potential to cope with the ongoing effects of climate change and human interaction on modern ecosystems.