SURVIVORS OF THE ICE AGE: ECOMORPHOLOGICAL CHANGES IN THE AMERICAN BADGER FROM THE PLEISTOCENE TO MODERN-DAY

The megafaunal extinctions, climatic transitions, and arrival of human predators at the end of the Pleistocene epoch (approximately 11,000 years ago) produced ecological shifts that impacted North American mammals. Some of these mammals have survived to the present day, including small to medium-sized carnivores, or “mesocarnivores”. One such mesocarnivore is the American badger (Taxidea taxus; order Carnivora, family Mustelidae), which has been understudied in the fossil record. This species is preserved as body fossils in the Pleistocene to Holocene-age Rancho La Brea (RLB) asphaltic deposits in Los Angeles, California, and currently lives in the Great Plains of North America, through the central western United States and southern Mexico. To track how the American Badger may have responded to ecological and environmental changes over the past 40,000 years, we measured fossil skulls and jaws (n=2 to 10 individuals) and limb bones (n=4 to 8 individuals) at La Brea Tar Pits and Museum and modern individuals from southern California (n=22) at the Natural History Museum of Los Angeles County. Calculating RLB badger body size using a regression of body size on lower first molar length in extant mustelids, we find that the modern American badger is significantly smaller than RLB badgers. RLB badgers have more robust muscle attachments (e.g. on the olecranon process, p=8.17E-05) and a larger skeleton overall (e.g. longer ulnae, p=0.00246). These differences may signify that RLB badgers were more powerful diggers or that they needed to fend off larger predators or potential competitors. Furthermore, RLB badgers have deeper jaws (p=0.0342), suggesting that they ate harder food items or pray on larger animals compared to modern specimens. Modern specimens feed from birds, squirrels, rats, fish, insects and mice. These ecomorphological shifts potentially reflect environmental changes, such as a shift in aridity that affected soil hardness, along with mesocarnivore/mesopredator release from the extinction of carnivorous megafauna, highlighting the potential for the fossil record to shed light on the responses of extant species to disturbance in deep time.

Funding Citation:

National Science Foundation DBI-1812301 (PI: Mairin Balisi).