Regional variation in the browsing diet of Pleistocene Mammut americanum (Mammalia, Proboscidea) as recorded by dental microwear textures

Analyses into the feeding ecology of Mammut americanum have reconstructed this extinct proboscidean as a forest-dwelling browser that thrived across North America during the Pleistocene. However, the level of variability in mastodon diet that may have existed across its spatio-temporal range remains unresolved. We address this deficiency through comparison of dental microwear textures in a large sample (N = 65) of M. americanum teeth from six geographic and chronologically distinct locations from the Late Pleistocene of North America. Mastodon microwear textures correspond to a woody browsing diet, congruent with results from other dietary proxies. However, microwear textures reveal that southern populations from Florida (associated with a cypress swamp habitat) had a slightly softer, tougher browsing diet compared to northern populations (associated with boreal forest and open-pine parkland habitats) in the Late Pleistocene. In addition, there was no significant difference in microwear variables associated with food hardness or toughness in mastodons from two temporally distinct populations from Missouri, despite a significant environmental shift from open-pine parkland to boreal forest through time. Our findings elucidate M. americanum as a species with some plasticity in its browsing strategy across its range, with regional populations capable of having different diets yet able to maintain their ecological niche in the face of local environmental shifts in the Late Pleistocene. This has implications for the future testing of environmentally-induced extinction hypotheses during the latest Pleistocene and also illustrates the importance of measuring population-level dietary variation to better understand total feeding ecology in an extinct species.