Microwear variability in a spatially and temporally constrained elephant population: Implications for interpreting the diets of extant and extinct proboscideans

Abstract

Proboscideans, including mammoths, played a crucial role in past herbivore communities, where resource partitioning helped reduce competition and promote coexistence. Stable carbon isotopes are frequently employed to differentiate between the consumption of C3 and C4 plants in the fossil record. However, as geographic variability influences {delta}13C values, dental microwear texture analysis (DMTA) is often used in tandem to infer dietary preferences among extinct taxa (e.g., the consumption of grass vs. browse). Interpreting the dietary ecology of proboscideans, like mammoths, rests on our ability to compare fossil specimens to modern taxa with known diets. Here, we established a modern reference for interpreting mammoth DMTA by analyzing teeth from 11 African bush elephants (Loxodonta africana) culled in 1993 from Kruger National Park (KNP), South Africa (CITES permit certificate no. 780873). These specimens, housed at the Illinois State Museum, originated from the arid bushveld of northern KNP and were collected during the beginning of the dry season. Previous studies indicate that modern elephants in this region consume a mixed diet, consisting of [~]40% grass in the dry season and 50% grass in the wet season. The well-documented dietary and environmental context of these individuals provides an opportunity to assess dental microwear patterns in a modern analog and compare individuals with known diets to extinct mammoths. Specifically, we compared newly acquired modern African bush elephants DMTA to published DMTA data from fossil specimens of Columbian mammoths (Mammuthus columbi). Comparisons with fossil assemblages reveal few statistically significant differences in microwear between mammoth and KNP elephants, with the exception of mammoths from Leisey Shell Pit 1A having significantly lower complexity values than modern African bush elephants--indicative of some mammoth populations eating softer foods and/or less woody browse. Variation and breadth of DMTA from mammoths are similar to the temporally and geographically constrained population of L. africana. Despite potential time averaging in fossil assemblages, the variation in mammoth DMTA aligns with that of a geographically and temporally constrained modern population, indicating that microwear variability in fossil taxa is not necessarily greater than that observed in extant species and is consistent with the highly varied diets of modern African elephants.