Diet reconstructions for end-Pleistocene Mammut americanum and Mammuthus based on comparative analysis of mesowear, microwear, and dental calculus in modern Loxodonta africana

摘要

We analyse mesowear, microwear, and dental calculus for end-Pleistocene Mammut and Mammuthus from North America, and modern Loxodonta africana to reconstruct diet. These three methods allow both short- and long-term diets to be distinguished. As microwear analysis shows a negative correlation between the numbers of pits and scratches counted, the proportions of pits/(pits + scratches) were used for analyses rather than gross counts. The three types of analyses confirm that modern Loxodonta africana are grazers or mixed-feeders. Microwear analysis demonstrates that end-Pleistocene Mammut were primarily browsers but may have changed their diets opportunistically or seasonally to graze. Mesowear analysis of end-Pleistocene Mammuthus indicates a grazing diet, but microwear analysis indicates a mixed-feeding diet. Dental calculus analysis demonstrates that all three species were mixed-feeding to varying degrees. Results show that extinct proboscidean diet was more complex than previously thought, and may contradict previous work suggesting that Mammut were browsers and Mammuthus were grazers. Using mesowear and microwear, we found no significant differences in pre- and post-glacial diet for fossil proboscideans. However, using dental calculus, we found that for pre-glacial specimens there was a larger proportion of tiny (i.e. less than 8 mu m wide) grass starch granules, whereas for post-glacial specimens there is a larger proportion of large (i.e. greater than 20 mu m wide) grass starch granules with lamellae, suggesting with a shift in Mammut and Mammuthus diet during the end-Pleistocene. Specimens commonly had different dietary signals depending on the method utilized, suggesting that a multi-faceted approach is required to fully elucidate proboscidean diet.