Microwear in Modern Squirrels in Relation to Diet

Dental microwear consists of microscopic damage features on the occlusal surfaces of tooth enamel and reflects physical properties of the diet, as well as enamel structure and post-mortem history of the tooth. Microwear analysis has been used to infer the diets of extinct mammals through comparison of features on fossil teeth with those on teeth of living mammals with known diets. A method for documenting microwear of large mammals using a light microscope was developed as an alternative to approaches based on scanning electron microscopy. We adapted this method for investigating microwear features on squirrel teeth. Both modern and fossil squirrels occur in diverse terrestrial habitats and eat a range of herbivorous to omnivorous diets. We compared microwear features from upper molars of several modern species of frugivorous tree squirrels and omnivorous ground squirrels. We also examined fossil sciurids from the Miocene Siwalik sequence of Pakistan and a Pliocene locality in the central plains of the United States. We found significant differences in microwear features among modern squirrels of different diets and habitats, suggesting that microwear features can be used to infer the diets or preferred habitats of extinct species. Microwear features were preserved on some of the fossil specimens. A comparison of Pliocene Spermophilus rexroadensis to modern Spermophilus suggests a diet similar to that of the modern species examined. Microwear of Miocene Eutamias differed from the pattern in any of the living squirrels examined. The approach presented here holds strong potential for illuminating the trophic ecomorphology of small-mammal fossils. Sherry Nelson. Museum of Paleontology, University of Michigan, Ann Arbor, Michigan 48109, USA [email protected] Catherine Badgley. Museum of Paleontology, University of Michigan, Ann Arbor, Michigan 48109, USA [email protected] Emily Zakem School of Art and Design, University of Michigan, Ann Arbor, Michigan 48109, USA [email protected]