NEOICHNOLOGY OF BATS: MORPHOLOGICAL, ECOLOGICAL, AND PHYLOGENETIC INFLUENCES ON TERRESTRIAL BEHAVIOR AND TRACKMAKING ABILITY WITHIN THE CHIROPTERA

Abstract

Among living mammals, bats (Chiroptera) are second only to rodents in total number of species with over 1100 currently known. Extant bat species occupy many trophic niches and feeding habits, including frugivores (fruit eaters), insectivores (insect eaters), nectarivores (nectar and pollen-eaters), carnivores (predators of small terrestrial vertebrates), piscivores (fish eaters), sanguinivores (blood eaters), and omnivores (eat animals and plant material). Modern bats also demonstrate a wide range of terrestrial abilities while feeding, including: (1) those that primarily feed at or near ground level, such as the common vampire bat (Desmodus rotundus) and the New Zealand short-tailed bat (Mystacina tuberculata); (2) those rarely observed to feed from or otherwise spend time on the ground; and (3) many intermediate forms that demonstrate terrestrial competency without an obvious ecological basis. The variation in chiropteran terrestrial ability has been hypothesized to be constrained by the morphology of the pelvis and hindlimbs into what are termed types 1, 2, and 3 bats. This thesis examines the terrestrial ability of a number of species of Latin American bats belonging to the families Emballonuridae and Phyllostomidae that represent many of the ecological niches and all three pelvic and hindlimb morphotypes. Within the species studied, terrestrial ability seems to be partially constrained by pelvic and hindlimb morphotype. The Type 3 bat Desmodus rotundus performed such typical quadrupedal gaits as the bound and the diagonal sequence walk. Among Type 1 bats, only Carollia perspicillata performed the diagonal sequence walk, and most Type 1 bats were restricted to an uncoordinated, asymmetrical gait herein termed the breaststrokelike crawl. Type 1 bats also frequently performed a nonambulatory behavior, termed the searching behavior, which produced distinctive tracks. Type 2 bats in this study performed terrestrial behaviors more similar to those of Type 1 bats than to Type 3. The searching behavior produces distinct radial pes track patterns, and complete trackways are indicative of well-coordinated gaits like the bound. Trackways produced by all bats shared (1) elongate manus tracks, which may include the impressions of either digit I, the wrist and distal forearm, or both, and (2) pes tracks consisting of three or five parallel digit marks. These tracks and trackways can be used to establish criteria for identification of bat trace fossils in the geologic record, and eventually used for comparisons to pterosaur trace fossils to better understand their locomotor behaviors. As the only extant quadruped capable of powered flight, bats are likely the closest living analog for understanding pterosaur locomotion.