PRELIMINARY REPORT ON THE TRACKWAY-MAKING ABILITY OF BATS (PHYLLOSTOMIDAE, CAROLLINAE)

Little is known about bat trackways and trackmaking abilities, and no detailed neoichnological studies have been published. Modern bats (Order: Chiroptera) occur on every continent except Antarctica. The oldest known microchiropteran bat is from the Eocene of France, whereas the oldest known megachiropteran bat (i.e., flying foxes) is from the Oligocene of Italy. No bat tracks or trackways have been found in the rock record and, therefore, nothing is known about the trackmaking ability of ancient bats. Equally important is that bats, as quadrupedal flyers, may be an appropriate proxy for pterosaur locomotion; however, numerous neoichnological experiments would need to be run to determine which bat genera, if any, are appropriate analogs. Our initial trackway experiments with bats used the neotropical fruit bat Carollia perspicillata for locomotion trials on moist medium-grained sand. We used a Plexiglas cover placed over a tray of sand for the locomotion trials and digitally recorded video of the bats crawling. Resulting trackways were cast using dental plaster. C.perspicillata exhibited at least four different crawling behaviors, the most common being an alternating left manus (LM) – right pes (RP) – right manus (RM) – left pes (LP) pattern. C. perspicillata also frequently used a “swimming” motion, in which the bat brought both forelimbs forward simultaneously and dragged the body forward, with minimal help from the hindlimbs. The bats also exhibited a hybrid of these two methods, dragging both hindlimbs as well as one forelimb, while pulling the body forward with the opposite forelimb. One bat appeared to hop using a method similar to the “swimming” method of locomotion. The bat simultaneously extended both forelimbs; however, neither manus nor pedes were in contact with the medium before the forelimbs were fully extended. Trackways produced do not readily appear as though they were not produced by bats but do reflect the locomotion patterns observed. Individual C. perspicillata track morphology appears to be a poor comparison for pterosaur locomotion based on the rotated hip joint and backward-pointing feet; however, more studies involving adept walkers, such as the common vampire bat (Desmodus rotundus), could prove to be an appropriate analog for pterosaur locomotion and such trackways as Pteraichnus.