Growth and development of two species of bats in a shared maternity roost

Skeletogenesis was studied in two species of bats, Myotis austroriparius (southeastern brown bat) and Tadarida brasiliensis (Brazilian free-tailed bat), occupying a maternity roost in central Florida. These bats often use distinct maternity roost environments, so this provided an opportunity to examine differential patterns of long bone growth while fetuses and newborn developed under similar environmental conditions. Some differences in the timing of onset of osteogenesis were revealed in the bats, indicating that some elements of the hindlimb develop relatively more rapidly in T. brasiliensis than in M. austroriparius. Some variance was also noted, with similarity to other species previously studied by others, in the exact timing and elongation of both long bones, as well as carpal and tarsal bones. In contrast to many elements of the long appendicular skeleton of developing Mus musculus, the bats all exhibit relatively precocial patterns of osteogenesis during which cartilaginous precursors are replaced by bone tissue. The relative advanced timing of osteogenesis in select hindlimb bones of T. brasiliensis may account for its relatively low neonatal mortality compared to M. austroriparius newborn in the same roost.