Biomechanical and ecological relationships of wing morphology of eight Chilean bats

Abstract

In this study we compared the wing morphology of eight species of bats inhabiting Chile, including two previous studied species. We correlated the results with ecological information. Aspect ratio, wing span, wing area, wing loading and the second moment of area of humerus midshaft were estimated for the molossid Mormopterus kalinowskii, the phyllostomidae Desmodus rotundus and the vespertilionids Histiotus montanus, Histiotus macrotus, Lasiurus borealis, and Lasiurus cinereus. The free-tailed bats T. brasiliensis and M.kalinowskii and D. rotundus, without uropatagyum, showed a low wing area, but whilst the molossids showed large aspect ratios, that of D. rotundus was only moderate. Desmodus rotundus showed the lowest wing span (relative to the expected one) and the largest wing loading. The second moment of area of the humerus midshaft of M. chiloensis is lower than the expected values from the allometric predictions, suggesting poorer resistance to bending and torsional forces. All other vespertilionids, showed a high second moment of area of humerus. This may be explained by the highly expensive form of locomotion, especially in species with high parasite power as a consequence of their long ears. The high Ih of D. rotundus that can be explained by its high body mass which increase the torque produced by the weight and a low aspect ratio. The principal component analysis showed two orthogonal axes, the first correlated positively with the wing loading and negatively with the mass corrected wingspan and the second component with the aerodynamic efficiency parameter, AR. Four functional groups, one per quadrant, were described: (1) Desmodus rotundus, with high wing loading but low corrected wing span, was in the increased agility zone, with moderate power consumption during flight; (2) the molossids were located in the high speed flight and low total power zone, showing a high aerodynamic efficiency; (3) most of vespertilionids were in the zone of low speed but increased maneuverability, their aspect ratios and wing loading were relatively low; (4) Lasiurus cinereus was in the zone of fast speed flight and the low aspect ratio predicts an increased agility. The functional groups (2) and (3) exploit similar habitats but with different life styles, the molossids foraging in open areas at fast flight speed and the vespertilionids foraging in more wooded areas with maneuverable and slow flight. Desmodus rotundus clearly constitute a single group that may be related to flights from a far communal roost and their particular mode of locomotion.