No apparent ecological trend to the flight-initiating jump performance of five bat species

Abstract

SUMMARYThe jump performance of five insectivorous bat species (Miniopterus schreibersii, Myotis blythii, Myotis capaccinii, Myotis myotis and Rhinolophus blasii) was filmed using a high-speed camera. All study bats jumped using a similar technique, with the wing musculature providing the force. The bats jumped off the wrist joint of their wings, typically with their feet already off the ground. Contrary to expectations, jump performance did not correlate with ecology and was instead strongly determined by body size. In general, the larger bats produced more jump force, left the ground at higher speeds and jumped higher than the smaller bats. The differences in force production disappeared when the data were corrected for body size, with the exception of Myotis capaccinii, which produced significantly less force. Scaling of jump performance with body size measured here was compared against two existing muscle performance scaling models. The model suggesting that muscle contraction velocity is proportional to muscle length was better supported than that based on muscle cross-sectional area. Both models, however, failed to accurately predict the scaling of jump forces, with the slope of the relationship being significantly steeper than predicted, highlighting the need for further investigations of vertebrate muscle performance scaling. The results of this study indicate that a bat's jumping ability is a secondary locomotor ability that uses the strongly selected-for flight apparatus with no apparent ecological trend present, i.e. flight so dominates bat locomotor morphology that other locomotor abilities tend to be derivative.

Excepting Myotis capaccinii, the wings' contribution to take-off performance does not correlate with foraging ecology in six species of insectivorous bat

“…Indeed, the jump performance of the same study bats (excluding Rhinolophus euryale ) was previously reported by Gardiner and Nudds (Gardiner and Nudds, 2011), but please note that none of the wing induced take-off performance data has been published previously. Miniopterus schreibersii is an aerial hawker feeding in open areas at relatively high altitudes (Norberg and Rayner, 1987).…”

“…Alternatively, slowing down and then accelerating back to cruising speed may be essential for some prey capture strategies such as gleaning from both vegetation and water, or for negotiating cluttered environments. Several studies have focussed on take-off performance and accelerating flight in birds (Askew et al, 2001; Berg and Biewener, 2010; Earls, 2000; Jackson and Dial, 2011; Tobalske and Dial, 2000; Tobalske et al, 2004), but far fewer studies have examined bat take-off (Altenbach, 1979; Gardiner and Nudds, 2011; Schutt et al, 1997). In contrast to birds where the wings only play an aerodynamic role, bat wings have two separate functions during a two-phase take-off (Gardiner and Nudds, 2011).…”

“…Several studies have focussed on take-off performance and accelerating flight in birds (Askew et al, 2001; Berg and Biewener, 2010; Earls, 2000; Jackson and Dial, 2011; Tobalske and Dial, 2000; Tobalske et al, 2004), but far fewer studies have examined bat take-off (Altenbach, 1979; Gardiner and Nudds, 2011; Schutt et al, 1997). In contrast to birds where the wings only play an aerodynamic role, bat wings have two separate functions during a two-phase take-off (Gardiner and Nudds, 2011). The initial jump phase using the wings as levers to jump off the ground (which has been the focus of studies so far) and then the accelerating flight phase using the wings as aerodynamic surfaces (the focus of this study).…”

“…bats that forage on or near the ground) was not significantly better than hawking bats (i.e. bats that catch prey on the wing) (Gardiner and Nudds, 2011). Bats use their wings as levers to catapult themselves into the air when taking-off from the ground and wingspan ( b ) in flying vertebrates is tightly constrained by aerodynamic requirements to a geometric scaling with body mass i.e.…”

“…M b 1/3 (Norberg, 1990; Norberg and Rayner, 1987; Nudds, 2007; Rayner, 1988). Hence, the fact that the levers bats use to catapult themselves into the air are similar among species, coupled with the fact that a bat's jumping ability is derivative, being enabled by the strongly selected for flight apparatus, may explain the finding that mass-specific jump performance in five species of bats was similar with no ecological trend apparent (Gardiner and Nudds, 2011). In contrast to wingspan ( b ), there is considerable variation in other features of bat wing-morphology (e.g.…”