Kinematic Plasticity during Flight in Fruit Bats: Individual Variability in Response to Loading

Abstract

All bats experience daily and seasonal fluctuation in body mass. An increase in mass requires changes in flight kinematics to produce the extra lift necessary to compensate for increased weight. How bats modify their kinematics to increase lift, however, is not well understood. In this study, we investigated the effect of a 20% increase in mass on flight kinematics for Cynopterus brachyotis, the lesser dog-faced fruit bat. We reconstructed the 3D wing kinematics and how they changed with the additional mass. Bats showed a marked change in wing kinematics in response to loading, but changes varied among individuals. Each bat adjusted a different combination of kinematic parameters to increase lift, indicating that aerodynamic force generation can be modulated in multiple ways. Two main kinematic strategies were distinguished: bats either changed the motion of the wings by primarily increasing wingbeat frequency, or changed the configuration of the wings by increasing wing area and camber. The complex, individual-dependent response to increased loading in our bats points to an underappreciated aspect of locomotor control, in which the inherent complexity of the biomechanical system allows for kinematic plasticity. The kinematic plasticity and functional redundancy observed in bat flight can have evolutionary consequences, such as an increase potential for morphological and kinematic diversification due to weakened locomotor trade-offs.

Speed-dependent modulation of wing muscle recruitment intensity and kinematics in two bat species

“…Furthermore, the variation in aEMG is similar to that observed in metabolic power measurements for the same species, in some cases the same individuals, over this range of flight speeds (von Busse et al, 2013). Relatively high levels of individual variation have been observed previously in bat flight kinematics as well; for instance in response to added loads, Cynopterus brachyotis (Pteropodidae) modulated wingbeat kinematics in multiple distinct ways, including increased wingbeat frequency, increased camber and increased wing area (Iriarte-Diaz et al, 2012).…”

Influence of Wing Loading on the Selection of Prey Size in the Indian False Vampire Bat Megaderma Lyra

“…Wing loading is one of the important parameters that explain the flight characteristics of flying animals like bats (Iriarte-Díaz et al, 2012;Riskin et al, 2010). In the present study the wing loading of bats increases with increase in the body weight of frogs.…”

Gait kinetics of above- and below-branch quadrupedal locomotion in lemurid primates

“…In the trees, some animals have the ability to switch between above-and below-branch movement, and primates seem particularly adept at this behavior compared with other mammals (Table S1; but see Fujiwara et al, 2011). The idea that primates have a well-developed capacity for adjusting aspects of gait in order to effectively adjust to particular environmental circumstances is not new (Nyakatura et al, 2008;Schmitt, 1999;Vilensky and Larson, 1989), and this mechanical flexibility (Iriarte-Diaz et al, 2012;Wainwright et al, 2008) mechanisms that may have allowed for the great amount of locomotor diversity within the primate order (Schmitt, 2010;Vilensky and Larson, 1989). The finding that our animals have adapted the forelimb to be the primary propulsive and weight-bearing limb is reminiscent of bimanual suspension observed in brachiating and arm-swinging species, and may reflect the best possible biomechanical solution for primates to effectively move below branches.…”