Forelimb and hindlimb loading patterns during quadrupedal locomotion in the large flying fox (Pteropus vampyrus) and common vampire bat (Desmodus rotundus)

Abstract

Adaptations for flight have greatly modified the forelimbs and hindlimbs of bats compared to other mammals so that terrestrial and/or above branch quadrupedal locomotion is awkward and unusual for most species. However, suspensory quadrupedal gaits are quite common for bats, but little is known about this type of movement and no data are available on how these animals load their limbs and support the body. Values for vertical, fore‐aft and mediolateral peak forces were collected for the forelimb and hindlimb during suspensory quadrupedal locomotion in the large flying fox (Pteropus vampyrus) and common vampire bat (Desmodus rotundus), and during terrestrial locomotion in the common vampire bats. During suspensory quadrupedal locomotion in both species, the hindlimbs serves as the primary weight‐bearing and braking organ, whereas the forelimb has a reduced weight‐bearing role and acts as the primary propulsive limb. Mediolateral forces are dominated by medially directed forces by the animal that likely serve to help maintain ‘grip’ while moving below supports. Kinetic patterns of terrestrial locomotion in the common vampire bat are completely opposite, and resemble data that has been reported for most mammals with the exception of relatively high lateral forces. The data presented here add to the growing body of knowledge that suspensory quadrupedal locomotion does not represent a neuromuscular mirror to non‐suspensory quadrupedal gaits. Furthermore, this study demonstrates that suspensory quadrupedal gaits are not the same across mammals, and species have adopted multiple mechanical strategies for moving quadrupedally below a support.

Variation in limb loading magnitude and timing in tetrapods

“…2). All data collection protocols were approved by the relevant IACUCs and followed previously published methods (Andrada et al, 2015;Bishop et al, 2018;Butcher and Blob, 2008;Granatosky, 2018;Granatosky and Schmitt, 2019;Granatosky et al, 2016Granatosky et al, , 2018bMcElroy et al, 2014;Nyakatura et al, 2014;Nyakatura et al, 2019;Schmitt, 1999;Schmitt and Hanna, 2004;, so are only summarized below. Limb loading data collected from common quails (Coturnix coturnix) by Andrada and colleagues (2014a) were downloaded from the Dryad Digital Repository (Andrada et al, 2014b).…”

Comparison of spatiotemporal gait characteristics between vertical climbing and horizontal walking in primates

“…All procedures were approved by the appropriate Institutional Animal Care and Use Committee (IACUC; West Virginia School of Osteopathic Medicine: 2007Medicine: -1, 2008Medicine: -1, 2009; Duke University: A104-09-03; A130-07-05, A270-11-10; State University of New York: 91-94-0131). The data collection procedures have been described extensively elsewhere (Granatosky, 2018a;Granatosky et al, 2016aGranatosky et al, , 2018Hanna et al, 2017) and will be simply summarized here. Subjects were encouraged by food reward to climb a pole attached to a wall (climbing trials) or the ground (walking trials).…”

“…steady-state locomotion) throughout the climbing or walking trial, in which a full forelimb and/or hindlimb contacted the pole, and which exhibited a symmetric footfall sequence were retained for analysis. For all data, steady-state locomotion was determined by a combination of video, force and symmetry data following previously established methods (Byron et al, 2017;Granatosky et al, 2016aGranatosky et al, , 2018aHanna et al, 2017). For all trials, symmetry was determined using the methods of Cartmill et al (2002), with a ±10 criterion such that the timing of opposite limb touchdown could vary between 40 and 60% of the stride cycle (50% indicates the timing of opposing limbs is exactly 1/2 of the cycle).…”

“…For data collected from a single laterally positioned camera (i.e. horizontal walking data on D. madagascariensis, S. sciureus, M. fascicularis and A. nancymaae), the subject's speed was calculated by digitizing a point on the subject's head over the entire stride based on a known distance on the runway [see Granatosky (2018a), Granatosky et al (2016a) and Granatosky et al (2018) for details]. From video recordings, we considered diagonality, gait type, percentage of limb support, stride duration, forelimb and hindlimb duty factor, stride length, speed, and stride frequency (see Table S2 for information about variables).…”

“…Second, quadrupedal primates exhibit relatively larger limb excursions, resulting in relatively long stride distances (Larson et al, 2000(Larson et al, , 2001Schmitt, 1998). Finally, most primates exhibit functional differentiation between the forelimbs and hindlimbs, where the hindlimb serves as the primary support and propulsive limb (Demes et al, 1994;Granatosky et al, 2018a;Hanna et al, 2017;Kimura et al, 1977;Schmitt and Hanna, 2004;Schmitt and Lemelin, 2002). It remains unresolved what selective factors initially drove primates to adopt these unusual locomotor characteristics.…”