A Review of locomotor diversity in mammals with analyses exploring the influence of substrate use, body mass and intermembral index in primates

Abstract

Locomotor diversity has meant many different things depending on the subject area or investigator. While no concrete definition of locomotor diversity is currently available, this has not stopped researchers from making a number of assertions about the underlying mechanisms that determine whether a species will have high or low locomotor diversity. Some of these claims include that: (1) arboreal primates demonstrate higher locomotor diversity than terrestrial species; (2) anatomically generalized and small-bodied primates demonstrate higher locomotor diversity than anatomically specialized and large-bodied taxa; and (3) primates demonstrate higher locomotor diversity compared to non-primate mammals. None of these claims have been tested in any sort of comparative framework. Using previously published locomotor repertoire data from 110 mammalian species, this study co-opted the Shannon–Wiener diversity index to calculate a singular measure of locomotor diversity. Phylogenetic analyses of these locomotor diversity indices reveal that within primates, small-bodied species demonstrate greater locomotor diversity than large-bodied taxa. However, this effect becomes non-significant when accounting for differences in substrate-use (i.e. arboreal vs. terrestrial). Anatomical specialization has no effect on locomotor diversity in primates. Furthermore, primates do not inherently have greater locomotor diversity than other mammalian taxa. Findings from this study suggest that movement on arboreal substrates requires all mammals, regardless of taxonomic affiliation, to demonstrate high locomotor diversity. These data further highlight the challenges faced by arboreal animals and raise the possibility that being able to switch fluidly and frequently between many different locomotor modes may be advantageous for animals moving in an arboreal milieu.