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Leaping is an important locomotor behavior for arboreal taxa such as primates, providing means to cross discontinuous substrates, escape predation, and/or capture prey. Primates that leap frequently have relatively longer hindlimbs than those taxa that leap less often. However, it is unknown if this pattern holds across a broader phylogenetic sample that includes non-primate arboreal taxa and non-primate specialized leapers. Here, we examine if relative hindlimb length and segmental proportions correlate with locomotor category across a sample of small-bodied (800g) mammals. Lengths of six hindlimb elements (summing to total hindlimb length) were measured on micro-computed tomography scans. Total hindlimb length was regressed against body mass to calculate relative hindlimb length. Segmental proportions were calculated as the ratio of femoral, tibial, and pedal (the sum of calcaneal, cuboidal, metatarsal, and phalangeal lengths) lengths to total hindlimb length. We found that while three arboreal/scansorial taxa (common marmosets, greater dwarf lemurs, and palm squirrels) exhibit short hindlimbs relative to their body mass, all other arboreal and scansorial taxa have relatively long hindlimbs. Most arboreal, scansorial, terrestrial, and fossorial taxa distribute length evenly across segments (femur, tibia, and pes each comprise 33% of total hindlimb length). Saltatorialists (e.g., jerboas and kangaroo rats) were the only locomotor group with exceptional proportions, with pedal segments contributing 38% of total hindlimb length. These results suggest to us that segmental proportions may distinguish specialized ricochetal hoppers from taxa that leap sporadically, while relative hindlimb length may predict general leaping ability across mammals.
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A simple skeletal measurement effectively predicts climbing behaviour in a diverse clade of small mammals
Abstract Arboreal locomotion allows access to above-ground resources and might have fostered the diversification of mammals. Nevertheless, simple morphological measurements that consistently correlate with arboreality remain indefinable. As such, the climbing habits of many species of mammals, living and extinct, remain speculative. We collected quantitative data on the climbing tendencies of 20 species of murine rodents, an ecologically and morphologically diverse clade. We leveraged Bayesian phylogenetic mixed models (BPMMs), incorporating intraspecific variation and phylogenetic uncertainty, to determine which, if any, traits (17 skeletal indices) predict climbing frequency. We used ordinal BPMMs to test the ability of the indices to place 48 murine species that lack quantitative climbing data into three qualitative locomotor categories (terrestrial, general and arboreal). Only two indices (both measures of relative digit length) accurately predict locomotor styles, with manus digit length showing the best fit. Manus digit length has low phylogenetic signal, is largely explained by locomotor ecology and might effectively predict locomotion across a multitude of small mammals, including extinct species. Surprisingly, relative tail length, a common proxy for locomotion, was a poor predictor of climbing. In general, detailed, quantitative natural history data, such as those presented here, are needed to enhance our understanding of the evolutionary and ecological success of clades.
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- PAR ID:
- 10118083
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Biological Journal of the Linnean Society
- ISSN:
- 0024-4066
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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