Adaptations to cursoriality and digit reduction in the forelimb of the African wild dog (Lycaon pictus)

Abstract

The African wild dog (Lycaon pictus), a rare canid native to southern and eastern Africa, lives and hunts in complex social groups. It is currently classified as Endangered on the IUCN Red List of Threatened Species, with approximately 1400 mature individuals present in the wild. L. pictus is distinct among canids in lacking a digit I or “dew claw” and in its use of exhaustive predation to capture its prey instead of speed, strength, or stealth. These behavioral and morphological traits suggest a potentially unique set of adaptations. This study is the first detailed anatomical description and functional analysis of the forelimbs of L. pictus.The forelimb myology of L. pictus is generally similar to other canids; however, it shows some notable exceptions. While a complete digit I is absent in L. pictus, a vestigial first metacarpal is present, resulting in changes to insertions of mm. extensor digiti I et II, abductor (et opponens) digiti I, and flexor digiti I brevis. M. triceps brachii caput laterale had a larger origin in L. pictus compared to other carnivorans, and m. triceps brachii caput longum had an additional accessory head. Electromyographic (EMG) studies have shown this muscle is active during the stance phase of trotting and galloping and is important for storing elastic energy during locomotion. Mm. anconeus, brachialis, and flexor carpi ulnaris caput ulnare all had more extensive origins in L. pictus than other canids. In domestic dogs, these muscles have a relatively high proportion of Type 1 (slow‐twitch) fibers and are important for posture and elbow stability. Statistical analyses of the quantitative muscle data reveal similar proportions of antebrachial muscle groups to other large‐bodied carnivorans. However, L. pictus has relatively smaller wrist rotators than any other included taxon, suggesting a need for stability over rotatory movement in the carpus of L. pictus.We interpret these differences in size and attachments of muscles in L. pictus compared to other canids as adaptations for long distance running in this highly cursorial species, likely important for exhaustive predation. Absence of a digit I in L pictus, typically used to reduce torque during quick turns and for lightly gripping onto objects, may be related to a reduced need for gripping and quick agile movements in its cursorial lifestyle.Support or Funding InformationThis project was funded by Midwestern University, including a Kenneth A. Suarez Summer Research Fellowship to RK.