The African wild dog, Lycaon pictus, is classified as Endangered by the IUCN, with as few as 1400 mature individuals currently surviving in the wild, due primarily to habitat fragmentation. African wild dogs are unique among canids in relying upon exhaustive predation, in which they chase prey to exhaustion rather than employing hunting strategies centered around speed or stealth. They are also extremely nomadic, with packs traveling up to 50km per day. Given these behaviors, it has been hypothesized that their hindlimb musculature will exhibit adaptations for this cursorial lifestyle. However, despite their dwindling numbers, detailed documentation regarding their hindlimb anatomy has not yet been published. Additionally, unlike other species in the canid family, African wild dogs lack a fifth pedal digit or “dewclaw”. The absence of this digit on the hindfoot likely alters the structure, position, and functions of the musculature of the hindlimb relative to other canids. This study involved detailed dissection, photo documentation, and descriptions of the hindlimb musculature and neurovasculature of Lycaon pictus. Throughout the study, muscles were described and weighed, and their origins and insertions were mapped for comparative purposes with other canid taxa.

Findings revealed similarities in hindlimb musculature of the African wild dog compared to other canids, including the domestic dog (Canis familiaris). However, some interesting differences were noted. In comparison to other canids, the strength and thickness of the fascia investing the lower extremity muscles were notably increased. The tensor fascia lata (TFL) muscle was enlarged in mass and apparent size within the lateral aspect of the fascia lata. The fascia lata of the TFL coursed deep to and was invested with the rectus femoris. The rectus femoris was also demarcated with a separation from the other quadriceps femoris muscles, and continued to its insertion onto the patella mostly in isolation without compartmental fusion with the tendon of the vastus muscles. The vastus intermedius composed a majority of the central portion of the quadriceps tendon with some laterally investing muscle fibers from the vastus lateralis. These muscular configurations may permit a functional decoupling of the hip flexor and knee extensor components of the thigh musculature, such that the TFL + rectus femoris act to flex the hip, while the vasti act separately to extend the knee. This arrangement may function as a method of energy conservation during prolonged locomotion. Biceps femoris and abductor cruris caudalis inserted onto the crural fascia further distally down the crus, and were similarly noted to be more heavily invested in fascia than other canids. The muscles contributing to pes anserinus were each tightly invested in fascia, and attached in the typical order onto the medial aspect of the proximal tibia. Gracilis also inserted via an additional tendon that coursed inferiorly to insert onto the distal 1/3 of the tibia. The key differences identified in this study compared to other published canid species likely reflect adaptations that facilitate the unique cursorial and nomadic habits of African wild dogs.

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.