PARENT SESSION

Morphology -- Session Chair: Stuart Landry-- Van Duzer Theater

FORELIMB MORPHOLOGY AND FUNCTION IN THE BLACK-FOOTED FERRET, MUSTELA NIGRIPES. Virginia Naples^1,2. ¹ Division of Vertebrate Zoology, Osteoprep Laboratory, National Museum of Natural History, Washington, D. C.; ² Department of Biological Sciences, Northern Illinois University, DeKalb, Illinois.

ABSTRACT- The black-footed ferret is the most endangered mammal in North America, probably as a result of it's unique subterranean predatory lifestyle, and near total dependence on prairie dogs as prey. Although black-footed ferrets share the slender, elongate mustelid body form, their habit of spending much of their lives in cramped prairie dog burrows has subtlely but significantly affected their morphology. Ferrets must be able to run, capture and kill prey in the cramped space of tunnels dug by the prairie dogs. This restricted habitat requires the ferrets to run with their elbows and knees bent and held close to the body. Capturing and killing prey that may outweigh them has selected for alteration of the typical ferret movement patterns. Forelimb specializations that distinguish black-footed ferrets from the closely-related domestic ferret, and the more distally related mink, include some relatively more robust features of the scapula, such as an enlarged metacromion process. The M. omocervicalis inserts on the metacromion, and in black-footed ferrets is a more forceful retractor and depressor of the neck, and therefore, the head, than in closely related species. Enhanced head depression capabilities in black-footed ferrets are coupled with a reoriented transverse process of the atlas (angled downward posteroventrally) that allows increased anterior scapular rotation and protraction by contraction of the M. atlantoscapularis. This muscle arrangement increases the ability of the ferret to flex the forelimb, an adaptation likely to enhance the ability to maintain a grip on large prey for the length of time necessary for strangulation to occur.

KEY WORDS: Mustela nigripes, morphology