Functional specialization in the forelimbs of two digging mammals: the American badger (Taxidea taxus) and groundhog (Marmota monax)

Limb muscles are often studied for their properties related to locomotion, but studies of architectural properties in limb muscles of animals specialized for other behaviors, such as digging, are less common. This study quantified muscle architectural properties in the forelimbs of badgers ( Taxidea taxus ) and groundhogs ( Marmota monax ), two digging species from phylogenetically different clades (Carnivora vs Rodentia), and estimated maximum force production and power output of their forelimb muscles. Architectural properties measured included: muscle mass, belly length, volume, physiological cross‐sectional area, fascicle length and pennation angle. Both species showed massive elbow extensors and digital flexors that together accounted for approximately 60% of intrinsic forelimb muscle mass. The elbow extensors displayed a low degree of pennation with longer fascicles, an architecture consistent with appreciable shortening capability and high power. The digital flexors showed relatively greater pennation and shorter fascicle lengths in addition to compartmentalization of muscle heads for both force production and range of contraction. These findings suggest both the elbow extensors and digital flexor muscles in badgers and groundhogs have the capacity for high force during scratch‐digging, while the elbow extensors are better suited for high power during rapid digging movements. URC #3‐11. Grant Funding Source : URC, Youngstown State University