Anatomical correlates to scratch digging in the forelimb of European ground squirrels (Spermophilus citellus)

In northern Greece, European ground squirrels or sousliks (Spermophilus citellus) construct complex burrow systems by scratch-digging behavior. The present study investigated the presence of anatomical characters related to digging in the forelimb of S. citellus. The forelimb of 3 preserved specimens was dissected and several qualitative and quantitative variables on selected muscles were collected. In addition, selected osteological variables and indices were calculated in a sample of 207 sciurid postcrania representing 14 burrowing and nonburrowing genera. Both analyses showed that the forelimb of S. citellus was characterized by enlarged and powerful shoulder retractors, well-developed arm retractors with distal insertions upon a relatively robust humerus, enlarged elbow extensors associated with a long olecranon, and dominant pronators and carpal and digital flexors. Similar morphology is also encountered in other semifossorial mammals, indicating significant adaptations to scratch-digging behavior. However, the characters examined designate a more compromised morphology, associated with the generalized postcranium of sciurids. On the other hand, S. citellus exhibits a more specialized forelimb morphology, compared to that of other marmotines, for a semifossorial way of life, in association with the sub-generic derived morphology, lack of social interactions, and exploitation of a habitat with harder soils. © 2006 American Society of Mammalogists.