Positional behavior, habitat use, and forelimb morphology of Père David’s Rock Squirrels Sciurotamias davidianus (Milne-Edwards, 1867) (Sciuridae, Rodentia) in the Qinling Mountains, Shaanxi, China

Rock piles, boulder stacks, and vertical cliffs with ledges represent terrestrial habitats with a complex and irregular network of variably positioned available substrates demanding special morphological and behavioral adaptations. In this context, the current study integrated forelimb functional morphometrics with data on the positional behavior of wild Chinese rock squirrels (Sciurotamias davidianus) in the Qinling Mountains, China. Similar information is important for understanding the adaptation of squirrels in specific habitats and is fundamental for elucidating shifts between arboreality and terrestriality within this group. This endemic Chinese squirrel used extensively rocky and cliffy habitats, with rocks as the primary substrate used. Quadrupedalism, claw climb, stand, and claw cling were the dominant modes. These findings indicate that its ecology is best described as petrous or saxicolous. In terms of forelimb morphology, Chinese rock squirrels displayed scansorial adaptations, associated with increased climbing activities. Considering the phylogenetic position of S. davidianus, our findings on the locomotor ecology and the morphological adaptations of the forelimb suggest that early marmotins were also scansorial. Moreover, Chinese rock squirrels likely retained the ancestral marmotin morphotype, in relation to the challenging habitats they exploit. Climbing and clinging adaptations are necessary to overcome the irregularities of rocky habitats and occasional use of trees, seeking shelter, and increasing access to differential resources. Similar research on other rock-dwelling mammals will help elucidate morphological and behavioral adaptations for exploiting this particular habitat.