Foot morphology and locomotor behaviour of squirrels in Gabon rainforests

Equatorial rain forests of Gabon contain nine species of squirrels that exploit different environments along a vertical gradient from the ground to the forest canopy. This study aims at identifying morphological traits of the hind foot that are related to environment preferences, using seven of the nine species. The morphology of the foot was defined by the coordinates in three dimensions of twenty five landmarks on the foot. These were analysed using Procrustes analysis and principal component analysis (PCA). The first axis of the PCA corresponded to a gradient of adaptation to tree-dwelling, in relation to foot morphology. Species living on the ground had a longer, narrower and thinner foot, adapted to horizontal locomotion on the ground. Species with an arboreal habitat had a shorter, wider and thicker foot, adapted to vertical locomotion. The second axis of the PCA could be interpreted in terms of phylogeny.