Skull Shape predicts arboreal activity of Sigmodontinae rodents

Brain enlargement is an adaptation in animals that use the space in three-dimensions and need to integrate information of complex environments. We directly tested for the relation between cranial shape and arboreality of 11 neotropical Sigmodontinae rodents. Geometric morphometrics analysis considering both dorsal and lateral views of the cranium showed that arboreal rodents present more expanded crania, suggesting larger brains. The dorsal view showed a general cranial expansion in arboreal rodents, whereas the lateral view showed a more rounded and posteriorly expanded cranium. This later suggests a larger cerebellum, which is responsible for orientation and sense of balance. Our study provides evidence that the cranial shape can be used as a proxy to infer arboreal activity of sigmodontine rodents. Moreover, the observed differences in cranial shape between arboreal and terrestrial species are probably related to brain enlargement in the former driven by the need to cope with a 3-dimensional environment.

Our new study is now published in the Journal of Zoology and can be accessed at: https://doi.org/10.1111/jzo.12659

Relationship between skull morphology and arboreal activity level of 11 species of sigmodontine rodent species. Species in the left are the arboreal Rhipidomys macrurus (top) and the terrestrial Calomys expulsus.