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Keywords:

  • brain volume;
  • sociality;
  • skull adaptations;
  • independent contrasts;
  • hypercarnivory

Abstract

The ways in which the taxonomic differences in morphology, behavior or life history relate to each other have been used regularly to test ideas about the selective forces involved in their evolution. Canid species vary significantly in diet, hunting techniques, sociality and cranial morphology. The main goal of this study is to test and explore the possible correlation between bite force and brain volume in canids. For that, we calculated the bite force based on the beam theory, and the brain volume based on three cranial measurements. The species with biggest values of bite force quotient (BFQ) were Speothos venaticus (162.25), Cuon alpinus (129.24) and Lycaon pictus (124.41) due to several adaptations acquired along with hypercarnivory. Species with the highest values of brain volume quotient (BVQ) were S. venaticus, Cu. alpinus and L. pictus with, respectively, 141.35, 139.01 and 131.61, possibly due to the same adaptations that resulted in their bigger BFQ. The highest values of bite force belonged to Canis lupus (830.51 Pa), L. pictus (719.03 Pa) and Ca. rufus (530.52 Pa) and the smallest values belong to Urocyon littoralis (98.14 Pa), Vulpes macrotis (92.53 Pa) and V. zerda (72.6 Pa). Ca. lupus, L. pictus and Chrysocyon brachyurus possess the largest brain volumes with respectively 159.29, 146.94 and 120.84 mm3 and the smallest values belong to Nyctereutes procyonoides (28.2 mm3), V. rueppelli (27.86 mm3) and V. zerda (20.65 mm3). The independent contrasts correlation showed that there is no correlation between BVQ and BFQ (r = 0.14/P = 0.46), as well as no correlation between BFQ and BF (r = 0.22/P = 0.26), which indicates the efficiency of the size correction. Bite force and brain volume estimates are much higher in the group hunting hypercarnivores (Lycaon, Cuon and Speothos) and only these showed correlation between BFQ and BVQ. Our results indicate that cranial adaptations for hypercarnivory also influence braincase size.