Similar skull morphologies are found in seals and sea lions due to combat or to feeding style

Abstract

Many carnivorans exhibit sexual dimorphism in the skeleton, variously due to aggression, feeding styles, or other behaviors. Some species of seals and sea lions only use vocal displays between males for access to mates and territory, but other species engage in outright combat between individuals. Species with higher intraspecific aggression are characterized by skulls with more crest development for the emplacement of biting muscles than less‐aggressive species. Are these more prominent skull characteristics due entirely to levels of aggression?To answer this, we observed the placement of 26 bony landmarks on 14 species of seals and sea lions (n = 45, including 29 adult males and 16 adult females) using a geometric morphometric approach. We categorized these species by reported level of intraspecific aggression and diet. We found that skull proportions did differ between males from more‐aggressive and less‐aggressive categories. Particularly, we found that the skulls of most less‐aggressive species were characterized by little dimorphism between sexes, a more rounded cranium, and a relatively narrow zygomatic width. On the other hand, within more‐aggressive species, notable dimorphism in skull morphology existed between males and females. Most males from highly‐aggressive species developed more prominent nuchal and sagittal crests and wider zygomatic arches while females retained a more rounded skull morphology similar to less‐aggressive species.However, there were species that were categorized as being less‐aggressive but still possessed the more developed skull morphology of more‐aggressive species. For example, the Weddell seal and the leopard seal both developed wider zygomatic arches and taller cranial crests and they also lack notable intraspecific sexual dimorphism, but are not reported to engage in frequent combat. We propose that their skull morphologies are more likely due to the emplacement of larger muscles for feeding on larger prey.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.