A negative association between horn length and survival in a weakly dimorphic ungulate

Brains vs Brawn: Relative brain size is sexually dimorphic amongst weapon bearing ruminants

Here, we investigate the relationship between relative brain size and sexual weapons in ruminants. In most cases, sexual weaponry is heavily male-biased, and costs resulting from growing, maintaining, or wielding weapons will be suffered primarily by males. We used comparative phylogenetic analyses to test whether increased investment in sexual weapon size (tusks, antlers, and horns) across four families (Tragulidae, Moschidae, Cervidae, and Bovidae) was associated with decrease in relative brain size, and whether the difference in weapon investment relative to conspecific females led to sexual differences in relative brain size. We found no relationship between relative brain size and relative weapon size within males or females, but when we compared males directly to conspecific females, we found that as males possessed larger weaponry, they had smaller brain sizes, regardless of weapon type. Our finding suggest male investment in some types of elaborate weapons could be related to male reduction in larger brains.

Face markings in Northern chamois: cues of dominance?

Black and white face markings in Artiodactyls are thought to be broadly associated with intraspecific communication. Evidence-based studies on the fine-scale mechanisms of signaling, however, are scant. The occurrence of black and white face markings is one of the most distinctive features of the Northern chamois Rupicapra rupicapra. Although their function is unknown, they might possibly signal fighting abilities: if so, the intensity of face color contrast should positively correlate with traits involved in aggressive contests, i.e. body mass and horn size. We collected data on face marking ‘blackness’ as a proxy of color contrast, dressed body mass and horn length on 103 chamois of either sex harvested during the hunting season of 2019 in the central Italian Alps. To investigate the relationship between color contrast and sex-specific body mass and horn length, we fitted an ordinal multilevel regression model in a Bayesian framework. Contrast score positively associated with increasing body mass in both sexes, but this relationship was much stronger in females than in males. Contrast score positively related with horn length in males but not in females. Our results offer some first insights into the potential correlates of chamois facial mask, suggesting that face markings might provide age-specific cues of mass-based dominance in females, while their role in males appears more uncertain. Behavioral studies on marked or hunted individuals in different environmental settings are necessary to confirm these findings, and provide further understandings of face color patterns in chamois.