Brains vs Brawn: Sexual dimorphism in brain size and sexual weapon size�in ruminant mammals |
Theodore Stankowich1, Nicole Lopez1,2, Jonathon Moore Tupas1. 1California State University Long Beach, Long Beach, California, United States; 2University of Montana, Missoula, Montana, United States |
We investigated 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 phylogenetic comparative 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 invested more in larger weaponry relative to females, they had smaller brain sizes relative to females, regardless of weapon type. Our findings suggest greater male investment in some types of elaborate weapons could be related to increased investment in female brain size for life in more socially complex groups or enhanced assessment of males’ larger weapons.� |