Sexy Males Live Less!

Being the hunk in the group surely brings a lot of sexual advantages for a male. For animals and for humans too. But a new research shows that having huge muscles comes with a severe downside. At least in hoofed mammals, large bucks and bulls have relatively small teeth, which wear out rapidly and impede their proper feeding, a fact translated in a premature death.

The shorter life span of large hoofed species males is a well-known fact. In 2005, a team led by Juan Carranza, a behavioral ecologist at the University of Extremadura in C�ceres, Spain, revealed that molars in male red deer were relatively smaller than in the case of the females (outcome till 3 times in size by the males) and that this difference was linked to a shorter lifespan.

The team imagined that the size difference was caused by a different wearing rate in male and female, possibly linked to different feeding habits between the genders. But the research also suggested that male teeth were never that large.

To check this idea, the team gathered data on body size and measurements of the chewing surfaces of molars and premolars from museum specimens in the case of hoofed mammals, a total of 123 species, about 50 % of all living ungulate species. The data included species in which males and females were about the same size, like in roe deer, but also the more prevalent case of greatly outsized males, including the North-African Barbary sheep and the Nilgai, an Indian antelope.

In the case of males and females of similar size, so were their teeth. But in case of pronounced sexual dimorphism (physical differences between sexes), tooth size difference was incredibly small. That's why females had much larger chewing surfaces than the males of the same species.

The teeth probably didn't follow the same evolutionary growth rate with the rest of the body because they did not increase males' success on competing for females. Once they wore down and turned ineffective, the animal general health dropped, but it seems that these males, already too old to compete with younger rivals, had no biological reason for longer life. Anyhow, these males father more offspring during their life.