Small Teeth, Shorter Life

Female hoofed animals, such as deer, tend to outlive their male counterparts—and differences in teeth size might have something to do with it, a new study suggests.

The study, published in the September issue of The American Naturalist, finds that male ungulates have smaller molars relative to body size and wear out sooner than the females' bigger, longer-lasting chompers.

Researchers Juan Carranza of the University of Extremadura in Spain and Javier Pérez-Barbería of the Macaulay Institute in the United Kingdom, compared body and teeth sizes of males and females of 123 species of ungulates and found that for species where a single male has many females and where the males and females are different sizes, the rate of increase of dental size was lower than that of body size. As a result, smaller teeth were produced in males.

Natural selection favors reproduction over survival. In ungulate species where there is intense competition for access to females, the male's reproductive success is determined within the few years where they can win contests and maintain their dominance.

Male ungulates generally don't increase their mating success by living longer after their prime, so it's possible that natural selection didn't produce larger, more durable teeth since having bigger molars didn't increase their success in the mating department.

"These findings,” the authors state, “provide us with interesting insights into how natural and sexual selection design our bodies and their longevity."

—LiveScience Staff 

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Credit: Juan Carranza