In blue wildebeest, sexual selection affects the size of the horns of both males and females

(ORDO NEWS) — We usually think that in the wild, the most prominent secondary sexual characteristics—bright tails, tufted tufts, or spreading horns are most often owned by males who have to compete with each other for the right to mate with a female.

However, after examining a collection of blue wildebeest skulls from South Africa, the researchers found that in these ungulates, the size of the horns does not depend on sex – only on the size of the animal itself.

In horned animals, males “traditionally” wear the most impressive head growths – just remember the magnificent horns of red deer or fallow deer, in which females are hornless.

Even in reindeer and argali , in which both males and females have horns, the horns of males look disproportionately more impressive than those of their girlfriends.

Biologists explain this difference by sexual selection , which is based on the competition of males for the right to mate with females.

Since females do not need to fight each other for their cavaliers, their horns do not outgrow the “ecological optimum”, when their size is enough to protect against predators, but not anymore to impress a competitor.

Blue wildebeest , the most numerous African antelopes, also have horns in both males and females, but only males mark the boundaries of their territory and fight other males who have invaded their possessions.

It would seem logical to assume that the horns of male wildebeests will grow larger and more massive – however, after studying 75 skulls of these animals from the museum collection, the researchers did not find the expected dependence of the size of the horns on the sex of the wildebeest.

If we consider the shape of the horns, males and females clearly differ in their thickness, but when a correction for size is introduced, these differences completely disappear. In other words, if you take a small male and a large female blue wildebeest, then their horns will be almost the same.

In blue wildebeest sexual selection affects the size of the horns of both males and females 2
Digitized blue wildebeest skull used in the study

So far, scientists cannot say for what reason selection acts on the horns of female wildebeests: it is possible that females also fight with each other, for example, for access to the best pastures.


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