Peter Cairns/Minden Pictures

To grow bigger antlers, these elk risk life and limb

For female elk, there’s nothing sexier than two 250-kilogram male suitors tussling for her favor, their 1.2-meter-tall antlers locked in a battle of strength and determination. But growing such powerful racks is risky, according to a new study, because males must shed their previous headgear early in the season to do so—putting them at risk of being killed by wolves.

Elk regrow their racks every year, and the longer they have to do this, the bigger—and better—those antlers are when the fall mating season comes around. Some drop them by early March, whereas others—particular young ones—keep them through April. No one really knew why all elks don’t drop their antlers sooner.

Now, wildlife biologists chronicling the lives of wolves and their prey in northern Yellowstone National Park may have the answer. A dozen years of data suggest wolves tend to target males who have lost their antlers. So, the earlier a male casts off his headgear, the greater his risk of getting eaten, the team reports today in Nature Ecology and Evolution. These males tend to be the healthier males in the herd, so the finding runs counter to the conventional wisdom that predators focus on the weaker, sicker members.

The study illustrates a difficult choice male elk have to make every year, one that likely keeps the size of the population’s antlers in check. Such compromises, the authors say, may be common in the animal kingdom.