Male elk need large and elaborate antlers to battle with rivals in autumn for mating opportunities, and to grow them they must shed last year鈥檚 antlers early in spring. But doing so seems to leave them vulnerable to predator attack.
The discovery came from studies of wolves hunting elk each March in Yellowstone National Park from 2004 to 2016. 鈥淲e suggest that wolves 鈥� formerly everywhere across the northern hemisphere 鈥� have shaped the timing of when elk and [their relatives] shed their antlers,鈥� says Matthew Metz of the University of Montana in Missoula, who led the study.
Like other deer species, elk shed their antlers after competing for females during the breeding season. In March, when the breeding season is over for Yellowstone elk, some males begin the shedding process.
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Metz and his colleagues found that the elk that shed their antlers earliest were typically the fittest individuals, as measured by the amount of fat in the marrow of their leg bones, and were also older and more dominant. By shedding their antlers earliest these males also gained an edge over their rivals because they have more time to grow larger, more complex and more intimidating antlers in time for the fight for mates that begins in September or October.
But there was a trade-off: elk who shed early also turned out to be most vulnerable to wolf attacks.
Fatal encounters
Metz and his colleagues made the discovery by recording and analysing in great detail 55 encounters between male elk and wolves. In 18 cases wolves attacked a lone male, and it made no difference whether or not he had shed his antlers. But the remaining 37 encounters involved attacks on groups of two or more male elk, and wolves targeted antler-less individuals. Groups containing at least one antler-less animal were 10 times more likely to be attacked.
Elk don鈥檛 have a choice about when they shed their antlers 鈥� it鈥檚 probably linked to testosterone levels 鈥� but shedding early seems to carry long-term benefits for a potential short-term but fatal cost. 鈥淢ale elk were almost three times more likely to be killed by wolves if they鈥檇 shed their antlers,鈥� says Metz.
Nature Ecology & Evolution
