Female caribou grow antlers as a built-in snack after birth

Female caribou grow antlers as a built-in snack after birth

By Emma Gomez edited by Andrea Thompson

Caribou, large deer native to the northernmost parts of the world (and sometimes called reindeer), are the only deer whose females grow antlers. In a study published today, researchers observed behavior that may explain why: female caribou appear to gnaw on shed antlers as a sort of supplement after giving birth.

Caribou migrate great distances each year between the places where they graze in winter and the grounds where they calve in spring. They can walk thousands of miles per year and probably have the longest land migration of any animal. Caribou mothers complete these extremely long treks with antlers on their heads and a calf in their bellies. The period is very nutritionally demanding for them, but culminates in a reserve stock of nutritional supplements when they need it most.

The researchers behind the new study found this out when they observed bite marks in more than 80 percent of the 1,500 caribou antlers that littered the part of the Arctic National Wildlife Refuge in northeastern Alaska where the deer give birth.

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“(Caribou) just go for the antlers. They’re very selective,” said study co-author Joshua Miller, a paleoecologist at the University of Cincinnati.

Female caribou shed their antlers just days before giving birth. Miller and co-author Madison Gaetano, a conservation paleobiologist, say the findings suggest that female caribou are essentially nutrients in the form of antlers before they give birth and then gnaw on the newly shed antlers to get a boost of protein, calcium and phosphorus they need to make up for having less time to groom.

“It’s a mineral that’s available to you at the time you need it, and it’s presented as a very efficiently consumed resource relative to feed,” says Gaetano.

There are other theories as to why female caribou have antlers. One is that these bony protrusions make females resemble young male caribou and thus help them avoid aggression from older males. Another is that they use the antlers as a personal defense mechanism against predators. But antlers are on the ground much longer than they are ever on the body of the animal they came from, says Gaetano.

“It’s possible that (female antler use as nutrition) is one of the reasons they evolved, in addition to some of the other things that we think females do with the antlers,” says Danielle Fraser, a paleoecologist at the Canadian Museum of Nature, who was not involved in the study. “It can evolve to play multiple roles.”

Caribou antlers can remain in the Arctic landscape for decades and even centuries, preserving the evidence of how these bones are recycled back into the environment. The location of the bones and their condition can also tell researchers how a herd may change over time, and can give researchers insight into how they can help boost caribou numbers, Miller says.

The study reveals that antlers are so much more than showpieces or something to fight with – they also appear to be part of keeping young caribou families alive, Gaetano adds. “It’s so interesting to me how creative animals will be when it comes to meeting their nutritional needs,” she says.

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