Female caribou grow horns as a post-birth snack

Female caribou grow horns as a post-birth snack

By Emma Gometz 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 gnawing on shed horns As a type of postpartum supplement.

Caribou move large distances each year between the places where they graze during the winter and the grounds where they breed in the spring. They can walk thousands of miles per year and possibly longest terrestrial migration Of any animal. Caribou mothers complete this extremely long migration with horns on their heads and a calf in their womb. This period is very demanding for them nutritionally, but ends up with a reserve of supplementary food for when they need it most.

Researchers of the new study discovered this when they observed bite marks on more than 80 percent of 1,500 caribou antlers scattered across the part of the Arctic National Wildlife Refuge in northeast Alaska where deer give birth.

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“(Caribou) are really going after the horns. They’re highly selective,” says Joshua Miller, a paleontologist at the University of Cincinnati and co-author of the study.

Female caribou shed their antlers a few days before giving birth to their babies. Miller and co-author Madison Gaetano, a conservation paleontologist, say the findings show that female caribou essentially store nutrients in the form of antlers before giving birth and then gnaw on their freshly fallen antlers to get a boost of protein, calcium and phosphorus, allowing them to need less time to raise their calves.

“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 forage,” says Gaetano.

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

“It’s possible that (females’ use of horns as nutrition) is one of the reasons they evolved, in addition to some of the other things we think females are doing with their horns,” says Danielle Fraser, a paleontologist at the Canadian Museum of Nature who was not involved in the study. “It may have evolved to perform multiple roles.”

Caribou horns can remain on the Arctic landscape for decades and even centuries, preserving evidence of how these bones are returned to the environment. Miller says the location of the bones and their condition can also tell scientists how the herd may have changed over time and give researchers information about how to boost caribou numbers.

The study shows that the horns are more than display objects or something to fight with, Gaetano says — they also seem to be part of keeping young caribou families alive. “It’s very interesting to me how creative animals will be in meeting their nutritional needs,” she says.

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