Curious Case of Reindeer Cannibalism May Have Led to Deadly Prion Disease

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About four decades ago, reindeer in the high alpine Nordfjella region of Norway began to engage in a bizarre, new behavior: They would eat each other's antlers.

Termed osteophagia, the act actually isn't all that rare amongst hoofed mammals. Animals have been known to gnaw on shed antlers to make up for mineral deficiencies in their diets. However, in this case, reindeer were eating antlers straight off their herdmates' heads!

In 1984, surveys suggested that about 8% of Nordfjella reindeer showed signs of having their antlers gnawed. In 2009, that rate climbed to 72 percent. In a new survey published Thursday to the journal Scientific Reports, researchers from the Norwegian Institute for Nature Research found that 97 percent of reindeer had had their antlers eaten. And that's for both males and females – reindeer and Caribou are the only two members of the Cervidae (deer) family in which both sexes grow significant antlers.

Adding to the mystery of this rampant antler cannibalization is the fact that all of the roughly 2,000 reindeer in the region are now dead, culled between August 10, 2017 and May 1, 2018 because the herd had become infected by Chronic Wasting Disease (CWD), a contagious, lethal disease caused by a misfolded form of a normal protein called a prion.

The researchers hypothesize that the herd's acquired 'taste' for antlers may have contributed to the spread of CWD. The prions that cause the disease can be found throughout the central nervous system, including the brain, spinal cord, and eyes. It's conceivable that some stray prions could have been present in antlers, as well.

"If ingestion of a reindeer’s antlers with sporadic prion disease was the event that initiated the outbreak of CWD in Norway, prions would have to be present in the antlers. Antlers show an impressive growth rate of up to 2 to 3 cm per day, where growing antler tissue is well innervated with sensory nerves originating from the trigeminal nerve," the researchers wrote.

But why did the Nordfjella reindeer begin their buffet-like antler feasting in the first place? The herd has consistently been in poor health in the past, so it's possible that the antler gnawing served to sate some sort of nutritional deficiency. If the researchers' hypothesis proves to be correct, this may ultimately have been their undoing.

Source: Mysterud, A., Ytrehus, B., Tranulis, M.A. et al. "Antler cannibalism in reindeer." Sci Rep 10, 22168 (2020). https://doi.org/10.1038/s41598-020-79050-2



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