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Some white-tailed deer on the Costa Rican coastline have a macabre habit: chewing sea turtle bones.聽Researchers have recently documented scores of the herbivores scavenging on the remains, possibly to augment their uptake of key minerals.

at the National University of Costa Rica and his colleagues were studying jaguars and their prey using motion-activated cameras set up throughout Costa Rica鈥檚 Guanacaste Conservation Area. Along some parts of the coastline, jaguars regularly kill and eat nesting sea turtles, leaving a carcass behind in nearshore vegetation. When the researchers reviewed photos taken by a camera pointed at one turtle鈥檚 remains, they were surprised to see multiple instances of white-tailed deer (Odocoileus virginianus) snacking on the skeleton.

鈥淭o our best knowledge, this is the first record of white-tailed deer chewing on sea turtle bones,鈥� says Morera.

As the team looked through more photos taken over much of 2017, it became clear that bone eating was common among deer in this location.

鈥淎t first, they seemed like anecdotal observations,鈥� says Morera. But once the 183 different sightings were broken down by seasonal timing and the age and sex of the deer, a pattern emerged.

Bucks with antlers and does with fawns chewed turtle bones most in June to August, shortly after the region鈥檚 dry season. This is a time of nutritional stress as food and water are scarce, says Morera.

The researchers think the deer are supplementing their diet with minerals like calcium and phosphorus as the need arises.

This would certainly make sense for antler-growing males and does with young, says at Texas A&M University-Kingsville. Gestation and lactation require months of high nutritional demand, for instance. Bucks will draw minerals from their bones to feed antler growth.

鈥淪o [the bucks] have got to have a strong appetite for minerals,鈥� says Hewitt.

Hewitt points out that deer are well-documented mineral munchers and that they have been spotted eating snail shells and gnawing the skeletal remains of non-turtle species before. But the crucial link to the jaguars is unique, he says.

鈥淚f the jaguars weren鈥檛 in the picture, the sea turtle bones probably wouldn鈥檛 be a big source of minerals for the deer,鈥� says Hewitt. 鈥淪o, it鈥檚 kind of a neat system that they were able to document.鈥�

Morera says the findings show how the behaviour of herbivores can be indirectly influenced by the impacts of top predators, 鈥渁s well as how important these species are within the flow of nutrients in coastal ecosystems鈥�.

Hewitt is curious just how dependent the deer are on the sea turtle bones for meeting their nutritional needs and what might happen if that resource were to disappear.

鈥淭here are all kinds of interesting things out there [in nature] and connections that you never would have guessed,鈥� he says. 鈥淎nd this [study] is a neat illustration of that.鈥�