Oh deer! Eagle kills deer in startling glimpse of alpha bird behavior.

Three trip-camera images of a Siberian golden eagle taking down a deer are an extremely rare glimpse not only into nature at its wildest, but also into little known raptor behavior in an area of the world where hunters use the massive birds to hunt and kill wolves.

The images were taken at camera trap station in the Lazovsky Nature Reserve in Russia's Primorsky Territory, and published by the Journal of Raptor Research.

They show the eagle landing on the deer’s haunch but don’t give any clues as to how the bird killed the deer. Researcher Linda Kerley of the Zoological Society of London discovered the deer carcass, which posed a mystery. For one, there were no predator tracks around the carcass, and it appeared as if the deer had been running “and then stopped and died,” Ms. Kerley told Fox News.

The mystery of the fallen deer was solved later in the day when Kerley clicked through the trip-camera pictures and found the three images, captured in a span of only two seconds. “I couldn’t believe what I was seeing,” she said.

Such attacks are believed to be exceedingly rare, but they are far from unprecedented. Mongolian and Kazhak falconers, for example, have exploited the eagle’s size in order to use it to hunt and kill wolves, says Mark Fuller, director of the Raptor Research Center at Boise State University.

The photos of the bird taking down the deer “certainly says something about the capabilities of these animals, along with documented cases in North America of golden eagles taking down pronghorns and other large prey as opposed to taking rabbits, groundhogs, squirrels and so forth,” says Mr. Fuller. “The circumstances in which these predators are motivated to take on these riskier prey, however, is not well understood.”

Also unknown is how the bird finally meted out the killing blow. “The behavior is so uncommon that people haven’t actually observed it,” which means that scientists don’t yet “understand the sequence of behaviors that go into the ultimate success of a bird that size killing prey that’s much larger,” says Fuller.

There are several theories behind the behavior. One is that the eagle came upon a possibly injured deer unexpectedly, and took the opportunity. But it’s also clear that an individual bird can learn such behavior.

A golden eagle was reported to have taken a black bear cub in 2004, and there are a handful of reports of eagles attacking people. One such attack happened on Kodiak Island in 1991, where an amateur photographer was talon-slashed by a bald eagle protecting a nest. Another attack by a trained eagle on a child was recorded by a tourist to Mongolia in 2011.

“The circumstances in which these predators are motivated to take on riskier prey is not well understood, but I do think there is recognition by the predator that certain prey are potentially more risky than others,” Fuller says.