This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
On December 15, 2011, conservation biologist Linda L. Kerley was conducting a routine check of a camera trap that had been placed in a small forest in eastern Russia. She regularly visited each of her cameras to swap out memory cards and batteries. But it was different this time when she came upon a deer carcass just a few meters away from the camera. Something "felt wrong about it," she said in a prepared statement. "There were no large carnivore tracks in the snow, and it looked like the deer had been running and then just stopped and died."
Kerley, who works with the Zoological Society of London, and her colleague Jonathan C. Slaght of the Wildlife Conservation Society study tigers. Together, the two zoological organizations have been working together to monitor Amur tigers, also known as Siberian tigers (Panthera tigris altaica), for almost twenty years. As part of their work on the world's largest cat, the researchers placed camera traps throughout the Lazovsky State Nature Reserve in Russia's Far East. Whenever an animal passed in front of one of the cameras, an infrared sensor activated and caused the camera to snap a photo.
Given the lack of prints in the snow it was clear that, whatever killed the deer, it wasn't a tiger. She would have to wait until she could look at the photos stored on the memory card to see if they held any answers.
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What she discovered when she checked the photos later that day is probably the first recorded evidence of golden eagle (Aquila chrysaetos) predation on sika deer (Cervus nippon). While the three photos were taken over the course of just two seconds, they made scientific history.
Golden eagles are found throughout the Northern Hemisphere, which makes them the most widely distributed of all the eagle species. While not the largest eagle, their size makes them formidable hunters. Their wingspans average between six and eight feet. Their massive talons are capable of exerting 440 pounds per square inch of pressure, which is some fifteen times more pressure than exerted by the human hand. When hunting large prey such as deer, they fly low before landing on the deer's back or neck. Once latched on, their talons pierce the beast, either damaging internal organs or crushing its spine. After several minutes the prey usually collapses, either from exhaustion or from internal injuries.
Golden eagles are known to hunt all manner of ungulates both domesticated and wild, along with foxes, coyotes, and brown bear cubs, but the predominant wisdom was that sika deer were not part of their diets. In their letter in the Journal of Raptor Research, Kerley and Slaght write that they were able to find no records in the scientific literature of a golden eagle ever preying upon a sika deer. Further, prior researchers had explicitly stated that golden eagles did not attack sika deer, at least in Russia.
Indeed, Kerley says, "I’ve been assessing deer causes of death in Russia for 18 years—this is the first time I’ve seen anything like this.”
The find was even more remarkable because, of the 5805 photos that Kerley captured during the November 2011 - March 2012 trap season that did not include a tiger, only 0.1% of photos contained a bird at all. And, they write, "as most Golden Eagle attacks documented elsewhere have occurred in open spaces, the fact that this predation occurred in a forest was also noteworthy."
Kerley and Slaght think that it must be incredibly rare for a golden eagle to hunt and kill a sika deer, and when an attack does occur it is probably opportunistic. Given the unlikelihood of such an attack, golden eagles probably do not pose a threat to sika deer populations. Still, this is yet another reminder that dinosaurs continue to rule the earth.
Kerley L.L. & Slaght J.C. (2013). FIRST DOCUMENTED PREDATION OF SIKA DEER (CERVUS NIPPON) BY GOLDEN EAGLE(AQUILA CHRYSAETOS) IN RUSSIAN FAR EAST, Journal of Raptor Research, 47 (3) 328-330.
Camera trap images via Wildlife Conservation Society, used with permission. Carcass photo via Kerley & Slaght (2013).