In Kenya, martial eagles hunt lion cubs for lunch
Martial eagles, with wingspans that can exceed six feet, can take out young impalas or gazelles. Recently, researchers have seen them targeting another species’ young.
In December 2012, tour guides in Kenya’s Maasai Mara National Reserve witnessed a series of killings targeting one of the savannah’s top predators. An adult martial eagle followed a pride of lions for weeks, waiting for the right time to swoop in and kill three cubs in total.
“This is an eagle really looking at these lions and thinking, ‘I’m going to systematically hunt these lions,’” says R. Stratton Hatfield, a Ph.D. candidate at Wageningen University and Research in the Netherlands.
While the supposed kings of the jungle may dominate the land around them, this incident and others like it show that African lions (Panthera leo) may not always sit on top of the food chain when it comes to the skies. In fact, martial eagles (Polemaetus bellicosus) likely prey on lion cubs when the opportunity arises, Hatfield and his colleagues recently reported in Ecology and Evolution.
“It’s really a testament to the predatory nature of martial eagles,” Hatfield says.
Queen of the skies
Martial eagles’ wingspans can exceed six feet. Adult females weigh more than 10 pounds, while adult males typically weigh around seven pounds. Though comparable in size and ecology to golden eagles, the species often kills larger prey. The birds swoop in and dig their razor-like talons into their prey’s spine at the back of their skull, sometimes taking out young impalas or gazelles far above their weight class. “[Their talons] are just massive killing utensils,” Hatfield says. “From a predator perspective, they are impressive in what they’re able to do.”
Hatfield’s team only recently realized the birds also preyed on other predators. The team collected seven records, including the 2012 incident, that describe martial eagles preying on lion cubs, resulting in the deaths of nine cubs and one near miss. Most of these episodes probably involve larger females, Hatfield suspects, though two records included juveniles preying on cubs.
The earliest case comes from 2008, when a photographer captured an image of an eagle feeding on a freshly killed cub, while the most recent was in 2023, when a safari guide saw a juvenile eagle hunt and kill a cub large enough that the raptor couldn’t fly off with it.
Risk versus reward
Despite their aerial antics, martial eagles are typically risk averse. “When they go to take a lion cub, it’s with a lot of recognition of the risks,” Hatfield says. But not all records seem to show this careful calculation.
In the one failed killing, a martial eagle swoops in to snatch a six-week-old cub right next to its mother. The lioness spots the approaching danger, and “literally leaps in the air to try to take the martial out of the sky,” Hatfield describes. “You can just see the lioness’s eyes lock onto something, then she crouches and launches.”
The eagle dodged the counterattack, and didn’t get the cub, but the whole maneuver “was just stupid.” Hatfield speculates that the raptor didn’t see the lioness. Episodes like this are so dangerous for the eagle, “you wonder if they are doing something ever just for fun,” he says.
Amy Dickman, a conservation biologist at Oxford University in the U.K., isn’t surprised that eagles will go after cubs again and again if the strategy proves successful. She also leads Lion Landscapes, a nonprofit focused on coexistence of humans and wildlife in Kenya and Tanzania, and says the conclusions of Hatfield’s team “seem sound.”
As far as the lions are concerned, “it’s just another kind of risk that lions have to deal with,” Dickman says, like predation from hyenas or male lions from competing prides. While she doesn’t think the eagles pose a conservation threat to the big cats, an individual pride in a given area might feel pressure if a martial eagle has honed in on their cubs as a food source. “It shows you how interesting and diverse the natural world is,” Dickman says.
Predators or prey?
Martial eagles aren’t picky when it comes to big cats. Some have taken cheetah and leopard kittens, as well. Hatfield also notes the risk probably goes both ways—lions could and probably have hunted adult eagles or nests. At least one YouTube video shows a leopard killing a martial eagle.
“The relationships between top predators at the top of the [food] pyramid are complicated,” Hatfield says.
Martial eagles are considered endangered by the International Union for Conservation of Nature, and Hatfield hopes that studies like this bring more attention to their plight. Like other large raptors in Africa, the species faces habitat loss, poaching for parts, electrocution on power lines and persecution.
“We are all so focused on the elephant and lion and rhino,” Hatfield says. “A lot of these big eagles and vultures are going to go extinct right in front of our eyes.”
