Know your Sloth Predators: The Great Harpy Eagle

Know your Sloth Predators: The Great Harpy Eagle

The Harpy Eagle holds the crown as the most powerful eagle in the world – and it also happens to be the sloth’s main predator! With talons larger than a grizzly bear and a grip strong enough to crush a human arm, you can see why sloths take camouflage so seriously. Here we explore the terrifying world of the Harpy Eagle and explain how protecting sloths also means protecting these magnificent birds!

A living myth

Have you heard of the harpies of Greek mythology? A harpy is a mythological creature that was depicted as a fearful, winged beast with the head of a woman. Known for their cruelty and destructive nature, they were nicknamed, the “Hounds of Zeus.”

Photos: First photo, Second photo: kabeza

It’s not surprising that in some areas of Latin America, stories and local legends still exist about witches living in the tops of tall trees. For those few fortunate enough to see a harpy eagle in person, they do look like the silhouette of a robed person sitting on a branch.

harpy eagle
Photo: leon_moore_nature_experience

Claws as big as a grizzly bear’s

Unlike the harpies of Greek mythology, harpy eagles (Harpia harpyja) are very real and rank among the largest birds in the world. They can weigh up to 11 pounds/5 kilograms and females are often twice the size of their mates. They are also some of the most powerful birds: with the ability to lift prey the size of monkeys, sloths or even a baby deer!

These massive birds of prey can be 3.5ft/1m tall and have an impressive wingspan of 6.5ft/2 meters! Unlike other raptors, they rarely soar through canopy of the rainforest and instead prefer to move from tree to tree.

With a grip strength up to 10x higher than humans: 13cm of pure raptor power. / Photo: DecorahPagent

It’s dinner time!

Harpy eagles don’t hunt every day because they can feed on the same kill for several days in a row. Their bodies have adapted to tolerate meat that has spent several days in the hot environment of the tropical forest. Because they don’t need to eat every day, they can actually spend an entire week or more without ingesting any food!

Although Harpies prefer tree-dwelling animals, such as sloths, monkeys, iguanas, and other birds, they can also prey on ground dwellings species such as coatis, large rodents, deer or wild pigs.

harpy eagle sloth
A harpy eagle catching a sloth. @LaSalle museum of natural sciences, Costa Rica

They make great parents

Harpy eagles reach adulthood when they are about 5 years old. Like a lot of species of birds, they mate for life, which, for a harpy eagle, could mean 25 to 30 years! Once an individual finds a partner, it’s time to build a nest in one of the tallest trees of the forest.

Both parents participate in the building of the nest, which is 6ft/2m in diameter and more than 1ft/40 cm deep. Two adult humans could easily fit in the nest! The female lays two eggs, however, usually only one of the chicks survive. The parents look after their offspring for the first two years until they become a juvenile.

The relationship between sloths and harpy eagles

Harpy Eagles are what scientists, biologists, and zoologists call an “umbrella species“. Just like several people are protected by one umbrella under the rain, different species of wildlife can also be protected by conserving one particular species.

Harpy eagles depend upon on a healthy population of monkeys and sloths. So to safeguard the future of this raptor we must protect these species. By protecting harpy eagles, we conserve the amazing rainforest in which they live, which is also the home of sloths, monkeys and many more incredible creatures.

Conservation status

Unfortunately, according to IUCN Red List, the population of harpy eagles is declining all over the continent.  It’s hard to accurately determine their population numbers – some estimate that there are between 10,000 to 50,000 individuals remaining, although the data is still insufficient. In some countries, the species is considered extinct. The Harpy Eagle is near threatened or vulnerable in most areas of South America, and critically endangered in Central America.

harpy eagle home range
Home range of harpy eagle

Big predators usually require large territories to provide all of their needs: hunting, mating, etc. Habitat loss, logging, and the effects of the climate crisis are undoubtedly the biggest threats to harpy eagles. Trophy hunting, poaching, and trafficking for the illegal pet trade are also big issues. Some people kill them because they fear that the harpy eagle could hurt them, their children or their livestock. As mentioned earlier, there are a lot of misconceptions and mysticism surrounding these raptors.

However not all hope is lost: several organizations across the continent are working hard to conserve and protect harpy eagles. The Peregrine Fund has a fantastic project that breeds harpy eagles in captivity and releases them into the wild in Panama. You can also read this great article about the experiences of PhD Eduardo Alvarez Cordero in Venezuela – one of the first people to study harpy eagles.

harpy eagle
Photo: Jitze Couperus

A witch of the rainforest, a mythological creature, an inspiration for movie characters. Harpy eagles not only capture our imaginations, but are indispensable to the health of our tropical ecosystems.

Thunderbird from Fantastic Beasts and Where to Find Them, Photo: Gavin

-Cecilia Pamich