Know your Sloth Predators: The Great Harpy Eagle

Know your Sloth Predators: The Great Harpy Eagle

Harpy Eagles Quick Facts

  • Biggest claws of any bird
  • Can lift their own body weight in prey
  • Females are much larger than males
  • They mate for life
  • Chicks grow so fast that parents can care for only one at a time
  • Broad wings give them aerial agility in the thick jungles
  • The largest bird of Central America

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

These eagles are named after the harpies of Greek mythology who were depicted as fearful, winged beasts with women’s heads. Known for their cruelty and destructive nature, they were nicknamed, the “Hounds of Zeus.


Photos: Animals LibraryFio, Second photo: kabeza


It’s not surprising that in some areas of Latin America, stories and local legends still exist about witches living on 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, dressed in black, white, and grey.


harpy eagle
Photo: leon_moore_nature_experience

Claws as big as a grizzly bear’s

Unlike the creatures of Greek mythology, harpy eagles (Harpia harpyja) are very real and rank among the largest birds in the world. They can weigh up to 5 kilos (11 lbs) 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 the canopy of the rainforest and instead prefer to move from tree to tree.

Harpy eagles have thick, powerful legs, keen eyesight, and keen hearing. Like some owls, the harpy eagle has what’s called a “facial disk” of feathers around its neck that turns its head into a radar dish, focusing sound and aiding in the eagle’s sharp hearing. This is an unusual trait in a diurnal bird, but harpy eagles are unusual birds!


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 to use their nimble flying abilities to hunt 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. They have also been observed to eat parrots, porcupines, coatimundis, raccoons, black vultures, and foxes.


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 five years old. Like a lot of bird species, they mate for life, which, for a harpy eagle could mean 25 to 30 years! Once an individual finds a partner, they build a nest in one of the tallest trees in the forest.

Both parents participate in the building of the nest, which is 2 meters (6 ft) in diameter and more than 40 cm (1 ft) deep. Two adult humans could easily fit in the nest! The female lays two eggs, and usually only one of the chicks survives.

Harpy eagle chicks are little balls of grey and white fluff that start off so small they could fit into a human hand, but quickly grow to reach their impressive adult size in only five or six months, after which they begin to fly. The parents look after their offspring for the first two years until they become a juvenile. At four or five years old the eagles are adults and will begin looking for a mate of their own.


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 a healthy population of monkeys and sloths. Therefore, in order 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 conservationists 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.

In Brazil, they have been pushed out of the Atlantic Rainforest, though they exist still in some remote parts of the Amazon. The actual number of harpy eagles in Brazil is currently unknown. They are only found in Mexico in the Chiapas in the Selva Zoque regions and are so rare in Costa Rica that there have only been a couple of sightings in the last decade; they are possibly extinct in the country.


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 Ph.D. Eduardo Alvarez Cordero in Venezuela – one of the first people to study harpy eagles.

There are even a few local traditions that may help this magnificent bird: some South American cultures consider it bad luck to cut down the kapok tree in which they nest. The harpy eagle has been named the national bird of Panama, features on the Venezuelan 2,000 bolívares Fuertes note, and was even the inspiration for Dumbledore’s pet phoenix in the Harry Potter film series.


harpy eagle
Photo: Jitze Couperus


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


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


-Cecilia Pamich