Harpy Eagle

Built Around the Talons

The harpy eagle (Harpia harpyja) is the largest species of eagle, according to Animal Diversity Web, with a body up to 102 centimeters long and a wingspan reaching up to 2 meters (6.5 feet). The San Diego Zoo puts females at 6.3 to 9 kilograms and the smaller males at 3.8 to 5.4 kilograms. A 2019 study on the species put the average at 6.6 kilograms and called it “the largest extant raptor on Earth,” beaten in size only by the extinct Haast eagle of New Zealand. Its curved rear talons are about 13 centimeters (5 inches) long, which the San Diego Zoo says makes them larger than a grizzly bear’s claws, and they sit on legs as thick as a small child’s wrist. Animal Diversity Web estimates that a healthy wild harpy eagle lives 25 to 35 years, but the maximum AnAge lists is 16.8 years, for a captive bird recorded in a 1938 study of bird longevity.

Crushing grip The San Diego Zoo describes talons that can exert several hundred pounds of pressure, enough to crush the bones of their prey and kill it instantly.

Hunting Below the Canopy

A harpy eagle never soars over the top of the rainforest. It flies below the canopy instead, and in a serious chase it is capable of reaching 80 kilometers per hour (50 mph). Its eyesight can pick out something under 2 centimeters across from almost 200 meters away. A good part of the hunt is patience: a harpy eagle will perch silently for up to 23 hours, waiting to catch unsuspecting prey. Sloths and monkeys, including howler monkeys, are its main food sources, and the San Diego Zoo says the monkeys and sloths it snatches from the branches can weigh up to 7.7 kilograms (17 pounds).

A Face That May Funnel Sound

Long black crown feathers rise into a crest when the harpy eagle feels threatened, and some have suggested it also raises them to direct sound to its ears. A separate set of smaller face feathers forms a disc that the San Diego Zoo says may focus sound to improve hearing, similar to owls. Mantled howler monkeys are “one of their primary prey,” and after harpy eagles were reintroduced to Barro Colorado Island in Panama, where they had been extinct for 50 to 100 years, researchers played eagle calls to the island’s howlers. The monkeys quickly picked up an anti-predator response to those calls, ignored other birds’ calls, and kept it up several months after the eagles were removed.

Running Out of Canopy

Harpy eagles range from southern Mexico to the eastern part of Bolivia, southern Brazil, and northern Argentina, and a 2019 study found that Amazonian forests held 93% of the species’ current distribution. The IUCN lists the species as Vulnerable. A 2021 study of 16 active nests in Amazonian landscapes that had lost 0 to 85% of their forest found that harpy eagles could not switch to open-habitat prey in deforested areas, that feeding rates fell with forest loss, and that landscapes deforested by more than 70% supported no nests. Three fledged eaglets in that study died of starvation in landscapes that had lost 50 to 70% of their forest.