Aye-ayes: The strange nocturnal lemurs with long, creepy fingers

Native to Madagascar, this lemur looks like a strange mix of several animals. It has the round eyes of an owl, the ears of a bat, rodent-like teeth that never stop growing and a wiry, bushy tail longer than its body.

Aye-ayes are the world’s largest nocturnal lemur, weighing around 4 pounds (1.8 kilograms) and reaching up to 24 inches (60 centimeters) long from nose to tail tip. Young aye-ayes have a silver front with a stripe down their backs, but as they develop into adults, their thick fur turns a yellow-brown with white tips. During the day, they sleep in spherical nests crafted from leaves and branches, while at night they roam the treetops in search of food.

Aye-ayes have extra-long, bony middle fingers. As the animals move along tree branches at night, they tap the wood rapidly with their long fingers, listening for subtle changes in the echoes that signal the presence of hollow chambers where wood-boring insect larvae hide. Once a grub is located, the aye-aye gnaws a small hole into the bark using its teeth, then inserts its thin finger to fish the meal out. These long middle fingers have ball-and-socket joints, giving the lemurs a wide range of motion to better reach their prey.

However, biologists also found that the lemurs use these elongated fingers for another task: nose-picking. In a 2022 paper published in the Journal of Zoology, researchers described how aye-ayes reach through their noses to the back of the throat, then lick off the gathered mucus. The team noted that the lemurs may be attracted to the "texture, crunchiness and saltiness" of the mucus — which may also prevent bacteria from sticking to their teeth.

Like rodents, aye-ayes have continuously growing incisors. Their upper and lower front teeth never stop growing, but they are worn down by the wood, bark and nuts that they gnaw through.

In Malagasy folklore, aye-ayes are considered omens of death, and some believe that if an aye-aye points its finger at you, it's a death sentence, according to the Natural History Museum in London. Because of these superstitions, aye-ayes are sometimes killed on sight, contributing to their declining population. Once listed as extinct, they were rediscovered in the wild in the 1950s, but they are still endangered.

To defend themselves against predators, aye-ayes rely mostly on stealth and camouflage. Their dark fur helps them blend into the nighttime shadows of the rainforest. Their large, sensitive ears enable them to detect the slightest rustle of leaves — a crucial ability for avoiding predators like fossas (Cryptoprocta ferox), carnivorous mammals endemic to Madagascar.

When threatened, aye-ayes may freeze in place, relying on stillness and silence to avoid detection. They are also very agile and are able to leap and climb rapidly through dense forest canopies to escape danger.