One night, 10-year-old Sebastián Montilla heard a creature moving over a tree branch on his father’s farm in Pijao, Quindío department, one of Colombia’s renowned coffee-growing regions. As he pointed a lantern up to the canopy, he saw a wild creature with big red eyes and a long tail watching him before moving away from the light. It was a night monkey, from the genus Aotus. This brief encounter would decide Montilla’s path of studying Colombian night monkeys.

“I became very passionate about those animals, in fact, when I was in school, my favorite pastime was to go outside and lie down under their sleeping place, to watch them do nothing,” Montilla, now a doctoral student in biological sciences at the University of the Andes in Bogotá, told Mongabay in a video call about Colombian night monkeys.

“I’m very surprised by the fact that [night monkeys] have gone unnoticed for so long, both in the scientific community and in the public sphere,” he added. “It’s astonishing because at midnight they are moving right past our houses and we don’t even notice.”

Night monkeys, also known as owl monkeys, are the only primate group in the Americas that have adapted to be active at night. These monkeys have evolved enormous round eyes with retinas 50% bigger than those of daytime-active primates to better capture the scarce light available in their environments. Unlike other nocturnal primate species in Asia and Africa, such as lorises (family Lorisidae), tarsiers (Tarsiidae) and lemurs (Lemuroidae), which tend to be solitary, night monkeys form lifelong monogamous pairs, raising one to three offspring at the same time. Most of what we know about the reproduction and behavior of these primates comes from biomedical laboratories and zoos that held night monkeys in captivity. The difficulty of following these monkeys in the dark has made Colombian night monkeys almost impossible to study in the wild.

Read the full article about Colombian night monkeys by Manuel Fonseca at Mongabay.