Lemur leaf frogs are bright yellowish-green with dark flecks or spots on their dorsal (back) side. Their hands, feet and flanks are yellow, and their bellies are white. A thick, black line surrounds each eye. Their color can change depending on their activity. At night, when they are active, their yellow-green skin turns brown and their eyes turn dark gray.

Leaf frogs have thin bodies, arms and legs, and their fingers and toes are not webbed. They move slowly, walking hand over hand, and rarely jump unless escaping from danger.

Female leaf frogs are typically larger than males, ranging from 4-5 centimeters long while males are 3-4 centimeters long.

Lemur leaf frogs are found in Costa Rica, Panama, and some areas of Colombia. They live in forests on sloping mountainsides and in the humid uplands and lowlands. These frogs have been extirpated, or wiped out, of parts of their previous range and are critically endangered where they currently live.

Lemur leaf frog lifespan is estimated to be between five and 10 years.

Lemur leaf frogs are territorial, and males call with a short “tick” to warn other males they are nearby. Calls are around 0.2 seconds long, with about 40 pulses per second. 

Male leaf frogs aggressively defend their territory. A resident male will clasp an intruder male or unreceptive female and try to push them off their perch. Males also produce a release call if grasped by another male.

In the wild, lemur frogs eat insects and other small invertebrates. At the Smithsonian's National Zoo, they are fed crickets, fruit flies, worms and beetles.

These frogs typically breed during the rainy season (April to July). Males call to females from plants near (or overhanging) pools and slow-moving streams. Males grasp females in the mating position, called amplexus, and females lay clutches of 15 to 20 eggs. They may lay two or three clutches per night, depositing the egg masses in a single or double layer.

Eggs are deposited on the surface or underside of leaves that hang over the water. The ambient humidity keeps the eggs moist as they develop, and rain triggers the larvae to "wiggle" out of the eggs and fall into the water below.

The larvae hatch seven to 14 days after fertilization, and the embryos are light green. Metamorphosis, the transformation from an immature to an adult form in stages, generally occurs 69 to 98 days after hatching. Lemur leaf frog tadpoles can also change color day to night but do not have the same yellow or orange side coloration as adults.

Lemur leaf frog populations have declined more than 80% in the last 10 years. This continuing trend is believed to be a result of rapid habitat loss, as well as chytridiomycosis, the disease caused by amphibian chytrid fungus.

Although leaf frogs appear to have some resistance to chytridiomycosis, they have had tremendous population losses and currently only occupy about half of their historic range. Their greatest threat is habitat loss, especially in Costa Rica where their range is impacted by deforestation.

This species has been bred successfully in managed care at a handful of zoos, including the Smithsonian's National Zoo and Conservation Biology Institute. The continued successful breeding of these frogs ensures that the population in human care maintains a high level of genetic diversity. The goal of breeding programs like these is to build an assurance population that could be restored to the wild, if and when the time and conditions are appropriate.