Overview
The Blue-sided Tree Frog (Agalychnis annae), also celebrated as the Golden-eyed Leaf Frog, is an extraordinarily colorful, endangered hylid endemic to the lush highland valleys of Costa Rica. Closely related to the famous red-eyed tree frog, it trades scarlet eyes for mesmerizing golden-yellow or amber irises, complemented by brilliant lavender-blue or violet flanks and glowing pumpkin-orange hands and feet.
Biology and Physical Characteristics
Agalychnis annae has a slender, elegant arboreal build with smooth, leaf-green dorsal skin that provides immaculate camouflage when sleeping flat against jungle leaves by day. At night, its vibrant hidden colors emerge: intense royal blue, lavender, or magenta along its hidden flanks and inner thighs, contrasting dramatically with bright yellow or orange webbing on its large, suction-cup tipped toes.
Behavior and Ecology
Exclusively arboreal and nocturnal, this gentle leaf frog awakens at dusk to hunt flying insects in the mid-canopy. During the rainy season from May to November, males gather in low vegetation overhanging forest ponds and slow-moving streams, emitting short, metallic clucking calls. Females lay gelatinous egg clutches on the undersides of leaves hanging directly over water, allowing freshly hatched tadpoles to drop straight into the stream below.
Conservation and Human Impact
Classified as Endangered by the IUCN, the Blue-sided Tree Frog suffered catastrophic population crashes across pristine wilderness national parks in the 1980s and 1990s due to the global chytridiomycosis epidemic. Miraculously, thriving remnant populations have persisted and rebounded within polluted urban rivers, suburban gardens, and shaded coffee agro-ecosystems around San Jose.
Interesting Factoid
In a remarkable ecological paradox, the Blue-sided Tree Frog vanished from pristine mountain national parks due to deadly fungal disease, yet survived and flourished in the urban parks, drainage ditches, and coffee farms of downtown San Jose.