Tiger-legged Monkey Frog

Most frogs move by jumping, using powerful hind legs to leap between perches, but the monkey frogs of the genus Phyllomedusa, including the tiger-legged monkey frog, have evolved a different, slower strategy suited to life high in tangled vegetation. Each hand and foot has an opposable first digit that can be brought around to grip a twig or stem from the opposite side, much like a thumb, so the frog can walk deliberately along branches, reaching forward with one limb at a time and maintaining a secure hold throughout, rather than launching into open space and hoping to land safely. This careful, gripping locomotion is safer in a dense three-dimensional canopy environment where a missed jump could mean a long fall or landing somewhere exposed to predators.

It solves the basic problem that amphibian skin is normally thin, permeable, and prone to drying out, which usually confines frogs to shaded, humid microhabitats. Phyllomedusa monkey frogs have specialised skin glands that secrete a lipid, or fat-based, substance, and the frog actively spreads this secretion evenly over its body using slow, deliberate wiping motions of its limbs, essentially applying its own sunscreen and moisture barrier. With this coating in place, the frog can perch in direct sun and drier air on exposed branches for extended periods without losing dangerous amounts of water through its skin, a capability that most rainforest frogs, which rely on staying in constantly moist, shaded spots, do not have.

The tiger-legged monkey frog's back and upper surfaces are a fairly plain, uniform green that blends into leaves, while the bold orange-and-black barred pattern is confined to the inner surfaces of the thighs and flanks, areas that are folded against the body and completely concealed when the frog is sitting still. This is a classic flash colouration strategy — at rest the frog is well camouflaged, but if a predator approaches and the frog suddenly jumps or kicks its legs out to flee, the hidden bright pattern is briefly exposed and then vanishes again the instant the frog lands and folds up, which can startle or momentarily confuse a predator that was tracking a plain green shape and now cannot relocate it.

Breeding is tied closely to ponds and slow water, even though the adults are highly arboreal. A male calls from vegetation near water to attract a female, and the pair, clasped together, whip a fluid secretion into a stable foam using their hind legs, depositing the resulting foam nest, with the fertilised eggs inside, onto a leaf that overhangs the water. The foam protects the developing embryos from drying out and from many predators and parasites while they develop over roughly a week or two. Once the tadpoles are ready, they wriggle free of the foam and drop directly into the pond below, where they complete their development as typical aquatic, algae-grazing tadpoles before metamorphosing and returning to life in the trees.