Diasporus diastema

Despite their small size, Tink Frogs liven up the jungle night with their delicate chimes. Adult males, the ones that do all the singing, measure just over 20 millimeters at their largest. Females are a bit larger and may measure up to 24 millimeters when fully grown. Still, their call is one of the loudest night sounds you will hear during the rainy season. During the dry season they are completely silent.

There are two species of Tink Frog in Costa Rica. The Common Tink Frog (Diasporus diastema) and the Montane Tink Frog (Diasporus hylaeformis). Both species are very similar, but the Montane Tink Frog inhabits highlands whereas the Common Tink Frog is mainly a lowland species. The Common Tink Frog is the species found in Drake Bay. They inhabit the humid lowlands on the Caribbean and southwestern Pacific regions of Costa Rica. They are also found at the base of the Guanacaste and Tilaran Mountain Ranges.

During their mating season, males generally call from hidden locations. We have found them calling inside dead leaves, in very tangled vine clumps, and in the cavities of plants like Bromeliads and Corn Plants. Tink Frogs are strictly tree dwellers and they are typically found from 1 to 35 meters off the ground. We often hear them calling from bromeliad laden treetops.

Their call is a very loud, high pitched "Tink!". Studies suggest there is a calling order, where a dominant male inaugurates the calling sessions and other males in the group respond in their respective order. The calling order helps to throw off any predator locating the frogs by hearing. This, along with their small size, their habit of calling from hidden perches and the fact that their call is nearly impossible to home in on, makes every encounter with this very common frog a special occasion.

They must be secretive when they call because a whole host of predators, including Smoky Jungle Frogs, Fringe-lipped Bats, Marine Toads and Four-eyed Opossums all locate male frogs by their call and make a mini-meal out of them.

While calling a male frog's throat sac becomes quite inflated, as can be seen pictured on the right. If a female is attracted into his territory, he will approach her immediately calling repeatedly. The male will stop in front of her and lift his legs up and down. She will respond by bumping his extended throat sac with her snout. The male will then bump and touch the female. This ritual may be repeated several times.

Eventually, he will lead her back to a nest he has previously prepared. Nest sites are generally a few centimeters to several meters off the ground and may be located hidden in Bromeliads, leaf petioles, or under bark.

Once they reach the nest site, they will join in axillary amplexus and mate. She will usually lay between 11 and 19 eggs. The eggs go through direct development, so what will hatch out is not a tadpole, but a fully formed frog. Embryos do go through tadpole stage inside the egg, but will never have a free swimming aquatic phase.

The very next night, after mating, that little male will be out calling again. If he attracts another female, they will go through the same process again and he will lead her back to the same nest, where she will lay her eggs. Scientists have found from three to seven egg clutches at Tink Frog nests, all in different stages of development.

Egg clutches will normally hatch 23 to 26 days after being laid. When the tiny froglets emerge from the eggs, they are just incredible. You can get an idea of their size from the picture on the left. We discovered this neonate, photographed perched on Tracie's thumb, while on a Night Tour in the month of August.

References:

Forsyth, A.  1990  Portraits of the Rainforest  Camden House Publishing

Janzen, D.  1983  Costa Rican Natural History  University of Chicago Press

Leenders, T.  2001  A Guide to Amphibians and Reptiles of Costa Rica  Zona Tropical

Savage, J.  2002  The Amphibians and Reptiles of Costa Rica   University of Chicago Press