The Iberian tree frog as a bioindicator


Merel Breedveld

Why does the frog sing?

The distinctive mating song of the Iberian tree frog is audible at a distance of more than one kilometre. The males sing to attract the females and gain the opportunity to mate with them.

The males stay close to the ponds for almost all of the reproduction period (until late spring) in order to mate with the highest possible number of females and thus optimise their biological efficiency.

When the mating season begins in spring, the males are the first to head for the reproduction pools to attract the females with their singing, which mostly takes place at night in chorus with their fellow males.

The females generally only stay in the ponds for one night, during which amplexus with the male takes place, and they lay thirty to sixty eggs.

Larva development takes around two weeks and ends with the hatching of independent tadpoles. The metamorphosis of the tadpole into an adult frog takes around three months, and sexual maturity is reached in the third year of life.

Why do we like to hear its song?

The main goal of DIVAQUA is to improve biodiversity in the Picos de Europa. One of the most iconic species of interest is the Iberian tree frog (Hyla arborea), which is under threat because of aquatic pollution and the introduction of invasive alien species of fish and crabs. DIVAQUA aims to conserve the populations of this amphibian by restoring its aquatic habitats and improving the connectivity between water points. Hearing the song of the frog not only reveals the presence of the species in a particular place, but can also be used to estimate the density of its populations. Its song may therefore indicate the quality of the habitat and the effectiveness of the conservation measures taken.