"Temporary Ponds: a natural habitat to be protected!"

Amphibians

> European tree frog

Hyla molleri


This tree frog, which until recently was considered a western European species, It turned out to be an Iberian endemism.

It is a small anura with 3.5 to 4.5 cm long and rarely exceeds 5 cm. The head is longer with a short, rounded nose. It has prominent eyes, with an elliptical horizontal pupil and golden iris. The tympanum is small but very visible. It has long anterior and posterior extremities, with 4 and 5 fingers respectively. The tree frogs have adhesive discs at the fingertips, allowing them to climb through the vegetation. The interdigital membranes are relatively well developed in posterior legs.

The skin of the dorsum is very bright and without warts, of green color, sometimes they have shades brownish or yellowish, varying according to the substrate, temperature and humidity. Because they are of a light green color, mostly, near the plants that grow near the water, they pass easily unnoticed.

It has a long continuous lateral band and marked well from the eye to the groin that distinguishes it well from the congenial Hyla meridionalis (Mediterranean tree frog). The belly is whitish or yellow.

There is sexual dimorphism with females being larger and more robust than males. Males have a large vocal sac that rests as before yellow in the throat region, while females have smooth and clear throat skin. In addition, during the breeding period, males exhibit small bristles on the first toe of the forepaws.

At the time of mating, the male croaking an intense and successive guec-guec-guec that is heard well at a distance and is not confused with a vocalization of the competition Hyla meridionalis.

Hyla molleri - Photo of Bruno H. Martins

Behaviour

It is a kind of dusk and nocturnal habits, although it can have daytime activity on rainy or cloudy days. During the day it is common to observe specimens exposed to the sun on the vegetation, in the proximities of the Mediterranean Temporary Ponds.

Reproduction

The breeding season begins in the spring, when males begin to migrate to breeding sites (Temporary Ponds). In the breeding sites, the males croak in chorus, being very territorial. When they croak, the males display their vocal bags in the aquatic environments and attract the females, as can be seen in the film.

Credits: Claudius Buser

The fertilization in Anura is external. The males position themselves on the female in an embrace called amplexus, so that they can deposit the sperm, fertilizing the eggs at the moment when the female deposits them in the base of aquatic plants or involved in the mud of the bottom of the puddles, as can be seen in images 1 and 2.

The amplexus is by the armpit and occurs within water and may take several hours.

Image 1. Beginning of Hyla molleri's spawn.

Photograph by Vasco Flores Cruz in Amphibians and Reptiles of Portugal

Image 2. Spawn of Hyla molleri.

Photograph by Vasco Flores Cruz in Amphibians and Reptiles of Portugal

Each female can deposit about 200 to 1400 eggs, according to the age of the female, doing it in small clusters in the stems of aquatic plants.

Image 3. Eggs of Hyla molleri. 

Photograph by Vasco Flores Cruz in Amphibians and Reptiles of Portugal

Image 4. Embryos of Hyla molleri. 

Photograph by Vasco Flores Cruz in Amphibians and Reptiles of Portugal

Tadpoles hatch a few days later and larval development may take between 2 to 3 months. The newly metamorphosed are about 20mm in length and may not have the dark band on the flanks.

Image 5. Juvenile of Hyla molleri.

Photograph by Vasco Flores Cruz in Amphibians and Reptiles of Portugal

Sexual maturity is reached at 3-4 years of age and maximum natural longevity is less than 10 years.

Feeding

The diet of adults includes various invertebrates, such as, spiders, flies, ants, small beetles, bedbugs and centipedes. Tadpoles feed on vegetable matter and debris.

Its main predators consist of water snakes and numerous birds. Tadpoles can be preyed by water snakes, dragonfly larvae, aquatic beetles, and even larvae and adults of other amphibians.

The main defense mechanism of this tree frog consists of the ability to mimic, since it seeks refuge among vegetation, where its coloration makes it go unnoticed.

It occurs in wetlands with abundant vegetation due to its climbing habits, usually in the vicinity of temporary ponds, water courses, marshes and lakes.

Uses the vegetation as a refuge, especially during the day.

Its distribution extends to all the continental territory, however, south from Tagus River, this tree frog is more dispersed in the western half of Alentejo and Algarve.

Nevertheless, there is a strong and highly competitive presence of the Mediterranean tree frog (Hyla meridionalis), a more eclectic specie that has gradually occupied the most beneficial habitats.

In the places shared by both species, the Hyla meridionalis is almost always more abundant than the Hyla molleri.

 

Besides the threat of competitive exclusion by the H. meridionalis, there is also the possibility of genetic contamination by non-fertile hybrids. This situation caused the local decline of some H.molleri populations in the Southwest regions of Portugal.

Other threat factors arise from the intensification of agriculture: the destruction of habitat and water contamination with chemicals.


Your browser is outdated!

Update the browser to see the website correctly. Update now

×