European tree frog (Hyla arborea)

Appearance▲ Back to top

''H. arborea'' are small tree frogs. Males range from 1.3-1.8 in in length, and females range from 1.6-2.0 in in length. They are slender with long legs. Their dorsal skin is smooth, while their ventral skin is granular. Their dorsal skin can be green, gray, or tan depending on the temperature, humidity, or their mood. Their ventral skin is a whitish color, and the dorsal and ventral skin is separated by a dark brown lateral stripe that goes from the eyes to the groin. Females have a white throat, while males have a golden brown throat with large vocal sacs. The head of ''H. arborea'' is rounded, the lip drops strongly, the pupil has the shape of a horizontal ellipse and the eardrum is clearly recognizable. Also, the discs on the frog's toes, which it uses to climb trees and hedges, is a characteristic feature of ''H. arborea'' . Also, like other frogs, the hind legs are much larger and stronger than the fore legs, enabling the frog to jump rapidly.

Distribution▲ Back to top

''H. arborea'' are the only members of the widespread tree frog family indigenous to Mainland Europe. ''H. arborea'' is found in Europe , northwest Africa, and temperate Asia to Japan. It is native to the following countries:

Albania; Armenia; Austria; Azerbaijan; Belarus; Belgium; Bosnia and Herzegovina; Bulgaria; Croatia; the Czech Republic; Denmark; France; Georgia; Germany; Greece; Hungary; Italy; Liechtenstein; Lithuania; Luxembourg; Macedonia, the former Yugoslav Republic of; Moldova; Montenegro; the Netherlands; Poland; Romania; the Russian Federation; Serbia; Slovakia; Slovenia; Sweden; Switzerland; Turkey; Ukraine.

It has also been introduced to the United Kingdom, and it has been reintroduced to Latvia.

''H. arborea'' can be found in marshlands, damp meadows, reed beds, parks, gardens, vineyards, orchards, stream banks, lakeshores, or humid or dry forests. They tend to avoid dark or thick forests, and they are able to tolerate some periods of dryness; therefore, sometimes they are found in dry habitats.

Status▲ Back to top

According to the IUCN Red List of Endangered Species, ''H. arborea'' is “listed as Least Concern in view of its wide distribution, presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category.” However, according to the IUCN, the population trend of ''H. arborea'' is that the population is decreasing.
Some of the main threats to ''H. arborea'' include habitat fragmentation and destruction, pollution of wetlands, predation from fish, capture for the pet trade, and climate change. Besides these main threats, other possible reasons for the decline in ''H. arborea'' populations include increased UVB radiation and local and far-ranging pesticides, fertilizers, and pollutants. It has been observed that trout are predators for ''H. arborea'', and in Europe it has been seen that when trout are introduced into a pond, there is a significant decline in the ''H. arborea'' population.
While ''H. arborea'' are sensitive to habitat fragmentation, habitat restoration has been successful to increase ''H. arborea'' populations. Besides habitat restoration, other attempts to increase ''H. arborea'' population have included building of new breeding ponds, creation of “habitat corridors to connect breeding sites”, and reintroducing ''H. arborea'' individuals. This has been successful in Sweden, Latvia, and Denmark. It has been observed that habitat protection is the most important approach to conserving ''H. arborea'' populations.

Behavior▲ Back to top

*Historically, tree frogs were used as barometers because they respond to approaching rain by croaking.
⤷ Depending on subspecies, temperature, humidity, and the frog's 'mood', skin colour ranges from bright to olive green, grey, brown and yellow.
⤷ ''H. arborea'' eat a variety of small arthropods such as spiders, flies, beetles, butterflies, and smooth caterpillars. Its ability to take long leaps allows it to catch fast flying insects, which make up most of the food it eats.
⤷ ''H. arborea'' hibernate in walls, cellars, under rocks, under clumps of vegetation, or buried in leaf piles or manure piles.

Habitat▲ Back to top

''H. arborea'' are the only members of the widespread tree frog family indigenous to Mainland Europe. ''H. arborea'' is found in Europe , northwest Africa, and temperate Asia to Japan. It is native to the following countries:

Albania; Armenia; Austria; Azerbaijan; Belarus; Belgium; Bosnia and Herzegovina; Bulgaria; Croatia; the Czech Republic; Denmark; France; Georgia; Germany; Greece; Hungary; Italy; Liechtenstein; Lithuania; Luxembourg; Macedonia, the former Yugoslav Republic of; Moldova; Montenegro; the Netherlands; Poland; Romania; the Russian Federation; Serbia; Slovakia; Slovenia; Sweden; Switzerland; Turkey; Ukraine.

It has also been introduced to the United Kingdom, and it has been reintroduced to Latvia.

''H. arborea'' can be found in marshlands, damp meadows, reed beds, parks, gardens, vineyards, orchards, stream banks, lakeshores, or humid or dry forests. They tend to avoid dark or thick forests, and they are able to tolerate some periods of dryness; therefore, sometimes they are found in dry habitats.

Reproduction▲ Back to top

''H. arborea'' reproduce in stagnant bodies of water, such as lakes, ponds, swamps, reservoirs, and sometimes puddles, from late March to June. They croak in the breeding season, even when migrating to their mating pools or ponds. Males will often change breeding ponds, even within the same breeding season. After a spring rain, the males will call females from low vegetation or shallow ponds. About 800 to 1,000 eggs are laid in clumps the size of a walnut. Individual eggs are about 1.5 mm in diameter. After 10–14 days, the eggs hatch. Then, after 3 months, tadpoles metamorphose into frogs. Metamorphosis usually peaks from late July to early August. They are able to live for up to 15 years.