Blue-sided tree frog (Agalychnis annae)
|Also known as:||blue-sided leaf frog, golden-eyed leaf frog, orange-eyed leaf frog, orange-eyed tree frog|
|Size||Male length: 5.7 - 7.4 cm (2)|
Female length: 6.7 - 8.4 cm (2)
- The blue-sided tree frog is named for its striking blue flanks and sides, which contrast with its green upperparts.
- The yellow-orange eyes of the blue-sided tree frog give this species its alternative name of ‘golden-eyed leaf frog’.
- Juvenile blue-sided tree frogs lack the distinctive blue colouration of the mature adults.
- The blue-sided tree frog lays its eggs on leaves, and once hatched the tadpoles fall into pools below.
The blue-sided tree frog is classified as Endangered (EN) on the IUCN Red List (1) and is listed on Appendix II of CITES (3).
The blue-sided tree frog (Agalychnis annae) is a very colourful amphibian with pink, lavender, orange and blue on its limbs and sides, contrasting with its uniform green upper surface (2) (4). The large eyes of the blue-sided tree frog are yellow-orange, which gives the frog its other common name, the golden-eyed leaf frog (5). As in other Agalychnis species, the eyes of this frog have vertical pupils (2).
The most notable characteristic of the blue-sided tree frog, and the feature for which it is named, is the striking, purplish-blue colouring on its flanks and thighs (2) (5). The underside of its body is creamy-yellow to orange. Interestingly, the blue-sided tree frog has some ability to change colour, becoming darker green and bluish-purple at night (2). This medium-sized tree frog has large discs on the ends of its fingers and toes, and all the fingers and toes are webbed (2) (4).
The males and females of this species are similar in appearance, although the females are slightly larger than the males (2). Juveniles lack the blue colouration of the mature adults (2), while the tadpoles of the blue-sided tree frog are greyish-brown above, with blue-grey sides, a silvery blue underside, and brown flecks on the fins (2) (4).
The blue-sided tree frog is endemic to Costa Rica, and can be found at elevations ranging from 780 to 1,650 metres on the slopes of the cordilleras of northern and central Costa Rica (1) (2). Today, the species remains almost exclusively in disturbed and polluted habitat in areas around Costa Rica’s capital city of San José (1).
The blue-sided tree frog prefers humid pre-montane and lower montane rainforests. However, this species can tolerate disturbance to its habitat, with stable populations being found on plantations, vacant lots, and gardens in the metropolitan areas around San José (1) (2).
The blue-sided tree frog is both nocturnal and arboreal, and like other Agalychnis species it typically moves around by walking, although it will also leap between branches (2). This species breeds during the wet season, between May and November, with mating taking place three to ten metres above the ground. Male blue-sided tree frogs call to attract a mate, usually sitting in vegetation overhanging ponds and giving a repeated ‘wor-or-orp’ every 40 seconds or so (2) (4).
During copulation, the female carries the male to a pond below only to return to the trees to find a place to deposit her eggs (2) (4). The eggs are usually deposited on top of leaves up to three metres above still water. However, the blue-sided tree frog is also known to deposit its eggs on alternative forms of vegetation such as vines or branches. The pale green eggs of this species measure around 4 millimetres in diameter, and are laid in irregularly shaped masses (2). Clutch size varies from 45 to 162 eggs (2) (4).
After the eggs hatch in five to seven days, the larvae of the blue-sided tree frog either intentionally fall into the pond below or are washed down during heavy rainfall, and this is where they then mature and metamorphose into adult frogs. In captivity, this has taken around 247 days (2) (4). The larvae of the blue-sided tree frog are frequently found in garden fountains and swimming pools of Costa Rica’s upland cities, including San José and the surrounding urban areas (2).
The blue-sided tree frog has suffered a precipitous decline in its population, with an estimated 50 percent or more loss in population since the 1990s. Some factors believed to have contributed to this sharp decline are the international pet trade, the fungal disease chytridiomycosis, and larvae predation by an introduced fish species (1).
The blue-sided tree frog is a popular species in the international pet trade, along with other frogs in the genus Agalychnis. In 2007, the United States alone was reported to have imported 221,960 Agalychnis frogs over the previous decade (4).
Another major threat to this species comes from chytridiomycosis, an aggressive fungal disease that prevents respiration in amphibians. The fungus that causes chytridiomycosis can be found in most habitats suitable for the blue-sided tree frog. The blue-sided tree frog is now limited to the disturbed and polluted habitats surrounding San José, purportedly due to the frog’s greater ability than the fungus to withstand pollution (1).
In addition to these threats, populations of the blue-sided tree frog face another obstacle in an introduced fish, Xiphophorus hellerii, which preys on the larvae of the frog (1).
If the fungus that causes chytridiomycosis is actually more susceptible to pollution than the blue-sided tree frog is, then actions typically taken to maintain habitat integrity for amphibians, such as limiting pollution, may actually hinder the blue-sided tree frog’s ability to maintain wild populations (1).
Given the threats to the survival of the blue-sided tree frog and other species in the genus Agalychnis, all Agalychnis species, including the blue-sided tree frog, have recently been granted protection under Appendix II of CITES (3) (4). The creation of a captive breeding programme for the long-term survival of the blue-sided tree frog has been recommended by the IUCN (1).
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- Arboreal: an animal which lives or spends a large amount of time in trees.
- Endemic: a species or taxonomic group that is only found in one particular country or geographic area.
- Genus: a category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.
- Larvae: stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
- Metamorphosis: an abrupt physical change from the larval to the adult form.
- Montane forest: forest occurring in mountains.
- Nocturnal: active at night.
IUCN Red List (January, 2013)
- Savage, J.M. (2002) The Amphibians and Reptiles of Costa Rica: A Herpetofauna between Two Continents, between Two Seas. University of Chicago Press, Chicago.
CITES (May, 2013)
AmphibiaWeb (January, 2013)
- Duellman, W.E. and Dennis, D.M. (2001) The Hylid Frogs of Middle America. Society for the Study of Amphibians and Reptiles, Marceline, Missouri.