Costa Rica brook frog  (Duellmanohyla uranochroa)

The Costa Rica brook frog is classified as Critically Endangered (CR) on the IUCN Red List (1).

One of Costa Rica’s most highly endangered frog species (3), the Costa Rica brook frog is a small, beautiful amphibian with bright leaf-green upperparts, yellow underparts and a yellow throat. There is a whitish-yellow stripe running along the side of the body from the upper lip to the groin, as well as whitish stripes along the edges of the arms and on the feet (2) (4). The Costa Rica brook frog is also notable for its striking red eyes, which give it the alternative name of ‘red-eyed stream frog’ (2) (4).

The Costa Rica brook frog has a fairly rounded snout and a large, distinct tympanum. The skin on the upperparts, chin and chest is smooth, while the belly has a more granular texture (2) (4). There is some webbing between the fingers and toes (2) (4). As in other members of the Hylidae family (5), the tips of the digits have enlarged, adhesive discs, which aid in climbing (2) (4).

The male Costa Rica brook frog is slightly smaller than the female, and also possesses dark ‘nuptial pads’ at the base of the thumbs (2) (4). The tadpoles of this species are quite large, at up to 4.2 centimetres in length, and have low fins and a long, rounded tail. The body of the tadpole is usually olive brown, flecked with bluish-white, and the fins are creamy-brown with brown spots and tiny white flecks (2). As in all members of the genus Duellmanohyla, the tadpole of the Costa Rica brook frog has a huge, downward-hanging mouth (2) (4) (6).

The call of the male Costa Rica brook frog is an unmistakable series of deep, melodic, bell-like notes, described as ‘boop-boop-boop-boop’ (2) (4).

The Costa Rica brook frog occurs on the Atlantic and Pacific slopes of the Cordillera de Tilarán, Cordillera Central and Cordillera de Talamanca in Costa Rica. It is also known from western Panama (1) (2) (4) (7).

This species inhabits humid lowland and montane forest, at elevations of around 300 to 1,750 metres (1) (2) (4). As its common name suggests, the Costa Rica brook frog is typically found near brooks and streams (1) (2).

The Costa Rica brook frog is active at night, when individuals often congregate along small, fast-flowing mountain streams. During the day, it is commonly found sheltering at the bases of the leaves of epiphytes, or of aroids (members of the Araceae family) on the ground (1) (2) (4). Little information is available on the diet of this species.

The bell-like calls of the male Costa Rica brook frog are typically given from dense vegetation several metres from a stream, and from up to three metres above the ground (1) (2) (4). Although this species may call at any time of year, breeding activity is thought to peak between May and June, and again between September and November, coinciding with the wet season (2) (4).

The eggs and egg-laying behaviour of the Costa Rica brook frog has not yet been described (2). However, like some other members of the Hylidae family (5), it is possible that it may deposit its eggs on vegetation over water (2). The tadpoles develop in relatively quiet pools (1) (2) (4), but may attach themselves to large rocks in the stream bottom when the streams rise after heavy rains (1) (2). After metamorphosis, the young frogs, known as ‘metamorphs’, measure around 1.6 to 1.7 centimetres in length (2).

Although once common, the Costa Rica brook frog has undergone a severe population crash in recent decades (1) (3) and is now one of the most endangered frogs in its range (3). As of 2002, only a remnant population was known from Monteverde in Costa Rica, although a second population was subsequently found in Tuis de Turrialba in 2007 (1). This species is also believed to have declined in Panama (1).

The main cause of the Costa Rica brook frog’s decline is thought to be the fungal disease chytridiomycosis (1), which is a major threat to amphibians worldwide (8). This threat may be exacerbated by the effects of climate change, as well as by habitat loss due to farming activities (1).

There are not known to be any specific conservation measures currently in place for the Costa Rica brook frog (1). However, plans are underway to try and translocate some tadpoles to new sites to establish populations within a protected reserve near Guayacán in Costa Rica (9). Conservation work and biological research are also being undertaken at the Costa Rican Amphibian Research Center (CRARC), which operates two reserves (9).

The Costa Rica brook frog has been recorded from several protected areas in Costa Rica, as well as from at least three protected areas in Panama. Recommended conservation measures for this Critically Endangered amphibian include further survey work to monitor its populations, research to determine the threat posed by chytridiomycosis, and a possible captive-breeding programme (1).

View information on this species at the UNEP World Conservation Monitoring Centre.

Find out more about the Costa Rica brook frog and about amphibian conservation in Costa Rica:

• AmphibiaWeb:
  http://www.amphibiaweb.org/
• Costa Rican Amphibian Research Center:
  http://www.cramphibian.com/

More information on amphibian conservation:

• Amphibian Ark:
  http://www.amphibianark.org/
• IUCN/SSC Amphibian Specialist Group:
  http://www.amphibians.org/