The Golfo Dulce poison dart frog
After a short amphibian and reptile survey one day, we decided to keep walking up Rio Carate to see what we could find! At this point I was getting frustrated, not having seen many of the small hoppers that are meant to be found in this well-forested part of the Osa Peninsula. Suddenly a friend stopped and pointed out a flash of red, which quickly disappeared under a leaf. We came closer and I immediately recognised the not one but five little juvenile frogs jumping around under the shelter of a big rock. We got super excited and high-fived all around. It was our first sighting of the Golfo Dulce poison dart frog (Phyllobates vittatus). We hadn’t even been aware that a small population of this enigmatic species persists on the river, so close to camp.
The Golfo Dulce poison dart frog is a beautiful frog, endemic to the Golfo Dulce region. It is a diurnal species inhabiting the understory leaf litter or rock crevices of primary forests near streams. During mating season, courtship behaviour lasts for one to seven days, after which the female lays clutches of 7-21 eggs, usually deposited on leaves off the ground, which the father then visits to moisten frequently until they develop into tadpoles. They then climb onto his back and he brings them to a little pool of water where they can finish their development into froglets. The Golfo Dulce poison dart frogs feed mainly on ants and other arthropods, and are, like other frogs of the Dendrobatidae family, poisonous. The poison is believed to stem from melyrid beetles or other ingested sources; it does not develop in captive-bred specimens. Along with other iconic frogs, this species draws in tourists from all over the world, and is appreciated by the locals as a flagship species for the amphibian diversity of the Osa Peninsula. What many perhaps don’t know is that it is endangered.
The majority of amphibians of the world are found in the tropical forests. These same forests are vanishing at the highest rate of all forest types, and amphibians, who are often specialists to their forest niches, are among the first species to be lost. Costa Rica is known for having turned the tables on deforestation but as you drive through the country, you will notice vast areas of cattle ranches and palm plantations. Even though the “crown jewel” of Costa Rica’s national park system, Corcovado, lies within the mere 4,080 km2 range of the species, there is, as with most other amphibians, a “continuing decline in the extent and quality of its habitat.”
The species is often spotted by locals, guides and tourists alike, giving the impression that it is common. However, the species has not been recorded in Dominical since the year 2002. The extant populations outside of the Osa are severely fragmented, and the subpopulations on the Osa appear to be isolated from one another.
Population fragmentation and isolation are known by scientists to cause decreased persistence of the species. It results in a lack of genetic transfer between the subpopulations and in the case of local extinctions, there will be no possibility for other populations to repopulate those locations. Basically, if the species is hit by one or more of the identified threats, which include severe climatic events, further loss of suitable habitat, contamination of freshwater breeding grounds from gold mining activities, epidemic infectious diseases or over-collection for the pet trade, it will not be able to recover efficiently through repopulation.
According to the IUCN, there is plenty of work to be done. They suggest further strengthening of the management of the national parks in which the species is found, as well as expanded protection of connecting forest patches outside of the parks. The species is listed on the CITES (Convention for the International Trade of Endangered Species) Appendix II. Further legislation and management practices to allow sustainable, commercial harvest of the species for the pet trade is recommended. The harvest of endangered species for captive breeding and flooding of the international pet market is a rather conventional and debated idea in conservation still, and proof of its effectiveness is vague. This is why we need further studies on the viability of the idea before implementation. Other studies suggested by the IUCN also include natural history of the species and current threats. But most important of all are the close monitoring programmes of the subpopulations in order to assess the real impact of the pet trade and the general population trends.
So remember to take a second the observe and appreciate this beautiful frog next time you see it.
AmphibiaWeb, 2009. Phyllobates vittatus. [Online] Available at: http://amphibiaweb.org
Dumbacher, J.P., Wako, A., Derrickson, S.R., Samuelson, A., Spande, T.F. and Daly, J.W., 2004. Melyrid beetles (Choresine): a putative source for the batrachotoxin alkaloids found in poison-dart frogs and toxic passerine birds. Proceedings of the National Academy of Sciences of the United States of America, 101(45), pp.15857-15860.
IUCN, 2013. Phyllobates vittatus. [Online] Available at: http://www.iucnredlist.org/details/55265/0