Tomato frog  (Dyscophus antongilii)

Tomato frogs live up to their name by possessing a vibrant, orange-red colour (2). Females are much larger than males and have brighter tones of red or orange on their back, with a pale undersurface (4); some individuals also have black spots on the throat (2). It is thought that the brilliant colours act as a warning to potential predators that these frogs are toxic (5); a white substance secreted from the skin acts as a glue to deter predators (such as colubrid snakes) and can produce an allergic reaction in humans (2) (4).

Endemic to Madagascar, tomato frogs are found in the northeast of the island around Antongil Bay (from which they gain their specific name, antongilii) (5), and south to Andevoranto (4). The exact distribution of this species is unclear however, due to confusion with the closely related D. guineti (6).

Breeding occurs in shallow pools, swamps and areas of slow-moving water. These frogs are found from sea level to elevations of around 200 metres (4).

Tomato frogs breed in February to March following heavy rainfall; the sounds of males calling to attract females can be heard around small water bodies in the dark Malagasy night (2). Following copulation, females will lay a clutch of 1,000 to 15,000 eggs on the surface of the water (2). Tadpoles hatch from these small black and white eggs about 36 hours later (2); they are only around six millimetres long and feed by filter-feeding (5). Tadpoles undergo metamorphosis into yellow juveniles and this stage is completed around 45 days after the eggs were laid (2).

Ambushing potential prey, adult tomato frogs feed on small invertebrates (5). When threatened, these frogs can inflate themselves, giving the appearance of greater size (7).

Numbers of the tomato frog have been declining as a result of habitat degradation and pollution and the over-collection of these brightly coloured amphibians for the pet trade (4). Collecting activity, and the associated decline in population, was predominately focused near to the town of Maroantsetra (6). The tomato frog was rapidly included on Appendix I of the Convention on International Trade in Endangered Species (CITES) in response to this pressure (6).

Research into captive breeding techniques has been carried out by Baltimore Zoo in the United States in an effort to boost the currently small and genetically deprived captive population that exists in that country (4). A consortium of U.S. zoos that form the Madagascar Fauna Group (MFG) (8) have established an exhibit at the Parc Zoologique Ivoloina, Madagascar in an attempt to help educate local people about this attractive member of their natural heritage (4). Very little is known about the tomato frog and further research into its distribution, behaviour and potential threats is urgently needed before effective conservation measures can be put into place (6). It is currently listed on Appendix I of the Convention on International Trade in Endangered Species (CITES), but this move has been criticised by some authors as an ineffective strategy and one that has undermined the status of the unlisted D. guineti (9). Furthermore, research is needed to determine if D. antongilii is in fact a separate species or merely a variant of D. guineti (6).

For more information on amphibians see:

• Amphibia Web:
  www.amphibiaweb.org

Authenticated (23/6/03) by Franco Andreone. Museo Regionale di Scienze Naturali, Torino, Italy.
http://www.francoandreone.it/