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#Natureology Species of the Day – Sao Tome giant treefrog (Hyperolius thomensis)

January 17, 2013

jukh

Sao Tome giant treefrog (Hyperolius thomensis)is an endangered species of frog that is endemic to São Tomé Island in São Tomé and Príncipe.

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Biology

The São Tomé giant treefrog is endemic to the island of São Tomé in the Gulf of Guinea, 255 kilometres off the coast of Gabon There is little information on the population status of this species, since it is notoriously difficult to find. The São Tomé giant treefrog is restricted to the remnants of original primary forest that occur at elevations above 800 metres.

As the largest member of the genus Hyperolius, the large, flamboyant São Tomé giant treefrog (Hyperolius thomensis) presents a classic example of ‘island gigantism’, the tendency of certain colonisers on islands to evolve to become larger than their mainland relatives .

While the back of the São Tomé giant treefrog is a uniform green to blue-green colour, the underside is attractively marbled with orange, white and black. In the male São Tomé giant treefrog, the back is densely studded with small spines .Like other species within the genus, the São Tomé giant treefrog has expanded toe pads and long legs that make it an adept climber.

São Tomé giant treefrog breeds in standing water, but instead of utilising slow streams or ponds, this remarkable species lays its eggs in water-filled holes in trees, often at a considerable height . The eggs are deposited in masses of 20 to 40 , and the same tree hole may be used for breeding by several different individuals at different times . Like most other frogs, the eggs develop into free-swimming, gilled tadpoles, which then metamorphose into the adult form

Threats

Sao Tome giant treefrog  is listed as ‘Endangered’ on the IUCN Red List of Threatened Species. Little information is available on threats, though it is likely to be impacted by habitat loss for agriculture, livestock, wood extraction, and human settlements.

Since the São Tomé giant treefrog is so notoriously difficult to find, very little is known about its population status or the threats it faces, but habitat loss is likely to continue to have the biggest impact on this species . This species also seems to be occasionally offered in the pet trade in Europe, although the extent to which this occurs and impacts the population is unknown.

Conservation

There are no known specific conservation measures in place for the São Tomé giant treefrog, but this species does occur in the proposed 295km² protected Obo National Park (Parc Naturel Obo) which may provide some sanctuary to this elusive specie, However, with so little known about its ecology, population status or threats, further studies are urgently required and conservationist must initiate captive breeding and reforestation programme to save this declining species from extinction.

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