26 July 2010

Breeding boost to Singapore's native frogs?

In her study of our sticky frogs, Teo Yea Tian provided artificial habitats in plastic and bamboo cups and plastic and ceramic basins to see if these encouraged the frogs to breed.
Black-spotted Sticky Frog
The black-spotted sticky frog got its name because it secretes a glue-like mucus when threatened. It is tiny with a huge call! And is horribly difficult to spot.

The study found an increase in mating calls when artificial habitats are provided. However, the study also suggests that introducing artificial breeding habitats had a wider effect on the ecosystem as dragonfly larvae, which eat the tadpoles, were also found in the basins. Another unforeseen consequence was that thirsty macaques drank the water from some of the test sites and destroyed the basins. Also, a sudden and marked increase in the number of these frogs may affect the food chain; they feed on ants and termites and they are eaten by snakes.

Assistant Professor David Bickford from the NUS Department of Biological Sciences said that following on from Miss Teo's study, there needs to be a strategy for all the rare and endangered frogs in Singapore.

'These frogs need specific kinds of phytotelms (water-holding plants or tree holes) or pristine streams. Those will be what we try and provide for them - in quantities and qualities that have deteriorated in Singapore in the past decades,' said the frog expert, who supervised Miss Teo's project.

Dr Leong Tzi Ming, a National Parks Board research officer in charge of a survey to document nature in Bukit Timah and the Central Catchment nature reserves, said the findings had important implications for future conservation efforts.

'It shows that this particular species is receptive to artificial micro habitats which could help in the conservation of species that may be affected by prolonged dry weather,' he said.

There are 25 frog and toad species in Singapore and the survey found that while numbers do not seem to be declining, the locations of populations have shifted as these amphibians move to be closer to reliable water sources.

'This is good news for the island's biodiversity,' said Dr Leong, as frogs are seen as an indicator of the health of bio-diversity. This is because they are most rapidly affected by changes in the environment from pollutants or a lack of water as they have thin skin. If the frogs are doing well, it is likely that the ecosystem is in good shape.

One of the key findings of the survey was the first evidence of breeding of the thumbnail-size St Andrew's cross toadlet which is critically endangered in Singapore.

Thanks to the findings in Teo's study, there are plans to put artificial breeding spots on trees to help increase the population and distribution of this tiny toadlet.

The NParks survey also found several American bullfrogs in the nature reserves. A native to North America, these introduced animals could pose a threat to our native wildlife.

Survey leader Dr Leong Tzi Ming said "Most of the bullfrogs were quite young, so it seems that they are not breeding well here, probably because they are not used to a tropical climate. But it is quite alarming as they can hang on for a couple of days and they have been known to carry the chytrid fungus, which has been identified as a serious threat to amphibians around the world."

It is thought that these frogs, which can grow up to 20cm, have been released by pet owners and animal lovers who wish to spare them from being eaten as this species is traditionally used for local cuisine.

Dr Leong urged people not to release these frogs into the wild as they could harm local species.

More about the harmful effects of animal release and impact of exotic animals on our native wildlife.

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