They take to artificial habitats set up by NUS student in her project
Victoria Vaughan Straits Times 24 Jul 10;
FROGS are happy to have a helping hand when it comes to mating, a National University of Singapore (NUS) student has found.
Miss Teo Yea Tian, 23, found that the average number of mating calls from the frogs rose from nine to 13 a night after she provided artificial breeding sites in rain-filled cups, basins and dishes.
Her study centred on the black-spotted sticky frog, so named because of a glue-like mucus it secretes from its skin when threatened.
The frog is highly dependent on rainfall as it lays its eggs in puddles collected in leaves or water collected in declining pitcher plants.
In October last year, Miss Teo began to measure the numbers in her study area along the 400m catchment path in Bukit Timah Nature Reserve.
She went into the reserve three to four times a week for about two hours each time.
These ground-dwelling frogs can grow up to 3cm for males and 5cm for females and are brown in colour, making them tricky to spot against fallen leaves.
The student carried out audio surveys at night as these little frogs make a big noise. The mating call of the male sounds like a high-pitched, short, repetitive whistle.
At the start of December, Miss Teo took two days to set up various artificial habitats in plastic and bamboo cups and plastic and ceramic basins to see if it encouraged breeding.
The cups were filled naturally with rainwater and it took less than two weeks for the frogs to make use of them, with batches of 10 to 120 eggs laid.
Its takes 14 to 16 days for the frogs to develop from the egg.
Froglets that developed in the plastic basin were found to have the best survival rate of 53 per cent.
However, introducing these cups 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.
Miss Teo said: 'I think we should continue to help vulnerable species, but we have to have a more complete study of the surrounding effects.
'This is possible but it will require more money and it would be good to try and get the Government involved as they are the ones with the money to put into it.'
The study cost about $500 and Miss Teo is in the process of trying to get it published in a journal.
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 Miss Teo's study, there are plans to put artificial breeding spots on trees to help increase the population and distribution of this tiny toadlet.
