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Inviato da Wes von Papinešu on Novembre 25, 1999 at 11:44:36:
AUSTRALIAN BROADCASTING CORPORATION 12 November 99 Rare frog found near Gosford backyard
A new, fairly healthy population of the endangered green and golden Bell Frog has been found by backyard frog watchers on the central coast of New South Wales, Australia.
It is one of only half a dozen healthy populations, each numbering 200 or so adults, in New South Wales, where the frog has declined dramatically during this century. It used to be the most common frog species in the state, totalling tens or hundreds of millions.
The frogs were found by Newcastle University student Ms Melanie Bannerman, who along with Dr Graham Pyke, principal research scientist at the Australian Museum had recently helped set up a Friends of the the Green and Golden Bell Frog group in the Davistown area, near Gosford. They had targeted this area because it was the only place between Hawkesbury and the Hunter Rivers where the species was known to occur.
Someone told Ms Bannerman about some frogs living in a friend's backyard, so she went looking -- and listening -- in the swamp nearby.
"Melanie heard our frog calling in the swamp, and then she found some tadpoles," said Dr Pyke, who was called upon to join the search.
They found more tadpoles, another positive sign: "Calling plus tadpoles equals breeding". While Ms Bannerman had originally thought there might be 20 or so animals, a survey put population estimates at 200. Most populations in New South Wales are tiny, with only five or ten adults.
Destruction of its favoured wetland habitat was the main reason for the frog's endangered status, said Dr Pyke. "Before European settlement, the largest populations would have been in inner Sydney, in areas close to water in the Sydney Basin -- the areas that were settled first."
Other factors were human disturbance of the flooding regime by damming rivers, and predation of the frogs' eggs by the plague minnow -- a fish purposefully introduced to control mosquito numbers which has itself reached pest levels.
Strangely enough, the places where the green and golden bell frog does survive are not necessarily wild and pristine. The newly-discovered Davistown population lives in a swamp created by an artificial embankment, and one population of between 250 and 500 adults lives at the Olympic site at Homebush Bay. "We humans dug this hole in the ground which turned out to be the right kind of habitat for the frog, so it hopped over and set up shop in the brickpit," said Dr Pyke.
Though encouraged by the new discovery, Dr Pyke says it is probably not a sign that numbers of the frog are increasing -- rather that "there are still healthy populations living in people's backyards, and these are important in the conservation of the species."