AMATEUR conservationists are threatening the survival of the frogs they are
trying to help, says an Australian herpetologist.
Since the early 1990s, environmentally conscious Australians have been
reintroducing tadpoles into ponds and streams in an attempt to bolster flagging
populations. But the practice could drive some species of frog to
extinction.
鈥淭here are many risks: gene flow into new areas, the introduction of new
species, and obviously the spread of diseases,鈥� says Gerry Marantelli, manager
of the Amphibian Research Centre in Melbourne which specialises in frog
conservation.
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Frog numbers have plummeted worldwide in recent years, largely due to the
spread of the fungus chytrid, which attacks keratin in the animal鈥檚 skin. It
kills amphibians either by producing toxins or by stopping them from using their
skins to breathe. In Australia, chytrid has helped wipe out several species of
frog.
Amateur conservationists have reacted by trying to reintroduce the frogs by
moving tadpoles from one location to another. 鈥淲e鈥檙e desperately trying to have
that practice stopped,鈥� says Marantelli. Tadpoles do not have keratin in their
skin, but they have hundreds of little teeth that contain the keratin protein
and can carry the fungus. Once the tadpole metamorphoses into a frog, the
infection takes hold.
鈥淧athogen pollution is a problem that is on the increase and not only for
frogs,鈥� says Alex Hyatt of the Australian Animal Health Laboratory in Geelong,
near Melbourne (快猫短视频, 5 August 2000, p 32). 鈥淏oth professional
and amateur conservationists need to reassess what they are doing.鈥�
Marantelli and his colleagues know of four exotic frog species, all potential
carriers of disease, that have been introduced by amateur conservationists. Two
of them鈥攖he western banjo frog and the spotted-thighed
frog鈥攑reviously only lived in south-western Australia but are now moving
east across the Nullarbor Plain. 鈥淏y talking to the local people, we鈥檝e
discovered that the frogs were deliberately introduced into the ponds of the
little roadhouses on the Nullarbor,鈥� says Marantelli. 鈥淧eople thought frogs were
in trouble, and with the best intentions, but not enough information, they tried
to do some good.鈥�
Amateur conservationists also introduced a Tasmanian frog to Melbourne. 鈥淚t鈥檚
effectively a pest animal, and we鈥檙e looking to see if it can be eradicated,鈥�
says Marantelli, who presented his findings at a conference on amphibian
diseases held in Cairns earlier this week.
Exotic frog species are also travelling to new places in supplies of fruit,
vegetables and flowers. When Marantelli organised a survey of wholesalers in
1995, he found that this was bringing eight to ten thousand foreign frogs each
year into the city.
To help combat the problem, Marantelli has enlisted volunteers who visit
wholesalers and asked them to phone a local number when they discover a frog.
The animals are then collected, treated for any infectious diseases and fostered
out to schools, zoos or as pets.