New research on cane toads is generating heated discussion as
scientists may have finally cracked a biological method of control.
Professor Rick Shine from the University of Sydney, has studied
cane toads in Queensland that lagged behind the invasion front and
may discovered a way to control the invasion using parasites and
toad communication signals. However it is his proposal that small,
sterile male cane toads be introduced ahead of the invasion that
has divided opinion.
Releasing smaller toads as Teacher Toads may give native fauna
an opportunity to learn. If their first encounter with a cane toad
is not fatal, by the time the large colonising toads arrive, the
predators know to leave them alone. The release of the sterile
males would also add competition for females and remove the females
that they mate with from the breeding equation as the eggs will not
be fertilized. Teacher Toads could also be infected with a lungworm
parasite discovered by the team.
Professor Shine found the toads that had lagged behind were
infected with a lungworm parasite which slows down adults and, in
laboratory tests, kills around 30% of baby toads. It was originally
thought that this lungworm parasite came from Australian frogs,
ruling out using the parasite for toad control due to potential
frog impacts. However, DNA sequencing has shown the parasite
species came from the Amazon and is genetically different to those
found in Australian frogs.
The team has also discovered that pheromones used to communicate
danger between toad tadpoles have significant impacts on their size
and survival. The release of the pheremone stresses the toad
tadpoles so much that in field trials around half of them died
before they became adult toads, and those that become adults were
half the size they should have been. The pheromones were also found
to be different to those of Australian frogs and didn’t
Using the lungworm parasite and the alarm pheromone together
would be particularly powerful as the pheromone either kills or
produces smaller ‘toadlets’, and the parasite is more
effective at killing these smaller sized toads.
Professor Rick Shine, University of Sydney,
Tel: 02 9351 3772 Mobile: 0417 247 573