Captive-bred animals, who have never before seen a predator, generally
have low survival rates when introduced into the wild as they lack
the necessary survival skills. But Macquarie University PhD research
on captive tammar wallabies shows that these animals can be taught
to recognise and fear predators before release, and once taught
they can also demonstrate this behaviour to other naive wallabies
in their group.
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Andrea
Griffin with the model fox she used to train tammar wallabies
to recognise and fear
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Psychology PhD candidate, Andrea Griffin, has been conducting
her research under the supervision of Macquarie's animal behaviour
expert, Dr Chris Evans, and with the assistance of the Cooperative
Research Centre for the Conservation and Management of Marsupials.
A biologist by training, Griffin was drawn to this area of research
by her fascination with animal cognition and her wish to make a
contribution to the conservation of endangered species.
Her research is unusual in that it combines the theoretical study
of predator recognition with an applied conservation issue. Her
findings may help to ensure the survival of other captive species
that have lost their natural response to predators when they are
reintroduced to the wild.
Griffin chose tammar wallabies because they are almost extinct
in their native Australia, thanks mostly to foxes, but they manage
to survive on islands, such as Kangaroo Island, and in New Zealand
where large predators are absent. In addition, research into marsupial
behaviour and cognition has been, until now, a largely neglected
topic when compared to learning in eutherian mammals (mammals nourished
before birth via a placenta and born in a more developed condition
than marsupials).
Griffin explains that Macquarie University's Marsupial Park has
a large population of tammar wallabies (some bred in captivity in
the park and others brought from Kangaroo Island) as they are the
main species used in marsupial reproductive research. None of the
wallabies in the park have any experience with being preyed upon.
"Tammars seem to have some innate predisposition to recognise
predators, but their response is not sufficient for them to survive
if they encountered a fox or cat in the wild," she says.
Griffin explains that in order to teach an animal to be afraid
of something, you first need to find out what they are afraid of.
For captive wallabies this fear was of humans trying to catch them
with a net. "When a person enters their enclosure carrying
a net, the wallabies show the full alarm response and run away,"
she says.
So Griffin and her team used a model stuffed fox as a signal for
the arrival of a captor.
"Five seconds after the wallabies saw the fox a human would
jump in with a net and chase the wallabies around as if trying to
catch them. The wallabies soon came to associate the fox with the
arrival of a human, and would become alarmed at the sight of the
fox alone," she says.
Griffin also found that when she showed the wallabies a stuffed
model cat, their response to this predator was also heightened.
However, when she introduced a stuffed model goat and conducted
exactly the same experiment (pursuit by a human with a net), the
wallabies showed no fear of the goat whatsoever.
Griffin explains that captive wallabies recognise their predators
by sight alone - they show no recognition of predator smell or sound,
although there is evidence that in the wild macropods do recognise
smell.
"Predatory animals, such as foxes and cats, share certain
features. Frontally placed eyes are necessary for binocular vision
to detect prey. However, goats have laterally placed eyes,"
she says. "This may be the mechanism tammars use to assess
whether another animal is a danger to them or not."
Griffin conducted her experiment four times over four days, but
she said that after that time, while the wallabies had learned to
be afraid of the fox, they had also learned that they were not actually
going to be caught by a human so the training stopped at that point.
Some six to eight months later, Griffin then used some of the trained
wallabies to demonstrate the anti-predatory behaviour to other naive
wallabies in the group.
"We would hold the predator-naive wallaby in an enclosure
by itself and then introduce the trained wallaby. When the fox was
brought in, the trained wallaby would show fear and run away while
the naive wallaby watched," Griffin explains. "Even without
being chased by a human, the apprentice wallaby could learn the
behaviour."
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A
tammar wallaby at the Macquarie University Marsupial Park
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The social transmission of anti-predatory behaviour is particularly
important because when a group of captive animals is released into
the wild, many need the support of a social group. Social transmission
of the trained behaviour, for instance between trained mothers and
their wild-born young, will maintain predator awareness within the
wild population.
Griffin says that the idea of the training is to give the wallabies
enough experience in encountering predators to heighten their awareness
to enable them to survive their first experience in the wild.
"Their first natural experience with a predator is likely
to be a traumatic one, possibly with one of their group being caught
and killed. However it is hoped that pre-release training will be
enough to trigger the predator response, and that their first experience
in the wild will reinforce this behaviour so that it becomes their
natural response," she says.
"Few reintroductions have succeeded in establishing self-sustaining
populations in Australia because captive bred animals lack effective
survival skills, and soft release programs that involve pre-release
training are not as widespread as in other countries. Here we are
more likely to try to eliminate the predators from the environment
than to train animals to respond appropriately."
Other programs that have involved getting captive animals to practice
their skills in foraging for food, dealing with other animals as
well as with predators in larger but still controlled environments
before being released have been very successful.
Griffin says that while it's early days yet, she would like to
see her training method implemented in conjunction with low levels
of predator control so that tammar wallabies and other captive macropods
can once again enjoy their natural habitat.
Story by Kathy Vozella
Images by Effy Alexakis
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