BILBIES AND FERAL CATS
[1] More than 20 species of Australian mammals have been exterminated by feral cats. These predators, which arrived with the European settlers
[colonizadores], still threaten native wildlife – and are too abundant on the mainland to eliminate, as has been achieved on some small Australian islands
that were previously infested with them. But Alexandra Ross of the University of New South Wales thinks she has come up with a different way to deal with
the problem. As she writes in a paper in the Journal of Applied Ecology, she is giving feline-attentiveness lessons to wild animals involved in re-introduction
programs, in order to try to make them more aware of the dangers of feral cats.
[2] Many Australian mammals, though not actually extinct, are confined to fragments of cat-free habitat. That offers the possibility of taking colonists
from these refuges to places where a species once existed but now is no longer found. This will, however, put the enforced migrants back in the sights of
the cats that caused the problem in the first place. Training the migrants while they are in captivity, using models of cats and the sorts of sounds cats make,
has proved expensive and ineffective. Ms. Ross therefore wondered whether putting them in large naturalistic enclosures might serve as a form of trainingcamp to prepare them for introduction into their new, cat-infested homes.
[3] She tested this idea on bilbies, a small Australian mammal that superficially resembles a rabbit. She and her colleagues raised a couple of hundred
bilbies in a huge enclosure that also contained five feral cats. As a control, she raised a nearly identical population in a similar enclosure without the cats.
She left the animals to get on with their lives for two years, which, given that bilbies breed four times a year and live for around eight years, was a
substantial period for them. After some predation and presumably some learning she selected 21 bilbies from each enclosure, fitted radio transmitters to
them and released them into a third enclosure that had ten hungry cats in it. She then monitored what happened next.
[4] The upshot [resultado, conclusão] was that the training worked. Over the subsequent 40 days, ten of the untrained animals were eaten by cats, but
only four of the trained ones. One particular behavioral difference she noticed was that bilbies brought up in a predator-free environment were much more
likely to sleep alone than were those brought up around cats. And when cats are around, sleeping alone is dangerous.
[5] How the bilbies that have undergone this extreme training will survive in the wild remains to be seen. But Ms. Ross has at least provided reason for
hope.
Adapted from The Economist, May 18th 2019.
In the context of paragraph 2, the term “enforced migrants” most likely refers to which of the following?
