Grey
squirrels beat reds in 'battle of wits'
University of Exeter
Problem-solving powers may help to
explain why grey squirrels have taken over from native red squirrels in the UK,
according to new research.
The study tested wild squirrels with
an "easy" task (opening a transparent lid) and a
"difficult" task (a more complex process of pushing and pulling
levers) to get hazelnuts.
The two species were equally
successful at the easy task, but a more of the grey squirrels cracked the
difficult one.
The researchers, from the
universities of Exeter and Edinburgh, said this "superior behavioural
flexibility may have facilitated their invasion success."
Red squirrels have lived in the UK
for thousands of years, but grey squirrels -- which arrived from North America
in the 19th Century -- now outnumber them by more than 15 to one.
"Many factors have been considered to explain why grey squirrels are more successful when they move into areas where red squirrels live," said Dr Pizza Ka Yee Chow, of Exeter's Centre for Research in Animal Behaviour.
"These factors include disease
resistance and the fact grey squirrels are bigger, but our research shows
problem solving could be another key factor for the success of greys.
"This might be especially
important for an invasive species like grey squirrels, as they have evolved
elsewhere and have to adapt to their surroundings."
The researchers set up the tasks and
observed squirrels, which can be identified by their unique body
characteristics.
About 91% of grey squirrels
eventually solved the difficult task, compared to 62% of red squirrels.
The study says
"inefficient" foraging and food extraction are likely to mean poorer
fitness among red squirrels, harming their chances of reproduction -- and
reduced breeding is known to be a major factor in the decline of the species.
"It is not yet clear whether
grey squirrels are born better problem solvers, or whether they work harder
because they're an invasive species living outside their natural
environment," said Dr Chow.
"The current stage of our
research is to look at this, and the results may give us more insight into the
likely future of both species."
The findings did offer some hope for
red squirrels, as among those that succeeded at the difficult task, a few
solved it more quickly than greys in subsequent attempts.
The successful red squirrels were
also quicker to change tactics after trying a method that did not work.
Professor Stephen Lea, also of
Exeter's Centre for Research in Animal Behaviour, added: "These results
illustrate how investigating animals' differing cognitive abilities can help us
understand important issues in conservation."
Ideally, the researchers would have
studied wild squirrels living in the same area but -- as red squirrel numbers
usually decline rapidly when grey squirrels arrive -- they chose similar but
separate locations.
The grey squirrels studied were in
woodland around the University of Exeter's Streatham Campus, or on the campus
itself, while the red squirrels were in woodland around Brodick Castle on the
Isle of Arran, Scotland.
The paper, published in the journal Animal
Behaviour, is entitled: "A battle of wits? Problem-solving abilities
in invasive Eastern grey squirrels and native Eurasian red squirrels."
