Grey squirrels’ superior problem-solving powers could explain why they now outnumber red squirrels by more than 15 to one in the UK.
Researchers from the universities of Edinburgh and Exeter found grey squirrels have ‘superior behavioural flexibility’ over native red ones.
In layman’s terms: red ones just aren’t as clever.
This flexibility from the greys ‘may have facilitated their invasion success’, researchers said.
Dr Pizza Ka Yee Chow, from the University of Exeter’s Centre for Research in Animal Behaviour, said: ‘Many factors have been considered to explain why grey squirrels are more successful when they move into areas where red squirrels live.
‘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.’
A study tested wild squirrels with one easy task and one more difficult to get hazelnuts.
Both species were equally successful at the easy task – opening a transparent lid – but more of the grey squirrels cracked the difficult one, a more complex task of pushing and pulling levers.
About 91% of grey squirrels eventually solved the difficult task, compared with 62% of red squirrels.
Researchers said ‘inefficient’ foraging and food extraction was likely to mean poorer fitness among red squirrels, harming their chances of reproduction.
‘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,’ Dr Chow said.
‘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.’
One positive finding for the red squirrels was that, of those who solved the difficult task, some did so 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, said: ‘These results illustrate how investigating animals’ differing cognitive abilities can help us understand important issues in conservation.’