Red and grey squirrels go head to head in nut IQ test

The rise of grey squirrels across the UK could be down to the fact they are cleverer than their red coated cousins.

A series of tests involving hazelnuts inside sealed containers has found that grey squirrels have superior problem-solving skills to red squirrels.

Eastern grey squirrels, which came to the UK from North America in the 19th Century, now outnumber native Eurasian red squirrels by more than 15 to one.

Animal behaviour experts from the universities of Exeter and Edinburgh first tasked the wild animals with opening a transparent lid to reach the nut.

They then presented a second, more complicated test, involving the pushing and pulling of levers.

While both species were equally good at the simpler task, grey squirrels beat the reds hands down in the more difficult challenge.

About 91% of grey squirrels eventually solved the difficult task, compared with 62% of red squirrels.

Researchers said the grey's "superior behavioural flexibility may have facilitated their invasion success".

It is not known if the invasive species are born better problem solvers or have simply developed a better cognitive ability as they learned to adapt to their new surroundings.

Previous studies into the success of the grey squirrels have looked at their larger size and disease resistance.

Reasons behind the decline of red squirrels has been put down to "inefficient" foraging leading to reduced breeding and shrinking forest habitats.

It is a common misconception that grey squirrels chase red squirrels away, they simply seem better at adapting to new surroundings.

One silver lining for the red squirrels is that of those who cracked the more difficult task, some did so more quickly than greys in subsequent attempts.

They were also quicker to try new tactics when unsuccessful in their approach.

It is hoped the new findings will help experts develop their understanding of red squirrel conservation.