Squirrels, with their nut-burying habits and uncanny knack of finding them later, are known for their ability to recall important details. But scientists have discovered a new squirrel trait they see as a different kind of memory skill, an ability to remember problem-solving techniques from almost two years earlier.

"This is not just remembering where things have been left, it shows they can recall techniques which they have not used for a long time," said Dr. Théo Robert from the University of Exeter, co-author of the new study. "It's also different from what we see in the wild because they're remembering things for longer than the few months of memory needed to find hidden food."

The new discovery came by way of an experiment conducted by Robert and his colleagues at the University of Exeter. Working with five grey squirrels, the team tasked the animals with pressing levers in order to get their mitts on some tasty hazelnuts. The first time around, the squirrels took an average of eight seconds to complete the task. With practice, they eventually reduced their hazelnut retrieval time to just two seconds.

Then, 22 months later, the team presented the same squirrels with a modified version of this same task. The puzzle appeared differently, but actually required the same technique to obtain the hazelnuts and at first this threw the squirrels off. They hesitated for an average of 20 seconds before even beginning the task, something the researchers attribute to a neophobic response, or a fear of new things.

But once the squirrels got going, they were able to retrieve the hazelnuts in just three seconds on their first try, and then finally in an average of two seconds. This, the researchers say, is evidence of the squirrels' long-term memory skills as they recalled and applied the same technique used in the earlier challenge.

"This might be why grey squirrels can survive very well in towns and cities," says Dr. Pizza Ka Yee Chow, of Exeter's Centre for Research in Animal Behaviour. "For example, they're very good at getting food from bird feeders. People may try different types of bird feeders to keep the squirrels away, but this research shows grey squirrels can not only remember tricks for getting food but can apply those skills in new situations."

The team's research was published in the journal Animal Cognition.