CROWS have been observed storing tools they no longer need in case they find a use form them later.

A study by scientists at the University of St Andrews looked at the way birds and other animals avoid accidental tool loss.

New Caledonian crows are famous for using sticks in their beaks to extract insects from tree holes and other hiding places, but need to put them down to eat their prey.

However, the researchers found that wild-caught birds crows will carefully place tools under their feet to use them again later, and even get upset if they accidentally drop a stick.

Barbara Klump, lead author of the study, said: "This makes perfect sense because the higher up you are, the more challenging it would be to recover a tool."

Humans use many different tools every day, and are very good at keeping them safe for later use. Dr Christian Rutz, team leader and one of the study's co-authors, said: "When you put a treasured pen in a pen holder, you know where it is, and can quickly find it again. It turns out that crows do exactly the same, sometimes storing their tools in tree holes or behind bark."

The crows were extremely good at keeping track of their tools, remembering where they had put them, and reusing them again to extract more meals shortly after.

This tool 'safekeeping' may be very important, as it means crows don't have to repeatedly manufacture new tools and can spend more time on the critical business of finding food.

Exactly how long wild crows use individual tools for, and how far into the future they can plan, remains to be explored.