The birds have to be able to assess very quickly how close to a wolf or fox they can get when one is eating a dead animal: they need to get close enough to get food, but not be attacked themselves.However, Heinrich cautioned against stating unequivocally that the raven is the cleverest animal on Earth after humans. Scientists such as Heinrich and Bugnyar believe that ravens evolved their surprisingly high intelligence because of their complex social lives and scavenging lifestyles. The New Caledonian crow has been shown to fashion tools of leaves and to use them to extract grubs from crevices in trees, for example. Birds related to the raven also show surprising intelligence. In the wild, they have been known to make calls that bring wolves and foxes to dead animals so that these large carnivores can break the carcass apart, making meat accessible to the birds. Other experiments by biologists have shown that ravens often let other animals do work for them.

That capacity is probably lacking, or present only to a limited extent, in most animals.' 'Ravens have the ability to test actions in their minds. 'The birds acted as if they knew what they were doing,' the two researchers say in Scientific American. By contrast, ravens have demonstrated that they can work out complex sets of actions, involving no tests or trial and error. However, such creatures are programmed genetically to undertake the different steps involved in such behaviour. Many animals, birds and insects are capable of carrying out complex actions: nest-building, for example. These birds have never seen string before or encountered meat hanging this way, yet they worked out exactly what they needed to do to get a treat.' I was extremely surprised the first time I saw one of them do this.

'However, I found ravens could perform this complex sequence of actions straight away. 'Some animals can be taught how to get food this way,' Heinrich said. By repeating this process half a dozen times, a raven could reach the end of the string and get the meat. To get a treat, a raven had to perform a complex series of actions: pull up some of the string, place a loop on the perch and hold it with a claw, then pull up another section of string and hold that loop on the perch.

One startling experiment they outline involved ravens who were allowed to sit on perches from which pieces of meat dangled from string.

Bernd heinrich raven