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February 27, 2007

Resourceful Ravens

Legend has it that England will not fall to an invader so long as there are ravens at the Tower of London. The last time I visited the Tower (as a guest, I assure you), the British government-appointed Ravenmaster was doing his utmost to assure that the black-winged birds could never possibly leave. In fact, the six well-fed ravens had been rendered flightless not just by wing trimmings, but by their hearty and frequent meals of liver, eggs and the occasional foolish tourist's finger.

I always thought the legend gruesomely suggested that England was "safe" so long as the Tower served its purpose as a place of execution and torture, thus it would always have ravens around to snack on traitors. If the ravens weren't there, then clearly England wasn't actively protecting its interests. Perhaps, though, King Charles II, who ordered that there should always be six ravens on hand, really wanted them for their keen intelligence.

It's probably pretty clear by now that I am fascinated by animals that are intelligent enough to make and use tools, like chimps as well as other primates and dolphins. I had always thought that macaws were the smartest birds, but many argue that ravens are actually more intelligent. Both macaws and ravens can mimick human speech. In fact, the head crow at the Tower, Thor, frequently greets visitors. Ravens are likely the smartest birds around and recent studies have shown that they also have the largest brains for their size.

Ravens live almost everywhere, from the Sahara to the Arctic Circle. Scavengers by nature, young ravens are inquisitive and playful.

Ravens ... have been recorded playing in the wild. Their antics, photographed in Wales in 1980, involved two birds taking it in turn to slide on their backs down a frozen snow bank. The birds covered about 10ft each time and returned on a second day for more fun and games.

More At: BBC: Smartest Of All Birds

Not Just Sharp, But Highly Flexible

As adults, ravens tend to settle down and mate for life, building long-term nests and then raising chicks together using highly complex mating rituals.

One of the most interesting examples of raven intelligence and specifically tool usage was beautifully illustrated at Oxford recently by a pair of Caledonian Crows named Betty and Abel.

They placed a tiny bucket of meat inside a pipe, and left two pieces of wire in their cage, one hooked and one straight, to see if the birds would choose the hooked wire to retrieve the bucket of meat, proving that birds were "tool users" on a par with higher levels of animal intelligence.

"We were delighted and extremely surprised" reported Alex Kacelnik, one of the bird experts studying the crows, when Abel stole the hooked wire from Betty, and rather than giving up, Betty "modified" the straight wire into a hooked wire, and was thus able to hook the bucket, pull it up, and retrieve her snack. This elevates ravens from "tool users" to "tool makers", which places them on a par with primates.

More At: The Raven.

It also proves, yet again, that women are smarter than men. Here's a video of a raven solving the bottle bait problem, so you can see for yourself.

You Can't Fool A Raven

Scientists believe that ravens are one of the few birds capable of simple math. Most birds will assume that if two people go into a hide and then one comes out, then it is safe to approach the hide because no one is there. Ravens, however, are capable of keeping track of people entering and then exiting and it requires a much greater number of people coming and going (a whole class of school children, for example) to get past the raven's keen eyes.

I'm curious about macaws and counting. If my father-in-law put one treat in one hand, and two in the other, would his macaws choose the one with more treats? Does this count? Heh.

I'd love to see some of the experiments that were done with capuchin monkeys and token values done with ravens. You'd have to decide on tokens carefully, since young ravens do love shiny stuff.

The Clark's Nutcracker, a member of the raven family, also has very impressive spacial memory. During the warm months, it stores up to 100,000 pine seeds (pine nuts?) to eat later. It spreads little caches of about a dozen seeds in each spot, over a large area of up to 150 square miles and yet, even half a year later, the bird can track down the seed caches, even under heavy snow. The nutcracker shows forethought as well, often storing more than it needs to live in order to cover problems like seed-stealing squirrels. This seed spreading also helps maintain the bird's habitat and food source since leftover seeds will germinate in the spring.

Posted by sorsha at February 27, 2007 4:01 PM