Are crows really clever?

Jo Wimpenny is an animal behaviour expert with a particular interest in crow cognition...

Jo - It's a great question. The crows are members of the corvid family of birds. That includes the ravens and magpies, jays, rooks, and others. And, it's fair to say that, over the last 20 to 30 years, they've really risen in prominence and got a bit of a reputation for being really, really clever birds.

So, the first thing to say, I think, is what do we mean by clever? What is intelligence? These are questions that are not easily answered. They are things that have plagued the field since the earliest days. You could still have an entire conference on the topic of animal intelligence and what it actually is, and actually human intelligence! We don't know how to easily define it even for our own species. So, being able to roll a definition out to animals is really, really difficult. That means that there's no single gold standard test for intelligence that we can just roll out across the animal kingdom and compare them and rank animals in terms of cleverness.

The consensus seems to be that, when we talk about intelligence, we're really talking about a package of different abilities, which animals use to solve problems in their environments. That could be rapid learning speed; the ability to generalise; the ability to solve problems creatively or insightfully; flexible memory skills and social manipulation... It's sort of a whole package of things.

I have to say that the corvids are probably ticking every box when we go through that. So they really do have a well-deserved reputation. Unlike the foxes, we have the scientific studies to show that they are sort of living up to their reputation, to such an extent that they have been labeled feathered apes for their incredible similarity. They show this striking convergence in ability which is quite astounding given that the last common ancestor was at least 280 million years ago. Something like that.

So, then we come on to the next part of the question I think, which is how do they do it when their brains are so small? You think about the selective pressures that birds have gone through in evolutionary history. It's really been jettisoning non-essential weight because they need to fly. That means they need to be light and efficient, so their brains are very small and very light. But, what they do is they pack the brains full of neurons, at a much higher density than mammal brains. So, for something like a corvid or a parrot, they might have the same number or even more neurons in the parts of their brains associated with higher cognitive abilities compared with a monkey. We're not even correcting for body size here. So a monkey, which is bigger in absolute terms, might actually have fewer neurons in the parts of the brain that are associated with that. Birds have kind of got around that by structuring their brains very differently, compared with mammals.

One of the other big differences is that they don't have what we think of probably as the typical brain structure. They don't have this wrinkly layer around the brain. It's called the neocortex. The first anatomical studies of birds showed that they didn't have this, sa mammals do. So, the association came to be that mammals probably are more intelligent and it must be down to this wrinkly outer layer. We now know that beds have a functional analog in their brain, but it's structured differently. The neurons are in clusters.