Let's move from the seas to the skies with Christian Ritz's, the animals you study, the New Caledonian crows. Many people will know about the corvids, crows being tool users. But before we get into what they can do with their tools, what is it? What is the definition of a tool? Well,

it's an object that is being handled in its entirety to achieve a goal. So in the case of the crow, it's a stick or a piece of leaf or other plant material, which the bird holds in its bill. They are birds after all. They don't hold their tools in their feet. They hold everything in the bill. And they will insert these sticks or other tools into holes and crevices in deadwood and in vegetation to winkle out grubs and other prey that may be hiding there. And this kind of behavior is incredibly rare in the animal kingdom. There are about 65,000 vertebrate species on this planet, and only a handful of them are tool users naturally in the wild. But interestingly, spread across lots of different types of animals,

lots of different taxa, and we are obligate tool users, but it's birds, there are some in the seas, there are even mollusks that use tools. So it's an important part of

evolution. That's right, there is some taxonomic spread but the most prominent and seemingly most skilled tool users are the primates. And so it's quite surprising to see a bird rival that supremacy. The tools these New Caledonian crows make are the most sophisticated and the most structurally complex tools any non-human animal is making.

But it's not all crows as well. It's not even all crows within one family. There's lots of variants of who does what and who is capable of crafting these tools.

That's right. So there are over 40 species of crows and ravens all around the world. And the New Caledonian crow is one of them. And it is that species that has this remarkable ability to use tools for foraging. For many of the others, we hardly know anything. They live in remote places. We are, of course, very familiar with the crows that live around us, the carrion crow here in the UK, the rooks, the We know that they are not tool users, but there are many species in Southeast Asia, for example, we know nothing about. And so it's reasonable to wonder whether amongst them there are undiscovered tool users. And actually, my team did exactly that a few years ago, where we tried to predict whether amongst the 40 or so species, there might be another tool using species. And my top ranked candidate was the Hawaiian crow. And that was based on its appearance. New Caledonian crows, when you look at them, look very unusual. They don't have your typical crow, bill-shaped, powerful, decurved bill. No, they have a very straight bill, a bill that is very good for holding a stick. They also have very large and very mobile eyes, which create a large field of binocular vision, which is very important when you hold a tool in your bill. And once we'd made these discoveries, we started wondering whether we could use these telltale signs to predict which other species might be tool users, look for straight bills and large eyes, similar to how we humans have the archetypal tool-related adaptation. It's the opposable thumb. And so the Hawaiian crow stood out with its very straight bill, and it turns out they are tool users too.

Now, in studying, as so many naturalists do, you get to know your subjects quite well. And

do

you see individual variants you see different behaviors in different specific birds oh

there's a huge variation so with the new caledonian crows we see variation in their tool making behavior at the the family level at the population level at at scales across the landscape. It looks as if these technologies are constantly evolving, are changing. But then we also see what some researchers describe as different personality types. Some crows we work with are very happy to engage with our puzzle boxes. We give to them to find out how they use tools, and others are slightly shyer and don't want to play.

Do you think that skews the results? I mean, it's a wonderful image, but does that skew the results? If you're only getting the gregarious crows who like showing off their tool use rather than the shy ones, does that mean the data set gets skewed? That is a very good point.

And it's something we started thinking about a few years ago when we realized that when we do these experiments, we end up testing just a subset of the total population. And we actually developed a framework. Scientists are now using across animal species for catching these sampling biases. In some cases, it's very obvious. If you only, say, test females, you can't make inferences about males. You haven't tested them. But in other cases, these biases are much more subtle, and personality is one example. If you only study and test the bald ones, you can't say how the shy ones behave.

Simon, this feels like very much your domain. It feels almost poetic that you might get different personalities showing off their tool use to the researchers while the others are hiding in the bushes.

Yeah, this idea of personality. And also, I think one thing that became really apparent to me when I was talking to scientists who were trying to measure emotional response in animals and sentience in animals was the importance of recognizing animals as individuals and not just in swarms and colonies and so on and so forth. just as a measure of sort of straightforward respect in some ways, but not just to group all these things together, because when you do that, that's when it becomes sort of easier to use pesticides and so on and so forth, because you're addressing something that's become slightly anonymous. I went on one day to an equine therapy centre to have some equine therapy and I stood in the middle of a horse arena whilst a horse was sort of let loose around me and this horse seemed very very tame and friendly and then at one point for reasons I don't quite understand started booking and galloping and charging and kicked out and with its hooves put a great big hole in the metal sign at the side of the arena and we were talking about it afterwards you know my response to that but they they said then that one thing that they don't do when the horse has come into the arena with you know with the client is to is to say what the horse's name is because in giving it a name at that moment you give it a personality and you you impose personality traits on them this horse as it turned out in the end was called prince so you can draw your own conclusions from that depends

which prince you're talking about now christian another one of your projects all of this conversation is about how we interact with with the natural world and with with animals that are domesticated in that example, Simon.