Animal Communication, Sexual Signalling and Emotions

11 December 2005
Presented by Chris Smith, Kat Arney


This week we learn about animal communication straight from the horse's mouth. Dr Gillian Forrester, from the University of Sussex, describes how gorillas use tactile signals to communicate, Dr Katie Slocombe, from the University of St. Andrews, talks about her work on how chimpanzees use certain grunts to refer to specific food sources, Professor Joan Silk, from the University of California, discusses whether chimps are charitable to their chums, Professor Keith Kendrick from the Babraham Institute in Cambridge discusses how sheep recognise emotion, and Dr Vicki Melfi, from Paignton Zoo, tells of how the red swellings on a baboon's bottom work like a sexual traffic light.

In this episode

Jumping Gives Kangaroos The Jitters

Kangaroos can be a real pest to Australian farmers as they damage crops by hopping all over them. It's a big problem when you realise there's three kangaroos to every human in Australia. Until now, the best roo deterrent has been the use of artificial high-pitched squealing noises. But these don't work very well, and the animals get used to them quickly and start to ignore the sounds. Helena Bender at the University of Melbourne has found another sound that the kangaroos fear - their own feet. When roos are afraid or sense danger, they beat their feet on the ground. Bender recorded the noises, then played them back. She found that the thumping kept the roos away more effectively than the high-pitched noises, and the animals also didn't get accustomed to it. As well as damaging crops, many kangaroos die every year on the roads, causing serious accidents. So this new scaring tactic could help to keep farmers, motorists and kangaroos happy.

Scientists Make a Smell of a Difference For Residents Downwind of Farms

Researchers George Preti and Charles Wysocki, from Philadelphia's Monell chemical senses centre, have hit upon a way to make the lives of people who live near farms more bearable at times of the year when farmers fertilise their land the natural way - they've come up with a chemical that makes you think that manure smells nice! It's been known for some time that when an odour is present for a long period of time the nose learns to ignore it, a process called adaptation. But certain chemicals can also fool the nose into ignoring other smells too, termed cross-adaptation, and this is the approach taken by the Monell scientists. They first tracked down the identity of the molecules that make manure hard to live with, and then set about testing pleasant-smelling chemicals to find examples capable of "blinding" the nose to the "bouquet de manure". They eventually tracked down the perfect example - the ethyl-ester of 3-methyl-2-octanoic acid which, when added to manure, can counteract its odour. Naturally, the smell still reaches your nose, but you just don't notice it. If combined with other odour-combating chemicals, say the scientists, it could make a smell of a difference to life downwind of the farm at fertilising time.

- Non-Vocal Communication in Gorillas

The Naked Scientists spoke to Dr Gillian Forrester, Sussex University

Non-Vocal Communication in Gorillas
with Dr Gillian Forrester, Sussex University

Chris - We as human beings have quite complex patterns of language, but we presumably got this from somewhere. Looking at our next nearest relatives, such as apes and primates, must be a good starting point. What have they told us?

Gilly - Well first of all I'm going to back up a bit and tell you why it's important to look at communication in apes. Firstly, it's interesting because the way great apes communicate with each other may not be the same as how we communicate. Secondly, it may help us place ourselves within the evolutionary process, and see how evolution evolved in humans. As humans, we mainly use vocal signals such as speech. However, we don't use this in isolation. We also have facial expressions, body postures, manual gestures and eye gaze, which are all very important aspects of relaying information.

Chris - Do apes do that too?

Gilly - Absolutely.

Chris - So in the same way that I might wink at you, do apes resort to body language in the same way?

Gilly - They do. Gorillas in particular are non-vocal animals and they do resort to a lot of manual gesture and facial expression to convey information. I'm using this information to see if there are any structures or patterns in the way they communicate with one another.

Kat - What sort of gestures do they use? What means good, or bad?

Gilly - That's an interesting question. At this point, I'm trying not to label anything because I really don't want a subjective component in how I'm looking at how they're relaying information to each other. What I really want to find out is to look at all the modes of communication that they use and code every tiny bit of these actions. I will then run it through some fancy statistics to see if any patterns come out. For instance, if you use a manual gesture consistently with the same facial expression in the same context over a period of time, we might be able to say that that is a gesture.

Chris - Where do we get our gestures from though? I learned a "thumbs up" from people saying to me, 'are you ok?' I then copy. Do the great apes have the capacity to look and see what others do, apply them and copy them?

Gilly - They do but you're opening a big can of worms. There's a big debate over something called ontogenetic ritualisation and social learning. These are the differences between things that are somewhat innate to the species versus things that are learned over time. There have been a lot of studies about how this arises within and between species of great apes. To my knowledge, there is no real certainty.

Kat - Are you just studying one group of gorillas?

Gilly - Currently, yes.

Kat - Because there have been a few studies that have found that groups of animals have regional accents. Some ducks quack in slightly different ways. Do you think that gorillas have regional accents?

Gilly - Definitely, in terms of the way they gesture and communicate with one another. We've already seen from the few papers that have been out that different captive gorillas have different types of gestures within their own groups.

Chris - How do they actually learn these things? Are they pretty good at picking up skills? If you show one gorilla how to do something, does another immediately copy.

Gilly - Again the definition of whether this is social learning or imitation is quite difficult. But I can tell you a little anecdote from the gorillas I work with. They are semi-free-ranging gorillas in that they have an absolutely massive enclosure, and one of the things they have in the enclosure is what they call a honey pot. This is a stable metal device that's permanently there. It has a hole in it and they can choose to pick up a stick and put it into the honey pot every Thursday when it's refilled. They can get this treat out of the honey pot. Two gorillas were taught how to perform this task about twelve years ago by the original keepers. Now the whole family group of thirteen are very proficient at learning this. The youngsters do learn from either imitation or social learning.

- Chimp Grunt Refer To Different Food

The Naked Scientists spoke to Dr Katie Slocombe, University of St. Andrew's, Scotland.

Chimp Grunt Refer To Different Food
with Dr Katie Slocombe, University of St. Andrew's, Scotland.

Chris - So tell us a bit about your work and how you got into what you're doing.

Katie - I'm interested in how chimpanzees use their vocal sounds to communicate with each other about things about the world. One of the really key things about our own language is that we use words to refer to things in the world. If I say table, I'm sure you can all visualise a table in your mind. You know what that word refers to, and that's a key part of our language. Without that ability, we wouldn't be able to talk about very much. We're interesting in finding out where this ability has come from. I started looking at chimpanzees.

Chris - Are they actually our closest relatives?

Katie - Yes.

Chris - So at a genetic level they're actually our closest relatives, but do you think they're our closest relatives as far as how they function as well?

Katie - I haven't had much experience of working with other apes but I think yes, they are most like us. The ability to refer to things in the world has been quite confusing until recently because there's actually quite good evidence that monkeys can do this. Baboons and vervet monkeys all give alarm calls for different types of predators. The listening monkeys seem to understand what they mean. When they give a snake alarm call, all the listening monkeys will stand up on their back legs and scan the ground as if they're looking. If they hear the eagle call, they'll all look up to try and find the eagle.

Chris - As Kat was saying earlier, there are regional differences in some animals. Is the same true for these monkeys? If you were to record those calls, take them to another part of the world where those monkeys also live, and play them the recording, would they be interpreted in the same way?

Katie - No, I don't think so with the monkeys. I think it's quite hard wired and there isn't much learning. All the monkeys have to learn to understand the meaning, so they basically have to have the experience of hearing the eagle alarm call and then an eagle appearing. They must learn this when they are youngsters, because young monkeys will give the eagle alarm call for anything that's falling. This includes leaves and small birds. The adults know that there's no actual risk to them, but the youngsters have to learn when it's appropriate.

Chris - So do the adults avoid the youngsters because they cry wolf too many times?

Katie - Yes.

Chris - Well that's intriguing because sometimes the youngsters are going to be right.

Katie - That could happen, but generally they won't continue giving the call. However, if an adult male gave an eagle alarm call, most other monkeys would then reply with the correct behaviour and give alarm calls of their own. If it's a juvenile, they might look up to check if there's an eagle there, but not assume that the youngster is definitely correct.

Chris - Now turning to chimpanzees for a minute, what do we see in chimps as a precursor to human language?

Katie - This is the confusing thing. Up until now we didn't know anything about vocal communication in apes. There's all this evidence that monkeys can do clever things with their alarm calls but there's nothing comparable for apes. I started to look at chimps both in the wild and in captivity. I looked at the calls chimpanzees make when they're finding food, and the idea was that in some monkey species, it's been shown that the monkeys give different calls depending on the quality of the food. They have one call for high quality food and one call for low quality food. Listening monkeys can then understand something about the type food that's available to them and maybe decide whether they fancy going to eat or not. I started by recording the noises that the chimps were making when they were eating different types of food, and then recorded each individual's preferences. I did this by giving them two choices of food and seeing which food they chose over the other. In the end we could list the foods in the order they liked them. They absolutely love bread, and bananas come second.

Chris - Ok, so you knew what order they like the food in and you know the sounds that go with that particular food. What did you do then?

Katie - We then wanted to test whether listening chimps could take information about the food quality from these vocalisations. To do this we set up a playback experiment. This means that we play the calls back from a speaker, when in reality, there's no food there at all. We could just look at natural reactions, but then you can't tell what they're picking up from visual cues or if they've just seen the food directly. The idea is to give the calls in complete isolation and to say on the basis of what they're hearing, what they can say about the outside world. Before we did that, we established two trees in the enclosure. One of these gave out bread, and one gave out apples, which was a low value food.

Chris - So when you played these vocalisations back, what happened?

Katie - When the chimp heard bread grunts, he would look for longer and more thoroughly under the bread tree than he would under the apple tree. When he heard grunts that had been given to apples, he would then go and look for longer under the apple tree than the bread tree.

Chris - So that suggests that these are meaningful sounds that mean a particular thing about a particular food to these animals.

Katie - Yes.

Chris - I know we keep coming back to this, but if you have different animals in different geographical settings, do the same sounds mean the same thing to them?

Katie - We've got preliminary evidence from the wild that the grunts do sound the same and a high value food will elicit a similar call. Obviously in the wild it's not bread they're grunting at; it's a type of fig. If it's quality, it should transfer across. The only possibility that we are yet to test, is that they may not be labelling food as high and low quality, but be labelling them as something as specific as bread and apples. If it is as specific as bread and apples then that obviously wouldn't transfer across groups because they must have learnt those associations. Hopefully after we complete the experiments in the summer, we'll learn how specific these vocalisations actually are.

- Red Baboon Bottoms As Sexual Traffic Lights

The Naked Scientists spoke to Dr Vicki Melfi, Paignton Zoo

Red Baboon Bottoms As Sexual Traffic Lights
with Dr Vicki Melfi, Paignton Zoo

Vicki - Seasonal or sexual swellings are the big red bottoms that you see when you look at certain baboons and macaques, and are invariably the things that visitors love to point at. These big bottoms are a signal that the females are ready for breeding. Different individuals will have different sizes of sexual swelling, different colours and turgidity. What we're particularly interested in is that in different zoos it would seem that these characteristics clump together. For example, in zoo A, you might get particularly large swellings, whereas in zoo B, they might be a lot smaller. We're interested in finding out what factors contribute to these differences between institutions. It could be genetic or it could be nutrition. If it's the latter, we need to moderate our husbandry to ensure that the swellings remain pretty consistent between institutions.

Chris - Because there are obvious implications for when these animals go back into the wild.

Vicki - Yes, there are implications for breeding in zoos and also for conservation. In terms of reintroducing animals back into the wild, if these swellings have been sustained by very very high nutrition, then in the wild, these swellings might not be sustainable because the animals can't get enough food. Equally, these bottoms can become so large that the animals may have trouble escaping form predators or locomoting. It sounds very amusing, but it could be quite an important thing that we need to look at.

Chris - So are you thinking that breeding these animals in zoos, you're slowly selecting for a bigger and bigger bottom genetically. You might be breeding a population of super bottoms.

Vicki - The bigger my bottom, the more fertile I am, therefore I'll have more offspring. This will mean I'll have babies that will go on to have bigger bottoms. At some point there has to be an environmental factor that stops these bottoms getting bigger than they can be sustained. Not only can this tell us what is the function of these bottoms as signals, we might also be able to tell which of our females is the most fertile. It might be by size, or it might be the colour. The reddest bottom may be the most attractive to a male. These are very pure reasons for us to be interested in this. On the applied side, it's very important for us as a zoo to understand the implications if we are breeding animals that don't have this environmental cut off. There bottoms shouldn't be allowed to just keep getting bigger.

Chris - Now to get to the bottom of the problem, if you'll pardon the pun, why do their bums actually go red? What's going on?

Vicki - It's something that when the males goes past he cannot miss that this female is ready for breeding and for certain primates, the colours change as the female gets closer to ovulation. If you're a male in charge of lots of different females, then they may be coming into season at different times and you want to make sure that you don't leave that female over the couple of days of ovulation. Sometimes the bottoms can get reddest when that female is ovulating. The make wants to stay net to her so no other males can mate with her first.

Chris - So it's a bit like a sexual traffic light isn't it?

Vicki - It most definitely is, but red doesn't mean stop in this scenario.

- Emotion Recognition in Sheep

The Naked Scientists spoke to Professor Keith Kendrick, the Babraham Institute, Cambridge.

Emotion Recognition in Sheep
with Professor Keith Kendrick, the Babraham Institute, Cambridge.

Chris - Tell us a bit about your work.

Keith - We're very interested in finding out and understanding whether sheep are in many way like humans in the way that they use facial cues to recognise each other. They use the same specialised parts of the brain for doing that as we do. Of course, we don't just derive identity from faces, but we also derive emotional information from facial expressions. It occurred to us to ask the next question, which was if sheep can recognise and use faces, can sheep use faces to recognise emotional states? We looked at this not only in sheep, but looked at whether they can identify emotion in their human carers.

Chris - Do sheep have particularly expressive faces?

Keith - Not particularly, but they don't have the musculature that we do to generate the almost hundreds of different facial expressions that we can. However, they do show quite marked changes in the appearance of their faces when they are fearful or stressed. If you look at the same animal's face when it's happy, such as after a meal, it looks relaxed and its ears are laid back and its eyes are almost closed. If you socially isolate a sheep, which they don't like, their heart rate shoots up, and their ears start going back and their eyes bulge. Their nostrils often flair too. It's quite easy to tell the difference if you see the pictures.

Chris - It seems odd that they should be able to recognise human facial expression though. Why should they be able to do that?

Keith - The face recognition system is very much an expertise based system. You have the hardware in the brain that allows you to use it whether you're a sheep or a human, but you need a lot of experience to hone it to a fine art. What we think happens is that they learn through the large amount of exposure they have to humans during the course of their lives to actually interpret the smiling and angry versions of the same individual's face. They can generalise from their familiar handler to any other human to see whether they're happy or angry as well.

Kat - How long have you been working with sheep for?

Keith - About twenty years.

Kat - So can you recognise sheep and tell the difference between individuals?

Keith - Let's put it this way: I'm a lot better at recognising sheep than most other people would be. But then I'm not the one who spends the largest amount of time with them. The people who spend four or five hours a day with them are really good at recognising sheep faces. However, it is a expertise based thing, just like recognising dogs or any other kind of species. Once we've been exposed to them for so long, we suddenly get very good at recognising the faces, although never as well as human faces.

- Why Chimps Won't Give To Charity

The Naked Scientists spoke to Professor Joan Silk, University of California.

Why Chimps Won't Give To Charity
with Professor Joan Silk, University of California.

Chris - Tell us about your experiment because it's fascinating.

Joan - Humans are really quite nice to one another, and we wanted to see whether this was also true for chimpanzees. If you were out shopping today for example, and you had a lot of packages, somebody may have held the door for you. This somebody is probably someone you don't know and will never have the chance to thank or hold the door for in return.

Chris - So it's a selfless act.

Joan - Right. Usually when you ask people why they do these sorts of things, they say that they feel empathy and people seem to express sentiments that they feel concern for how other people are doing.

Chris - So the key question is why we should give a toss about other people.

Joan - Yes and where did it come from? Is it something that we just find in humans or can we also see it in other primates?

Chris - So how did you answer that?

Joan - We did an experiment which was very simple. We gave chimps a choice between one option that would give a reward to themselves and to another chimp that they knew; or an option where food was given just to them.

Chris - You also did this with humans, and as it doesn't cost anything for either the chimp or the human to let the other person or chimp have food, you would expect that they let the other have something too.

Joan - Exactly. But the chimps seem entirely indifferent.

Chris - So they don't really care if their friends are better off or not.

Joan - That's right.

Chris - So that begs the obvious question, where do we get it from?

Joan - That is the obvious question and what we now know is that if this experiment is robust and replicated in other groups, then humans must have got it at some point after the humans and apes split.

Kat - So are chimpanzees very social animals?

Joan - They are indeed. They're very social and co-operate in many different contexts. They hunt together, they share meat, they support each other when they get in trouble, and males at some sites even team up to prevent access to females.

Chris - So it's really strange that they're not intelligent enough to think 'I'll give my mate a reward as well as getting one myself'.

Joan - Well it may be that in the wild, most co-operation is a form of turn-taking. I'll do something nice for you, and you do something nice for me. That's the way it works. Reciprocity may be common in other animals, but what the experiment suggests is that maybe what chimps don't have is a real concern for the welfare of others.

Chris - Do you think that that's the thing that catalysed the evolution of humans. When we did evolve the ability to care about other people, it gave us a big advantage and we had lots of offspring.

Joan - It's certainly true that we are one of the most co - operative species on the planet and that co-operation gets us things like war and charity. I think that the ability to co-operate has made humans incredibly powerful. When you can manage co-operation, it is a very effective mechanism for accomplishing things. Why other animals don't co-operate as much as humans do is a big question because you'd think it would be useful for them as well.

Chris - But isn't it surprising that other animals don't express these tendencies because they clearly give us a big advantage.

Joan - It is surprising, but that's the beauty of science, right? We have a puzzle that we have to explain. Before, we didn't have the puzzle. Now we have to solve it.

- How and why does your skin get thin when you get older?

How and why does your skin get thin when you get older? Does it really get thin or is there something else going on?

How and why does your skin get thin when you get older?

Skin does get thin as you get older. If you zoom in on skin, you'll see that the two main things that make up skin are collagen and elastin. They get less and less frequent in the skin as you get older. In other words, as you get older, you lose some of the elasticity and you lose some of the matrix that makes up the skin, making your skin thinner and more papery. You can also make your skin thin by using certain drugs, such as steroid creams. This can make your skin very thin and brittle.

- Why have our eyes evolved to take in more information than our brains can process?

Why would our eyes have developed to take in more information than our brains can process? Secondly, if we only use about five per cent o...

Why have our eyes evolved to take in more information than our brains can process?

The eyes are connected to the visual apparatus in the brain, and collect information for the brain to process. If your eyes were going to do all the filtering and processing of information, you'd have to have the brain inside the eye. Since that's not the way that we've evolved, the eye just takes in the information and the brain does the processing. As for humans only using 5% of the brain, I think any neuroscientist would say that this isn't true. Brains are very expensive to maintain and use a large proportion of the body's energy. Evolution is also known as being very frugal, so if we didn't need to have all the parts of the brain, then we wouldn't have them. Although different parts of the brain are active at different times, if you took away any part of it, you'd end up with a profound disability. If you stimulate a person's brain, you will become conscious of whatever process that part of the brain controls. You can do this by using trans-cranial electromagnetic stimulation (TCMS). To do this you take a big magnet shaped like the number eight and hold it over someone's skull. You can make the bit of the brain it's held over become active. You can make people move their arms and say things when they don't want to.

- If your voice goes croaky, does anything happen to your voice box to make it go all croaky?

If your voice goes croaky, does anything happen to your voice box to make it go all croaky?

If your voice goes croaky, does anything happen to your voice box to make it go all croaky?

The way you make sounds with your voice box is that you have these things called vocal chords. These are just flaps of tissue found in your neck just about where that bulge is. That's your voice box. When air rushes out of your lungs past your vocal chords, it makes them vibrate. When they vibrate, a bit like a string on a guitar, they make little vibrations of sound waves, and that's how you talk. When you get a really heavy cold, which is usually caused by a virus, it attacks the cells in your nose and on the back of your throat. This can make a lot of mucus, and the mucus can get onto your vocal chords. When a string has something sticky on it, it doesn't vibrate as well as when you've got a clear string. So when you try and vibrate your vocal chords and they're covered in gloop, they don't vibrate in the way they would normally and make a funny noise. That's why it goes all funny and croaky when you get a cold.


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