The Sounds of Mother and Calf

While for humans, speech is our primary means of communication, for many mammals scent-marking is more important. This is not to say, however, that audible signals are irrelevant. This can be especially true for social mammals (such as ourselves), which often have a need for something more immediate and complex than the sort of long-lasting "keep away" or "I'm ready to mate" signals that scent marks can provide. Communication through sound can help keep a herd together, signal aggression, provide instant warnings, and so on. It's key to many primates, for instance, because most of them live up in the trees where it may be difficult to keep sight of all troop members when they are out foraging.

It's also important for many hoofed herd animals and, at least in the wild, few North American mammals are more sociable than the bison (Bison bison). While herds are no longer as vast as they were 200 years ago, recovery plans for the species are underway, and, in many cases, may rely on some degree of fencing or other containment at least for the time being. Understanding bison behaviour, including communication, could help with that, making it easier to assess how comfortable the animals are feeling - and, perhaps, the likelihood of a 750 kg (1,600 lb) bull deciding it's had quite enough of that fence and heading off somewhere it doesn't realise is less safe.

The Vocabulary of Sperm Whales

It's well known that whales and dolphins can communicate using sound, sometimes over long distances. In some cases, this can involve sophisticated "whalesong" that animals can use, for example, to identify each other, and that may impart other information, too. But there are a great many species of cetacean, and what is true for one won't necessarily be true for all of the others, just as what's true of chimps won't always be true for baboons or marmosets.

We'd expect the most complex messages to come from those species with the most complex social lives. In these cases, it would be useful for the animal to identify not only its gender, fitness, sexual status, and so on, but also which other whales it might associate with, and where it stands in the local hierarchy. Most (but not all) cetaceans live in pods although, for many, we haven't gotten very far in identifying how those are structured. They all, however, have relatively large brains and it can be worth asking, for any given species, just how complex their communication really is.

Call of the Elephants

Arguably the single most significant feature that has enabled our own species to dominate the Earth is our possession of language. This enables us to communicate and cooperate to achieve things we could not do individually, to an extent unparalleled outside of social insects, which lack our ability for complex thought in other ways. Without language, it's hard to see how we would have built cities, or maintained the incremental advance in knowledge that has marked many thousands of years of our history.

Yet language, of course, did not arise from nowhere. There is an understandable interest among scientists in determining how it might have evolved, and what from. Since we can't go back in time to perform linguistic analysis on the likes of Homo erectus, one of our major sources of information is determining how other species of mammals communicate using sound, rather than the scent marks that are so important to many of them. Much of the focus here is on primates, since these are the most likely to hold clues to our own origins, but this can be extended to other species, too. To what extent do other animals have something that could be considered ancestral to language?

Social Posting - Bear Style

Communication between animals is an important feature of all mammalian species. For those living in groups, it can help to maintain social bonds and provide urgent information, such as the unexpected arrival of a predator. If a mother has young, she may need to find them if they become lost or attend to them if are distressed, and so on. Even solitary adult animals need to communicate with others of their species, whether it be to mark out a territory and ensure that others don't poach their food source, or to find a mate at the appropriate time.

At least among mammals, there are two primary modes of communication that are generally studied by researchers. Perhaps the more obvious of these to we humans is vocal communication, since that's the main one we used in pre-literate societies. Not all species are especially vocal, but many are, and some are using sound outside of the human hearing range - such as the ultrasound squeaks of many small rodents such as mice. One estimate suggests that around 95% of mammal species use acoustic communication and this may be on the low side (it's 100% in birds and 90% in amphibians, but apparently less than 5% in reptiles, suggesting that it has evolved at least three times).

Hanging Out in the Heliconias

Bats are usually sociable animals. Since large caves are relatively rare, when bats find one, literally millions of individuals can pack themselves into a single one, often comprising several different species. But the shortage of suitably large roosts means that many cave-dwelling bats will roost elsewhere including, in human-dominated landscapes, inside attics or other manmade spaces. Furthermore, of course, many bats don't live in caves at all, spending the day roosting in trees or other suitable sources of shelter.

One might think that these tree-dwelling bats would be less sociable than those forced to cram themselves into caves. But, while it's true that they certainly don't tend to form colonies numbering in the millions, this doesn't mean that they live on their own. In some species, the males do in fact do this, following a pattern that's often seen in other social mammals, while the females gather together in maternity roots or breeding colonies. But very few bat species are entirely solitary, with both sexes living alone and, when bats do gather together, the exact structure of their social groups varies considerably between species.

He Said, She Said

One of the most distinctive behavioural features of the human species is our ability to communicate. So far as we know, no other animal can convey even remotely as much information as we can by speech alone, never mind the advantages that writing brings. But we didn't come out of nowhere, and other mammals can also communicate vocally, something that may have particular relevance to the development of our own species when we look at other primates.

A number of primate species are highly vocal, such as gibbons or the aptly named howler monkeys. Another example, which may be less obvious. is the common marmoset (Callithrix jacchus). This is a species I've talked about before, a small monkey native to South America with a number of unusual biological and anatomical adaptations related to its reproduction and diet. (Unusual for primates in general that is, not compared with other marmosets). But it is behaviourally interesting as well.

Chorus of the Dolphins

It's well-known that cetaceans - dolphins, porpoises, and whales - make calls to communicate with one another, in addition to the sonar pings used to navigate. The complexity of these calls varies significantly between species, although even sperm whales, for example, producing little more than a regular pattern of clicks, while humpback whales produce what appear to be sophisticated 'songs'.

Among the most studied of such calls are those of bottlenose dolphins (Tursiops spp.) which are the type most commonly seen in aquaria, making them relatively easy to observe. Having said which, it was only in 1998 that scientists confirmed that there was more than one species of bottlenose, leading to some confusion as to which one lived where and, by extension, which one any given prior study referred to. And, as I blogged about when the announcement was made back in 2011, we now know of a third one as well.

Screaming Monkeys

Animals, mammals included, produce a wide range of different sounds. Some species are relatively silent or have a very small repertoire of calls, but others are much more vocal, being able to tailor the nature of their call to a specific purpose. Cetaceans and primates are perhaps the most obvious here, but it's worth noting that cats, for example, can purr, mew, hiss, chatter, growl and (in some species) roar.

Some of these sounds - such as a cat's purr - are found only in a single group of related animals. (Not all wild cat species purr, of course, but many do). Others are, at least in general terms, produced by a range of different species, often in quite similar circumstances. One of these is the 'scream', an unusually loud call that is typically high-pitched. Screams also commonly include rapid, chaotic, changes in frequency and amplitude that we humans interpret as a harsh, inherently unpleasant, sound - and there's likely good reason for that.

With a Little Help from My Friends

There are a number of disadvantages to living in groups. Some of the more obvious are that the group will be, collectively, easier for predators to spot, and that they will all have to compete for the same resources. Other problems, which might be less obvious, include the fact that infections and parasites are more likely to spread amongst a group of similar animals that remain in close contact. All of these are good reasons for solitary living, as seen in a great many mammal species.

Despite which, of course, there are many mammals that do live communally. For these animals, whatever costs there may be are obviously outweighed by the benefits, of which there are several. While a large group of animals may be easier to see, it's also easier for them to keep a lookout, since not everyone needs to be actively scanning the horizon (or whatever) all of the time. They can also share in communal tasks, such as child-rearing, putting less strain on the individuals. Predators that hunt in packs can take down prey far too large for any one of them to kill on their own. Even huddling together against the cold can be a worthwhile benefit.

Land Mines and Scent Marks

For primates such as humans, vision is our primary sense. For the majority of mammal species, however, the most important sense is probably that of smell. In addition to using this sense to scope out the natural environment around them, many mammals leave scent marks as messages to one another, marking out a territory, advertising their willingness to mate, or whatever else they wish to convey.

Much research on the nature of scent marking focuses on how and where the animal leaves these messages, or how they may differ based on sex, maturity, and so on. This is obviously important if we want to understand why they're doing it, and what it is that they're trying to 'say'. But, naturally, it's also useful to understand how other animals of the same species respond to those marks - there's no point leaving a message if everyone else is just going to ignore it.

Requiem for a Dolphin

Dolphins are social animals, living in pods and engaging in what seems to be fairly sophisticated communication. It's likely that such behaviour is part of the reason for their success, with well over 30 species spread across the world's oceans... and that's excluding porpoises, and some other "dolphin-like" animals outside the dolphin family proper.

Sociability involves a number of different traits and behaviours, but one that's known to exist in cetaceans and relatively little else, other than primates, is what's technically known as epimeletic behaviour. This is, in essence, the act of helping other members of your species when they are in trouble, typically due to an injury of some kind. (For what it's worth, this compares with etepimeletic behaviour, which is acting in such a way as to make it easier for others to care for you).

The Grunting of Baboons

Olive baboon

While they also often have other means at their disposal, mammal species typically communicate with one another through sound. For those that live solitary lives, this tends to be fairly unsophisticated, beyond, perhaps, the need to attract and woo a mate. For social animals, sound production can, however, be more complicated, allowing the sort of short-term immediate communication for which scent-marking is not appropriate.

An obvious example are alarm calls, in which one member of a herd or other group will alert its fellows of a predator or other threat. Another are the distressed 'separation calls' that young mammals use when they can' find their mother. And then, of course, there are mating calls, or aggressive roars and the like intended to intimidate a rival.

But there are also peaceful, non-sexual, contact calls whose primary intent appears to be simply maintaining the cohesion of the group. For example, meerkats regularly use calls to decide when to move on to new foraging grounds, keeping the group together using the principle that if three or more members 'vote' to move by making the appropriate call, then everybody moves at once. African elephants can even use long-distance communication to maintain social bonds with individuals that may be literally miles away.

Silence of the Pacas

Whether or not a given species of animal lives in groups is something of a trade-off. Several different factors are involved, but just one example is that you will simultaneously be more visible to predators and be protected from them by "safety in numbers". For many animals, the benefits outweigh the downsides, although a lot depends on the individual environments and lifestyles of those creatures.

But living in groups also brings its own requirements, perhaps most notably the need to communicate with other members of your herd or pack. Safety in numbers, after all, is of limited utility if one member of the group can't warn others of something dangerous it's just seen. And this isn't simply a yes/no situation; the more complex the group structure, it is argued, the more sophisticated the communication needs to be.

The Strong, Silent Type?

Compared with many other kinds of animal, mammals can often have complex social lives. While many kinds of mammal live in packs or herds, with sophisticated dominance hierarchies and the like, the most complex of all mammal societies (at least as defined by we humans) belong to species belonging to one of just three mammalian orders. It's likely no coincidence that these also happen to be the three orders with the proportionately largest brains.

Perhaps the most obvious of these are the primates, the group that includes our own species. Many species of monkey have flexible social structures where members join and leave groups, adjusting their social positions accordingly, and relying on sophisticated interactions with one another to keep everything functioning. However, the social lives of cetaceans (whales, dolphins, and porpoises) can be equally complex, with, for example, multi-level associations between different pods. The third group to exhibit this sort of behaviour are the elephants.

Socially Awkward Mice

Many mammals have complex social lives, in which they have to interact with others of their kind in a multitude of different ways. Even those that predominantly live alone still require some degree of social interaction, especially during the breeding season, or when raising young. But for those that regularly encounter other members of their species, social interaction is particularly important, and its sophistication in primates was likely one of the key factors in the rise of humanity.

In the case of humans, of course, much of our social knowledge is built up as children, learning social rules through observation and experience as well as through more explicit instruction. And, while out ability to use language to impart detailed information is something that's essentially unique to us, the need for a suitable environment to fine tune social behaviour isn't something that just arose out of nowhere. Raising an animal in isolation from others of its species might not be as cruel as trying to do the same to a human child, but that's not to say that it wouldn't have some effect on them.

The Alluring Scent of Bat Pee

Southern long-nosed bat

As I've mentioned many times before, scent is an important mode of communication for many mammals. A great many species possess scent glands of some kind or another, often located on the face or in the ano-genital region. In addition to their variable location, these can be of varying levels of size and complexity, arguably reaching heir apogee in the well-developed glands of animals like musk deer or the defensive sprays of skunks and zorillas. Apart from those that spend their entire lives in the water, some sort of scent producing structures seem to be present in just about all kinds of mammal; even humans have modified sweat glands in the armpits and groin that secrete something different from the normal odour-free sweat produced elsewhere on the body.

Having said that, humans can't really be considered to have scent glands in the sense that some other animals do, and our sense of smell is pretty rubbish compared with most non-primate mammals. We do not, as a general rule, communicate by wafting our smelly armpits at one another. But many other mammals do something that isn't quite so far from that, and in a variety of different ways.

Bats are no exception to this general rule. Many bat species have scent glands, often located on the throat or the upper part of the chest, and they can leave scent marks behind to communicate with others of their kind - often signalling something like sexual availability. By no means all bats have fully formed scent glands, but that doesn't mean that the others don't use scent in some way.

The Sound of Squirrels

It is, of course, well known that bats and cetaceans use ultrasound to help them navigate the world using sonar. However, there is no particular reason why animals should always make sounds that happen to be in the range of human hearing (and, arguably, some good reasons why they might not want to). So, taking the usual definition of ultrasound as anything higher than 20kHz - the approximate upper limit for the hearing of a young, physically fit human - it shouldn't be too surprising that other mammals use ultrasound for purposes like communication. Or, in the case of shrews, for actual echolocation.

There has been significant laboratory research on the use of ultrasound by mice and rats since at least the 1970s, but it has also become clear that they are far from the only rodents to make sounds beyond our hearing range. Last year, I talked about the potential use of ultrasound for sexual seduction among hamsters (and, to be honest, didn't reach much of a conclusion) and we also know that, for example, baby voles call to their mothers ultrasonically if they become separated.

In the case of squirrels, though, we know rather less, and much of what we do know applies to various kinds of ground squirrel. As recently as 2013, however, it was discovered that flying squirrels also use ultrasound, presumably for social communication. Indeed, the sounds were quite complex and varied, not mere repetitive squeaks, implying that they might impart rather more information that one might think at first glance.

Seals, Sea Lions, and Finding Your Children

As I discussed just a few weeks ago, there are advantages to being able to identify your own children. It really does save the mother a lot of effort, especially when she can only look after a limited number of children at a time. As I pointed out then, mistakes do happen, and there are sometimes good reasons to look after other mothers' children, especially if the other mother happens to be your sister or something. But, generally speaking, getting the right child is a good idea.

Mother mammals can use three different methods to identify which child is their own, and likely often use a combination of them. Perhaps the most common method is smell, since most mammal species have a quite remarkable sense in this regard. If each child has a unique smell, or even if it just smells of you, that's a good way of identifying it. The other possibilities are identifying them by the sound of their voice, and, finally, by what they look like. For we primates, the latter may seem the most obvious, but facial recognition is something we're particularly good at.

Ultrasonic Hamsters

Animals can make a lot of different calls, for a lot of different purposes. There are alarm calls, aggressive warning growls, mating calls, the contact calls between a mother and her young, and so on. Not all of these sounds, however, are audible to us; some are at such a high ultrasonic pitch that we humans simply can't hear them.

The most obvious example is, perhaps, the sonar of bats, but bats are not the only mammals to make ultrasonic calls. We know, for example, of fifty species of rodent that use ultrasonics, and, since such studies are still largely in their infancy, and there are over 2,000 species of rodent to pick from, it's a fair bet that there are far, far more we don't know about yet. Obviously, though, the rodents aren't using these calls for sonar (at least, not that we can tell) so what's the point of it?

It's likely just that there's no particular reason why a rodent should want to make sounds that humans happen to be able to hear. So far as they're concerned, their ultrasonic calls aren't really any different from all of their others, and they're using them for much the same sorts of purpose. For the most part, they have been observed during courtship, suggesting that they're basically mating calls. That's probably not the only thing they're used for, and there's evidence that mice, for example, can encode information for quite complex social interactions in their calls, but it does seem to be a common one.

Eau de Raccoon

Most mammals have a better sense of smell than we do. They are able to use this in a range of different ways that suit whatever their particular needs are, such as identifying food, avoiding predators, and so on. But another key use, one that's essentially lost in humans, is as a means of communication. For the most part, this means scent marking, that practice, so familiar to dog owners, of leaving signals around for other members of your species to identify.

There are basically three ways that mammals leave scent marks. There's urinating, leaving dung around, and using glands specifically evolved to create smelly secretions. Having abandoned scent marking, we humans lack proper scent glands, and the closest we get are some modified sweat glands in the armpits and groin that create a special kind of sweat that smells, instead of the usual odourless watery stuff that the rest of our skin makes. And, really, compared with proper scent glands, that's pretty pathetic.