Dishonest Bears

Mammals use a variety of means to communicate with one another: vocal, scent, and visual. Even those that are mostly solitary need to do this from time to time, whether to mark out their territories as a warning to others or to attract mates. 

Often these signals need to convey more than the basic message, but also provide some information about the animal that left them. This often includes physical fitness, whether to intimidate potential intruders or to advertise oneself as a sexual partner. At close range, this can be achieved through such things as growing huge antlers, proving that you have the physical capacity to waste resources on something that's otherwise pointless. But, at longer range, a simple indicator of size may be all that's required.

Viverrids: The Odd Ones Out

Binturong

Most viverrids have a similar appearance: slender, long-snouted animals, many of them spotted or brown-coated. One, however, stands out as particularly distinctive. This is the binturong (Arctitis binturong) and it's the largest species of "civet", with a total body length ranging from 61 to 96 cm (24 to 38 inches) and weighing between 9 and 20 kg (20 to 44 lbs), similar to small dog such as a Jack Russell or border terrier. Moreover, they appear somewhat larger than they are because, unlike other civets, they have a thick shaggy coat that obscures their actual body.

They are mostly black in colour but with grizzled fur that makes them look grey, and prominent white whiskers. The tail is long and prehensile, and the feet have large, rough pads, giving them an enhanced grip. In other respects, however, they are civet-like, with the same general pattern of teeth and other detailed anatomical features, including a simple perineal scent gland.

Viverrids: Half-Weasel Palm Civets

Banded palm civet

The word "civet", as currently used in English, is a rather broad term, referring to a wide range of vaguely similar-looking animals. Not all of these are even members of the "civet family" as we currently understand it, and even those that are don't form a natural biological group within that family. 

The word was originally Arabic (pronounced something like "zabad") and would have referred to the animals that medieval Arabs were familiar with, which, given how far they traded, would have included both African and South Asian species. These are still regarded as "true civets" today, but the word now also appears in the name of the "palm civets", long thought to be merely a variant of the true sort.

Viverrids: Civets Great and Small

Small Indian civet

Most species of true civet weigh somewhere between 7 and 9 kg (16 to 20 lbs), somewhat larger than a domestic cat, and similar to a King Charles spaniel or a Highland terrier - albeit of a more slender shape. The large Indian civet (Viverra zibetha) is at the upper end of this range, the second-largest species of true civet. The name of the large Indian civet, however, tends to imply that there must also be a smaller version in the same general area, and so there is.

The small Indian civet (Viverricula indica) is the smallest of the true civets, between 48 and 68 cm (19 to 27 inches) long, not including the tail, and weighing just 2 to 4 kg (4½ to 9 lbs) - more of a toy poodle or a Pomeranian in terms of dog weight. Otherwise, it looks much like its larger cousin, although it has block spots like a Malay civet, rather than the fainter blotches of its larger namesake, and does not have the crest of erectile hair running down its back. The smaller size caused it to be placed in a separate genus from the other civets as early as 1838, and modern genetic analysis has shown that this is fair; the two parted company about 12 million years ago, while the other Asian civets are much more recent than that.

Viverrids: Rise and Fall of a Wastebasket

The carnivorous mammals have been recognised as a taxonomic order since the official dawn of biological classification in 1758. In that first publication, Systema Naturae, Carl Linnaeus listed 36 species. The concept of "families" was a later innovation, but Linnaeus used the rank of "genus" much as we would use families today, and, in the case of what we now call the carnivorans, there were six.

These were the cats, dogs, bears, weasels, seals, and a sixth group that he called (in Latin) "ferrets".

Jiggling on the Ecotone

It might leave a slightly different message if a human did it, but leaving piles of droppings in the territory around your home can be an important signal for many mammal species. Although making such piles visible may help other animals find them, the primary signal is, as one might expect, the smell. And not just the smell of the faeces, of course, but complex chemicals mixed in with it from urine or the secretions of anal scent glands. These can allow an animal with a sense of smell more subtle than our own to glean a lot of useful information about who left the deposit - and why.

In many species, this takes the form, not of solitary deposits, but of latrines. In the zoological sense, this refers to a single location for defecating shared by many animals of the same species. The animals who use the site may belong to a particular pack or herd, all using the same communal site, but they could equally well be rivals or neighbours leaving messages for one another. How the latrines are distributed can give researchers significant clues about what those messages might be.

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).

The Importance of Blue Bullshit

Monkeys and apes in general, and humans in particular, have a relatively poor sense of smell but the same is far from true of most other mammal species. For such animals, scent can be an important method of communication and this is often done through scent-marking, leaving long-term messages that can be understood by other passing members of your species.

A common way to do this is by rubbing specially adapted scent glands onto objects - these glands are often on the feet or the sides of face, which is why many animals will rub their heads against things to mark their territory. An alternative is to either urinate or defecate in a particular location, the natural aroma of the excreta often being aided by anal scent glands. We are all familiar with a dog's need to mark its territory in this way and it's hardly alone in this respect.

This can provide all sorts of useful information to other animals from the same species, such as territorial ownership, social dominance, willingness to mate, and so forth. When the method used to deposit this information is defecation rather than urinating, the result is termed a latrine or midden - which, in the biological sense, are basically alternative words for "dungheap". Animals that use this method of scent-marking include rhinoceroses, lemurs, and antelopes. (And we can but wonder what human cities would be like had we evolved from a species that communicated in this way).

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.

Being Top Cat

If you happen to own a cat, especially an un-neutered male, you may have noticed that they sometimes pee on things. Shocking, I know.

Spraying is just one way that cats leave scent marks, whether to warn other cats away from 'their' territory, or to advertise their availability to members of the opposite sex. And, as we'd reasonably expect, this is as much true of large wild cats as it is of the domestic moggy. Indeed, we have a reasonable understanding of how some wild cats use these markings. For instance, we know that, just as in the domestic animal, male North American cougars spray more than females, both to mark their territory and to advertise for females.

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.

The Crusty Forearms of Male Bats

Bats, of course, are not blind. There eyesight is, in fact, pretty good in the majority of species. Which makes sense for an animal that has to fly around at night when the light is dim but not entirely absent. It's only for animals like moles, which live underground, where the light can't penetrate at all, that vision becomes an expensive and unnecessary luxury.

Having said that, many species of bat do spend a lot of time in caves, and, in there it really is too dark to see anything, no matter how good your night vision might be. As a result, the other senses of bats are often highly tuned. Hearing is the obvious one, since bats rely on that for their sonar abilities, but many species also have well-developed senses of smell. In particular, since bats also tend to be highly social, scent often forms a crucial part of their ability to communicate with one another - as it does for many other mammal species.

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.

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.

Making your Mark

For most humans, the dominant sense is that of vision. Although the other senses are important, vision is particularly important to us, and it is generally well-developed in other primates, too, perhaps because most of them spend a lot of their time swinging through trees, where a good idea of the location of nearby branches is definitely helpful. But, for most mammals, the sense of smell is much better developed than it is in us, and far more important to the way they interpret the world.

One of the many ways that they make use of this is through scent marking. Apart from those that spend most of their lives in the water, the great majority of mammals scent mark in some way, and humans are a bit of an oddity in this respect. To assist them in scent marking, many mammals possess special glands producing smelly secretions that they can place on prominent landmarks, or in other locations that fellow members of their species might come across. And, of course, any cat or dog owner is familiar with the concept of using urine as a mark - the urine contains unique chemicals that can provide far more information to the animals concerned than it does to us.

The actual purpose of scent marking varies depending on the nature of the animal, and, particularly, its lifestyle and habits. For many animals, it can be used to stake out patches of territory, or to advertise sexual receptivity, for example, and that will depend both on how the animal claims territory, and on the details of their mating habits, such as how promiscuous they might be.

Along with polar bears, brown bears (Ursus arctos) are amongst the largest of all carnivorans. Like many carnivores - although unlike, say, wolves, lions, or otters - they are solitary animals as adults. Scent marking is therefore particularly useful for them, allowing them to record their presence and leave information for any other bears that may happen to wander through the same area. However, they are not particularly territorial. They do, like most other mammals, have a "home range" through which they habitually travel, but this regularly overlaps with those of other bears, of either sex, especially where food is abundant, and several bears live relatively close together.