When the Desert is Too Dry

The round-tailed ground squirrel lives
further east, and is not threatened

Many mammal species are territorial, carving out a patch of land for themselves which they then defend from same-sex members of their own species. Typically, they are less bothered about members of the opposite sex, for obvious reasons, and such territories will often overlap. Male territories tend to be larger than those defended by females, making it easier for them to meet as many females as possible. 

The size and relative location of such territories naturally vary between species, but also depend on the local conditions of terrain, climate and so on. The harder it is to find food, for instance, the larger your territory will need to be. As young animals grow up and leave home, they will need to find unoccupied territories to inhabit, or else somehow drive an existing resident out and take over. Males commonly travel further than females so that they don't end up with only their sisters or close cousins as potential mating partners, although there are a few species where it works the opposite way around.

Haring About

One of the reasons that there is such a large number of mammal species in the world is that many of them are restricted to relatively small areas. There are a great many species that can be found only in one place, perhaps because it's a remote island or otherwise physically difficult to leave, or perhaps because they have very specific requirements and can't traverse the terrain between the patches of land that meet them. Others, of course, may have lived across wider areas in the past, but are now endangered, perhaps because their land has been converted to agriculture or urban areas, or because they are seen as either especially tasty or a threat to humans or their crops.

On the other hand, many species are widespread with large populations and seem to be happy in a variety of different habitats. Often, these are animals with a broad diet, able to eat a range of different foods and still remain healthy - the red fox is a good example of this, especially once it started exploiting suburban habitats in the 20th century. Typically, they will not be as good at finding or processing these foods as those that specialise in one particular type but the fact that they can switch food sources easily makes up for this. Indeed, this can be a driver for evolution - an animal becomes really good at exploiting one narrow food source, out-competing the generalists, but the latter remain in the background and, when the world changes and the narrow food source is replaced by something different, become the basic stock from which the next round of specialists will arise.

Dunnarts in the Sandhills

It's a recurring theme of this blog, especially notable in last year's series on Old World leaf monkeys, that a great many mammalian species are threatened in some way. Population numbers of many species are declining, to the point that their continued existence is in doubt, often due to human encroachment on their habitat, but also due to the habitat itself changing as climate change continues. In this context, the quest of zoologists to understand how mammals (and other animals) behave is not just one of intellectual curiosity but can be of direct benefit to the creatures themselves.

For example, it is useful to conservation efforts to understand not only where a given species lives, and the habitat requirements it may have, but how it makes use of that environment. (Obviously, there's more to it than this, for example, how different species in the same area interact with one another but we'll stick with this one point for today). What particular features of the habitat are important to it? How much land does it need? How is its population distributed across the area? 

Monitoring Mandrill Movement

Understanding how animals move about during their daily lives can be important for a number of reasons. It's a crucial part of their behaviour and ecology and, perhaps more significantly, it can provide information that we need if we are to help conserve those that are endangered. How much space do they need? What sort of places do they go to that we might need to ensure they have access to? And so on.

There are many ways of determining where animals travel on a regular basis and different methods will work better for some animals than they do for others. For example, we hear a lot in modern times about the use of remote telemetry, attaching GPS tags to animals and watching to see where they go. This is a useful technique, especially for tracking long-distance migrations. But it still requires that you capture your animal to fit it with the tag and then hope that having the thing attached won't affect its behaviour... which may, in turn, depend on how large it has to be. Not to mention the risk that it might fall off.

Armadillos Looking for Love

We can tell a lot about animals by simply observing where they go. While studies on wild animals can cover a wide range of different topics, many of which require close observation of what the creature is actually doing, many of the most basic simply require us to tag the animal with some sort of transmitter and watching it move remotely.

Of course, while I say 'basic', this isn't necessarily all that simple to do in practice. You need to capture the animals, ensuring that they aren't overly stressed by the experience so that they modify their behaviour after the fact, and then you do need to spend a lot of time collating all the date, likely over the course of several months. Still, we do have many such studies for most well-known mammals. Some groups, however, have been comparatively overlooked.

Sharing Your Burrow

One of the key features of animal behaviour is sociality - to what extent the animal associates with others of its kind. Many mammals are solitary, meeting up to breed, but otherwise spending their adult lives alone, except when mothers are raising their young. That so many aren't is probably partly due to that period of long parental care. Mammals are defined by their ability to produce milk, which necessarily implies some degree of mother/child bonding, and it may well not take too many behavioural modifications to get from there to just not leaving home at adulthood.

Social behaviour has both benefits and drawbacks. On the plus side, pack hunting makes it easier to take down larger and otherwise unavailable prey, if you're a predator. If you're not, there's safety in numbers, and the more of you there are, the easier it is to spread out the duties of looking out for threats. On the downside, large numbers do make you rather more obvious, and if you're all after the exact same kind of food, there'd better be a lot of it about or some of you will go hungry.

The Hunting Grounds of Small Cats

The big cats - lions, tigers, leopards, and so on - are arguably amongst the well-known of all wild animals. They frequently figure in zoos and nature documentaries, and, from the scientific perspective, they have been the subject of numerous studies down the years. Even the medium-sized cats, such as lynxes, bobcats, and ocelots, are well known, and, at least in the case of the European and North American species, also well-studied.

We know somewhat less about the assorted species of genuinely small cat - the ones that are about the size of the typical domestic moggy. Yet there are an awful lot of them, even if most members of the public would likely have a hard time naming more than one or two.

One such example is Geoffroy's cat (Leopardus geoffroyi) named for - though not discovered by - the pioneering French naturalist Étienne Geoffroy St Hilaire. This lives in southern South America, reaching Bolivia, Paraguay, and the southern tip of Brazil in the north, and also found just over the border in Chile, but mainly inhabiting Argentina and Uruguay. While they prefer terrain with scattered trees and plenty of bushes, the also live in open grassland, and are found right down to the very southern coast of South America, although not on the islands beyond.

Jackals on the Motorway

Mammals tend to have a particular area in which they live most of their lives and conduct their various activities. This is known as the animal's "home range", and it's not quite the same thing as a "territory". That's because the latter is an actively defended bit of land, that the animal strives to keep clear of rivals, perhaps marking it with scent as a warning, and using aggression against intruders if they have to. The majority of mammal species don't bother to defend territories, but that doesn't mean that they don't have a home range - after all, they have to live somewhere.

One key difference between a territory and a home range is that the former, by definition, is not shared with any neighbours. Of course, the animal might be social, living in herds, packs or other kinds of band, so that all members of the group share a single territory, but, again, it's not shared with outsiders. A home range, on the other hand, almost always overlaps with at least some others used by members of the same species, especially if they happen to be of the opposite sex. Breeding would be problematic if they didn't.