Caprines: Half-Goats and False Sheep

Himalayan tahrs

Sheep and goats are fairly closely related animals. In a sense, sheep are just goats that don't like climbing. However, even once we acknowledge that ibex, say, are really just another kind of goat, it turns out that there are a number of species that are also closely related to sheep and goats, without really being either.

Quite how they're related, and which ones are on the goat side of the tree, and which on the sheep side, has been a matter of some debate, and depends largely on whether or not you think that physical appearance is more important than genetic similarity. Even if you look only at the genetics, it seems that they're all close enough to one another that it makes a fair difference which genes you happen to consider most important.

Still, we can say that some look more like goats, and some look more like sheep. On the goat-like side are the tahrs - not to be confused with turs, which really are goats. There are three species of tahr, all of which look fairly similar to one another, and have traditionally been placed together in the genus Hemitragus - a word that literally means "half-goat". In the traditional, appearance-based, scheme it's thought that these are the closest animals to true goats, without actually being them. Genetic analysis, however, shows that this is just an illusion, and the three animals aren't especially close relatives. Two of them, therefore, have been removed from the genus, and given new scientific names to reflect their distinct nature.

Fossil Giraffes of Ethiopia

Giraffes on the Serengeti

There is some debate about exactly how many species of giraffe there are alive today. The official answer is 'just the one' (Giraffa camelopardis), but there may be two or even three, depending on how you define a 'species'. Certainly, it isn't very many, and if there really is more than one, then they all look pretty similar.

Looking slightly further afield, the entire giraffe family contains just one other living species - the okapi. Superficially, okapis may not look much like giraffes, but that's largely because, when we think 'giraffe' we tend to focus on the incredibly long legs and neck, and, perhaps, on the crazy-paving coat pattern. An okapi is quite different in both of these respects, but, when you look at the head alone, its resemblance to giraffes is much clearer.

Still, an okapi is not an actual giraffe, any more than a fox is a wolf. There may, therefore, only be one species of true giraffe alive today. But, as is so often the case with these small groups of animals, the family becomes rather larger once we include in all the extinct species. True, giraffes have never been as numerous as some other kinds of large herbivore, and the total number of species that we know of is far less than we have of, say, bovines. But it's certainly more than one.

Perhaps one of the most important questions we'd like such fossils to help us answer is why giraffes are so tall when okapis, for example, are not. This isn't as easy as it might appear. If you visit somewhere like the British Natural History Museum, or the Smithsonian, you'll see huge articulated skeletons of dinosaurs on display. It's perhaps natural to assume that what you see is more or less what somebody dug out of the ground. Sure, the original may have been squashed or distorted a bit, but generally speaking what they found was a single skeleton. Right?

Going for a Song

Aquatic mammals can be among the most difficult to study. Animals such as seals, dolphins, and whales spend a lot of their time below the water, or far from the shore, making long-term observation of them relatively difficult even compared with free-ranging animals on land. Learning more about their behaviour in the wild can therefore be a slow process. Seals and sea lions at least haul themselves onto land to breed and raise their young, which is handy for (among others) wildlife documentary makers, but, even then, that's hardly the whole of their life. Whales and dolphins, of course, don't even do that much.

So how can we study what they're up to? For land animals, there are a number of options. You could, of course, just watch them, and, for many purposes, that's enough. But if you want to know where they go on a 24-hour basis, that's not really going to work. For one thing, it's impractical, and, for another, you'll likely annoy the animal, so that (even leaving ethics aside) it isn't going to act normally. So, if you want to study an animal's movements over a long period of time, your best bet is to catch the animal, and fit it with a GPS tracking device. Then, having released it, you wait a while for it to calm down and get used to this collar thing around it's neck, and then see what it does.

Bears n the Hood

Got any apples?

One of the most significant effects on the patterns of wildlife across the world is that of the presence of humans. For many animals, it isn't such obvious culprits as pollution or hunting that are the main problem - significant though those often are. It's the mere fact that we're there at all.

Humans change the landscape around them, merely as a product of how we live. In order for our own species to survive, for instance, we need farmland, and lots of it. That brings competition with local wildlife, even if we're trying quite hard not to. Planted fields, and even open ranchland, are a change to the natural environment, and that's sure to have some effect. And that's before we start thinking about urban development.

Still, even leaving aside the fact that we can't really do without cities and towns, some animals have done quite well out of them. The house mouse is a particularly extreme example, and essentially doesn't live in the wild any more. But many other animals live in our cities, and even find them a benefit. Think of rats, pigeons, cockroaches... okay, so perhaps they aren't our most welcome neighbours, but from their perspective, we're rather a good thing.

And then there's animals that do well on the fringes, in the suburbs, or patches of urban greenery: urban foxes, badgers, raccoons, and so on. There's a balance for these animals to draw, between the risks of, for example, being hit by a car, and the advantages of nearby rubbish bins. Many of them become nocturnal, even if they aren't naturally, because that's the best time to be out and about if there's lots of humans nearby.

Caprines: Lands of the Ibex

Alpine ibex

The Ice Ages were, on the whole, not a bad time for goats. True, they had to leave the vertiginous cliffs of their mountain homes when they became too cold and barren to support life - and, in many cases, were swathed in vast glaciers. But, as the world grew colder, the vegetation also moved down the mountain slopes, so that, down in the lowlands, goats found plenty of food they had been used to. Indeed, they were better suited to it than most other animals, which had to move to southern climes, rather than merely heading downhill.

Since there are rather more lowland areas than there are mountains, goats could spread much further than they could during warmer times. When the Ice Ages ended, and the hot weather returned, they simply headed back up the mountains. But not, necessarily, the same mountains that they had previously come down from.

As a result, we now have quite a range of goat species across Asia, and, to some extent, Africa. After all, between (and after) the Ice Ages, each population was isolated from those in other ranges, and could develop on its own. Taking, at least for today, our definition of 'goat' to be "any species from the genus Capra", there are probably at least seven, and maybe eight or nine, wild species of goat. The wild goat itself is one, and the markhor, with its bizarre corkscrew horns, is another. Most of the others are collectively known as "ibexes".

Pleistocene (Pt 8): Mammoths v. Mastodons

American mastodons

The arrival of the first mammoths in North America was a significant turning point in the development of the local wildlife. It's so important that this date, 1.9 million years ago, marks the beginning of the first of just two 'land mammal stages' that define North American wildlife during the Ice Ages. It used to also mark the beginning of the Pleistocene itself, but for various reasons, that's now been shifted a little further back.

The mammoths in question arrived from Asia, crossing over the Bering land bridge, the recurring appearance and disappearance of which greatly influenced North American wildlife during this time. They were southern mammoths (Mammuthus meridionalis), the dominant species of mammoth in Asia at the time, but they quickly evolved into a home-grown American animal: the Columbian mammoth (Mammuthus columbi).

It used to be thought that, even ignoring any late-surviving southern mammoths, there were at least two different species of mammoth living in North America in the early to mid Pleistocene. We're now pretty confident that they're all just examples of Columbian mammoth. Nonetheless, you will often see references to the "Imperial mammoth" (Mammuthus imperator). Perhaps the biggest elephant that has ever lived - they were about thirteen feet tall at the shoulder - these were probably just really big Columbian mammoths. Not that that's anything to sneeze at, mind you.

Freedom to Dive

Mediterranean water shrew

There are well over 5,000 different species of mammal in the world. From a human perspective, a great many of them are very similar - at least a thousand of them can reasonably be described as either 'mice' or 'rats'. Where they live in different continents or unconnected parts of the same continent, that's not really an issue: European beavers don't care what the American sort are up to. It's a different matter when they live together.

But, of course, they often do. For example, there are fifteen different species of insect-eating bat in Britain alone. But if you have two different kinds of animal living in the same place, in the same way, eating the same thing, they have no choice but to compete. Inevitably, one of them will be slightly better at it than the other, and, given enough time, one of them has to either die out or change what it's up to. So how come there are so many similar animals?

Generally speaking, the answer is that they're not all doing exactly the same thing: there's some subtle difference in what they're up to. In some way or another, they're partitioning the available resources. One simple possibility, for instance, is that they aren't eating the same thing after all. If (to pick a rather unlikely hypothetical example) one of you eats only raspberries and the other eats only blackberries, there's plenty for both, and you don't have to fight over who gets to eat what.