The Teeth of Dead Kangaroos

Not exactly lush vegetation

How to tell what long-extinct animals ate?

Aside from those that died recently enough to leave us mummified, rather than fossilised, remains, your best bet is probably fossilised dung. In the case of carnivores you might even be lucky enough to find the bones of their kills. Of course, both do need matching up to the correct animal, but the former, in particular, is not especially common. Absent such direct clues, then, we have to deduce what we can from the skeleton, and that generally means examining the teeth.

The overall shape of the teeth can give us some pretty clear indications of whether an animal was a carnivore or a herbivore. This is even more true for mammals than it is for dinosaurs, since we have plenty of clear examples alive today. Powerful stabbing canines and flesh-shearing molars indicate a carnivore, while flat grinding plates and leaf-clipping incisors imply a herbivore. There's obviously some gradation in between, in the case of omnivores, insectivores, and, for that matter, weird specialists such as vampire bats, but it's a good starting point.

Mini-Monkeys: The Smallest Monkeys of All

Pygmy marmosets

As we've seen over the last few months, the marmoset family contains a number of species of unusually small monkey. Typically about 22 cm (9 inches) in length, plus tail, marmosets and tamarins are far smaller than any other kind of monkey. They're dwarfs, perhaps evolved that way so they don't have to eat as much food, perhaps to hide from predators, and perhaps for some reason we haven't thought of. But, if they're smaller than other monkeys, what is the smallest member of their own family? In other words, what is the smallest species of monkey in the world?

The answer is the pygmy marmoset (Cebuella pygmaea), and it most certainly is small. With fully grown adults measuring just 14 cm (5.5 inches) long, they're only two thirds the size even of other marmosets. The difference in weight is, of course, even more dramatic: typical marmosets weigh between about 350 and 400 g (12 to 14 oz.), while the pygmy species weighs a mere 85 to 140 g (3 to 5 oz.) As is typical for marmosets, the females are slightly larger than the males, but, in this case, not by very much.

Crash of the Bandicoots

Eastern barred bandicoot

Even by the standards of marsupials, bandicoots are a bit odd. The largest order of Australian marsupials are the diprotodonts, a generally herbivorous group that includes kangaroos, koalas, wombats, possums and the like. So most things you probably think of when you think of marsupials, then. The second largest group consists of broadly carnivorous species, most of which are shrew sized, but does also include larger forms, most famously the Tasmanian devil. (It's also this group that includes the antechinus, an animal where the females regularly kill themselves raising their young to adulthood, and the males kill themselves by having too much sex).

This leaves a little over twenty species unaccounted for; species that belong to neither group. All but two of these are bandicoots. These are relatively small animals, with the largest species being about the size of a hare or jackrabbit, and most of the others quite a bit smaller. They're omnivorous, eating things they can find close to the ground, like grass seeds and worms. They share with the herbivorous diprotodonts an unusual feature of the hindfeet whereby the second and third toes are fused into a single digit, albeit one that ends in two claws. Their front teeth, on the other hand, resemble those of, well... every marsupial except the diprotodonts.

Too Many Monkeys

You can never have too many herbivores.

Well, actually, yes you can, but it doesn't happen very often in the wild. Populations of animals are naturally limited by a number of factors. For large predators, for example, the primary limiting factor is how many other animals there are around that they can eat. If the population of predators grows too large some of them will starve, and the population drops.

For small to medium herbivores, however, the limiting factor is rarely food supply, at least in the long term. (In the shorter term, something like a summer drought may be a different matter). For them, the main thing that prevents their population growing too large is that any excess population will get eaten by the predators.

This is, of course, an oversimplification. Large herbivores, such as elephants and rhinos, have relatively little to fear from predators, especially once they reach adulthood. Small predators, such as weasels, have just as much to fear from large ones as herbivores do. And there can be all kinds of other factors coming into play, especially where mankind has mucked up a long-standing ecosystem. But it's not entirely false either, and the upshot is that we rarely get to see what would happen if herbivores multiplied as fast as they'd obviously like to.

What Does the Otter Say?

Animals use a variety of different means to communicate with one another. For we humans, speech is the primary means of communication, but even we also have body language as a useful adjunct. (And writing, of course, although that's arguably just a representation of speech, and it's not, that we know of, something our species has always done). For other mammals, scent is usually at least as important.

The human sense of smell is pretty rubbish, by broader mammalian standards, but for those species where it functions effectively, scent can be an effective and useful means of communication. All you have to do is urinate on a lamppost or do what bears do in the woods, and you've left a long-lasting message that conveys all sorts of handy information to anyone who comes by later. But, on the other hand, it does have its limitations. In particular, it's not much good for rapid signalling, such as alarm calls. So, while we may be the only species to "speak" (in the sense of having complex syntactical rules), it's not surprising that we aren't the only ones to make vocalisations.

Having said that, unless you're a whale, vocal calls are really only useful for communicating with other animals that are at least in your general vicinity. As such, they're much less useful to animals that don't lead rich social lives. If you live all your life on your own, then it may be that the only sound you need to make is something to warn off intruders, and perhaps a little something for the breeding season. Apart from that, scent may well be sufficient to meet your needs.

Mini-Monkeys: Madeiran Marmosets and More

Santarem marmoset

Back in the 1970s,  a survey of the monkeys of South America identified just two species of "typical" marmoset living in the Amazon jungle: a naked-eared form, and a tassel-eared form. Both species were fairly variable in appearance, and each was considered to include three distinct subspecies. Today, better knowledge of things like their genetic make-up means that we have elevated all of those subspecies to full species status.

The "tassel-eared marmoset" had first been described in 1811 by Geoffroy Saint-Hilaire (although the date is officially given as 1812, because it took a year to get the description published). Because it was the first to be so described, the other two were considered subspecies of it, rather than the other way round. Once they were split off, we were left only with the species to which the originally collected specimen belonged. While still sometimes called the "tassel-eared marmoset" or some variation thereof, it is now more commonly called the Santarem marmoset (Mico humeralifer) to distinguish it from its kin.

Pleistocene (Pt 14): Ice Age Africa

Giant warthog

In the earlier parts of this series, when I described the animals of Ice Age Europe, I said that the continent, at that time, had a feel reminiscent of present-day Africa. But, if that's so, what was Africa like during the Ice Ages?

The answer is, perhaps disappointingly, "not that different to how it is now". Indeed, of all the settled continents, it's probably Africa that has changed the least since the Ice Ages. You might think that this has something to do with Africa being close to the equator; in particular, that it's too close for whopping great sheets of ice to have rolled across the countryside.

Which they didn't, so that much is true. Indeed, the southern hemisphere in general had far less ice cover than Europe, Asia, and North America. That's due mainly to the way that the continents happen to be arranged, with glacial ice sheets only being able to get as far as southern South America (there are fjords in places like Tierra del Fuego). Presumably, sea ice extended much further across the Southern Ocean than it does now, but that would have little effect on land-based animals.

But that's not to say that Africa, or Australia, were unaffected by the Ice Ages. Africa was colder than it is today, and, to begin with at least, rather drier, too. The Sahara and Kalahari deserts were more extensive than they are today, with the semi-desert belt of the Sahel being quite a way south of its present position, running through what are now fairly lush countries such as Guinea, Nigeria, and northern Kenya.