Sunday 15 December 2013

Q&A 2013

These are not koalas
This time last year, I took a number of questions typed into Google that had brought people to this blog, and did my best to answer them. Obviously, it's not helping the people that actually asked the questions, most of whom had done so months before, but they may not be alone, and besides, it's a fun change of pace. So I'm going to do it again this year, before taking my customary end-of-year break.

A lot of the questions that showed up in the blogger interface were the same this year as last. With "is a rabbit a rodent?" topping the poll, as ever. I'll skip on the repetition, though, and look at some of the new ones. Whether or not that will leave enough new questions for next year is anyone's guess, but at least there's enough for now. So here goes.

Sunday 8 December 2013

The Beautiful Haired Monkeys

The Concise Oxford English Dictionary defines a monkey as "a small to medium-sized primate typically having a long tail and living in tropical countries." While perfectly good for everyday speech, that's not a viable scientific definition, for two reasons. For a start, you can't just say "typically" - you have to define exactly what you're talking about.

The other problem, though, is more subtle, and relates to how we define groups of animals. As I've mentioned many times before, a natural group of animals is one that includes a single common ancestor and all of its descendants. Apes are descended from monkeys, so, scientifically speaking, either apes are a special kind of monkey, or there is no such thing as a "monkey". You can take your pick, but scientists more commonly use the former option. A gorilla, therefore, is a kind of monkey, and it manifestly doesn't fit the definition given above.

Saturday 30 November 2013

Pleistocene (Pt 12): Dire Wolf Redux

I have previously discussed the dire wolves of Pleistocene North America, but really only in the context of how even earlier dogs were much scarier. Those earlier, bone-crushing, dogs were still around in the early Pleistocene, but they didn't survive the early Ice Ages, possibly because they were too specialised to cope as the climate changed. The dire wolf, on the other hand, first appeared at around this time, and survived long enough to live alongside humans.

The dire wolf (Canis dirus) was a very close relative of the grey wolf that we're all familiar with today. Grey wolves, despite their broad modern distribution, first evolved in Europe and Asia. Indeed, the sudden appearance of the Etruscan wolf (Canis etruscus), thought to be a direct ancestor of the living wolf, in the so-called "Wolf Event" shortly before the dawn of the Pleistocene, had a dramatic effect on European wildlife. Modern wolves, however, while widespread in the Old World, did not enter the Americas until surprisingly late, and did not travel south of the Canadian Arctic until the Ice Ages were almost over, around 0.1 million years ago.

Dire wolves, however, were there much earlier. So where did they come from? Although there was some suggestion back in the 1980s that they were actually South American in origin, the more modern consensus is that they were native to the northern continent. The most popular theory seems to be that dire wolves evolved from Armbruster's wolf (Canis armbrusteri). In fact, the latter continued to survive in its original form alongside its descendant until about 0.3 million years ago, although it does appear to have been steadily pushed eastward and southward during this time.

Sunday 24 November 2013

A Nice Warm Cuddle

Marianas flying fox,
a related species
One of the defining features of mammals is that they're warm-blooded - at least, when they're not hibernating. The only other living creatures that are truly warm-blooded are the birds... but what exactly do we mean by 'warm-blooded', anyway?

It's not the actual temperature of the blood that's relevant, here. The blood of a "cold-blooded" animal, such as a lizard, is, after all, pretty warm when it's basking in the sun. (Which is, in fact, why they bask in the sun in the first place). It's because of that that "warm-blooded" isn't the preferred term among scientists. Back when I was school I was told that the correct word was homoeothermic, but today, when we're talking about mammals and birds, the preferred term is endothermic. The two words don't mean quite the same thing, and it's actually possible for an animal to be one without being the other.

"Homoeothermy" means that the animal is able to keep a constant body temperature, largely regardless of what the environment around it is doing. Get too hot, and you find some way to cool down, and get too cold and you warm up somehow. There are a very small number of non-hibernating mammals that aren't homoeothermic. Naked mole rats are the clearest example; because they live in underground tunnels where the temperature doesn't change much, they've lost the ability to compensate if it ever does change. It's just not a problem they face, and it may be part of the reason why they don't have any fur - they don't need to keep their body heat in.

There are at least two ways for an animal to become homoeothermic. One of them is just to be enormous. Large objects lose heat slowly, so, perhaps with the aid of a few behavioural modifications, a really big animal can keep warm through a cold night simply because the night isn't long enough to have an effect on it. This probably won't work through a long winter, and the animal also takes a long time to heat up (though the latter might be an advantage in the noon-day sun), but, for many purposes, it may well be enough. This sort of homoeothermy isn't really relevant to mammals, but it may well have played a role in the lives of the really big dinosaurs like Diplodocus.

Sunday 17 November 2013

Hold On to Your Nuts

American red squirrel
The squirrel family is a particularly large one, with almost 300 recognised species. About half of these are ground squirrels of various kinds, including such animals as prairie dogs and marmots. The remainder are tree squirrels, which can be found on every tree-bearing continent bar Australia. Tree squirrels aren't a single group in evolutionary terms, because chipmunks are closer to marmots than to, say, fox squirrels, but they do at least have a fair bit in common.

Life for tree squirrels isn't too bad if they happen to live in the tropics, where trees provide abundant food year round. (The Indian palm squirrel has the added advantage of being a sacred animal in Hinduism, but that's another matter). It's all a bit tougher when they live somewhere with proper winters. By and large, tree squirrels don't hibernate - although many ground squirrels do - which means that those in the north need some way to keep eating throughout the year.

The solution for many, as is well known, is to hide nuts, seeds, and other easily preserved food sources in caches, and return to them when the weather gets bad. This can be important in seed dispersal, should the squirrel forget where it put the hoard, or die from some other cause before it can eat it all.

In Britain, the native tree squirrel, and, indeed, the only native squirrel of any kind, is the red squirrel (Sciurus vulgaris). Since the 1870s, however, it has been under increasing pressure from larger, foreign squirrels introduced from the United States. These are eastern grey squirrels (Sciurus carolinensis), simply called "grey squirrels" in Britain, on the grounds that there's no other sort. Over the last 140 years or so, they have almost entirely extirpated red squirrels from England and made a good start on Wales and Ireland, too.

Sunday 10 November 2013

Caprines of the Distant Past

Reconstruction of Myotragus balearicus
(Note the odd position of the eyes)
Having said something about all the living species of goat-like animal, it's time to wrap up with a review of where they all came from. Although fossil goats have not received the attention of sabre-tooth cats, let alone dinosaurs, we do have a number of remains, especially from the most recent epoch before today, the Pleistocene. Goats, after all, are reasonably sized animals, and both sexes have prominent horns, which can help to make them distinctive.

Indeed, goats and their kin seem to have done rather well during the Ice Ages of the Pleistocene. Because they are well-adapted to harsh and cold environments, vast ice sheets covering the north were less of a problem for them than for many other animals. They could not, of course, live on the ice sheets themselves, but then very little could. But with most of the rest of Europe, and large swathes of Asia and North America, covered in chilly tundra, that was as good a place for goats as mountainous plateaus are today.

It perhaps particularly suited muskoxen, which, unlike true goats, prefer lowlands rather than precipitous mountains. Even today they are found on the chilly tundra plains of Siberia and Canada and the coasts of Alaska and Greenland. During the Ice Ages, such terrain stretched further south, and (the world being a globe, and continental masses being where they are) that meant there was more of it. That muskoxen are exceptionally large by the standards of "goats" means that they also left some pretty big and impressive skeletons.

Sunday 3 November 2013

Spanish Painted Dogs (and What They Can Tell Us)

Members of the dog family can be broadly divided into two groups. One goup are the vulpines, including such familiar animals as the red fox and its Arctic relative. The other are the true canines, a rather more diverse group found wild on every continent bar Antarctica. While species in the first group are all basically fox-like, those in the latter are not necessarily "wolf-like". Indeed, the second group includes the zorros, or South American foxes, which descend from a more wolf-like animal that nipped south when the two American continents collided.

Still, the second group does include animals that are more obviously wolf-like, such as the wolves themselves, along with coyotes, jackals, dingos, and so on. But there are also a number of species that are more distinctive, and while (in most cases) clearly dogs of some kind, aren't that much like our normal ideas of either wolves or foxes.

Sunday 27 October 2013

Monkey Police

Monkeys can be a pretty violent lot. They will fight over access to resources or mates, or to establish dominance, which, in the long term, amounts to much the same thing. If it works, and you get more food, or more children, or whatever you're after, that's great, but there's always a cost involved: you might not win. Or, if you do, but you get injured in the process, it may be a short-lived, Pyrrhic, victory.

So many animals avoid fighting by simply avoiding each other. They mark out territories to warn off others of their species, to say 'this bit of land is mine, and you'll keep out if you know what's good for you.' When they do face each other, one of them - usually the interloper - generally backs down before things get violent. This is fine for animals that live on their own, but it's not so great when, as with many monkeys, the animal lives in a group, where you just can't stay out of each others' way.

The group may still mark out its territory somehow, and fight off outsiders when they need to. But there is still always going to be conflict within the group, especially where the society is clearly hierarchical, and one top monkey monopolises the mates, or just gets first pick of the food. Yet, while this conflict is necessary to establish the hierarchy in the first place, and gives benefits to those who come out on top, it's not good for the group as a whole.

Sunday 20 October 2013

When Size Matters

It is obviously important for a female mammal (or, indeed, any animal) to, so far as she is able, ensure that she mates with the males who are most likely to give her fit and healthy offspring. In the case of monogamous animals, the fact that the male is likely to hang around can be a key part of the equation - monogamy generally occurs where it takes two parents to successfully raise offspring. This is often the case, for example, with birds.

Although clearly there's an advantage, even then, in finding a fit mate, this becomes even more important when the animal isn't monogamous. If you can choose your mate from among several males - none of whom will be around to help you raise the kids, anyway - you might as well pick the best one at the time. There are at least three strategies that can be employed here.

Firstly, you could let them fight it out. Whoever wins is not only bigger and stronger, he's probably also older, which proves that he can survive to that age in an often hostile world. This is a common strategy for many mammal species, and it's perhaps best illustrated in animals that form harems, such as seals, or deer. Here, the males are almost always larger than the females, needing that bulk to fend off younger challengers to their position. They gather a bunch of females around themselves, and drive away weaker males that attempt to mate. (Not, it has to be said, with perfect success, but it's enough that they make a good attempt).

Sunday 13 October 2013

Almost a Caprine: The Chiru

If there's no clear and universal definition of what a species is, there's no definition at all of what the larger groupings - families, tribes, genera, and whatnot - are. These days, there is a rule that all such groupings should also be "clades" - that is, all the animals in them are more closely related to one another than to anything outside the group. But that's really all there is; there's no way of saying whether a particular clade should be called a "family", an "order", or not given any named ranking at all.

For instance, this rule tells us that humans must belong to the great ape family, since chimps are closer to us than they are to gorillas, but there's nothing in it to say that gibbons can't also belong. We could, in other words, have an "ape family", and the only reason we don't is that we figure gibbons are sufficiently different from great apes that we ought to give them a family of their own. (In fact, "apes" as a whole are considered a superfamily).

Sunday 6 October 2013

How Clever is a Baboon?

Humans were long considered quite different from the rest of the animal kingdom based on the fact that they're considerably smarter. While we now know that, biologically speaking, we're no different from any other animal, there remains no question that we are quite a bit more intelligent. This is why we're the dominant species on Earth - at least, assuming you happen to use human-biased definitions of 'dominant'. (There are other senses in which, say, bacteria have us beat hands down).

Anatomically, the clearest sign of this higher intelligence is the size of our brains. Relative to the rest of our bodies, they are huge, and they're also considerably more complex than those of many other mammals, let alone reptiles, fish, or insects. The 'relative' part is important, though. An elephant's brain is much larger than that of a human, and those of whales are larger still. Now, granted, elephants and whales are among the most intelligent of mammals, but it's not as if they've discovered quantum mechanics or (that we know of) have composed the equivalent of Dante's Divine Comedy. Their brain is large in part because they are large, and, when you allow for the size of the bodies, it's really not all that big in proportion to the rest of them.

On the other hand, when it comes to brains, as with certain other organs, size does matter. The brain of a mouse is, in proportion to it's body, almost exactly the same size as our own. (And something like, say, a chaffinch, has a brain that's even larger). Clearly, there is a minimum size below which you just can't fit all that much into a brain, in terms of neural connections and the like.  Smaller animals, therefore, will have proportionally larger brains, just in order to function.

Saturday 28 September 2013

Pleistocene (Pt 11): Sabretooth Smilodon

Smilodon fatalis
Over the  course of the last three parts of this series, I have looked at the various large herbivores that lived in North America during, and between, the Ice Ages. Naturally, there were also predators feeding on these animals, and none is more famous than Smilodon, the sabretooth cat.

However, Smilodon was by no means the only sabretooth cat, even in Pleistocene North America. Indeed, the trend for large cat-like animals to evolve huge, sabre-like canines, is one that arose many times during the Age of Mammals. So there are a wide range of, often quite unrelated, animals that look like "sabretooths." However, when we refer to "sabretooth cats" in particular, we're generally referring to the group technically called the machairodontines.

The machairodontines are one of three main subfamilies within the cat family, and the only one to have gone extinct; the other two are the big cats (lions, tigers, etc.), and the "true" felines (everything from cougars to house cats). They first appeared about 10 million years ago, long before the Pleistocene, and represent a genuine group of cats, descended from a single ancestor, and about equally related to the other two kinds, which arose slightly later. In fact, they don't all have enormous teeth - at least, no more so than a tiger does, which is quite large enough, really - but most of the later forms do.

Sunday 22 September 2013

Why Prairie Dogs Sleep Around

For the white-tailed prairie dog,
one male is quite enough, thank you
[Today is World Rhino Day. For past posts at Synapsida on the subject of rhinos, see here.]

The general pattern for mammals is that males seek to mate with as many females as possible, while females prefer to keep a single partner, at least in any one mating season. This is because females can't be pregnant with more than one litter at a time, so they may as well pick the fittest males around and get them to father all their children. Males, on the other hand, have no such investment, so the more females they mate with, the more children they have, and the better their genes survive.

But this is really a gross oversimplification. It's the basis of the polygynous mating system, where a powerful male drives off rivals and attracts a harem, or acquires multiple mates by some other means. This sort of thing is most apparent in animals like seals and deer, but it's by no means universal. For one thing, many mammals are more or less monogamous. This typically occurs where the male has to help to look after his children if they're to survive, thus putting him under the same pressure as the females.

But what are we to make of polyandry, where one female mates with multiple males in the same breeding season? It's surprisingly common, so there must be some reason for it. One, of course, is that they might not get much choice in the matter - if there's lots of randy males around, then it may be easier to give in than to put up a fight. It's hardly acceptable behaviour for humans, but, then, animals aren't human.

Sunday 15 September 2013

Caprines: The World's Largest Goats

Takin (Sichuan subspecies)
All of the various kinds of caprine that I have described so far in this series have looked, more or less, either goat-like or sheep-like. There are just two species left, and those form something of an exception. While most caprines are fairly medium-sized as hoofed animals go, these are much larger, more muscular, animals.

It used to be thought, on this basis, that they were closely related to one another, representing an early branch in the evolution of goat-like animals that split away from their relatives well before the appearance of actual goats or sheep. From modern genetic evidence, that no longer looks the case. They are, as we suspected, caprines, (although, despite the title of this post, not literally goats) but within that group, they are not particular closely related to one another. Instead, their apparent similarities are a coincidence, a case of parallel evolution where two animals, both fairly goat-like to start with, faced selective pressures to become larger.

The first of these animals is the takin (Budorcas taxicolor). Takins are very distinctive animals, quite hard to mistake for anything else, once you get a good look at them. The most obvious point, as I've already implied, is the size. A fully grown male takin stands over four feet high at the shoulder, and weighs upwards of 300 kg (660 lbs). The females are noticeably smaller, but still larger than even the males of any other caprine species (with, of course, one exception that I'll get to in a moment).

Sunday 8 September 2013

Island of the Giant Hedgehogs

Hoplitomeryx matthei
A well-documented phenomenon in evolution is that of insular dwarfism. What happens is that a population of large, usually herbivorous, animals become trapped by rising sea levels, finding themselves on an island where previously they had been able to roam free across a much wider region. In response, over the course of many, many generations, their descendants become smaller.

There are two main reasons why this happens. Firstly, there isn't so much food to eat on an island, so smaller animals that eat less will be at an advantage, and able to have more offspring that survive to have offspring of their own. But, while the problem of a limited food supply is more obvious on a smallish island, even on a large continent, the supply is never likely to be inexhaustible. In which case, why do large animals exist in the first place?

That, of course, is where the second reason comes in: predators. Being large is a protection against being eaten; lions and tigers, for instance, rarely eat elephants, rhinos, or hippos. Large predators, being at the precarious pinnacle of the food chain, and present in smaller numbers to start with, find it even harder to survive on small islands than herbivores, and they often simply die out. That removes the need for herbivores to avoid them: there's no real need to be too large for a lion to eat if the biggest thing you'll ever face is a fox, anyway.

Sunday 1 September 2013

That Funky Gibbon Song

A male agile gibbon
We humans learn to speak from our parents, with our mothers playing a particularly important role. It's because of this that we have different languages across the globe, rather than all speaking the same genetically-determined tongue, pre-programmed from birth. Yet, in other animals, communication seems to be primarily genetic, with social learning playing little, if any, role.

There are, of course, exceptions to this. We know, for example, that songbirds raised in isolation produce much simpler songs than those in a natural environment, able to hear, and respond to, other birds of their species. On the other hand, they do still sing, and the songs are much closer to normal ones than a similarly deprived human would be able to do with respect to English, French, or Gujarati.

Well, we're not songbirds, but we are mammals, and more specifically, anthropoid primates. Is there really such an absolute split between us and our close relatives? The calls of many primates can be quite complex, and this surely has something to do with why language became so important to us. Are these calls entirely genetically programmed, or are they, in some way, learned?

Sunday 25 August 2013

Welcome, the Olinguito

If you follow any sort of science news site, especially if you read the zoology bits, you cannot have failed to notice the recent announcement of the discovery of a "new species of carnivore" in South America. By the standards of such things, its a major news story - the last time this happened in the New World was in 1978, when the Colombian weasel was discovered. In addition to the news coverage, the original announcement is available to read (all 83 pages of it), free online, for anyone who cares to. There's probably not a lot I can add to all that.

Still, I feel that it's not something I should really ignore, so here's my take on it, and an attempt to put the discovery into some sort of context.

Let's start with the obvious: what is this new animal, exactly? The olinguito (Bassaricyon neblina) is a newly described species of olingo. Which may, in many people's minds, raise the question: "um... what's an olingo?"

Olingos are long-tailed, tree-dwelling, members of the raccoon family, found in the jungles of Central and South America. They were first scientifically described, as a group, by the American zoologist J.A. Allen in 1876, which is itself remarkably late (all the other main groups within the family had been discovered by 1830, and most of them well before that). They've never been seen to eat anything but fruit and flowers, although it's suspected that they also snack on the occasional passing insect.

Sunday 18 August 2013

Caprines: Goats of the Shadowed Cliffs

Himalayan goral
It is, of course, the case that all animals are continuously evolving, even if some of them don't change much visibly over protracted periods of time. So we can't really point to a modern species and say that this is the kind of thing that everything else in its group evolved from. But some have, at least on visible examination, changed far less from their ancestors than others. They have found some suitable niche in which to live, and, because they're environment hasn't changed much, they've been able to stay more or less the same. It's not that they haven't changed, of course, but just that the changes are relatively subtle.

In the case of the goats, the species that have probably changed the least from the ancestral form are the serows and gorals of eastern Asia. Both kinds of animal have retained a "resource defender" lifestyle, where they find patches of lush food in the otherwise rocky wastes of precipitous cliffs and mountainsides, and defend them from all comers.

Sunday 11 August 2013

Pleistocene (Pt 10): Of Armadillos and Bison

When the continents of North and South America collided, shortly before the dawn of the Pleistocene, a range of creatures wandered across the newly formed isthmus of Panama. Most were heading south, giving us such "normal"-looking South American animals as jaguars, ocelots, and grey foxes. The ones heading north were a lot stranger, and many of them didn't do so well in the long term. These include such wonderfully weird creatures as the giant ground sloths, which managed to get as far north as modern Canada before dying out.

But they weren't alone, and not necessarily any stranger than some of their fellow immigrants. The same event that saw the arrival of the ground sloths also saw the coming of the armadillos. Today, there is only one species of armadillo in the United States, and only two outside of South America (the other gets no further north than southern Mexico). But, back during the Pleistocene, there were others, and some of them were not quite what we'd expect today.

Sunday 4 August 2013

Leopard Cubs: The Struggle to Survive

It's obviously important to know, for conservation purposes, how populations of animals are changing. Are they increasing, or decreasing, and how rapidly? A clear factor in determining this is working out how many of them are dying, and ideally, what they are dying of. But we also need to know how many are being born, how often this happens, how likely they are to reach adulthood and have children of their own, and other factors more to do with birth than with death.

Probably the best way to really get a grip on births in an animal population is to study it for several generations, seeing what changes and when, and what factors are particularly important for infant survival. For the majority of small mammal species, a generation isn't a very long time, so it's practical to do that - although the sheer number of such species inevitably means that the great majority have never been studied. For larger, longer lived, animals, its a different matter, and the task can be far more difficult.

Saturday 27 July 2013

Dolphin Snouts: The Long and the Short of It

A franciscana
On the whole, you would probably expect to find dolphins in the sea. This is, indeed, where the vast majority of them are, at least in the wild. But not all of them.

That's because there are also a small number of freshwater dolphins, living in particularly large river systems. Strictly speaking, though, only one of these, the Amazonian tucuxi, is really a dolphin, in the sense of belonging to the dolphin family. The others are slightly different sorts of animal.

There is, for example, a subspecies of finless porpoise that lives in the Yangtze River in China. You may, perhaps, recall that this river was also home to the baiji, a freshwater 'dolphin' that has recently been declared to be almost certainly extinct. (It is, incidentally, still waiting on formal confirmation of that fact, but it's hard to imagine that the outcome will be anything else).

The baiji, however, while related to the 'true' dolphins, was instead a slightly different kind of animal, one more adapted to a freshwater life. Apart from the baiji, there are also three more of these 'river dolphins', one of them living in the Amazon, alongside the tucuxi, one living in the Ganges and the Indus, and one that... um... doesn't live in rivers.

Sunday 21 July 2013

Caprines: Goats Among the Volcanoes

Japanese serow
While most goat-like animals today are grazers, subsisting on relatively large quantities of low-quality forage, it's thought that their ancestors were originally browsing animals, defending small patches of high quality food in otherwise inhospitable and craggy terrain. In the west, the most familiar surviving "resource defenders" of this kind are the chamois of Europe. While the exact evolutionary relationships of chamois aren't entirely clear, they are part of a broad cluster of species that is otherwise crammed with grazing animals, such as "true" goats and sheep.

Not so their counterparts in Asia, which form their own distinct evolutionary line, one that never appears to have given rise to true grazing animals. It is these species, not the chamois, that probably most resemble the ancestral goats from which all others evolved.

Sunday 14 July 2013

Is a Platypus a Mammal?


Oh, you wanted more than that? Well, let's see what I can do.

I've been asked this question a couple of times recently, and I was somewhat surprised on both occasions. Yet why should I be? When I conducted a very brief straw poll at work this week, I discovered that most people I spoke to weren't sure, with all but one of those saying "probably not". (I had one response of "definitely not, because they're marsupials", an answer that's wrong on so many levels I'll ignore it from here on in). Only one was confident of the correct answer.

It's all very well for me to say "what else could it be?" because, if I'm honest, I spend a lot of time on this blog pointing out that porpoises aren't dolphins, rabbits aren't rodents, musk deer aren't deer, and so on. If a porpoise can be its own kind of thing, without being a dolphin, then why can't a platypus also be its own kind of thing - albeit at a higher level of strangeness?

Sunday 7 July 2013

Giving Birth While You're Asleep

A number of mammals living in temperate environments hibernate during the winter, or when food is otherwise scarce. The great majority of them are small animals, such as rodents, which normally have a high metabolic rate, and need to eat constantly to fuel their bodies. While hibernating, their body temperatures drop to virtually that of their surroundings - effectively making them temporarily cold-blooded. They do, however, have to wake up from time to time, if only to relieve themselves, and possibly have a light snack.

Bears, on the other hand, cannot really be described as "small mammals". Yet most of them do seem to hibernate. That hibernation is, however, rather different to what, for example, hamsters, are doing. In fact, it's sufficiently different that it's been argued that bears don't really hibernate at all. To be honest, it's a matter of definitions, of what exactly you consider the word 'hibernate' to mean. Today, most zoologists seem to consider 'hibernation' to be a perfectly good word for what bears are up to, although it's certainly possible to come up with a stricter definition.

Sunday 30 June 2013

Bats in a Changing World

Daubenton's bat is doing fine, thank you
After rodents, bats are the second largest order of mammals, in terms of number of species. Being small animals, they are also quite numerous in terms of their absolute population figures. Bats are found on every continent, except Antarctica, being among the few native placental mammals in Australia. Yet, despite this diversity, many bats are struggling to survive, with 14% of species worldwide being considered threatened, according to the latest (2008) edition of the IUCN Red List.

Now, in fairness, we do have to put that into a broader context. 14% may sound like quite a lot, and it is, in terms of actual number of species... but as a proportion, it's not unusually bad. It's about the same as for rodents, and considerably less than the 19% or so - nearly one in five - for all mammal species, worldwide. But still, bats are a fairly good indicator of how mammals in general adapt to the changing world around them.

There are a number of reasons for this that don't apply, for example, to rodents. Much of this has to do with their reproduction. Rodents and rabbits breed like... well, rabbits. They have multiple offspring, several times a year, that are themselves able to breed within months, or even weeks. This means that they can adapt rapidly to change; if it's a bad year, a lot of them will die, but the population zooms straight back up again if the next year is good. For bats, it's not quite so easy.

Sunday 23 June 2013

Caprines: Browsing Goats of the Western Mountains

Alpine chamois
The caprines as a whole can be divided into two groups, depending on which of two different lifestyles they happen to follow. The best known of these, since it is the lifestyle of sheep and "true" goats, is that of the grazing caprines.

Grazers feed fairly indiscriminately, munching down lots of grass and similar plants. In the case of the caprines, they survive in marginal habitats by eating pretty much anything that's available. They range across large areas in search of food, and adopt safety in numbers by packing themselves together in herds. Today, the great majority of caprine species adopt this lifestyle, and it's often what we think of when we think of goats and sheep.

But it appears that, in the evolutionary history of goat-like animals, it's a relatively recent innovation, one that was given a significant boost by the arrival of the Ice Ages. Before that, goats had adopted a rather different lifestyle, and there are still a minority of species - perhaps no more than five - that still live this way.

These apparently "primitive" goats were once grouped together in their own tribe, and given impressive sounding technical names like "rupicaprines" or "naemorhadins", but it's now less clear that they're really related. Instead, they represent at least two evolutionary lines within the goat-like animals, each a relic of the distant past when all goats were like this. Around them, some of their relatives switched to grazing, and, in the long run, proved the more successful.

Sunday 16 June 2013

Pleistocene (Pt 9): Before the Bison

The Pleistocene in North America can be divided into three 'land mammal stages', defined by the kinds of animal that inhabited the continent. The first, which was only recently added to the Pleistocene, is the one that comes before the Ice Ages proper, so that the Ice Ages themselves are, as I mentioned in part 8, divided into just two. As I said back then, the first of these starts with the arrival, not only of the ice, but also of the first American mammoths. The second, called the Rancholabrean after the famous tar pits, is much shorter, and essentially refers only to exceptionally bitter cold of the Last Ice Age. In terms of animal life, though, it is defined by the arrival of bison.

Today, when we think of America before the white man arrived, vast herds of bison are often part of our mental picture. And that, on the whole, is pretty much accurate, and is why their first appearance is deemed so significant in the ongoing evolution of North American wildlife. But what was the American wilderness like before there were any bison? What dominated the continent during the earlier, "Irvingtonian", stage?

As always, of course, the most common animals were the smallest. But, important though the teeth of (for example) voles are for the precise dating of geological deposits from this time, the eyes of any time travelling visitor would inevitably have been drawn to much larger animals. Obviously, mammoths and mastodons are a large part of the answer, and the presence of large elephantine animals crossing the plains would have been enough to tell our time traveller that, while he might still be in Kansas, it isn't really the same one he left. But there are many other beasts that would provide just as quick a clue.

Deer, peccaries, and horses are all examples of animals that aren't so unfamiliar today, although in many cases, the exact Pleistocene species were different from those alive now. Horses, for example, had, by this point, evolved to the modern single-toed form, but the last North American native horses died out around 12,000 BC, when the Pleistocene ended, leaving the ancestors of the domesticated forms behind in Asia. Exactly how many species of wild horse there were in America at this time, though, is unclear, with as many as fifty having been named - in my view, it's somewhat unlikely that they're really all distinct. There were, however, at least two broad types, one similar to the modern domestic horse, and the other, the so-called stilt-legged onager (Equus francisci, among others), which looked much more like a wild ass.

Sunday 9 June 2013

Lost Dolphins of the Mediterranean

The common dolphin (Delphinus delphis) still lives
in the Mediterranean
The largest family of cetaceans is the dolphin family, which includes well over 30 species. Most of them are what we'd normally think of as dolphins, but both pilot whales and killer whales are also included. However, as I've mentioned before, exactly how they're all related to one another if far from clear. We also have rather less fossils than we might expect, given the number of species and individuals alive today.

This may partly be due to something of a gap in the fossil record - a time for which we don't have many deposits of the right age from the right place - but there are other possible reasons as well. Many mammal fossils are identified from quite small parts, and often just the teeth. Mammalian teeth, especially those at the back of the mouth that grind up food rather than biting into it, have complex shapes that vary from species to species, enabling an expert to tell quite a lot from looking at only one. At least enough, in most cases, to tell what family it belongs to, even if you can't precisely finger the species in question.

But the majority of dolphin teeth look more or less the same. They have no cheek teeth at all, only stabbing teeth for grabbing onto fish, and those are usually quite simple in shape. So, while we may have plenty of dolphin teeth, and other scattered bits of their anatomy, they tell us rather less than they might for land-based mammals, making them useful than we might like for building up a picture.

Saturday 1 June 2013

One Gazelle or Two?

Mountain gazelle (probably)
According to the International Union for the Conservation of Nature, there are sixteen living species of gazelle. However, as I've mentioned before, counting species isn't always as simple as we might like to think, because the lines between them often blur. Are those two, similar-looking, animals separate species, or just two subspecies of the same thing? And how would we know?

You might suppose that the answer is something along the lines of 'do they cross-breed to produce fertile offspring or not?' Horses and donkeys are different species, you might think, because, while they can interbreed, the result is a sterile mule. Similarly, tigers and lions can also cross-breed, but the results are usually infertile. (Actually, fertile mules and "ligers" do exist, but they seem to be rare). If they don't cross-breed at all, of course, the answer is even simpler. So, take the two gazelles you're wondering about, mate them, and see what happens. Right?

Well, not really. For one thing, that's much easier said than done, especially if one of the possible species is endangered. It's hard enough getting pandas to mate with other pandas to be sure that mere lack of mating proves anything at all. Not only that, but there are, believe it or not, a number of cases where animals that are clearly different species can, indeed, interbreed to produce fertile offspring. Polar bears and grizzly bears, for instance, to give one example becoming more common of late.

Sunday 26 May 2013

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.

Sunday 19 May 2013

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?

Sunday 12 May 2013

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.

Sunday 5 May 2013

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.

Sunday 28 April 2013

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".

Sunday 21 April 2013

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.

Sunday 14 April 2013

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.

Sunday 7 April 2013

Life in Ngorongoro

The Ngorongoro Crater
There are a great many species of mammal (and, indeed, other animals) that are endangered, or at least have their continued survival threatened to some extent. If we're at all interested in conservation, we obviously need to know which ones those are, and a good starting point is seeing how much their populations have declined recently. However, we need to do more than just that. We also need to why they're declining, how unusual such a decline is, and so on. Without that information, we'll have no idea how to fix the problem, or even whether the decline is anything much to worry about in the first place.

Long-term population studies are one way to achieve this. If we can look at a population of animals over the course of several generations, we can map declines and rises against the times that various events occurred, to see which are most important, and how easy it was for them to recover from temporary problems. If we study several species at the same time, we can also see whether some events that were good for one species were bad for another - a vital piece of information if we want to protect both of them.

Saturday 30 March 2013

Caprines: At Last, The Goats

Wild goat
In English-speaking countries, and, for that matter, South America, sheep are a far more common sight on farms than goats are. (To be fair, in much of the US, even sheep aren't as common as they are in Britain, let alone Australia and New Zealand). However, while the worldwide population of sheep is, indeed, higher than that of domestic goats, it's not by as big a margin as you might think. In particular, goats are a vital mainstay of the agricultural economy in India, and throughout much of Africa.

The reason for this is their extreme hardiness. Adapted to living in habitats even more marginal than those of sheep - which, at least in their wild form, are themselves more resilient than, say, cows or pigs - they're ideal for raising in the sort of scrubby environments that you get in much of Africa and the Middle East. Even so, after approximately twelve thousand of years of selective breeding, the domestic goat has come a long way from its wild ancestors. They're often larger, with smaller horns, or none at all, and some have long, floppy ears. There are a number of different breeds, from milk-producers like Saanens and Toggenburgs, to the muscular Boer goats, bred for their meat, to the long-haired angora and cashmere goats that produce fine wool and mohair.

Saturday 9 March 2013

The First Placental Mammals

Shrews most closely resemble the ancestor
of all living placentals
I don't normally cover stories if they've had extensive coverage in mainstream media. I prefer to cover the interesting peculiarities that those outside the field are unlikely to hear about. But there's been a story recently that I'm going to make an exception for. Because, basically, I feel like it.

Last month, you may have seen a story about the origin of the placental mammals having been identified. Here, for example, is the BBC coverage. The study being discussed here, by Maureen O'Leary and co-workers, pinpointed the origin of modern placentals as around 65 million years ago. You might also recall a post I wrote in 2011, talking about the discovery of the oldest known fossil belonging to this group. That was 160 million years old.

What, you might wonder, the heck is going on?

Well, the first thing to point out is that the headlines of the two studies are not talking about the same thing. The new one is talking about the origin of the crown group of placental mammals, which doesn't necessarily mean all placental mammals ever. So what's a "crown group" when it's at home?

Sunday 3 March 2013

Caprines: Go West, Young Sheep!

Bighorn rams
As we've seen, the domestic sheep is descended from one of what may be quite a large number of related species native, broadly speaking, to southern Asia. Back in the Pliocene, however, long before those species separated from one another, one stock of ancestral sheep headed north, into Siberia. When the Ice Ages arrived, and sea levels dropped, these sheep were among several animals that headed... well, from their perspective, they were going east, but where they ended up was western North America.

Sheep, in general, inhabit high hills and rugged terrain in the shadow of mountains. They don't live on the cliffs and the impassable heights themselves, but they do like precipitous rocks nearby, so that they can flee into them at the first sign of predators. Given those requirements, western North America is an absolutely ideal place for sheep to be, and the descendants of those first colonists spread far and wide. However, while there's much argument about the exact number of wild Asian species of sheep, it's pretty much agreed that, in America, there are only two.

Probably the more familiar of these is the bighorn sheep (Ovis canadensis). It's also easily the more widespread of the two, and inhabits a surprisingly broad range of habitats, from the mountains of southern British Columbia and the hills of North Dakota down to Baja California and the Sonora Desert. That obviously includes both hot, scrubby, deserts and cold, damp, pine forests, as well as much in between. Indeed, aside from the insistence on rugged terrain that prevents them from reaching as far east as, say, Kansas or Nebraska, bighorn sheep don't seem to have much in the way of requirements.

Saturday 23 February 2013

Pleistocene (Pt 7): Meanwhile, Across the Atlantic...

Columbian mammoth
(It's likely that the real animal was hairier than the one in
this reconstruction, but it shows the tusks effectively)
Over the last five parts of this series I have described the history of Pleistocene Europe, describing some of the ways that the animal life of the continent changed over those thousands of millennia, and looking at a few particular animals in more detail. But one doesn't need a degree in zoology to notice that today, the wildlife of North America, for example, is different to that of Europe. North America has coyotes, raccoons, cougars, armadillos, and pronghorn antelope, to name just a few animals that are simply absent in Europe. (Or, in the case of raccoons, were absent until somebody made the mistake of releasing some of the furry nuisances in 1930s Germany).

It's hardly surprising that that continent also had different wildlife during the Pleistocene. One notable difference, for instance, is that we humans weren't there. Obviously, neither Columbus nor Leif Ericsson were genuinely the first person to discover America. But even whichever long-lost group of Native Americans was actually the first to discover the great western continent, they did so long, long, after the first Europeans discovered Europe. While Europe had at least some species of human inhabiting it for about two-thirds of the Pleistocene, nobody reached America until the epoch was all but over.

Sunday 17 February 2013

Tuco-tucos on the Edge

Flamarion's tuco-tuco (C. flamarioni)
There are a great number of endangered animal species in the world, and, as of the time of writing, 644 of them are mammals. These include, of course, such dramatic and visible animals as rhinos and pandas. But they also include many smaller, less glamorous animals. For example, over 200 species of rodent are endangered worldwide, and while that's not actually very many out of the total number of rodent species that exist, it's still quite high in absolute terms.

I realise, of course, that it's unrealistic to expect the public to get as concerned about obscure rodent species as they are about, say, endangered cats. Because, you know, snow leopards. But, in the semi-random style of this blog, inspired largely by whatever I happen to have seen in the literature recently, I want to talk about the social tuco-tuco (Ctenomys sociabilis).

For those who've not heard of them, tuco-tucos are a family of burrowing rodents native to South America. They look rather like voles, but are somewhat larger, at around 20 cm (8 inches) long, if you include the tail. They're good at digging, but they don't live underground in the same sense that moles or mole-rats do, since they leave their burrows during the day to feed on things like grass seeds. In fact, they've been described as the South American equivalent of gophers, although the two groups aren't really that closely related as rodents go. One of their distinctive features is their loose, wrinkly, skin, which apparently allows them to turn round easily in their narrow burrows.