Sunday, 14 December 2014

New Mammal Species 2014

Waiomys mamasae
New species of animal are discovered every day. That isn't hyperbole; I mean it literally. I'm not sure of the exact number of new species that were named last year, but it's in the thousands, and likely a five-figure number, at that. This is, you'll note, rather a lot.

The great majority, of course, are insects. "An inordinate fondness for beetles" and all that. Most of the ones that aren't are also invertebrates, typically small things like mites, spiders, or crustaceans. When we do look at vertebrates, most of the new ones are fish, with amphibians and reptiles not far behind. For instance, looking at the new species described in the daily journal Zootaxa (by no means the only source for such things, although it is one of the largest) on Friday 12th December 2014, I count seven beetles, two flies, three crickets, a frog, a salamander, a gecko, and (unusually) a bunting.

In fact, new birds are, if anything, even more rarely described than new mammals. But while while new mammal species are not discovered that often, there are still several each year. So, for this, the last post of 2014, why not look back at some of the mammals that were officially described for the first time this year? This will not be, by any means, a comprehensive survey, just a sampling, and I'm not even counting the various new fossils that have been described, but nonetheless, here we go:

Sunday, 7 December 2014

Struggle of the Marsh Antelopes

All things being equal, herbivores would prefer to live in those areas with the best and most lush vegetation. The reality, of course, is that all things are very rarely equal. There are all sorts of reasons why a herbivore might not wish to live somewhere where they can get the best quality food.

One of those reasons is the presence of predators. If predators also live where the vegetation happens to be best, a herbivore has to strike a balance between the quality of the food and the risk of getting eaten. But a herbivore also has to worry about... other herbivores.

If you eat exactly the same thing as some other animal, and try to do so in the same place, whichever one of you is even marginally better at it is going to, over a sufficiently long period of time, out-compete the other one and drive it to at least local extinction. We see this, for example, in England, where grey squirrels introduced from North America have out-competed the red squirrels native to the island. There are only a few places left in England where you can still see red squirrels, but the foreign grey squirrels are quite common.

Saturday, 29 November 2014

The Dog Family: Canidae

A wolf
The dog family does not have the same variety of different forms and species as does the weasel family. I also suspect that, with the exception of grey wolves, it doesn't get the sort of attention that the big cats do. Yet, of course, even apart from the wolves and their domestic descendants, it includes a number of familiar species, as well as some that are rather more exotic. So, with goats and marmosets out of the way, let's turn to the taxonomic family of man's best friend.

With, perhaps, one or two exceptions, most members of the dog family are instantly recognisable as such. Ignoring the domestic breeds, they typically have muscular bodies, long legs, large, mobile, ears, heads that are broadly triangular in shape, and bushy tails.

Their legs are the shape they are because they're adapted to chasing prey, and most dogs are therefore pretty good at running. They have four toes on each of the hind feet, and, while most of them do have the full set of five on the front feet, the thumb (or "dewclaw") doesn't reach the ground. Their snout is the length and shape it is, partly to get in a large and sensitive nose, and partly to fit in an array of teeth that don't restrict them purely to eating meat.

Sunday, 23 November 2014

Pliocene (Pt 2): Survivors of the Zanclean Flood

For verily, I shall inherit the continent!
As I noted last time, officially, the dawn of the Pliocene - the autumnal epoch immediately prior to the Ice Ages of the Pleistocene - is marked by one of many changes in Earth's magnetic polarity. However, that particular event wasn't picked at random; there really were visible changes at the time. And, in Europe, none were more significant than the Zanclean Flood.

To understand what this is, though, we have to turn to the latter part of the preceding epoch, the Miocene, and take a look at the Messinian Salinity Crisis. The Miocene was much longer than the two epochs that followed, long enough that, over the course of it, the continents moved about a fair bit. Towards the end of the epoch, then, moving northwards, Africa hit Europe.

Due to the shape of the respective continents, however, this didn't result in the sort of massive mountain building that we see in present day Tibet (or, at least, it hasn't yet - the continents are still moving). But it did have a dramatic effect nonetheless. Crucially, the continents didn't just nudge up against one another in the east, creating what is now the Sinai, but also in the west, creating a land bridge between modern Spain and Morocco.

The Mediterranean Sea became land-locked. The Mediterranean climate of the day was even hotter and drier than it is now, and, free from any connection to the Atlantic and Indian Oceans, the sea began to evaporate. Over the course of hundreds of thousands of years, the sea level dropped. Not just a little bit, but by as much as three miles.

Sunday, 16 November 2014

Growl Whistle Squeak

While scent marking, for example, is great for leaving long-lasting messages, for other purposes, vocal communication has a number of advantages. However, since non-human animals can't talk, this necessarily imparts less information than it does in our own species. But how much less? Or, to put it another way, how complex can animal vocalisations get?

The number of different sounds an animal can make depends on a number of factors. Many of these are physical, due to the way that their larynx and vocal cords are set up, and to their ability to modulate the sounds it produces with their mouth, lips, and so on. For instance, while there has been at least some success in getting chimps and gorillas to use human sign language, they can't actually speak because of purely physical limitations in their upper respiratory tract. Added to this is the matter of just how much complexity they need to get across anyway.

Broadly speaking, the more sociable an animal is, the more need it has for complex communication. If you rarely come across other members of your own species, you probably don't need to say much when you do. A simple "go away" is probably about as much as you need, and you can co-opt the same threat against hostile members of other species, too. Beyond that, you may need some kind of mating call, and a means for mothers to find their offspring, and you're pretty well sorted.

Sunday, 9 November 2014

Figs and Pepper: the Diet of Fruit Bats

Carollia brevicauda, the silky short-tailed bat
The majority of bat species eat insects, often caught on the wing, using their remarkable sonar abilities. But there are a vast number of bat species, and by no means all of them have this diet. Probably the best known exceptions are the fruit bats and the vampire bats, of which the former are far more numerous.

In fact, fruit-eating has evolved at least twice among bats, both times in the tropics, but on opposite sides of the globe. As a result, there are two, quite different, kinds of fruit bat in the world. In the Old World - Africa, Asia, and Australasia - we have the flying foxes, the exceptionally large bats with long, almost dog-like faces. Indeed, these look so different from other bats that they were long thought to represent an entirely separate lineage within the bat family tree, although the truth turns out to be more complex. When the term "fruit bat" is used without qualification, it's more likely to refer to these, and they've been somewhat in the news lately as the likely origin of the Ebola virus before it spread to humans.

The other group are found in South and Central America, and look much more like typical bats. This group includes the tailless fruit bats (Artibeus spp.), the short-tailed bats (Carollia spp.) and the yellow-shouldered bats (Sturnira spp.). One of the problems with talking about bats is that, especially with species outside of Europe and North America, they don't have common English names. Well, technically, most of them do, names made up by scientists because they feel they probably ought to, but nobody outside of a specialist knows what they mean, and they tend to be rather cumbersome. So, for once, I'm going to stick to those scientific names in what follows.

Sunday, 2 November 2014

Mini-Monkeys: The Odd One Out

Goeldi's monkey
Under the scheme that I have been using over the last year, there are 42 currently recognised species in the marmoset family. Of these, 22 are marmosets, and 19 are either tamarins or lion tamarins. It doesn't require much arithmetic to deduce that there must therefore be one member of the family that's neither.

This is Goeldi's monkey (Callimico goeldii). It is sometimes called "Goeldi's marmoset", or, less commonly, "Goeldi's tamarin", but these names are misleading and inaccurate. It is, undoubtedly, a member of the marmoset family, but it's equally clear that it is quite different from anything else within that family.

First, the similarities. Goeldi's is about the same size, at about 25 cm (10 inches) in body length, as other members of the family, and therefore much smaller than any monkeys outside the family. It has similarly luxuriant fur, in its case almost entirely black, with an almost mane-like ruff around the head. Like members of the marmoset family, but unlike other monkeys, it has claws, rather than nails - something it uses to cling on to rough bark. It also lives in roughly the same area, in the high altitude western margin of the Amazon, from Colombia down to Bolivia and in to western Brazil.

Sunday, 26 October 2014

Children of the Coal-beasts

The animals of the Pleistocene epoch, of which I've given an overview over the last couple of years, are, on the whole, readily recognisable; they may look different from those today, but it's pretty obvious which modern animals they're related to. Mammoths are clearly elephants, sabretooths are clearly cats, and so on. The further we push back into the Age of Mammals, however, the less clear such things become.

There are two main problems here. One is that the animals simply look less like the ones we have today, especially if they come from a time before the modern groups separated from one another. How do we tell which modern group (if any) an animal belongs to if it lived before that group developed the characteristics that define it today? Secondly, older fossils are both rarer and more fragmentary, so that we're literally missing pieces of the puzzle. As a result, there are a number of early groups of mammal that we know existed, but which it's hard to fit into a family tree, or, indeed, to know much about at all.

Sunday, 19 October 2014

How Elephants Bring the Rains

The largest species of land-dwelling animal alive today is, of course, the African bush elephant (Loxodonta africana). Especially since they're herbivores, and much of their food, such as grass, isn't terribly nutritious, they need to eat an awful lot of it to survive. Certainly not all their food is low quality, and, in fact, they'll eat just about any vegetation they can find, and they do have a digestive system that extracts more nutrition from low-calorie forage than a human one could, but even so, a full grown male has been estimated to eat about 150 kg (330 lbs) of food each day

Which isn't so bad, if you happen to live in a densely vegetated environment. The rather smaller African forest elephant (Loxodonta cyclotis) does just this, inhabiting jungles north of the Congo, but was only recognised as being a separate species in 2010. The bush elephant, while it, too, often lives in dense forest, also seems happy to inhabit less favourable habitats. For example, a significant number live in the savannah of the Serengeti in East Africa, and in similar environments. At the extreme, some live on the edges of deserts in places like Mali and Namibia.

Sunday, 12 October 2014

The Mysterious Songs of the Blue Whale

The blue whale (Balaenoptera musculus) is, as is fairly known, not only the largest animal alive today, but the largest that has ever lived. Far larger, for instance, than anything that lived during the time of the dinosaurs. Yet, because, like all whales, they are not that easy to study, they remain relatively mysterious, compared with large land-based mammals.

There, however, are a number of different ways in which we can study them, and one of them is to listen to their calls. Like other whales, blue whales produce 'songs' that travel for miles through the deep, and, by listening to them, we can get at least some idea of where they are, and how numerous they are, and perhaps further information besides.

Compared with cetaceans like the humpback whale, the songs of blue whale are not particularly complex - although they remain more so than deep clicking sounds of sperm whales. For the most part, blue whale songs consist of the same element repeated over and over. This element, termed a "Z-call" because of the shape it produces on a spectrograph, has three parts: a long, deep rumble, followed by a rapid dip and then a short, musical tone at an even deeper pitch. The first part is commonly somewhere about the A four below middle-C, which is the very lowest note than can be produced on a grand piano. The last part is about three or four notes lower than that, which is generally considered below the range of normal human hearing.

Sunday, 5 October 2014

Mini-Monkeys: Monkeys with Manes

Golden lion tamarin
The tamarins of the Amazon jungle and the forests bordering it to the north are sometimes known as "true" tamarins, to distinguish them from their relatives further south. Even when the marmoset family was first recognised as distinct from those of other South American monkeys, and all marmosets were placed into a single genus, the tamarins were already divided into two: the "true" tamarins in the north, and the lion tamarins in the south.

More recent molecular analysis, of the sort that also showed the clear difference between the Amazonian and Atlantic Forest marmosets, has shown that our initial instinct on the tamarins was correct. Indeed, it seems to be the case that lion tamarins are actually more closely related to marmosets than they are to other tamarins, something that makes the distinction unavoidable. Having said which, there's no dispute that, anatomically, they look much more like tamarins than they do their apparently closer relatives.

What this means is that it's the tamarins, not the marmosets, that most likely resemble the original members of their family. The marmosets are specialists, having changed further from their ancestor's body form because of their heavy reliance on gum as a food source, and the need to modify their teeth, jaw muscles, and bowel structure to accommodate this odd diet. Lion tamarins, which never did that, retain the original "tusked" teeth and fruit-digesting colons of their ancestors, just as true tamarins do.

Saturday, 27 September 2014

Age of Mammals: The Pliocene (Pt 1)

I suspect that when most members of the public think of prehistoric animals after the time of the dinosaurs, they think of the Pleistocene, the time of the Ice Ages. This was a time of bitter cold, the time of cave men, mammoths, and Smilodon cats. Even among scientists, it's easily the most researched of the various bygone epochs that make up the Age of Mammals, not least because it's the one closest in time to our own, and therefore the easiest to study.

But there are five other epochs that precede the Pleistocene within the Age of Mammals, and, compared with most of them, it isn't even very long. Heck, it isn't even 5% of the total. As it happens, though, the epoch that immediately preceded the Ice Ages, the Pliocene, isn't much longer. If we imagine, as we're often invited to, the entire history of the Earth as a single year, the Pliocene is, very roughly, the period between 2 and 7 p.m. on the evening of the 31st December. That's not exactly a large chunk.

On the other hand, on a human scale, the Pliocene is vast; the long autumn that leads from the summer of the Miocene into the freezing cold of the great ice sheets that follow. When I first discussed the Pleistocene, I used the example of a TV documentary that whizzes through the whole of history. In fact, it takes one minute to cover each decade of time. So the entire history of the world since the outbreak of World War I is covered in just the final ten minutes. Your life so far is, I can assume with some confidence, covered in even less time than that.

Sunday, 21 September 2014

Predator v Predator

Herbivores eat plants, carnivores eat herbivores. That, at it's simplest, is how food chains work. But, of course, food chains are almost never that simple in reality. For a start, it's surely obvious that, given the chance, big carnivores eat small carnivores. They generally aren't a high proportion of their diet, not least because the sort of parasites you might find inside a small carnivore may not be very healthy for the big ones, either (mammalian carnivores being fairly closely related, in evolutionary terms). But they'll certainly do it.

Carnivores eating other carnivores is called intraguild predation, which sounds like it ought to have something to do with World of Warcraft, but doesn't. (Unless your characters eat one another, which I'm fairly sure the game doesn't allow). Inevitably, such predation means that the lifestyle of a small carnivore is somewhat different from that large one. It's not just being eaten themselves that they have to worry about, either. There's also the risk of something larger coming along and pinching the dinner that you just spent so much time catching. Which, while we're on the technical terms, is called kleptoparasitism.

Sunday, 14 September 2014

Time of the Tiny Otters

An earlier fossil
(The new one still has the jaw attached to the rest of the skull)
A few months ago, the discovery of the "largest dinosaur ever" was announced. Again. Indeed, the "largest dinosaur ever" always seems to be being discovered, and, while we must at some point, surely get to the real end of the sequence, I wouldn't put any money on this latest one being it. But speaking more generally, I'd expect that when most people think of dinosaurs, "big" is going to be a fairly common adjective.

Even when we look at prehistoric mammals, it's the big ones that get most of the attention. Mammoths. Prehistoric rhinos. Enormous tank-like armadillos. Giant wombats. Big animals are cool, and there were some pretty large ones in the distant past.

Yet, at any point since their first appearance, small animals will always have been more common than large ones. Lots of small and interesting things doubtless scurried about under the feet of the dinosaurs, and so it was with the Age of Mammals, too. So today I want to look at the recently described fossil of a small mammal, and how it too, can tell us something interesting.

Sunday, 7 September 2014

Mini-Monkeys: Punk Monkeys of Colombia

Cotton-top tamarin
The Amazon rainforest is the region of dense tropical jungle that is drained by the Amazon River and its tributaries, and it is where the majority of marmosets and tamarins are found. In the northwest, it is bounded by the Andean mountain chain. Beyond this, on the northern side, there are more tropical forests, but these are much smaller than, and separate from, the Amazon proper. Once they would have stretched much of the way down to the Carribbean coast, interrupted only by patches of more open grassland and extensive swamps. Today, however, they form a belt of forested land, mostly in hilly terrain, that gives way to the more inhabited parts of Colombia, dominated at first by subsistence agriculture, and then by cities and areas of more intensive farming around the larger rivers.

The tamarins that live here, in the northern Colombian forests, must be descended from some group that crossed the Andes, presumably through some of the lower, shorter, passes near what is now the Venezuelan border, or else along the coast. There are three species here today, all apparently descended from that same original group, and including one of the first of any tamarin species to be formally described, back in 1758. This is the cotton-top tamarin (Saguinus oedipus), and it's at once one of the best known members of the marmoset family, and one of the most threatened.

Sunday, 31 August 2014

The Jungles of British Columbia

It's changed a bit since...
Earth's climate has changed dramatically over the billions of years of its existence. The recent warming events may be unusually fast, but they are by no means unusually large. Not much more than 12,000 years ago the world was in the grip of the Ice Ages, when the polar ice caps stretched much further than today, and places like southern Italy and northern California were cold, sparsely forested steppeland.

On the other hand, there were times when the world was much hotter than today, warm enough that there appear to have been no ice caps at all, even at the poles. During the Age of Mammals - the eon of time since the extinction of the non-avian dinosaurs - the hottest of these was the Eocene Climactic Optimum. This took place a little over 50 million years ago, and it lasted rather a long time, punctuated by short periods of even greater heat. (That's 'short' as in they lasted tens of thousands of years, but not millions).

Sunday, 24 August 2014

200th Synapsida

Yes, this is the 200th post on Synapsida, and with it, time for my biennial piece of navel-gazing. If the number of hits is any measure, the blog has certainly increased in popularity over the last two years, typically getting over 200 per day now. I originally picked the title to be distinctive, and, assuming you know to look for it, that's not doing too badly - I'm on the first page of Google and Yahoo searches for the term. Although, obviously, one does need to know it's there, and not be looking for the taxonomic definition of things like pelycosaurs!

Over the last 100 posts, I have added a further 16 living families (plus some fossil ones) to the list of those I've covered, from the reasonably well known, such as armadillos, shrews, and porpoises, to the possibly slightly more obscure, such as tuco-tucos and beaked whales. That, even after four years of the blog, leaves an awful lot of families that I still haven't touched. Many of them are, unsurprisingly, small or obscure families, some of them with just a single living species (the aardvark, say, or the Asiatic linsang). But there's still some obvious gaps. I said in my 100th post that I hadn't covered pigs, for instance, and I still haven't, apart from some fossil species.

Sunday, 17 August 2014

At Home with the Masked Palm Civets

There are approximately 5,500 known species of mammal. We can't possibly have studied all of them in detail, and many are known only from the barest of information. A lot of these obscure species are small mammals - bats, shrews, mice, and so on. That's not least because the differences between all the different species of mice, for example, are probably pretty subtle. With something like 40% of mammal species being rodents, and a further 20% being bats, that's not really surprising.

But even when we look at the larger, more charismatic, species there are plenty of holes in our knowledge. This is most likely to be the case where an animal doesn't live in Europe, North America, or Australia, and isn't quite as high in the fame stakes as, say, chimpanzees, elephants, or tigers. Living somewhere it's inherently difficult to get to, like a tropical forest, is also a factor, as is living at sea if you're not valuable to whalers or the like.

Which leaves plenty of opportunity for modern zoologists to do the sort of thing that naturalists used to do in days gone by, and make some pretty basic studies of a particular animal's behaviour while still breaking new ground. Assuming of course, you can go to wherever the animal is and spend a long time there. Which, if it were that easy, would probably have already been done.

The masked palm civet (Paguma larvata) is one such animal. They're not entirely obscure, living in forests from southern China down to Indonesia, and having first been identified as a species back in 1827. They're something like 60 cm (2 feet) long, plus tail, and, in the grand scheme of things, they aren't particularly rare or endangered. Certainly we know a lot about what they look like, where they live, what they eat when they're in captivity, and so on. But actual studies of their wild behaviour, while hardly non-existent, are fairly limited, and typically only of a small number of individuals.

Sunday, 10 August 2014

Mini-Monkeys: The Midas Touch and More

Midas tamarin
A great many species of marmoset and tamarin have been named and described over the years, and the process continues today. The very first three to be described were the common marmoset, the cotton-top tamarin, and the Midas tamarin. Two of these are well-known, well-studied species. But the third, despite the fact that it was first described, alongside the other two, all the way back in 1758, remains rather more of a mystery.

Not a complete mystery, by any means. Midas tamarins (Saguinus midas) are among the most common monkeys in the Guyanas, the three relatively small countries that lie east of Venezuela on the north coast of South America. They're also found further south, in Brazil, as far as the north bank of the Amazon. They're not at all endangered, partly because there's relatively little logging in that part of the Amazon, and partly because they don't seem that bothered by disturbed forest if they do have to live in it. No, the real issue is that most researchers just happen to have focussed on other species. Which, come to that, may not be entirely unrelated to the fact that they live in an area that nobody visits...

Sunday, 3 August 2014

Pleistocene (Pt 16): Giant Wombats and Marsupial Lions

While Australia is not the only continent to have marsupials today - they're also found in the Americas - it certainly has the largest ones. This was, perhaps, even more true during the Ice Ages than it is today.

Of course, being an arid, tropical to subtropical, continent the Ice Ages affected Australia rather less than they affected Europe or North America, or even southern South America. There were no glaciers to be seen, and not a lot of snow unless you wanted to climb a mountain. On the other hand, there were some pretty big animals, including lizards and flightless birds larger than anything we have today. And, yes, the marsupials were bigger, too.

Many weren't that much larger than their modern equivalents - although, to be fair, that's quite large in the case of a kangaroo. But not all of them, for this was also the time of the largest marsupial ever to have lived: Diprotodon optatum, the giant wombat.

Sunday, 20 July 2014

Learning To Be a Good Mother (If You're a Squirrel)

Like birds, but unlike many other kinds of animal, mammals spend a lot of time raising and protecting their young. It's therefore obviously important that mother mammals have some kind of instinctive understanding of what to do to look after their children. And instinct does, indeed, play a big role in maternal care - even among humans, we talk about a mother's "instinctive" desire to protect and nurture her children.

Among humans, though, it isn't all instinct; we have many ways of learning even something as basic as this. But how true is this of other mammals? In fact, there is solid evidence that other animals get better with practice. Instinct may be important, but animals are capable of learning from experience, and a second-time mother generally has a better idea of what she's doing than one who's new to the whole thing. Indeed, not all wild animals are equally good mothers. There is strong evidence, for instance, that animals that suffered the equivalent of child abuse when young grow up to be poor parents themselves.

Sunday, 13 July 2014

Mini-Monkeys: Monkeys with Moustaches

Emperor tamarin (bearded subspecies)
Monkeys of the marmoset family, which include tamarins, are known, not just for their small size, but also their luxuriant fur, which often forms extravagant tufts on the head. Arguably, none of these tufts are more distinctive than the drooping moustaches of emperor tamarins (Saguinus imperator).

Emperor tamarins live in the lowland jungles just east of the Andes, in the border regions between western Peru, northern Bolivia, and eastern Brazil. Perhaps because of this remote location, they were discovered remarkably late for an animal so distinctive; they were first described by Brazilian zoologist Émil Goeldi in 1907 (and we'll be coming back to him in a later post). On the plus side, this distance from civilisation has kept them relatively secure, with loggers and the like only recently having reached this far into the jungle.

Compared with some other members of their family, they are not especially colourful. Their bodies are grey, reaching near-black on the face and hands, and they have a reddish tail with a grey tip. What makes them so noticeable, of course, are those long, pure white, moustaches, which are present in both sexes.  Indeed, the more widespread of the two subspecies also has a thin and straggly beard hanging from its chin. The moustache apparently reminded Goeldi of Kaiser Wilhelm II, although to be honest, it's hard to see why (one would have thought that some of the Chinese emperors would have made a better fit).

Sunday, 6 July 2014

First of the Fossil Dolphins

The dolphin family is the largest family of aquatic mammals, by number of species. As I've mentioned a few times before, exactly how we're supposed to divide it up, and what scientific names we should give its various members is a matter of some debate. Genetic analyses designed to show which species are related to which just show a tangled mess. So, while we do know that the scheme we use at the present is wrong, we don't really know what we should replace it with, and, for the time being, we're stuck with what we've got.

The reason for this is likely a very rapid burst of evolutionary change, with numerous new species arising at more or less the same time. By examining the genetics of different species, and using what we know of mutation rates, we can make a guess as to when this happened. It turns out to be shortly before, or perhaps during the beginning of, the Ice Ages, in the late Pliocene to early Pleistocene. That at least one species seems to have arisen as a hybrid between two of the others - with the arms of the family tree effectively crossing back over again - doesn't really help matters.

Sunday, 29 June 2014

The Family Lives of Japanese Badgers

As I mentioned previously as part of my overview of the weasel family, we used to think that the "common", or Eurasian, badger inhabited much of that continent, with individuals found from Britain to Japan. We now know that that's not the case; there are at least three different species of badger within this area, albeit very closely related.

In Britain and Ireland, we think of badgers as living in communal setts, with multiple different family groups sharing the same network of tunnels and chambers, that may have built up over generations. Yet, while this is true in the British Isles, it isn't true anywhere else, even when we are looking at the exact same species where it lives on continental Europe. Here, as with most other members of the weasel family, European badgers live alone when they aren't raising their young.

The reason for this is thought to be a combination of Britain's climate and a diet rich in earthworms.The frequent rains in the British Isles are good for earthworms, and there are so many available to eat that the badger population in the islands is unusually high, something that they deal with by crowding together in larger groups. Elsewhere in Europe, there are less earthworms, and the badgers have a broader diet, but one that requires them to defend their territory from others of their own species if they don't want to starve.

Sunday, 22 June 2014

Fur Seals Going on a Winter Holiday

Once each year, animals like seals and sea lions haul themselves out of the water to spend time on rookeries located on remote coasts or distant islands. Once there, the females give birth to their young, raise them to the point that they can swim effectively, and then take part in the long orgy of reproduction during which the males fight for their affections. And then they all return to the water again, living out the rest of the year at sea.

For obvious reasons, nature documentaries tend to focus on this time of a seal's life. Scientists, too, know rather more about what the animals are up to when they're on land where they can see them, than they do about what they're up to when they're away from the coasts. Yet, fun though reproduction undoubtedly is, most of a seal's life is spent at sea, not at their annual breeding grounds. With modern tracking technology, however, we're beginning to get a better picture of what seals do during this time, and where they do it.

Take the northern fur seal (Callorhinus ursinus). Technically, these aren't seals, in the sense that they don't belong to the seal family, bur rather to the sea lion family. That's a bit confusing, so the term 'seal' is often used more broadly than that, and the two families are distinguished as 'earless seals' (the actual seal family, the Phocidae) and 'eared seals' (the sea lion family, including, of course, the sea lions themselves). That is, you can either consider sea lions to be a special kind of seal, or fur seals to be a special kind of sea lion. Or both, if you must. Take your pick.

Sunday, 15 June 2014

Mini-Monkeys: Chilling Out With the Mantled Tamarins

Golden-mantled tamarin
Over the last five months I have looked at the 22 widely recognised species of marmoset. However, as I mentioned back when I started, not all members of the marmoset family are actually marmosets. Almost all of the others are tamarins, the majority of which belong to the genus Saguinus, also known as the 'true' tamarins.

So what is the difference between a marmoset and a tamarin? On the face of it, they look quite similar, and, indeed, being members of the same family, that's not entirely inaccurate. They're roughly the same size, have the same luxuriant fur, often with extravagant tufts, and have the same basic body plan, with a long non-prehensile tail, clawed toes, and so on. The most significant difference though, and the one on which they were first separated back in the early 19th century, is in the shape of their teeth.

Unlike marmosets, tamarins have prominent canine teeth in their lower jaw. These are often called "tusks", although by a strict definition, tusks have to project outside the lips (as they do in wild boars or elephants), which these don't. In fact, they're actually no larger than those of marmosets, they just look that way because the incisor teeth that separate them at the front of the mouth are of a more normal size. In marmosets, the incisors are elongated and cylindrical, forming a straight line with the top of the canines, but in tamarins, the closer in size to what you'd expect in monkeys, making the canines stand out.

Saturday, 7 June 2014

Pleistocene (Pt 15): Ice Age Down Under

The island continent of Australia has today what is probably the strangest mammalian fauna of any continent. Yet it is also the continent that has, perhaps, suffered the greatest number of mammalian extinctions over the last 50,000 years or so. Many of those are relatively recent, or at least after the end of the last Ice Age around 10,000 BC. But even compared with the Australia of, say, the 18th century, the wildlife of Ice Age Australia looked pretty odd.

In climactic terms, Australia didn't suffer too badly from the Ice Ages. It's too close to the equator to have had ice sheets get anywhere near it, although doubtless there was rather more snow on the mountains. (Although perhaps not too much - even today, Australia is the only continent to lack glaciers). Then, as today, much of the continent consisted of desert, and the bits that weren't were mostly arid grassland, albeit with denser woodlands around the eastern and northern coasts.

Sunday, 1 June 2014

Chipmunks, Seeds, and Saliva

Least chipmunk
Chipmunks are a kind of small squirrel, found mostly in western North America. Spending the winter in underground burrows, they are more related to ground squirrels, such as prairie dogs and marmots, than they are to tree squirrels, such as the ubiquitous eastern grey. They share a lot of features in common with other squirrels, and I doubt it's much of a surprise to anyone that this is, indeed, what they are.

One thing they have in common with other squirrels is their habit of hoarding food. In fact, their scientific name, Tamias, is Greek for something like "steward" or "treasurer", implying an animal that carefully looks after its food stores. As with other squirrels, since they don't truly hibernate, this habit helps them to survive through the winter, especially in the colder or drier climates in which many of them live.

There is something of an art to this, since chipmunks (and squirrels in general) are no great respecters of property rights. If they can find somebody else's cache of food, they'll be in there like a shot.

They don't even particularly care if the cache was left by a member of their own species or not. If the owner is the same species as yourself then, well, he's probably a rival, since chipmunks aren't especially sociable. If, on the other hand, he isn't, then that's even less of an issue, since they all eat broadly the same kind of seeds and small nuts. This, however, leads to a problem - sure, you may be able to pinch his food, but what's to stop him pinching yours?

The trick, then, is to try and find somewhere to hide your food that's easy for you to remember, but hard for anyone else to guess. A bit like the password on your bank account, then. Not all chipmunks, it turns out, are equally good at this. Let's take a look, for example, at the two most widespread American species.

Sunday, 25 May 2014

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.

Sunday, 18 May 2014

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.

Sunday, 11 May 2014

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.

Sunday, 4 May 2014

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.

Sunday, 27 April 2014

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.

Sunday, 20 April 2014

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.

Sunday, 13 April 2014

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.

Sunday, 6 April 2014

Deep Dives to Dark Depths

There are something like ninety species of cetacean, which are usually grouped into fourteen families. Perhaps the most obscure and little known of these families - and among the most obscure of all mammal families - is that of the beaked whales. It's actually quite a large family, with over twenty species, representing almost a quarter of all known cetacean species, and around a half of all those that are noticeably larger than dolphin-sized. And, since they typically weigh a ton or more, they're hardly small themselves.

The main reason we know so little is where they live. These are deep-water animals, that rarely come in close to shore, and so just aren't seen very often. Combine this with the fact that they're mostly of little interest to whalers, and it becomes apparent that studying them is neither easy, nor likely to be commercially motivated.

Saturday, 29 March 2014

The Antlers of Early Deer

Dromomeryx, a palaeomerycid

Probably the most distinctive thing about deer is that they have antlers (and not horns). However, especially when we're looking at fossil species, it's important to remember that not all deer have antlers. Granted, the enormous majority do, and those that don't have lost them during their evolutionary history, rather than being holdovers from some ancient form that never had antlers in the first place. (This isn't true of musk deer, but that's partly why they aren't considered to be true members of the deer family).

And even that's assuming your fossil belongs to a male. (Or a female reindeer, oddly enough).

Antlers first appear on deer fossils in the early Miocene, on the general order of 20 million years ago. Still, in the grand scheme of the Age of Mammals, which has so far lasted 66 million years, that isn't all that long. It's a lot closer to us than it is to the dinosaurs, at any rate. So we ought to have a reasonable idea of what some of these first antlered forms look like.

Sunday, 23 March 2014

Mini-Monkeys: The Many Faces of the Silvery Marmoset

Silvery marmoset
The marmosets of the Atlantic Forest are, most likely, descended from a population that emigrated from the Amazon shortly before the Ice Ages. All of the other species of marmoset still live in those larger and more northerly jungles. But how many species is that?

In a wide-ranging and influential study of American monkeys in 1977, mammalogist Philip Hershkovitz identified two such species, one that had hairy tufted ears, and one that did not. He noted that the two species had more in common with one another than with their Atlantic Forest cousins. For example, while their teeth are adapted for scraping bark off trees to make nutritious gum ooze out, they aren't quite as adapted for this as they are in the more southerly species. He also noted that the two species had quite a lot of variety in their colouration, although that didn't necessarily mean much.

Since the 1970s, however, our knowledge of the miniature monkeys of the Amazon has increased dramatically. For one thing, we now place more emphasis on some of the minor differences Hershkovitz identified. For instance, today, we consider the Amazonian species to belong to a different genus from the common marmoset and its kin, using a name, Mico, first proposed by René Lesson back in the 19th century. In a similar vein, we have also raised many of Hershkovitz's subspecies to full species status. Finally, we have actually discovered species he simply didn't know about.

End result: there are now something like fourteen species of Amazonian marmoset known to science. And, given how recently many of them were discovered, there's no reason to suppose that we're done yet. There may well be more marmosets to find.

Sunday, 16 March 2014

Clearing the Wastebasket

Vulpavus ovatus, a "miacid"
Apart from whales, dolphins, and their kin, all large carnivorous placental mammals alive today belong to a group called, appropriately enough, the carnivorans. The carnivorans include several families, and they can be divided into two smaller groups, which are broadly described as either "dog-like" or "cat-like". The dog-like carnivores include, besides the dogs themselves, such families as the bears, weasels, and seals, among others. The cat-like carnivores are a slightly smaller group, including cats, hyenas, and a host of animals that look more or less like mongooses.

But, if we go back in time, we find a number of large, carnivorous mammals that, for various reasons, don't really fit. Some of them, such as Hyaenodon, are different enough that we can say that they're definitely not carnivorans in the modern sense. Others, such as sabre-tooth cats and dire wolves, clearly are, because they're so similar to animals we have around right now. And then there's others that are kind of in-between. So where do we draw the line?

One way is to look at what's called the "crown group". The idea here is that you take every living representative of the group you're interested in (in this case, carnivorans as a whole) and trace it back to its last putative ancestor. Anything descended from that animal, including all the extinct ones, belongs to the crown group, and anything that isn't, doesn't.

Sunday, 9 March 2014

Clicking Clans

There are two broad types of whale alive today: those with teeth and those without. Generally speaking, it's the members of the latter group that are physically larger: these are the great filter-feeding, krill-slurping, baleen whales. The toothed whales, in contrast, tend to be much smaller. The biological group of toothed "whales", after all, includes dolphins, porpoises, and all their strange fresh-water relatives. Even the big ones, such as killer whales, are smaller than the great majority of baleen whales.

But there is an exception, and its by far and away the largest of all the toothed whales. This is, of course, the sperm whale (Physeter macrocephalus), and, while it's merely average when compared with the great baleen whales, at up to 50 tons in weight, it's nothing to be sniffed at. (The second-largest, incidentally, is probably the relatively obscure Baird's beaked whale, at 12 tons, which is itself about half again the weight of the animal in the #3 spot).

Sunday, 2 March 2014

The Kindness of Wallabies

The most dramatic encounters between wild animals often involved physical conflict of some kind. Animals fight for all manner of reasons, by no means limited to the eternal struggle between predators and prey. Even within the same species, there is often conflict, typically over access to things such as food or mates.

Such interactions are called "agnostic". (In an oddity of the English language similar to the flammable/inflammable divide, "agonistic" and "antagonistic" sound like they should be opposites, but actually have exactly the same meaning). In the case of solitary animals, they are often the main form of interaction within the species other than mating. But, for animals that live in groups, it necessarily has to be different.

Even if we ignore any breeding season, when competition, especially among males, is likely to be intense, animals within a group are still likely to come into conflict from time to time. In order for the group to remain cohesive, there has to be some mechanism to defuse this tension, to ensure that the pressures of competition don't outweigh the benefits of staying together. Such "affinitive" behaviour helps strengthen social bonds, and reduce stress.

Sunday, 23 February 2014

Mini-Monkeys: Marmosets of the Southern Atlantic Forest

Geoffroy's marmoset
Last month, I looked at the three species of marmoset inhabiting the northern half of the Atlantic Forest along the east coast of Brazil. Further south, the forests naturally become cooler - which is to say, that they're merely subtropical, rather than fully tropical. All of the marmosets inhabiting the Atlantic Forest are closely related, belonging to the genus Callithrix, and many of them are capable of interbreeding with one another. They all descend, most likely, from a single species that lived around the early Pleistocene, just before the Ice Ages, and which presumably crossed over what is now the relatively sparsely forested cerrado from the more fertile Amazon to the north and west.

Leaving behind Wied's marmoset, we now hop over the Jequitinhonha River to its southern bank, and a stretch of forest that heads about another two hundred miles or so down the coast. This is the home of Geoffroy's marmoset (Callithrix geoffroyi), also called the "white-headed marmoset". In fact, Geoffroy has quite a few species named after him, and is a key figure in the development of mammalian classification. Living in France around the turn of the nineteenth century, he was an early proponent of the theory of evolution - although, dying fifteen years before the publication of On the Origin of Species, he had most of the details of how it worked wrong.

Sunday, 16 February 2014

Pleistocene (Pt 13): Giant Bears and Speedy Cats

The most famous predators of the North American Ice Ages were surely Smilodon and the dire wolves. But, of course, these were hardly the only carnivorous mammals on the continent at the time. For one thing, it's worth remembering that something like half of the species in North America in the mid Pleistocene are still around today. Even where modern species had yet to evolve, their immediate ancestors often had, and would have looked very similar to modern forms. So Ice Age North America would have had its share of coyotes, bobcats, and cougars, not to mention smaller creatures like badgers. And let's not forget jaguars, which entered South America from the north early on in the epoch, and are still found in parts of Mexico today.

But surely Smilodon was the most fearsome predator of its day? Well, probably... kind of. But it most certainly has a contender for that crown.

Sunday, 9 February 2014

Hunky Mother Squirrels

In general, among mammals, males are larger than females. We can see this in our own species: on average, men are taller than women, and, again on average, they also tend to have more muscles and a greater overall body mass. Compared with some other species, though, the difference isn't all that great. Seals are an extreme example, with males often many times larger than females. But, in many cases, the difference is more like that with us: it's a noticeable difference, but not a dramatic one.

The reason for this is generally thought to be male-male competition. Males often have to compete for mates, and the bigger you are, the more likely you are to win that contest. It doesn't even have to be physical; the mere fact that you've been able to 'waste' calories on bulking yourself up proves that you're physically fit, and therefore an attractive mate for females. Even the fact that you've survived long enough to grow to large size is a point in your favour.

How this manifests will depend a lot on the mating system of the species concerned. In species that are monogamous, it's not such a big deal, and it's even less so if females are highly promiscuous. It's most noticeable in polygynous species, where one male monopolises as many females as he can, perhaps defending a harem from all comers. This is what happens in seals, and it's also true, for example in deer. Stags, for instance, not only are quite a bit larger than hinds, but they have huge antlers that not only let them fight off their rivals, but also further demonstrate how many calories they've been able to waste growing something huge just for the heck of it.

Saturday, 1 February 2014

A New Kind of River Dolphin?

Amazonian botos (probably)

I could, perhaps, have titled this post "I Told You So".

Back in August, at the end of my post on the newly discovered olinguito, I said: "Should we expect more new species of mammal to be found, perhaps even large and interesting ones? You can count on it." I also suggested in that post that remote jungles were exactly the sort of place you'd expect to find one. Well, since I wrote that, we have discovered at least one, and possibly two, new species of large mammal that fit exactly that description.

The first was the kaboman tapir (Tapirus kabomani), which lives in the Amazon jungle, and which was described a couple of months ago. I'll refer you to Darren Naish's blog if you want to know about that, since I have nothing useful to add to what he's already said. There is, so far as I can tell, no dispute or argument about the reality of this tapir as a new species - the first new tapir to be described since 1865. The acceptance of other one, published just last week in the online journal PLoS One, appears to not quite be so clear cut.

The animal in question is a new species of river dolphin, and it, too, was discovered in the Amazon jungle. But, before we look at the details, it's probably best if I start by describing what a river dolphin actually is.

Dolphins, on the whole, live in the sea; this is surely not a great surprise. Yes, they sometimes travel a short way up particularly large rivers, and some of them even do it on purpose. But, generally, the sea is where you expect to find them. Now, there is an exception, and I discussed it back in 2012: it's the tucuxi (Sotalia fluviatilis). This spends its entire life in freshwater, and, as I said at the time, it's the only true dolphin that does this.

Sunday, 26 January 2014

Mini-Monkeys: Marmosets of the Northern Atlantic Forest

Common marmoset
The official name of every family of animals is derived from the name of the 'type genus' - a smaller group of closely related animals within it that are deemed to be 'typical', and which are used to define that family. Of course, what's 'typical' is a subjective opinion, and will only reflect what somebody thought at the time the family was named. So, really, it's more of a convenience than a truly meaningful statement. But, still, it's a convenience that we continue to use.

The type genus of the marmoset family is Callithrix, and the scientific name of the family is therefore 'Callitrichidae'. If we're honest, they're not really any more 'typical' than most other species in the family, but they're as good a place to start my survey of the world's marmosets and tamarins as anywhere else.

The Callithrix monkeys are true marmosets, a group that is distinguished from other members of the family by a heavier reliance on tree gum as a source of food. All callitrichids eat gum, but for true marmosets, it's a vital part of their diet that they eat all year round. Having evolved to do this, they have a number of physical adaptations that suit them for the lifestyle. Unlike their relatives the tamarins, they have no tusks in their lower jaws, meaning that the teeth at the front of their mouths form a relatively straight line. They feed by clamping the teeth of their upper jaw onto tree bark, and then scraping upwards with that flat row of teeth on the lower jaw.

Although they aren't born that way, over time, these teeth are honed to a sharp chisel-like edge. However, for this to work, they also need a remarkably wide gape, and their jaw and its muscles are adapted accordingly. Nor does it end there, because there's the business of digesting the gum.

Sunday, 19 January 2014

Fast-Running Hyenas of Tibet

Spotted hyena
The hyena family is one of the smallest families amongst the living Carnivorans. Only four species survive today, of which by far the best known is the spotted or "laughing" hyena (Crocuta crocuta). Hyenas are, oddly enough, closer in their evolutionary origins to cats than they are to dogs, despite their appearance, and, to be honest, much of their behaviour. Having said that, of course, they're hardly very close relatives of cats (they're closer to mongooses), but they do happen to be on that half of the family tree.

Today, hyenas fall into one of two basic body types. There's the one everyone knows, typified by the spotted hyena, which involves a relatively heavy build and adaptations to crunching up bone. These hyenas have a reputation for eating carrion, and they certainly do that, although spotted hyenas in particular are pretty good at hunting. Still, they'd rather jump out on their prey from a short distance away than have to chase it for long distances, as a wolf would. If their prey isn't going anywhere, because it's already dead, that's even better, and spotted hyenas are strong enough to chase leopards off their kills (the fact that they hunt in packs, and leopards don't, is doubtless helpful here).

Sunday, 12 January 2014

The Puzzling History of the Clymene Dolphin

The taxonomy of dolphins is, as I've mentioned on a couple of previous occasions, a complicated issue. The problem is that at least some dolphins underwent a very rapid diversification in the not-so-distant past. New species appeared so shortly after one another that, from the perspective of the present day, it's very difficult to figure out in what order it happened, or which dolphins are most closely related to which others. This particularly affects the genera Tursiops (the bottlenose dolphins) and Stenella (the spinner dolphin and its relatives), and likely has some effect on one or two others as well.

If you look back at those two posts (sorry, this won't work if you're reading this on a mobile) you'll see that I drew up a plausible relationship tree based on the research of Kate Charlton-Robb et al, who identified the existence of the Burrunan dolphin as a distinct species in 2011. One of the animals you'll notice that I mentioned was the Clymene dolphin (Stenella clymene), and that I said in one post that "the spinner, spotted, and Clymene dolphins were all assumed to be related, on the not unreasonable grounds that they look much the same as one another..." Emphasis on the past tense, because the study seemed to show that, despite their visual similarity, they weren't all that closely related after all.

Sunday, 5 January 2014

How Long to Make an Elephant?

Biology, on the whole, is not a great one for following mathematical laws. Physics has no such problem, and is replete with mathematical formulae for calculating this and that, which never fail, so long as you've understood them properly. Biology, not so much. It's squishy, and variable, and while it does follow rules at least some of the time, there are so many confounding factors that they're really more like guidelines. (Barring, of course, those imposed directly by physics, such as the minimum wing area needed to get airbourne).

Still, it does have some, and a lot of them are to do with the mass of an organism. We can say, for instance, just to pick an obvious example, that a bigger animal needs to eat more food. Or, more accurately, more calories, since otherwise you get into all sorts of difficulties depending on how nutritious their diet happens to be.

It's not simply a matter of twice the mass, twice the calories, either, because there are economies of scale here. Talking about mammals, as we do here, these economies have a lot to do with heat loss. A bigger animal retains more heat than a smaller one, and, since mammals are warm-blooded, that means a bigger animal doesn't need to work quite so hard to keep that body temperature at the right level.