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.