Saturday 29 September 2012

Weasels on the Savannah: Zorillas and their kin

Saharan striped polecat
Even before we had good molecular and genetic evidence for how the various members of the weasel family were related to each other, there were a number of different schemes proposed for dividing up the family into smaller groups. Otters were almost universally agreed to be something different from the other weasels, and, in the simplest scheme, everything that wasn't an otter was considered a "musteline". Once the genetic information arrived, it wasn't a terribly great surprise to learn that the martens were a group, the 'true' badgers were a group, and so on. Removing badgers, martens, and the like, meant that the term 'musteline' now referred only to the weasels themselves, and their closest relatives: stoats, polecats, and mink.

What was rather more surprising though, was that one group of what seemed to be quite clearly weasel-like animals actually constituted an entirely separate branch of the family tree. Mostly living in the southern hemisphere, it had not really been obvious before that these animals were especially closely related to one another. Because of that, unlike badgers, otters, and martens, they had no collective name in English. The scientific term for members of this group is "galictines", and that remains the best word we have for them.

Friday 28 September 2012

News in Brief #6

Japanese macaques

Baby Monkeys are Cute

For we humans, it's fairly easy to estimate how old another human is just by looking at them. It may not work perfectly, but we can instinctively assign someone to at least to a broad age class - young adult, middle-aged, and so on. There are plenty of clues to help us to do this, and it's a useful ability for shaping our interactions with one another, so it's not too surprising that other social animals can do the same thing. Perhaps one of the more striking examples is our reaction to the faces of our young.

Very young humans have a constellation of features that highlight their age: rounded face, large eyes in comparison to the face, and so on. The same set of features are found in other baby mammals, and were described by the great behavioural biologist Konrad Lorenz as "kindenschema". Perhaps a more everyday term for the same phenomenon is "cuteness". Cuteness triggers positive, maternal and protective reactions in humans, and its by no means restricted to our own species. Kittens and puppy dogs are undeniably also "cute" to the vast majority of humans and its for the same reasons. We can see the same phenomenon in the looks of toys such as teddy bears, the kawaii appearance of characters in Japanese cartoons, and so on.

Sunday 23 September 2012

Fossil Porpoises Muddy the Waters

Harbour porpoise
Dolphins and porpoises belong to two separate families, and there are clear differences between them. However, this isn't immediately obvious at first glance: they're both small cetaceans, with flippers, tail flukes, and so on. A comparison between, say, a bottlenose dolphin (Tursiops truncatus) and a harbour porpoise (Phocoena phocoena) does show a number of differences that are broadly true of their respective relatives - but not entirely so.

Porpoises, for instance, are smaller than dolphins, on average. But only 'on average', because, in fact, the smallest dolphin is smaller than the smallest porpoise. Similarly, dolphins usually have a 'beak' - a narrow snout projecting forward from the front of the head - that is missing in the more rounded heads of porpoises. But, once again, there are dolphins that don't have the beak, such as Risso's dolphin (Grampus griseus).

Sunday 16 September 2012

Discovery of the World's Newest Monkey

Hamlyn's monkey (left) and lesula (right)
Even today, new species of mammal are being discovered all the time. The majority are small animals, often nocturnal, or otherwise difficult to find. Just in the last few months I've seen the announcement of four new bats and a mole, and that's without me particularly trying - there may well be more discoveries I haven't seen. In many cases - as happened with the bats, for example - it's not that the animal had never been seen before, it's just that it wasn't obviously a different species. Until you look closely, one mole may look much like another.

The discovery of larger species is a rarer event. Which is why the announcement of an entirely new species of monkey is so exciting. This new animal, the lesula (Cercopithecus lomamiensis), is the first new species of African monkey to be discovered since the critically endangered kipunji in 2004, and only the second since 1984.

Sunday 9 September 2012

How Armadillos Get Their Armour

Screaming hairy armadillo
Reptiles are scaly, and mammals are furry. That's a broad general rule, and holds in most cases. But there are, of course, a number of exceptions. Many mammals, such as dolphins and hippos, are not at all furry, for example. And, while there are no hairy reptiles, there are two groups of mammals that have scales.

One of these, the pangolins, have scales that are quite unlike those of reptiles, giving them a unique appearance. The other is the armadillo family, and, in their case, the scales really are quite reptile-like. It's a form of parallel evolution, where two or more groups of animal independently evolve the same solution to a particular problem. The ancestors of armadillos would have been as hairy as any other mammal, but when they evolved protective armour, they ended up with something that is quite similar to the scaly plates of, for example, crocodiles.

Sunday 2 September 2012

Weasels Digging Holes: American and Honey Badgers

American badger
It was thought at one time that the various species of badger were fairly close relatives within the weasel family. More recent genetic evidence has shown us that that's not the case, and that there is more to their story than one might guess from simply looking at them. While the majority of badgers do indeed belong to a single, related, group - what we might call the "true" badgers - there are some exceptions.

In fact, the badger body plan and lifestyle appear to have evolved at least three times within the weasel family. One instance led to the "true" badgers, with at least four species, and possibly more not yet formally recognised. The other two are no more closely related to the "true" badgers, or even each other, than they are to, say, otters or stoats. In each case, only one member of the lineage survives today, giving us two "subfamilies" with just one living species each.

Of the two, the better known is surely the American badger (Taxidea taxus). Despite being as genetically distant from the European badger as its possible to be without belonging to an entirely different family, it's really not hard to see why early American colonists chose to give it the same name as the animal they were already familiar with. In addition to the short limbs typical of all members of the weasel family, it has a compact, muscular body, wedge-shaped head, and powerful digging claws. That's not really so surprising, when you consider that there are only so many ways to modify the body of a weasel to make it into an effective digger.