Sunday 20 December 2015

New Mammal Species 2015

Brown titi monkey
As 2015 draws to a close, it's time to look at some of the species of mammal that we didn't even know existed this time last year. Of course, the reality is that, in most cases, we knew that the animals existed, we just didn't realise that they were a species. Some we thought were subspecies, and we now have enough information to promote to full species status, while others we just hadn't noticed were different at all.

Telling the difference between a subspecies and a species is a difficult, and rather subjective, art. It essentially relies on you being able to demonstrate that the animals don't usually interbreed in the wild when they get the chance. Not that they can't. Not that they don't sometimes. Just that they don't usually. You can really only do this by showing that their genetics are distinct, and even doing that may depend on how good your sample is. As a result, while new species of mammal are named every year, it's worth noting that this isn't a one-way process... it's not that unusual to demote a species back down to subspecies as more information comes in.

And just because you officially named a species according to all the rules laid down by the organisation responsible for doing such things doesn't mean that anyone else will agree with you. Not every named species stands the test of time. But with all that in mind, and noting that I couldn't possibly catch every single mention of a (claim of) a new mammalian species, here's a selection.

You Can Never Have Enough Bats

Any list of new mammalian species is going to be dominated by bats. Bats only come out at night, aren't likely to be caught in any animal traps you've placed on the ground, and, to be honest, don't have that many people studying them (not least because of the first two reasons). There's also one heck of a lot of them, with an enormous species diversity, particularly in the depths of tropical jungles.

For example, in July a new species of horseshoe bat (Rhinolophus francisi) was discovered on the island of Borneo, with individuals found on both sides of the Indonesian/Malaysian border. Horseshoe bats are a widespread group, found across much of the Old World, and even into northern Australia. They are named for the unusual shape of their noses, and it was partly on the basis of the exact shape in these specimens that they were separated from the trefoil horseshoe bats (R. trifoliatus) that was already known to live in the area. However, to prove the point, the researchers also performed genetic tests on their specimens, and recorded the ultrasound calls that they made, demonstrating that these, too, were different. They even found a specimen in Thailand, which looked and sounded identical to the species they'd just discovered on Borneo, but had some minor genetic differences. Enough, they argue, to name it as a different subspecies of the island form.

It isn't even alone. In the very same issue of the specialist bat journal Acta Chiropterologica another group of scientists named another species of horseshoe bat from Malaysia (R. luctoides), this time from the continental, peninsular, part of the country. It's another very close relative of the trefoil horseshoe bat, and, to human eyes, virtually indistinguishable from it without genetic analysis. However, as is often the case, having proved that it ought to be different, the researchers were able to find some minor physical differences between the new species and the old one, most notably in the teeth of its lower jaw. They were also able to show that a known subspecies of trefoil horseshoe bat was genetically distinct enough (in their opinion) to promote to full species (R. morio).

Just to prove that nature scoffs at our attempts to neatly classify it, they even found a hybrid individual, the child of a R. morio mother and a R. luctoides father. Analysis of its chromosomes show that it was quite probably sterile, as mules are, but, it being dead, that's hard to prove.

Sticking to the same general area, we also have a new species of false vampire bat - fairly large tropical bat that, at least to my mind, doesn't look all that much like real vampire bats. Perhaps unusually, this one was identified on the basis that it really did look different from anything else ever seen before, and the study announcing it includes the most detailed analysis and comparison of false vampire bat penises ever published. (There's a claim to fame). Also having some fairly dramatic differences in the appearance of the head and teeth, genetic analysis showed that the new species was radically different from those already known. So much so that the researchers didn't just name it as a new species, but gave it any entirely new genus, naming it Thonagaree's disc-nosed bat (Eudiscoderma thongareeae).

Islands, especially tropical ones, are often a good place to look for new and distinct species. This year, for instance, saw the discovery of the 88th named bat species on Sumatra - a new thick-thumbed bat (Glischropus aquilius).  More dramatically though, we have managed to double the total number of native land-dwelling mammal species known on the Hawaiian islands.

Yes, we now know that there are two.

The one we already knew about was the hoary bat (Lasiurus cinereus), a species that is also found in both North and South America. We also knew that the hoary bats in Hawaii were a bit weird, being smaller than their mainland kin, having a broader diet, and roosting in caves (all the mainland ones roost in trees). Which, we thought, was enough to consider them a different subspecies. Trying to see if that was true was one of the aims of a study into the genetics of hoary bats and their close relatives. And, yes, they proved it: the hoary bats of Hawaii are genetically distinct from those from North America, even even further from those in South Americas. So, three subspecies, which was basically what we already thought.

Except that some of the bats turned out to have genetics that weren't even close to those of the others, well outside the range of variation found in the three subspecies. Indeed, the differences were greater than those between other known species of Lasiurus, demonstrating that these bats did not just belong to some previously unknown fourth subspecies, but a different species altogether. So, yes, there are hoary bats in Hawaii, and they are different from those on the mainland... but there are also what, for lack of a better name we will have to call Hawaiian hoary bats (L. semotus).

Small Furry Beasties

More specifically, ones that can't fly.

If you're not going to look for bats, your next best bet for finding a previously unidentified species of mammal is to look for something small, with rodents being a particularly good bet. One such example this year comes from the Valdivian forests of southern Chile, already known to be home to a number of unique mammalian species, including the endangered Darwin's fox, which I discussed earlier this year. One such species is Sanborn's soft-haired mouse (Abrothrix sanborni), but there have been questions as to whether it really counts as a species, or just as a subspecies of something else. As was the case with the bats in Hawaii, when researchers conducted a genetic survey to settle the question they proved that, not only was it a species, but it was actually two, with specimens from further north turning out to be less related to the southern ones than the latter were to the woolly soft-haired mouse (A. lanosus) of Tierra del Fuego and south-western Patagonia.

And so we now also have Mann's soft-haired mouse (A. manni), said to dwell in dense lowland forests, and to particularly favour fungi as a food source, although they also eat insects, seeds, and foliage. The researchers estimate that it likely separated from the Sanborn/woolly lineage around 2 million years ago, which likely means that the dawn of the Ice Ages had a lot to do with it.

They don't have to be rodents, though. Small-eared shrews are a genus of animals that live primarily in Central America, but with one species in the eastern US and Mexico, and a further 14 found as far south as northern Peru. In fact, they are the only shrews found in the whole of South America. One specimen, collected in 1989 from the Venezuelan/Colombian border had proved a bit of a puzzle, however, with the few people who had examined it being unable to agree as to whether it belonged to the Colombian species (Cryptotis thomasi) or the Venezuelan one (C. meridensis).

Although there has been no genetic analysis to back this up, as you'll have guessed, the researchers decided that it was neither, having a number of physical differences from its purported relatives - not least in being quite a bit smaller. It is now known as the Perij√° small-eared shrew (C. perijensis).

I should also mention the Ili pika (Ochotona iliensis), despite the fact that it's not a new species, having first being spotted in 1983, and formally described three years later. It gets a mention partly because, after having being identified and named, nobody saw one again until 2014. In the interim, it had been designated an endangered species, with the worrying possibility that it had already gone extinct. In March of this year, the fact that it had been sighted again was announced, making it a brief internet sensation. Largely because it's incredibly cute.

Three New Primates

Among larger mammals, I have already mentioned the naming of the golden wolf (Canis anthus), previously thought to be a kind of jackal. But that is by no means the only new species of mammal to be named this year that is larger than a rabbit.

As with smaller animals, though, the best place to look for them is still in the jungles, where it is easy to hide something new. But you don't actually have to go to the jungle to find your new species. You could instead just try looking in a drawer in a back room at the American Natural History Museum in New York.

In 2008, Dutch researcher Jan Vermeer did just that, as part of a project to research the diversity of monkeys in Peru. He found the preserved body of what was, according to the label, a brown titi monkey (Callicebus brunneus), a sort of small, long-tailed monkey with soft fur that dines mainly on fruit. To him, though, it didn't look quite right, having, for example, too much black fur around the face. He decided to take a trip to Peru to see if he could find more.

Which, indeed, he did. The description of the new species, the Urubamba titi monkey (C. urubambensis), was published this July. The same paper also promoted Toppin's titi monkey (C. toppini), which lives in the same area, from subspecies to species, meaning that there are now three species of titi monkey in the area. Toppin's monkey was already known to be quite widespread, whereas the new one seems to be restricted to the Urubamba River basin in central Peru. Fortunately, it's a pretty long river, and nobody much seems to visit the surrounding jungle, which means that the new monkey is probably not yet endangered.

The description was published in the 2015 edition of Primate Conservation, which also announced another new species of primate. This one isn't a monkey, but rather a dwarf lemur from Madagascar. Dwarf lemurs and their ilk are really not much studied, being nocturnal, small, and quiet, never mind living in the depths of jungles where they don't much like to come down from the trees. So its hardly surprising that new species are still being discovered, even if it's an impressive demonstration of the diversity of animals on this one tropical island (albeit quite a big island). Nonetheless, on the basis of both physical and genetic evidence we now have Sabin's dwarf lemur (Cheirogalus andysabini).

All of this shows, in different ways, the usual pattern: you take a closer look at an obscure species, and find that it's really two species. Sometimes though, you really do find something new.

There were long thought to be two species of macaque living in southeastern Tibet: the Tibetan macaque (Macaca thibetana), which, despite the name, mostly lives further east in southern China, and the Assamese macaque (M. assamensis), which is more commonly found further to the south. In 2005, however, researchers reported a new species, the Arunachal macaque (A. munzala), that is apparently found nowhere else in the world.

But, as I noted at the start, just because you name it doesn't mean that everyone else has to believe you. Although the evidence was good enough for the animal to be formally listed as an endangered species in 2008, in 2011 other primatologists began to question whether it really existed. Or, at least, whether or not it was really just a funny-looking Assamese macaque. It being endangered, and nobody really wanting to go and kill one to look at it more closely, a couple of Chinese researchers decided to undertake a large photographic survey of the local monkeys to try and prove that the Arunachal monkeys really were different from the Assamese sort.

As sometimes happens, they failed, because they couldn't actually find any Arunachal macaques. But, when they looked at the photographs their automated traps had taken in Medog County on the Indian border, they realised that the monkeys they were seeing there couldn't belong to any of the three known species. Their bodies were a different colour, they had shorter tails, and they had very visible patches of white fur on their cheeks, unlike any other species of macaque in the world. From a couple of recordings, they also discovered that their alarm calls were higher pitched than any of the known local species. It was enough, even without genetic evidence, or indeed the corpse that you normally need for this sort of thing, for them to declare that this had to be something never seen before: the white-cheeked macaque (M. leucogenys).

If they're right - and it seems to me that this one has a good chance of standing the test of time - this is a brand new species. Not something we'd seen before and misidentified, but something entirely new to science. The world still has more to show us.

[Photo by "Cliff", from Wikimedia Commons.]

Synapsida will return in the New Year. Merry Christmas!

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