Sunday, 24 May 2020

Stopping the Water Vole Killer

I have often referred on this blog to the number of mammal species that are currently faced with extinction, of being wiped totally from the face of the Earth. Depending on how strictly you want to define the threat, this could be anything up to 25% of the total known species, although it's worth noting that a great many other species have declining populations, if not ones that are likely to vanish altogether any time soon.

For many species, even if extinction is not a threat, extirpation can be. This is, essentially, a local extinction, where the species dies off entirely in some particular area, but still survives somewhere else. While it can be any area you like, in conservation terms, we tend to be talking about either countries or reasonably sized islands. Or, as is the case in Britain, both.

Many species of mammal have been extirpated from the British Isles over the course of our history. Wolves are one of the more famous examples here, with the last official record of a dead wolf dating from 1680 in Scotland (it's unlikely to have literally been the last, and rumours continued for another hundred years or so, although it's hard to know how many of them were accurate). In a number of other cases, such as the hazel dormouse, local populations today very much seem to be in decline.

Sunday, 17 May 2020

Small Cats: The Manul and the Rusty-Spotted Cat

The leopard cat and its relatives form one branch in the larger feline family tree, and one that's entirely native to Asia. These live, for the most part, in tropical parts of the continent, often close to plentiful water. But at least one other close relative instead prefers to live in environments that are both much colder and much drier.

Perhaps the most popular name for the animal in English is Pallas's cat (Otocolobus manul), which tends to lead to an argument as to whether there's an 's' after the apostrophe or not. (There usually is, these days, but it's far from universal). For convenience, however, I'm going to use the alternative name of manul, which derives from the original Mongolian name of the animal.

Saturday, 9 May 2020

Ancient Argentinian Armadillos

Nine-banded armadillo
Armadillos are, I suspect most people would agree, fairly odd-looking animals. Their unusual appearance is evident to a layman, and more detailed analyses of their biology and internal anatomy only bear this out. As one might expect for creatures with such a distinctive appearance, they have a relatively long fossil history, having split from other mammal groups a long time ago. The fact that their skin literally has bone embedded in it also helps when it comes to finding - and identifying - fossil remains.

Sunday, 3 May 2020

Let's Split the Party!

Last week, I described how, over the last few decades, populations of gray seals have recovered from a near-total local extinction in US waters. Clearly, other species facing similar threats, across the world, have not been so lucky. The rapid pace of human expansion simply overwhelms the ability of some species to cope, whether it be through direct effects (expansion of agriculture, cities, transport networks, and so on) or indirect ones (climate change, most obviously).

In the millions of years before humans appeared on the scene the world was changing at a slow enough pace that it was possible for mammal species to evolve their way out of a problem. Many didn't, of course, and went extinct, but others gave rise to newer species that outlived them. Today, it's not just the scale of the changes humans are making that has caused problems for some species, but also their speed.

When it comes to dealing with very rapid changes in the environment - whether human-caused or otherwise - mammals have both advantages and disadvantages compared to some other species. On the negative front, mammals, especially the larger ones, have long generation times, meaning that any effect of evolution, even on a relatively minor scale, is inevitably going to be slow.

Sunday, 26 April 2020

Grey Seals on the Rebound

According to the IUCN Red List, which is probably the most widely used catalogue of conservation statuses, roughly a quarter of all mammal species are "threatened with extinction". That's a broader category than "endangered species", but, either way, it's a proportion that's growing. (As it is, of course for non-mammalian species; amphibians, for instance, seem to be doing particularly badly).

Partly that's because we're getting better at evaluating such things, and identifying species as being at risk when we previously knew little about them - or, in many cases, didn't even know they were separate species. But it's also a consequence of mankind's ever-expanding ecological footprint, as some species become threatened that weren't previously.

Sunday, 19 April 2020

Small Cats: Leopard Cats and Their Kin

Leopard cat
(a northern subspecies)
The jungles of Southeast Asia are home to a particularly large number of cat species. These include tigers, leopards, and clouded leopards, but also a number of smaller species. Of these, the most common are probably the jungle cat, which is a particularly close relative of the domestic animal, and the leopard cat (Prionailurus bengalensis) which is slightly less so.

Leopard cats were first identified as a separate species back in 1792, on the basis of animals known to live in Bengal, and some variant of the name "Bengal cat" remains common in a number of non-English languages. That "leopard cat" is often preferred is doubtless due to the fact that the Bengal region is just one part of their much larger total range.

Indeed, leopard cats are known from Kashmir in the west right across to Vietnam and Malaysia in the east, and also through most of the non-mountainous parts of China, reaching into the Russian Far East north of Manchuria. They are one of only two species of wild cat native to Korea (the other being the Eurasian lynx) and they are also found on a number of islands, including Taiwan.

Sunday, 12 April 2020

Miocene (Pt 19): When Rhinos and Giraffes Went South

At the dawn of the Miocene, 23 million years ago, Africa was a very different place than it is today. This was as much due to simple geography as anything else. For one thing, the Sahara Desert didn't exist yet - even the most extreme estimates suggest that it didn't begin to appear until the Late Miocene, and it may well have not have formed until at least the Pliocene around 4-5 million years ago. Before this time, much of the continent was probably covered in warm, damp, forests interspersed with patches of more open woodland and scrub.

More significantly, perhaps, Africa was still an island continent, separated from Eurasia by a body of water called the Tethys Seaway. It had been like this, isolated from the rest of the world, for millions of years, during which time it had developed its own unique animal life, quite different from that elsewhere. At the time, the same was true of South America (and it still is for Australia), but that continent retained its unusual animals for much longer, not contacting the north until as recently as 2.5 million years ago, shortly before the first of the Ice Ages. When that did eventually happen, it led to the Great American Interchange, which set the scene for much of the American fauna we see today.