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.

Small British Mammals: Squirrels

Red squirrel

The majority of rodent species look, more or less, like mice or rats, depending on their size. But there are a number of exceptions among the many, many, kinds of rodent in the world. Probably the best known such exceptions in Britain are the squirrels.

By far the most common tree squirrel in Europe, and perhaps the most widespread species of squirrel anywhere in the world, is the red squirrel (Sciurus vulgaris), sometimes called the "Eurasian red squirrel" to distinguish it from the North American animal of the same name. This lives almost everywhere in Europe, apart from the Mediterranean islands, southern Greece, and Portugal, and is one of a relatively small number of native wild mammals in Ireland. Further east, they inhabit just about every temperate, forested, region of Asia, reaching as far as Korea, northern Japan, and the coast of the Bering Sea.

About twenty different subspecies are currently recognised, but there seem to be few reliable ways of distinguishing between them. For instance, while most red squirrels are, in fact, red, a significant proportion are darker, or even near-black. These are apparently more common in the dense highland forests of the Alps and the Altai Mountains, but are not a reliable indicator of subspecies, since they are found in other populations, too.

Invasion of the Fire Ants

Small, herbivorous mammals have a hard time of it when it comes to being attacked by larger carnivorous ones. Life expectancies are generally short in the wild, counter-balanced by the ability of most animals to breed like... well, rabbits. Many of their behavioural traits are also shaped by the need to avoid being eaten, including, not just general watchfulness, but trying to do things like foraging where (or when) predators are least likely to be a problem.

On the other hand, predators naturally have an interest in getting round this problem, and the result is a never-ending battle between the habits and skills of predators and prey alike. Over the course of thousands of years, this settles into a sort of equilibrium, changing perhaps only as new species evolve and as the geography or climate change on even longer time scales. Unless, of course, we humans get involved.

Humans can mess up the balance of life among wild animals in quite a number of ways, but the one we're concerned with today is that of invasive species. We purposefully carry species from one part of the world to others, especially when it comes to domesticated animals. Pre-Columbian America had no cows, no domestic sheep (although, of course, two native wild species), no pigs, and no horses or cats. There were dogs, but only because humans had brought them across much earlier. The introduction of all of these animals, and the changes in land use required to support them, have had significant effects on the local wildlife in at least some parts of America, and that's before we include animals deliberately introduced for other reasons, such as fur-farming or hunting, never mind those that we didn't introduce purposefully at all, such as rats.