Call of the Mole Vole

There are over 170 recognised species of vole. The exact number is hard to determine because new species keep being described and not all will necessarily stand the test of time but we can certainly say that there are a lot. Although we might typically think of voles as being all rather similar to one another - small, mouse-like animals with short tails and rounded snouts - within such a large group there is inevitably some variation.

Most obviously different from regular voles are the giant species. Although genetic data shows us that these are voles, in the sense of being offshoots of the vole family tree rather than something distinct, we don't normally refer to them as such in English. Instead, we call them "lemmings" or, in the case of the very largest species, "muskrats". To avoid potential confusion, in more scientific language we would therefore use the taxonomic name when referring to the subfamily as a whole and say that voles, lemmings, and muskrats collectively are "arvicolines". 

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.

Digging in a Winter Wonderland

Humans have a somewhat ambivalent attitude to snow, greeting it either with joy and wonder or with concern and frustration, in large part depending on how old you happen to be. It decorates Christmas cards, covers the countryside in pristine white, and provides plentiful opportunities for play. On the other hand, it makes travel difficult, and may even interrupt deliveries of food, making our lives awkward. (Plus, if you're in a city, it may not stay white for very long).

If heavy snow makes it difficult for us to get around and obtain sustenance, the same obviously goes for animals that live in the relevant parts of the world. Different species have different strategies for how to cope with its arrival. Some hibernate, while others avoid the problem by migrating somewhere else for the winter, but there are, of course, a number of species that simply have to put up with it. Those that live particularly far north may even have to do so for over half the year, and the difficulty of doing this is probably at least part of the reason why relatively few species do.

Small British Mammals: Bank Voles

I had intended to wrap up voles a couple of weeks ago, but it turned out that there was so much to say about water voles in particular that it made more sense to add in an extra post to cover everything else. So, here we are with the fourth and final species of vole found in Britain: the bank vole (Myodes glareolus).

Although water voles are more closely related to common voles and their kin than the bank voles, it is the latter that have the closest physical resemblance. While most voles are broadly similar in shape, bank voles are also roughly the same size as the common and field voles, and can be distinguished (without close examination of the skeleton) by the fact that the fur on their backs typically has a distinct reddish tinge. A few instances of individuals with other colours have been noted - including a pure white one that had somehow survived to adulthood without being eaten - but these are rare.

Small British Mammals: Ratty and the Water Voles

Four different species of vole live wild in Britain, with, perhaps, the field vole being the one that is most typical of the wider group. However, it's perhaps a different species that has the most claim to fame, appearing as one of the central characters (confusingly named "Ratty") in the popular children's book The Wind in the Willows.

Ratty is a water vole (Arvicola amphibius), an animal with a number of differences from common and field voles, despite being fairly closely related to them. Before discussing the species in more detail, we should acknowledge that, over the years, there has been considerable confusion as to what the scientific name of this animal actually is - and, for once there's quite a good reason for it.

Small British Mammals: Common and Field Voles

Field vole

In many respects, voles are extremely similar to mice. In many languages, the local word for 'mouse' also describes voles, and this was even the case in English prior to around the 19th century, when the term "vole-mouse" was borrowed from a now-extinct Scandinavian tongue, and shortly thereafter abbreviated to simply "vole". In its original language, it literally meant "field", and a similar etymology can be seen in languages such as German (Feldmaus) and French (campagnol) among many others.

Scientifically, voles have also been mixed in with the mice at different times. While they have recognised as a distinct group with their own scientific name since 1821, for much of the 20th century they were considered a subgroup within the wider mouse family. That's really only changed in the last 20 years or so, as genetic and biochemical evidence has shown that the two groups, while related, have distinct evolutionary histories.