Voles in general

Voles in general

(Photos - Creative Commons)

This year (2020) seems to be a very good year for bank voles. They seem to pop up, literally, everywhere. Out of the corner of your eye, in the garden, you spot a portly animal on the grass. If you keep still it is unconcerned and goes about its portly business of stoking up on the newly growing vegetation. If you move, its benign beady eye suddenly becomes aware of your presence and it dashes, with surprising speed for such a plump creature, into the circular hole that is the entrance to its abode. The entrance to its tunnel is dark and a near perfect circle which seems inadequate in diameter to accommodate the girth of its creator, but the vole nevertheless, enters with alacrity. It does not restrict itself to subterranean tunnels but will also create shallow runs just under the grass which appear as branching ridges in the vegetation.

A bumper vole year means a bonanza for predators such as weasels, stoats, kestrels, foxes, barn owls, short-eared owls to name but a few. Life may be short and brutish for voles but they have the satisfaction of knowing that they are a mainstay of the food chain.

In relation to kestrels voles make a serious mistake - they leave a trail of urine which reflects ultraviolet light and as luck (well, evolution) would have it, kestrels can see untraviolet. The hovering kestrel has an unfair advantage - an ultraviolet pointer to their lunch.

Foxes and owls make great use of sound and can locate the unfortunate vole by listening carefully and then pouncing. As a result the voles are not safe even under snow.

The majority of the voles in our garden are bank voles (Myodes glareolus), which are found throughout mainland Britain.

Bank Vole (credit soebe)

There are two other mainland voles - the short-tailed field vole or common vole (Microtus agrestis), which as the name suggests has a shorter tail than the bank vole and the water vole.

Short-tailed field vole (Common Vole) (credit David Pérez)

As is well known the water vole has been under great pressure from loss of habitat and from predation by the introduced American mink. A number of people in the Rannoch area have put out mink rafts designed to detect the presence of this predator. The rafts are generally made of polystyrene surrounded by wood and topped off with a tunnel floored by clay. If an animal such as a mink passes through the tunnel it leaves its footprints in the clay and therefore its presence can be detected. When the mink is detected the tunnel is replaced by a live trap and once caught the mink is shot.

Water Vole (Credit Peter Trimming)

The numbers of mink seem to have declined in Highland Perthshire and it is encouraging that upland areas such as Dùn Coillich still seem to have healthy populations of water voles. On Dùn Coillich, Liz Auty of the John Muir Trust and members of Dùn Coillich have detected water voles using trail cameras. The water voles also leave distinctive signs such as droppings and grass stems, which they have neatly trimmed at an angle of 45 degrees. The Highland water vole tends to be fairly large and dark in colour when compared with the lowland equivalent.

Many years ago I witnessed the demise of a large and dark water vole when it was caught in a burn at Dall by a heron. The heron held it aloft for a short time before downing it in one.

There is a very interesting vole found on some of the Orkney islands - the Orkney Vole (Microtus arvalis orcadensis). It is about ten percent larger than the average common vole. Some authorities would have it classified as a separate species but most would say it is a subspecies of the common vole. DNA analysis suggests that Neolithic people transported the vole to Orkney from Belgium. It may well be that the voles got into their grain stores.

Carbon 14 dating shows the earliest fossil Ornkey vole to be 4,600 years old and so the vole must have been introduced no later than that date. Presumably its isolation on the Orkney islands has allowed the differences from the mainland common vole to evolve. It is not uncommon for Island species to become larger.

Orkney Vole (credit Hauke Kozh)