Outdoors: The vole story
IT IS our commonest mammal, lives for little over a year and is the “bread and butter” staple for many of our predatory animals.
Seldom seen and secretive in habit, its place in the food chain is so fundamental that the humble little field vole must also rank as one of our most ecologically important creatures.
It is estimated that there are around 75 million field voles in the UK, although numbers fluctuate greatly over time, and in many areas typically undergo a four-year cycle of boom and bust. Populations in their preferred habitat of rough ungrazed grassland or young forestry plantations build up to a peak before crashing, only for the cycle to begin again.
Predator numbers will often mirror these peaks and troughs in field voles, and this is why in some years stoats and weasels, and birds such as short-eared owls and hen harriers, can be abundant, and in other years less so. David Stephen, the great 20th-century Scottish naturalist and former Scotsman columnist, recounted how even large birds of prey such as the golden eagle will take advantage of vole bounty years by wading through long grass and gulping the voles down, “…small prey for so large a bird; but the area is swarming with them and they are easily caught”.
In the so-called “vole plague” years, the damage that can be wreaked on vegetation can be considerable, including on young trees in forestry plantations. On my own home patch in the Ochil Hills in central Scotland, especially in areas of rough grass in the lower glens, it is common to stumble across the evidence of a vole boom year. By gently parting the tussocky grass, vole runs can be seen criss-crossing the ground, u-shaped grooves in the soil that are fashioned into shallow tunnels thanks to their grassy roofs. Sometimes, the voles can be seen too, as little flashes of brown scampering for cover. As a youngster, I found that one of the most reliable ways of finding field voles was to turn over a piece of corrugated iron or wooden board lying in a field – more often than not the grassy ball of a nest chamber and the associated runway system was revealed beneath. If you try this yourself, always remember to gently lay the covering back again.
In a fascinating piece of research, it has been shown field voles leave a trail of scent in their runs to warn off other voles, and that hunting birds of prey such as kestrels are able to detect the ultraviolet light that radiates from these trails and use these as a hunting aid.
In Orkney, the field vole is replaced by the larger Orkney vole, a sub-species of the common vole, which is found widely in continental Europe. It was probably introduced to Orkney by Neolithic settlers and over the centuries has evolved into a distinct sub-species. The Scottish hotspot for the nationally rare hen harrier is in Orkney, and the Orkney vole forms one of its most important prey items.
If the field vole is our most abundant species, then the prize for attractiveness has to go to its cousin, the bank vole. It is often found in our gardens, woods and hedgebanks, and is a frequent visitor to the garden bird table where it will quickly scuttle out for a few seconds to forage below for seeds dropped by birds before quickly dashing back to the nearest cover.
One of my favourite pieces of wildlife kit is a rodent live-trap called a Longworth trap, and in recent years my son and I have used it to good effect for catching bank voles in our garden and then releasing them again. Never hold a caught animal – it may bite – but instead release it from the live-trap into a plastic bucket so as to get a good view. It is indeed a handsome animal, a little russet bundle of fur, with greyish flanks and a blunt hamster-like nose. Unlike field voles, bank voles are great climbers and will often clamber among bramble stems in search of berries.
The vital role that voles play in the ecology of our environment cannot be overstated, and for this reason alone their presence should be cherished. And even when one looks beyond the bigger picture and considers the animal in the same way as we would a bird or a butterfly, then it is apparent that they are rather attractive creatures too.
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Weather for Edinburgh
Tuesday 18 June 2013
Temperature: 10 C to 21 C
Wind Speed: 9 mph
Wind direction: North
Temperature: 9 C to 18 C
Wind Speed: 16 mph
Wind direction: West