With a population of 75 million, the field vole is one of the UK's most common mammals. To put that number in perspective, the UK’s human population is 66 million, there are around 14% more of them than us! Unfortunately they are a bit harder to spot, but signs they are nearby are much easier to find. What are called ‘runs’ (little vole subways running from their burrows to their feeding sites) can be found anywhere grass has been allowed to grow long enough that it collapses on itself. If you gently part the grass with your hands you’ll almost certainly find a field vole run, along the sides of the well trodden little path will be grass clippings or grass that looks like it has been shredded and somewhere before the entrance to the burrow there will be a latrine area full of small pellet droppings.
Voles, of which there are 3 species found here in the UK - the bank vole, the water vole and the field vole - are often confused with mice or in the case of the water vole, brown rats! Voles however have an altogether ‘rounder’ appearance than mice or rats which could be thought of as more ‘pointy.’ Voles have blunter faces, smaller ears and eyes and much shorter tails. Field voles are grey-brown above and pale grey below, their fur is much shaggier than the similar bank vole, and they have a shorter tail, giving them their other common name the short-tailed vole.
Field voles are common in Otley and throughout mainland Britain and have been for the last 11000 years, since the end of the last glaciation, much longer than us humans! They are active day and night and will eat seeds, roots and leaves, but their favoured food is grass. Unlike mice, they are not great climbers, preferring to move along the ground through their network of runs. Further up the food chain, field voles form an extremely important part of the diet of many predators, such as foxes, stoats and weasels, as well as kestrels and owls. So important to the latter two, the number of young reared by kestrels and owls has been shown to increase when vole numbers increase or decrease as vole numbers decrease.
Field voles are about 10cm long and weigh only 20-40g, their average life span is up to 1 year, but they can live up to 2 years, if they are not eaten first! They breed from March/April until October but can keep going until December, weather permitting. A female can produce 3 to 6 litters of up to 7 young a year, but 4 or 5 young are typical. Shredded grass leaves are used to make their nests which are about 10cm in diameter and may be built at the base of grass tussocks, in underground burrows or even under sheets of corrugated iron. Into which the young are born blind and hairless, completely dependent on the mother but will have to become entirely independent within nine weeks, when the mother abandons the nest and finds a new territory where she will breed again.