Clethrionomys glareolus

  By: Calvin Jones

Search County Kerry

The Bank Vole is County Kerry`s and  Ireland’s only vole species and a recent addition to Irish fauna. It was discovered in Co Kerry in 1964, and is thought to have arrived as an accidental stowaway in a shipment of timber. 

Since then it has established itself in counties Cork and Kerry, and is gradually spreading its range northwards with reported sightings from counties Clare, Limerick and Tipperary.

Bank voles are common and widespread in Britain and throughout most of Europe. They are small stocky rodents with a blunt, rounded muzzle, a head and body length of about 8-12 cm (3-5 inches) and a 3.5-6.5 cm (1.4-2 inch) tail that is usually slightly bushy at the tip. 

The fur is reddish brown on the back, greyish on the flanks and a creamy beige colour underneath. They can weigh from 15-40 g (0.5-1.5 oz). 

Typically denizens of the woodland floor they are adaptable little creatures quite at home anywhere where there is ample herbaceous ground cover. They tend to avoid areas where cover is scarce as they then become easy targets for their many predators, including birds of prey like the kestrel and barn owl, and mammals such as stoats, foxes and domestic cats.

Bank Voles are active day and night, but intersperse their activity with periods of rest. They feed on a broad range of mainly herbivorous foods that include fruits, soft seeds, leaves, fungi, roots, grass, buds and mosses. 

They sometimes take invertebrate food such as snails, worms and insects, and the occasional bird egg may be taken if the Opportunity arises. They are good climbers and jumpers and often climb into bushes in their search for food. 

Bank voles sometimes store food caches for retrieval during the winter months when foraging becomes difficult. Breeding usually takes place between April and October, but when conditions are suitable may occur all year round. Ovulation in female bank voles is triggered by the presence of a male.  

After mating gestation usually takes around 21 days, but in optimal conditions may be as short as 17 days. The female is able to conceive again when still sucking her previous litter, but the subsequent gestation period becomes slightly longer — approaching 24 days.

A female bank vole typically gives birth to 4 or 5 litters a year, each litter consisting of 3-5 young. The young voles are born in a nest that is usually well hidden under a log, amongst tree roots, in a tree hole or in an underground burrow. 

Male bank voles play no part in rearing the young, leaving parental duties to the females. They are very protective of their litters, and should a young vole stray from the nest the female will locate t and carry it back to safety. 

Young become independent after about 4 weeks and are sexually mature at around 4.5 weeks of age, although those born late in the year don’t generally reproduce until the following spring. 

The maximum life span of a bank vole is about eighteen months, although few reach that age. Vole populations tend to fluctuate through the year, peaking towards the end of summer and plummeting dramatically through the winter to reach a low-point in April when breeding once again starts to Pick up their numbers. 

Predation is the major source of bank vole mortality but they can also be affected by exposure to pesticides fragmentation of woodland removal of hedgerows and overgrazing of suitable ground cover are all bad news for the vole population. 

However this adaptable and resilient little rodent is on the move and may eventually spread its range throughout the country from Kerry to Derry.

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