Owls and kestrels feast on plentiful supply of field voles

WATCHING BIRDS of prey and owls in daily action outside my village above the Aire Valley it is clear that their survival depends to a large extent on the UK’s commonest mammal, the field vole.

The prime habitat for these 3½in rodents, according to a study undertaken in the Sheffield area, is “areas of ungrazed grassland, verges, grass embankments and tussocky grass” as well as “bilberry and heather moorland, scrub and hedgerows, and well-vegetated inner-city derelict sites”.

Some years back a survey put Britain’s population of field voles at 70 million, but it is safe to say that not every single one of them was counted. That would be impossible given their highly furtive nature in thick grass. Rather, the small mammals were intensively surveyed in some sample plots to find their density per square metre, and the final figure was an extrapolation based on the total area of land covered by similar habitats.

In the book Yorkshire Mammals edited M J Delaney, it was stated that the “relatively unfashionable field vole” had been ignored or completely taken for granted by local naturalists. Most references related to their impact on agriculture.

According to a review of study work in Yorkshire from 1881 to the 1950s: “This little animal is ubiquitous and becomes at times an absolute pest as its numbers periodically rise to a peak after which an epidemic sets in and the numbers rapidly decline to a sub-normal level”.

More recently, a study in the Harrogate area concluded that the field vole’s distribution was restricted only by the availability of suitable habitat.

In my opinion field voles might well be twice as numerous as that 70 million figure. This view has not been arrived at after conferring with clipboardcarrying scientists plodding around in wellies but by many hours observing my local barn owls. Their very impressive catch rate in just one field of the above-mentioned tussocky grass suggests they are treating it as a well-stocked supermarket.

Sadly, I found a dead field vole on the edge of an adjacent golf course, which may have been dropped by the kestrel I had seen rise from area of heather. It wasn’t immediately retrieved by the bird because of horse riders on a nearby bridleway. I could easily distinguish the small mammal from its close cousin the bank vole by its lighter fur and shorter, hairier tail (an alternative name is the shorttailed vole).

The field vole’s biology makes it an exceptionally successful breeder. This occurs from February until October in nests well buried beneath those tussocks of grass and linked with burrows. They eat mostly grass and leaves.

The Mammal Society says there are between two and seven litters a year, each one having up to six young. The females are sexually mature after just 28 days, so you could easily turn the field vole’s cumulative reproduction rate into one of those old arithmetic questions from primary school.

Whatever the answer, it’s certainly good news for owls and kestrels.

OFFENDERS RELEASED from prison will be made to wear GPS tags to track their movements in a world first scheme to be launched in parts of Yorkshire, the Government has announced today.

Under new rules, burglars, thieves and robbers who have served a prison sentence of a year or more will be automatically fitted with a tag on release, allowing their whereabouts to be monitored by GPS satellites 24 hours a day for up to 12 months.

Police will be able to work with HM Prison and Probation Service staff to investigate whether those on the tags have been in the vicinity of recent burglaries, thefts and robberies. It could provide the crucial evidence needed to catch the perpetrators.

Policing Minister Kit Malthouse said: “Being burgled is devastating and I understand how frustrating it is when the perpetrators can’t be caught. Tagging these offenders so we know where they are 24 hours a day should be powerful persuasion to change their ways, and will help police find them if they don’t.”

The intention is the tags will also act as a deterrent, protecting the public from further burglaries and forcing career criminals away from offending. It is hoped the scheme will reduce the estimated £4.8bn burden the crimes place on the taxpayer every year.

The scheme will initially launch in six police force areas, including Humberside, Avon and Somerset, Cheshire, Gloucestershire, Gwent, and West Midlands on 12 April.

It is estimated 250 offenders will be tagged in the first six months, and the pilot will then be extended to a further 13 areas in September.