Monday, 21 May 2007

The field vole problem

On Sunday the vole group went to a local farm where the landowners have fenced off an area of marshy field, with the specific aim of helping wildlife. We need more farmers like this! Fencing off the ground stops cattle from destroying banks and vegetation. It's especially useful along ths margins of ponds, streams and rivers. In this particular strip there's a large section of glyceria reed (top photo) which water voles love.
As soon as we began to look for field signs, we found them: latrines, feeding stations and trackways were every few yards, plus a few burrows. However, we did run into a problem we hadn't anticipated last year, that of the similarity of field vole signs to those of water voles. Field voles also cut grass etc at a 45 degree angle; they also make little piles of chopped vegetation; they also form trackways through the grass. In the picture above, it's a water vole feeding station on the left, and a field vole one on the right.
Not always easy to tell them apart, but there are some indicators. Firstly, water vole stuff tends to be on a slightly larger scale. Their trackways are more rat-sized, as opposed to mouse-sized, they chop their food into slightly longer pieces, and their droppings are bigger and darker. Secondly, water voles tend not to put droppings on top of their food piles. (Why would field voles do this??? But they do. Teeny green ones.) And thirdly, the location's a bit of an indicator. A trackway leading straight into the water is going to be water vole.


Dave said...

I don't know about field voles but I believe that rabbits and other rodents will eat their own droppings as part of the digestive process. So perhaps they're not that fussy about their toileting. Each to their own!

Kate said...

Could be. The other thing I've been wondering is, do voles actually go back and eat these piles of chopped veg at any point? Because, from a vole's perspective, you'd be returning to eat dried up food while there's fresh all around you, which doesn't seem to make sense.

Then again, if they don't use these larders, why do they make them?

When I go down again, I'll try and get some photos of the two sorts of droppings, for comparison. (Bet you can't wait!)

dave said...

I know with rabbits it's a double digestion thingy. We had a Guinea Pig once that we "treated" to excessive greens and it had to be put down after something went wrong with his pipe-work. The vet attributed it to the diet.

Anyway look forward to the piccies!