How can you tell if a wood mouse visits a trap more than once? In my previous post, I referred a bit cryptically to clipping fur for identification purposes. You may be wondering how that works. Well here goes.
We divide the mouse’s back into 6 areas: left and right at shoulder, middle and rear. Left shoulder is A, right shoulder B; left middle is C, right middle D; left rear is E, right rear F – like so:
Then the first female mouse you find has a small amount of fur carefully clipped at position A, the second at position B etc, until you get to F. Then you have to clip in two places: AB, AC, AD, …, AF, BC … BF, CD … CF, until you get to DE, DF and EF. Then you move onto triplets: ABC, ABD, … , AEF, all the way to DEF. The same applies to the males. Presumably, eventually you get an ABCDEF – I’m not sure what happens after that. We’ve only got as far as CE so far at Gunnersbury Triangle.
In theory, this makes it very easy to tell not only if you’ve seen a mouse before, but also when and in which part of the reserve. But of course, it’s not as quite as simple as that. Mice tend to squirm when held, so you may not clip in quite the right place, leading to lots of “is that C or E?” conversations (in one memorable case – is that E or F?). Some may escape your hold before you’ve finished clipping the second letter, leading to duplication. And sometimes, like this morning, the mice themselves are wet from rain which complicates things further.
But imperfect information is better than no information, so I’m sure there will be lots of useful data from this study. Nothing increases your respect for the wildlife researcher quite so much as trying to do some yourself!