Apprentice diary: the weighing of the shrew

It’s a busy time on the reserve, as shorebird season demands so much of our energies, and at times I forget that there is anything but sand and shore and little terns. Last week, though, meant a break from shorebird wardening and a trip to the island to assist volunteer Veronica with a small mammal survey. 

I drove the work van across the causeway - very slowly - it’s still new to me and feels very strange to be so high up. Steering the whale very slowly into the car park, I spotted Veronica, wearing a bright yellow mackintosh. We waved.

I walked over, apologising - I’m afraid I don’t know anything about small mammal surveying but I’ll help however I can! Veronica smiled. These are the small mammals we have in the UK - she passed me a fold-out picture guide. And these are the shrews and rodents we’d expect to find here. I pricked up my ears. Aren’t shrews rodents? It would seem not. 

I had, I realised, come to define rodent as meaning ‘small furry creature resembling a mouse’. And somehow, over the years, there had never been cause to change this workable, but quite wrong, definition. Rodents (for those who don’t know) are characterised by their constantly growing incisors - the name comes from the Latin ‘rodere’, to gnaw. Shrews, on the other hand, are insectivores and play quite a different role in an ecosystem. Not just mice with long noses, I realised.

We gathered our kit - bedding, bait, one bucket, one large plastic bag, one small freezer bag, one set scales - and set off for the dunes. The traps were marked with ribbons, Veronica told me, pointing one out. I looked and looked again, then spotted it - a tiny slip of ribbon tied around some Marram grass. At its base, well concealed by mosses and grass, the Longworth trap. 

Longworth small mammal traps are one of the most commonly used - comprised of a box filled with bedding and bait, and a corridor section with a door which can be set to remain open or to shut when a point in the trap is triggered. These traps had initially been put out for prebaiting, with the door not triggered to shut - allowing the small mammals to discover the existence of a splendid new food supply and run in and out at will. To tempt them: sunflower seeds for the rodents (kibbled so the seeds don’t germinate and sprout sunflowers in the dunes); fruit to relieve thirst; and blow fly casters for the shrews. A few hours earlier, these traps had been baited and triggered and we were now off to see whether anything had been found. 

There probably won’t be anything, cautioned Veronica - they’re mostly active at night time or dawn and dusk. It was - I checked my phone - exactly noon. So perhaps not. But as we reached the first box, Veronica checked the door. It was shut. It could be a misfire but - she looked inside - we had something.

Placing the trap at the bottom of the large transparent plastic bag, Veronica unhooked the corridor section from the main trap and gently angled the trap. Slowly, a bundle of bedding, bait, and one small furry slid out. It was a shrew - a common shrew, to be precise - tiny, scurrying and, it seemed, absolutely furious. Nobody does indignant quite like a shrew, I thought, watching its nose quiver as it looked up at the enormous, rude humans who had disturbed its luncheon. How dare we? 

A gloved Veronica scruffed the shrew - catching it, holding it carefully in one hand and then gently decanting it into, of all things, a small freezer bag. She then clipped scales onto the top of the bag. 5 grams? She asked. I confirmed. 5 grams. The weight of a twenty pence piece. It really was very tiny. Veronica confirmed identification - a juvenile common shrew, too young to easily sex. And then, release - and with a wriggle into the undergrowth, it was gone. 

On to trap number two - three - four - and all the way to twenty seven, seeking ribbons in the long grass. All but trap no.1 were - unsurprisingly - empty. Beginner’s luck had served me well. Longworth traps must be checked every four hours - we would return later that afternoon, and then Veronica would check again, and again, into the night. She has carried out these surveys in spring and autumn for the past 9 years, forming a picture of the situation for small mammals on the island. 

We said goodbye in the parking lot. I thanked her, and drove away, smiling. I love to learn and it is a joy to meet someone so generous with knowledge and time. And I saw a shrew! I look forward to the autumn.