Sumo dormouse

I was buzzing all weekend thanks to a remarkable dormouse box check on Saturday. Firstly, we found five dormice – as many as we’ve seen in total for the rest of the year. All five looked in good condition. Two were clearly mums whose youngsters had mostly left the nest (although one of the litter of three we saw last month was still living with mum). Two were this year’s young, now at or near a weight that would probably see them through hibernation.

The fifth dormouse was definitely the most remarkable. It was a giant, weighing 34.5g. It looked like it was wearing a dormouse sumo costume. It’s easily the biggest dormouse I have ever seen. I am analysing data from all the Surrey Dormouse Group sites over the last five years at the moment, so was able to see how it compared. It’s the second biggest dormouse recorded: out of more than 2,000 dormice, only one was heavier (at 35g).

It’s not surprising that we had such a good month for both numbers and sizes of dormice. October tends to be the peak for numbers, as this year’s young disperse. And dormice have been busy fattening up for winter, gorging on plentiful hazelnuts. Most animals look cutest when they are small. But I think chubby dormice must be the most adorable things ever.

This time next month many of them may already be hibernating. Dormice can gain weight surprisingly quickly. Assuming it’s the same mouse, the mother we found in the same box as last month has increased from 20g to 31.5g – she’s increased her bodyweight by 58% in 28 days. She also seems to have become fiestier, managing to bite both me and one of my volunteers. It’s only the second time I’ve been bitten by a dormouse in 6 years.

The juvenile we found in a nest box by himself had taken advantage of the nest left by the dormouse we found in June. The other post-lactating female hadn’t even bothered to make a proper nest, nestling down in a thin layer of leaves on top of a bed of moss.