It’s all happening at the zoo - harvest mice too

25 of us descended upon Chester Zoo for a training session to survey for harvest mice. I was pleasantly surprised that local conservation work ranks so high on the zoo’s priorities – it’s not all about the exotic, we need to look after the natives too. “Conservation starts at home!” My 50 year old memories of the zoo are elephants and my Mum warning me not to fall into the polar bear pit.

Training was delivered by Sarah Bird (Biodiversity Officer) and Paul Hill, freelance ecologist with experience of captive rearing harvest mice. The event was commissioned by the Mammals In a Sustainable Environment Project (MISE) to grow capability for identification of harvest mice in Wales. From our local records centres we have a total of just 60 records, most of which are old, with only 10 being recorded in the last decade. Surely this has got to be an under recording or is it a catastrophe? 

Some years ago the zoo arranged a reintroduction of harvest mice on fields alongside a canal. We began our training event at this site unloading 20 traps which revealed loads of voles (field and bank) and some wood mice but not what we were looking for. Our second exercise was to search through the undergrowth for the distinctive nests, balls of woven vegetation made mainly with  leaves split lengthways, lashed together without being severed from the plant. 15 minutes later we found our first example, neatly built around the supporting trunks / main stems of a few reeds. Once we got our eye in there was no stopping us and a further 4 were found before returning to our lecture theatre.

We were shown some brilliant ARKive footage to bring the subjects to life. See this as an example: From this link you can navigate to lots more films of harvest mice and all other species. What a fantastic resource!

The characteristics and lifecycle were explained. Widespread distribution from UK to Japan but absent from Ireland! Prehensile tails a very distinctive feature acting as a 5^th limb. Very small size, just 4 to 6 grams, a third or a quarter the size of a field vole. Average life expectancy 6 months. Prolific breeders but 95% mortality in winter, mainly February.

The supposition is that they are in decline due to our changing farming practices but we don’t have much data to confirm or deny this. Thanks to MISE and Chester Zoo we are now going to get a fuller picture of what’s happening in Wales. If you’d like to join in please contact the MISE project website.

Here’s a short film of our training day: 

PS .... the polar bears have gone, their pit has been covered with a net and turned into an aviary.