Harvest Mice thriving after all!

Harvest mouseBack in the early years of the CRT, Barton resident and much missed friend, the late Jean Benfield, released some of her collection of Harvest Mice onto the farm. These are the smallest rodents in the UK, and are particularly associated with agricultural land (hence the name), but, like a lot of farmland wildlife, they have been in steep decline with intensification and mechanisation reducing their food supply and destroying their homes. They live in woven nests supported on the stems of plants, including crop plants. Due to their decline, they are now a Biodiversity Action Plan species.

In the few years after their release, Harvest Mouse nests were regularly observed in the protective guards around the young trees, and often came into the baited live-catch traps we used to survey the small mammals. One or two even turned up in the stash of prey in the owl boxes, or bones were found in owl pellets. For the last 3 years, however, our traps have not caught any Harvest Mice – lots of other species, but no Harvest Mice. The tree guards have all been removed or are full of well-grown tree trunks, and we have not had a positive sign of the species for quite some time.

To try to resolve the issue, a group of volunteers got together on Dec 7th to search for the distinctive nests which become easier to find once the surrounding vegetation starts to die down in the winter. Also, doing a search in the winter is less likely to disturb any active nests with young inside. We followed the guidelines produced by the Mammal Society, and set up two transects, each 100m long and divided into ten 10m sections. Each section was searched by one volunteer for 10 minutes.

We had a mixture of volunteers, some of the regular wildlife watchers were joined by a couple of the regular ‘Rustics’, who usually do more of the practical habitat management work on Lark Rise. Within about five seconds, Ray Thorne, of the stalwart rustics called out that he’d found a nest! Vince Lea, the CRT wildlife expert, went over and confirmed his finding. This bit of beginner’s luck gave the rest of the team a lot of confidence that we weren’t wasting our time looking for nests of an extinct species! The first transect was conducted on the CRT’s first field, called Telegraph field, searching in a thick grass margin between a strip of bird cover plants and a thick hedge. Ideal habitat, and we found a total of 7 nests in the 100m searched.

We then moved on to the area known as Millennium Wood, where the young trees have a lot of coarse grasses around them. Here, the habitat wasn’t quite so good, the grasses were not quite tussocky enough to support nests. Nonetheless, 3 nests were found, and given the large area of the wood which we didn’t search, there could be quite a large population here too.

The two search areas are about a mile apart, and there is lots of suitable habitat in between – so we can be pretty sure that Harvest Mice are thriving all over Lark Rise after all. Great news and great relief all round!

Harvest mice are unique in British mammals for having a prehensile tail – they can wrap it around plant stems like a fifth limb, and it helps them climb up stems of wheat to nibble at the seeds. They are only 5-9g in weight (less than a pound coin!) so can climb small stems of grass without bending them. They need a good supply of seeds, fruits and insects and rough areas of herbage to nest.

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