Successful Harvest Mouse Survey

When we carried out our first Harvest Mouse survey in January 2021, we found no nests. So this year I was pleased to come across a solitary nest in a tree-tube in April.  After finding another in early December, we realised it was a good idea to carry out a more systematic search.  Devon Mammal Group are running a Harvest Mouse Survey, where they train volunteers to search suitable habitats for old nests during the winter.  The most suitable habitat is rough grassland with Cocksfoot or other coarse grasses, Culm grassland or bramble.

So, we met up last week and carried out a dedicated search along a bramble patch, lasting about an hour and a half.  Maggie found the first nest in a matter of minutes and I found one soon after.  In all we found five nests in bramble and one in tall grass.

The Harvest Mouse is losing suitable habitat, due to the loss of rough grassland. The clumps of grass need to be thick enough to hide a tennis ball and, even in our wild space, these are uncommon.  This photo shows just how well they are hidden among the grass stalks. It is made entirely of woven grass and was 30cm above ground.

Harvest Mouse Nest 

Nest 1: Harvest Mouse 65mm diameter

Each nest is different, some are more neatly woven than others.  This one above is woven from coarse grasses.  Nest 2, below is woven from fine grasses and is smaller.  It was discovered in bramble.

Nest 2: Harvest Mouse 55mm diameter

The third nest was bigger with an 80mm diameter and also located in bramble. The larger nests are summer maternity nests, where one nest is built for each brood and then abandoned.

Nest 3: Harvest Mouse 80mm diameter

Our next nest was also found in bramble, but there are a few leaves incorporated into it. This makes is interesting, as it is possible that this is a Hazel Dormouse nest.  We sent a photo to People's Trust for Endangered Species and their Dormouse Officer has confirmed that it is very likely a Dormouse nest.  This is really exciting news to know that we definitely have this elusive mammal on our site.  See also my next post about hazelnut surveys.

Nest 4: Dormouse 75mm diameter

The Hazel Dormouse (Muscardinus avellanarius) is an endangered species and is protected under British and European Law. Nests 5 and 6 also had some tiny leaves around the outside, so at the moment we do not know if they were made by a Harvest Mouse or a Dormouse.  To my mind, Dormice are more untidy nest-builders compared with the Harvest Mice!

Nest 5: Unknown 60mm diameter

Nest 6: Unknown 50mm diameter

We are looking forward to more opportunities to do further surveying during the winter months.