Since March 2020, I have been delving into my new project that is focused around our County Wildlife Sites and wildlife on a piece of legislation called the Natural Environment and Rural Communities Act (NERC), 2006. The wildlife on the NERC Act (over 900 species!) are those which we consider to be of principal importance to England and some of those are now rare and threatened. My aim is to find as many of these species on our County Wildlife Sites as I can this year. These sites are spread from the very west of Cornwall and right up to Somerset.

Over the winter, I have been doing lots of reading, writing and planning but one particular winter survey has kept me busy - looking for an elusive NERC species: harvest mice. From October to March you can easily search for the nests of harvest mice, no fancy equipment needed. This is a gorgeous mammal, weighing less than a pound coin, which hides away secretly in vegetation like long grasses and reeds. See a blog written about harvest mice, and how to identify and survey them by our volunteer, Jacky Pearce, here.

So through November and February I made it my mission to search for this species at our suitable County Wildlife Sites and here is how I got on.

Throughout November, our Biodiversity Officer Deborah Deveney and I searched a County Wildlife Site at Burrator Reservoir (banner image). Unfortunately, we did not find any nests on this part but we do know they are close by on other parts of this site near the reservoir. 

I then made my way to Fernworthy Reservoir on Dartmoor in late January. I searched around in the long grasses of the meadows and found three field vole nests. These are slightly different to the harvest mice nests as they are made up of short pieces of grass and not as woven as the harvest mice nests. I also found a huge harvest mouse nest in the same area, so huge that it had to be an old breeding nest. This was the first harvest mouse nest that I had found myself and I must admit it was very special. 


In January, Lucy (one of our Environment and Engagement Rangers) and I searched a small part of Wimbleball Lake in Somerset. It was a really wet day and the habitat was perfect but we did not find any harvest mice nests, although we did find three field vole nests, an old bird nest and a common frog! 


In February, I went to Drift Reservoir, West Cornwall. The temperature did not rise above 0 degrees and my hands were almost frozen but I managed to search around the suitable bits of grass and was rewarded with a very tiny nest securely woven into the middle of the tussock. This nest is more than half the size of the one I found at Fernworthy so I think this is a solitary nest just used by one animal at a time. 

Finally, in February, Deborah and I decided to go back to Burrator Reservoir to search some other suitable areas, this time up on the wider moorland. We found five harvest mice nests in three different areas in just one day. This was Deborah's first harvest mouse nest and our payback for not giving up on this site!

Aside from looking for the nests of these mice, you might be lucky enough to see them at any time of year. When I visited Tamar Lakes in September with two colleagues from South West Water (Kate Hills and Jules Florey), we were lucky enough to see a harvest mouse scurry from the reeds and into the grass. These mice are lightning fast and will not hang around on open ground, as they are vulnerable to predation. We were not looking for them at this time - we were just very lucky indeed.

These surveys have been hugely rewarding and have improved our understanding of the County Wildlife Sites and the importance of grassy habitats, especially those untidy ones which the harvest mice love to nest in.

A big thank you is owed to Sarah Butcher of Devon Mammal Group for giving us the knowledge and inspiration in 2020. The Devon Mammal Group have a project dedicated to harvest mice, which you can read more about here.

Using data from the Local Record Centres, Fernworthy has not had harvest mice recorded until now; Drift only had one record from the 1960s, and we found new areas around Burrator with no previous records in that area. We have put harvest mice back on the map!

Emma Scotney