My mentor, BBOWT's senior ecologist, Colin Williams mentioned a day out surveying for harvest mouse nests at Chimney Meadows Nature Reserve in West Oxfordshire, provided the flooding subsided. And luckily enough it did.

I jumped at the chance to survey these creatures, having a keen interest in small rodents, due to the fact I own a long-haired Syrian hamster named Kinder who sparked my interest in this field.

These annual nest searches are carried out in November when nests are not yet too fragile due to winter weather but are also visible due to vegetation being less dense at this time of year. The best and easiest way to find these elusive mice is to look for their abandoned summer nests along field margins during wintertime.

The harvest mouse is Europe’s smallest rodent, a tiny 4–6-gram mammal, classified as ‘Near Threatened’ in Britain. These tiny mammals measure only 5-7 cm in length and can be seen all year round. The harvest mouse is the only British mammal to have a prehensile tail, which it can use like a fifth limb, wrapping around objects such as grass stalks to improve balance.

What a day we spent in the crisp cold air, heads down and bottoms up searching the field boundaries for the distinctive tennis ball sized nests tucked deep down under grass and brambles.

We had the pleasure of being shown around by Dr Amanda Lloyd, a specialist in harvest mice. Dr Lloyd showed us example nests alongside a tiny harvest mouse skull that had been previously found on one of her surveys.

After our introduction and briefing we went out as a team thoroughly searching field boundaries looking for these abandoned nests to establish the presence or absence of harvest mice on the site. Previous years have shown great results. We only hoped we would have the same outcome after weeks of heavy rainfall and flooding.

Not much is known about the distribution of these tiny mammals and therefore it is not really known how bad their situation might be or what conservation efforts need to be put in place to ensure their continued survival.

The best way to survey for the presence of harvest mice at a site is by looking for their nests. In 2021, the Mammal Society launched the National Harvest Mouse Survey across the British Isles and Ireland with the aim of improving the understanding of the status of harvest mice.

Once discovered, our nests were recorded on the Mammal Mapper app, allowing us to upload photos of the nests so that experts can confirm correct ID and log these records in their database.

Searches over the years by BBOWT volunteers have revealed nests at several Trust reserves, including Chimney Meadows, Wells Farm, and Moor Copse. These nature reserves seem to have offered a lifeline for this tiny mammal and there is scope for creating new habitats designed with harvest mice in mind.

BBOWT ensure that all field margins around these reserves have areas of rough grass that is cut on a three–five-year rotation to ensure suitable habitat for breeding, feeding and overwintering harvest mice.

After gently parting vegetation with our sticks, we came across our first nest. We called Dr Amanda Lloyd over to confirm our findings. To my delight it was in fact a harvest mouse nest.

Distinctive characteristics of split stems, intricately woven onto plant stalks and lined with finer grasses or thistle down which has good insulator properties. The nest was soft to touch with clear attachments to surrounding stems whilst suspended in tall tussocky grass in the field margin.

Our harvest mice nest search revealed a total of nine new nests along the boundaries of multiple fields at Chimney Meadows in addition to a good number of nests that were found in previous weeks by Dr Amanda Lloyd.

With the risk of this mammal becoming threatened with extinction in the near future, I only hope that people continue to have an interest in harvest mice and record all nests and sightings of these tiny mammals.

Hayley Beck
BBOWT volunteer ecology wildlife trainee