March Young Naturalists… on the search for elusive mice

What a weekend to run a Young Nats session! The weather was beautifully sunny and warm, a contrast to winter and a stark contrast to the cold snap we are having right now.

8 Young Nats arrived promptly at 10am, ready for the challenge of finding harvest mouse nests. Bob had kindly put the moth trap on the night before, so the Young Nats and Nigel set about checking the trap and identifying all the moths – I still have a lot to learn. I was very impressed with our Young Nats moth knowledge, and their eagerness to scrutinise the moth book when we found some we didn’t know straight away. We got a total of 11 species, including the Oak Beauty, and Hebrew Character.

Puzzling over moth ID

Having prepped some small mammal traps on Friday for Bob, the first thing I did after opening up in the morning was sneak around to see how many doors were closed.. quite a few! Once we were finished with moths we spoke about small mammal trapping and why you might do it (species diversity, species abundance if you were going to set out a grid and conduct a mark-recapture survey) and the requirements to ensure the animals’ welfare is catered to. These traps were set out close to the Education Centre, targeting voles and woodmouse/yellow necked mouse. We had more than half of the traps closed… but not all had occupants!

Some of our mice… especially our yellow necked mice have become rather crafty. They like to inhabit the loft in the winter, and become exceptionally adept at getting over the tripwire, eating the food, and out again. There were 5 traps during Young Nats that had tell-tale signs of mouse-habitation but open doors – I think the yellow necked mice we have released are playing tricks on us once more.

My focus for this trapping session was to have each Young Nat learn how to check a trap in a handling bag, and then to scruff the mouse/vole safely. The method is as follows – empty trap into bag, then remove trap and all bedding. Handling bags are large plastic bags with a seam along the bottom and two very useful corners. To keep the creature still you must wait until it is in a corner, and then bring a hand underneath the outside of the bag and around the animal to hold it snugly and firmly with its nose pointed into the corner. Then your other hand can enter the bag, and using thumb and forefinger you feel for the ‘scruff’ of the neck, focusing on feeling the shoulders and base of the back of the skull. Once you can feel these you take a pinch of skin and (if it’s enough skin and you’ve got an even amount from both sides) the animal will stay nice and still. This technique is used when surveying to sex the animal, place it in a bag for weighing, and to perform tasks like fur clipping safely if it’s a requirement of a survey.

I am very pleased to say that everybody managed to scruff a mouse or vole successfully, it does take a few tries to get it, and even though we had some apprehensive hands to start with everyone did well.

Fantastic scruffing of a woodmouse

After lunch we headed out to the north of the reserve, sticks and tape measures in hand to do a final search for harvest mice (winter surveying finished 31st March). I will do a separate blog about our winter harvest mouse surveys, to give final numbers etc soon.

In an attempt at a brief summary – we measured out two 10 x 20m squares to survey, in an area between Goosander and Lapwing Hides that isn’t accessible by the public. What does access it lots however.. is the deer. Frustrating though their numbers can be, they have made useful tracks so that we could navigate our way in and set up the survey.

Harvest mice build their nests around 30cm up in the grass, woven into little tennis ball sized spheres. They strip the grass into pieces and weave it while it is still attached, which means their nests stay suspended long after they leave. We were searching for 2021 breeding nests, which thankfully still persist in the grasses… but as the grass had been flattened by deer and wind we had to be very thorough.

Using gloves and sticks to help separate the grasses, we all begin a focused search for nests. Nigel, Geoff and I were assisting, and after about 15 minutes there was a yell of ‘I FOUND ONE’ from one of the girls, and excitement from the rest of that team. Once we knew they really were there, and we COULD find them… the focus turned into a forensic type search with some very careful searching and in total we found 4 nests. Absolutely brilliant work from everybody involved, and this adds to our previous finds from this winter’s surveying which is our first ever evidence of harvest mice in the northern part of the reserve. Well done Young Nats, and our volunteer surveyors this winter!

On the hunt for harvest mouse nests

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