Thundry Meadows, Surrey: SWT  Harvest Mice Survey Day 2

I am prepared to deal with most things I would find in a small mammal trap but this morning, still only half awake, I was not ready for the two enormous slugs that had taken up residence in the Sherman trap. They lay side by side along the length of the trap looking for all the world like a married couple stretched out in their cosy DFS kingsize bed. Its not that I’m repulsed by slugs at all: just prior to this encounter I had extracated a smaller fellow from  beneath the catch on the door of a Longworth and evicted his colleagues where they were curled up on the roof or jammed at one end of other traps. What gave me pause to count the goosebumps on my flesh was the resemblance these two had too a slumbering couple, dreaming their dreams before a day at the office or  a trip with the kids to the seaside.

Its the second morning of our five day harvest mice survey of Thundry Meadows. This is the first site of 36 in a three-year Surrey Wildlife Trust county-wide survey for harvest mice made possible by my old employer, the good folk at People’s Trust for Endangered Species. The sponsorship provided by PTES has provided me with some satisfactory feelings of continuity from my old job to my new post at Surrey Wildlife Trust and I’m really pleased that I’ve been able to bring my skills to the team working on the Harvest Mice Project. At the very least over the next three years I’m going to get a first class  introduction to some of Surrey’s premier wildlife sites.

The SSSI at Thundry Meadows  is one of the few remaining wet meadow complexes left in the county, comprising  unimproved wet and dry meadows,  alder carr, farmland and ditches by the River Wey,  Over 100 plant species have been recorded including bog bean, climbing corydalis, Dyer’s greenweed, golden saxifrage, heath spotted orchid, lady’s smock, marsh cinquefoil, 14 species of sedge and southern marsh orchid. is one of the few remaining wet meadow complexes left in the county. “Thundry” is apparently a derivation of the norse God Thor, and the beauty of the site deals its own  hammer blow to the senses to any new visitor. Its simply breathtaking.

The harvest mouse Micromys minutus is unlikely the timrous beastie that Burns was referring to, unless he saw one on a trip  to southern England where they are most abundant; despite a distribution  across the palearctic from GB to Japan they are  at the edge of their range in parts of south and east Scotland. First fully described by Gilbert White in 1748 just down the road from where I type this in Selbourne, Hampshire. Harvest mice are listed as a BAP (Biodiversity Action Plan) Species because they are thought to have become much scarcer in recent years. The latest UK Population estimate is  1.4 million but  their has been an estimated 71%decline in numbers over 25 years (SOBM2008). Changes in habitat management and agricultural methods are thought to have caused this, although there have been no studies to quantify this change. Weighing up to 6g they are our smallest rodent, easily disitinguishable by the ir size, small ears and blunt muzzle, with a fabulous prehensile tail making them Lords of the Swards. Their fabulous dexterity is exemplified in their nest construction techniqu. The female sits on a stem and grips with her hindfeet and tail, splitting the stems of still-attached grass leaves with her incisors. She weaves many stems together to form a framework of the nest, lining it by pulling more leaves through this structure and shredding their ends. She will line this structure with finely shredded leaves or thistledown (HMOBI, MSoc).

We have set our first 30 traps- 10 each of Shermans, Longworths and trip-traps to compare the effectiveness of these with hand searching for nests- in an area of tall sedge and grass adjacent to the alder carr. Half the traps are positioned on the ground and on wooden stakes in the stalk zone with the aim of capturing harvest mice going about their business amonst the tall grass stems. Our trapping grid consists of sets of 6 traps:  3 of each on stakes and 3 of each on the ground.

The start of the survey was nearly put off a week when the stakes went missing from the SWT HQ at Pirbright. Individually sharpened by Dave Williams, SWT Mammal Officer, with a ledge for each trap attached by your correspondent with shiny new screws. Arriving at work to load up the van only 10 of 60 remained. Panic insued until a call-out to all staff discovered the stakes had been mistaken for firewood and taken, placed as they had been on a pallet next to the firewood pile. Thankfully, the weather had not been cold enough overnight to warrant a fire and the stakes were recovered the next day.

Set-up at Thundry went smoothly until our planned grid pattern of traps met an unnexpected obstacle.  I set about putting the stakes in with Jo, our student volunteer who is collecting habitat data for the project. I set my mallet to the top of the next stake and then returned to pick up some more. Bending down to pick one from the flow I was jerked upright with a sharpn at the top of my leg. I cursed aloud as I turned round to see a wasp burried sting deep in my leg through the material of my Dickies Redhawk combat trousers. I pulled my assailant loose as the pain escalatebut and without thinking walked back with my stakes to knock the next two stakes in next to the one already in place. Within seconds I was cursing again and sending off another wasp after it had done the in the other leg, I was suddenly aware that I was being surrounded by wasps, and they got another sting in before I managed to get to safety. Despite expectations they didn’t pursue me, and we were able to continue putting out the stakes but giving the wasps a wide birth. The three cross-shaped stakes stayed abandon by the wasps nests like some aculeate golgotha.

So far we have no harvest mice:  two wood mice (one recaptured this morning) and a pygmy shrew. But its still early in this 5-day trapping session. We are also only just out of July and other studies have shown that harvest mice trapping success is lowest in this month and increases towards the autumn time. Their are records at Thundry, so we know they have been here.

Despite having woken early on a Saturday morning, I’m not dissappointed by the no- show of our elusive stalk-walker. Its always good to get up-close with wildlife, no matter how common. I have trapped many woodmice in my time, and have scars to show for it. The pygny shrew is a less frequent visitor to traps, and often they have shrew holes to allow the insectivores to escape. The little guys have such a high metabolism that traps need to be baited with insect prey as well as the seed and fruit for the mice and voles. All our traps are baited with casters in the event of a shrew capture . The records for the more common species are still a useful addition to our knowledge of their distribution in Surrey and for this particular site.

Shep waited very patiently while I checked the traps this morning, so he was rewarded with a walk round Thundry. Aside from the cows, we had the place to ourselves at 7am in the morning. Very nice indeed.