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Harvest Mouse in a Rush (c) Derek Smith

A blog about the Surrey Harvest Mouse Project written for SWT Nature Notes

“On Tuesday morning I allowed myself a sigh of relief as I held up the plastic bag in the chill and misty dawn in a wet meadow along the River Wey in Shalford.”

Source: Striking Gold! | Surrey Wildlife Trust



At 05:00 this morning I headed out onto almost deserted roads, the cars outnumbered by planes overhead on their final approaches: as I cruised up the A3 to junction 10 I waved farewell to those heading north into Heathrow and instead turned east onto the M25 with those Gatwick-bound. Our destination was the same, though I was not intent on the glitzy outlets for duty free shopping or awaiting a call, coffee in hand , for a flight to sunnier and more exotic climes. Instead I was headed for some grassy fields on the western side of the airport around the floodplain of the River Mole.

I had been invited to help out with some small mammal trapping at the airport by site ecologist Rachel Bicker and her friend and Sussex Mammal Group member Laurie Jackson. Rachel has been monitoring the site in order to make habitat management plans and has surveyed everything from moths to dormice to bats and herps. No mammal trapping had yet been undertaken, but Laurie and Rachel had found a harvest mouse nest on site. They had put 20 traps (locked open) in two locations on Thursday and the traps had been set on Friday morning by Rachel. On Friday evening at 5:45 I joined them with three others who were interested in gaining some trapping experience to check if the day had brought us any luck. We were rewarded with a bank vole!

I couldn’t attend on Saturday because I was tied up with our annual PTES Harvest Mouse workshop at Thundry Meadows (traps I had put out only caught a vole and nest searches of two areas were fruitless, the first time in 3 years). Rachel had two common shrews Sorex araneus and a wood mouse Apodemus sylvaticus on Saturday morning.

I arrived at the Greyhound Pub in Tinsley Green to pick up Katie May from the Bat Conservation Trust who had offered to help out. As the fog lifted and the morning brightened to a gorgeous sunsparkle October morning, we drove round past the monstrous hangers and the sleeping dragon-like jumbo jets, some roaring into the sky. I wondered if any passenger might spare a thought as they passed over the river to the figures emerging from a battered blue Peugeot van, to don wellingtons and fluorescent jackets and head out along the woodland edge into the surrounding fields, glittering with dew-bedecked spiders webs.
Our first ten traps quickly bought us up to match yesterday morning’s total with a couple of common shrews and a wood mouse. Sadly one shrew had died, not unusual at this time of year. Shrews have a relatively short lifespan and even those born in the spring are unlikely to make it through to the following year. A shrew’s high metabolism also means it need to feed constantly, so a good supply of mealworms- shrews being insectivores- is always required in a trap. Our wood mouse was a pregnant female, not unusual to find one this late in the year but in recent trapping events I have been finding quite a few-dormice also seem to be breeding quite late this year. Perhaps this is to be expected after the very late spring.



We moved on to our second site adjacent to the River Mole where the grass was long and fringing Phragmites reeds and soft rush made it ideal habitat for harvest mice Micromys minutus. Katie and I had just been speaking about harvest mice and then in our next trap we found one! A spectacularly tiny 3g juvenile( too small to sex!) the young of this year. the tiny creature tried valiantly to chew my finger, but his tiny teeth did little to cause me pain. The miniscule harvest mouse is not unlike the shrew in in its short lifespan. Most will be born and die in the same year, although research shows those born in October have the best chance of surviving over winter. Maybe this little chap will have that chance!

We found two more common shrews- one with a curious black rump which made it look half water-shrew! I wondered about the possibility of cross breeding between these two species but its unlikely as they are not even the same genus. Common Shrew –Sorex araneus, Water shrew Neomys fodiens.


2013-10-06 08.11.09

We did two ten-minute nest searches in 50m2 around the harvest mice location but failed to find a nest despite suitable habitat structure. I vowed to return with a few more bodies to help out since there was a lot of habitat to cover, not just the grassland but reedbed areas too.

Katie and I walked back to the van buoyant from our discovery. I’m certainly glad I’ve seen my first harvest mouse for the year, even if I can’t add the result to our Surrey dormouse map, Gatwick being just over the border into Sussex. We can however take the news to the River Mole Catchment Partnership newly formed to focus on a long-term vision for the river. Mapping the extent of harvest mice, which are known to fare better in well-connected habitat, along the course of the Mole will give us a way to gauge the success of projects to improve the ecological status of the river as required under the EU water framework directive.

Time for a bacon sandwich and a cup of coffee. Despite the still-early hour I’m too buzzing to snooze!

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.

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