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.
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!