There’s a bat in my kitchen
Hilary MacMillan spends an evening at Bryanston Old Kitchens in search of greater horseshoe bats
Published in September ’18
The charming exterior of Dorset’s five-star bat hotel. Credit Colin Morris
I am in the village of Bryanston. It’s dusk, and I wrap my scarf tightly around my neck in a vain attempt to foil a midge attack. I am sitting under a dense cover of cherry laurel in front of a once rather fine mellow sandstone building which, in its heyday, served as the kitchens to a country house. The Georgian façade has vestiges of a grand classical design, with later additions from the breeze-block era.
I sit and imagine the hustle and bustle as servants prepared food for the big house. The big house is no more. It was demolished in the late 18th century after the owners, the Portman family, gave up an endless battle with damp. Word has it that the damp was attributed to the use of unwashed sea sand in the mortar; the salt in the sand constantly absorbed moisture. Even re-routing the River Stour away from the house failed to stop the problem.
A baby greater horseshoe bat. Credit Beatrice Dopita
In one hand I have a tally counter and in the other a black box with dials and buttons. I am about to count bats. Not any old bat but the rare greater horseshoe bat, and this is one of only two greater horseshoe bat maternity roosts in Dorset; the other is near Wimborne. It is believed that there are just 25 such roosts in Britain, spread across Wales and south-west England, with a total national population of this bat species of less than 12,000. These figures make this building in front of me very special.
Greater horseshoe bats in a cluster. Credit Colin Morris
‘Of all the bat roosts I manage, this is my favourite. If I won the lottery tomorrow, I would buy it,’ says Colin Morris, Nature Reserves Manager with the Vincent Wildlife Trust. Colin’s enthusiasm is infectious as he talks of this ‘five-star hotel’ for bats, a site with which he has been involved since the 1980s. The building has not only a fascinating architectural and social history, but also an extraordinary ‘bat work’ history; it is possibly the longest-monitored bat roost in Britain. Famous names in the bat world have been involved with this roost long before the VWT bought it in 1994. ‘Two early pioneers of bat ringing, Andrew Watson and Michael Blackmore, were ringing bats from Bryanston as far back as the 1950s, when greater horseshoe bats were very common,’ Colin tells me, ‘and the roost has been studied ever since.’
Greater horseshoe bats are quite fussy, or so it seems. Historically, they roosted throughout the year in caves, but today most use buildings, and they have a particular fondness for stone-walled, slate-roofed structures that are uninhabited by people so that they are not disturbed. Luckily, the Old Kitchens in front of me clearly fit this bill. In winter, the kitchens’ residents will hibernate above or below ground, depending on the temperature outside.
Suddenly my black box leaps into life as a shadow sweeps silently past my shoulder. The ‘emergence’ has started, and it is a remarkable spectacle. At first just one or two bats tentatively check out the conditions. It is thought that these bats are ‘light sampling’, a behaviour characteristic of horseshoe bats. Scientists think that this behaviour is a mechanism for re-setting a bat’s circadian rhythm – well, you would want to do this if you found yourself living in total darkness. It is possible that this behaviour also has a social role.
Greater horseshoe bat in flight at Bryanston
Within minutes, this initial trickle of bats becomes a torrent. Some will travel more than ten kilometres to forage for their favourite fare, but others, especially the juveniles, will stay much closer to home. My tally-counting barely keeps up with the silhouettes of these extraordinary creatures, each flying gracefully from under the eaves over the trees and on to the restaurants beyond. Their butterfly-like flight is perfectly suited to weaving through the cluttered woodland environment in which I am positioned.
I can only describe the sounds emitted from my bat detector as an orchestral mix of cetaceans and the Clangers – a cacophony of warbling as the detector converts the bats’ echo-location calls to sounds that we can hear. These bats are seeing with sound. Horseshoe bats, unlike other British bats, echo-locate at very high frequency through a peculiarly fashioned ‘nose-leaf’ rather than through their mouth. To me, the horseshoe-shaped (hence the name) nose-leaf resembles a squashed pig’s snout; it gives them something of a comical but endearing appearance.
Digging out the chalk tunnel. Credit Colin Morris
Within 35 minutes the emergence is over and I have counted 321 bats, astonishingly close to Colin’s count of 316. Not quite a record but a very encouraging number; the roost is clearly doing well – at the moment. I say ‘at the moment’ because this five-star hotel for bats will only remain at five stars if the nearby restaurants don’t close. Over 300 guests require a lot of food and these guests are quite picky: cockchafer beetles early in the year, moths as a summer staple, and dung beetles a highly popular menu choice in the autumn and winter. Cockchafer beetles are particularly important to greater horseshoe bats. These beetles emerge from grazed pastures in the early spring and are the bats’ main food source until late spring, when moths become the menu du jour. As well as aerial hawking, this bat species has a rather laid-back passive hunting strategy that involves hanging upside down, secured to an overhanging twig by its spindly legs. From this position, the bat switches on its sonar and constantly echo-locates until an unwary cockchafer comes within range. The bat makes its move, catching the beetle in its mouth before returning to its perch to consume the soft body parts. The wing cases are left to drop to the ground below and these, along with large bat droppings, are a sign that horseshoe bats are feeding in the area. A decline in cockchafer availability could knock several stars off this bat hotel’s rating.
After the bats have left their roost, Colin allows me a sneaky look inside, in an area well away from the current guests. This bat hotel cuts no corners. Colin has created a choice of accommodation for the guests, with variations in temperature and humidity; the bats can move around as their needs change. As we move from one ‘room’ into another, I stop in my tracks. In the muted light of my headtorch, I catch sight of one of our rarest bats suspended and swinging from an oak beam. Its ears move back and forth, and its directional sonar has pinpointed our position. It knows we are here. The parchment-like wings are wrapped, cloak-like, round its body, the nose-leaf just visible. The bat seems unperturbed by our presence and remains there throughout our visit. Why it was there and not with its fellow-guests upstairs we will never know.
For Colin’s five-star hotel, there is no off-season. While most of the horseshoe bats will hibernate in the roof space, occasionally wakening in milder spells to find food and water, there are other bat species with a preference for a cooler ambience using the roost in the winter months. For these bats, there are two luxury subterranean wings offering a stable temperature of between 6˚C and 10˚C. I refer to two man-made chalk tunnels built in the late 1980s and early 1990s as optional winter hibernation sites, each one several metres in length. ‘It is thought that these are the first tunnels to be dug from solid rock just for bats,’ Colin explains with real pride. The later tunnel was funded by the Trust and excavated by some ex-Cornish tin miners who were more than happy to get back underground. The first, however, was dug during a long weekend by a group of bat volunteers, largely from the Dorset Bat Group, who between them shifted some forty tonnes of chalk. I am quite humbled at the dedication of bat workers.
We return outside to watch the exit points once more. All is quiet, the night’s silence broken only by the call of a tawny owl in the woodland behind us. The bats will be feeding perhaps several kilometres away, but Bryanston roost is a maternity roost and, at this time of year, these female bats must soon come back to suckle their young. Later, they will leave again for a further night-time refuelling, returning to the roost as dawn breaks.
After about seven weeks, the juveniles will become independent and many of the mothers will move elsewhere until autumn. Who can blame them if this is their chance to have a well-earned rest after an energetically demanding summer? It is a chance for a break before the arrival of the autumn mating season and the onset of another long winter.
To find out more about the work of the Vincent Wildlife Trust, visit www.vwt.org.uk
