The Island has 14 of the 16 British native species as well as rare visitors like Parti-Coloured Bats which have caused excitement recently. Several years ago we made the News of the World and foreign press when Colin Pope’s delight in receiving a report from Carisbrooke Castle of our first Bechstein’s for almost 100 years turned to disappointment when the castle’s cat got to it before him! Now, thanks to the latest equipment, they are found annually in certain ancient woodlands here along with Barbastelles and Brown Long-Eared.
We have one of the highest householder participations in the National Bat Count of any county, where owners with roosts in their houses enjoy counting the young mums emerging at dusk from the somewhere near the roof-line. (These roosts will all be maternal ones and are mainly Pipistrelles which particularly like modern dwellings). Pipistrelles are divided by frequency into 45 kilohertz (Common) and 55 khz (Soprano) species, and preliminary findings from the Roads Survey indicate that we may have the least Sopranos in England and that they are more common further North at more elevated altitudes.
Around 1919 at the time the Society was founded by Frank Morey he reported Greater Horseshoe Bats were quite commonplace on the Island, now we have a solitary one literally and metaphorically hanging on at Carisbrooke Castle and one or two others in the southernmost tip of the Island.
Although they are of opposite sexes the chance of them meeting to mate is very unlikely and, even if they did, the species needs a certain minimum number keeping warm close together in a roost to breed successfully. Amongst the bats’ problems was the dosing of cattle with the botfly insecticide Ivermectin which remained in their cowpats killing off insects like dungflies which lived off them and which the bat in turn would have eaten.
Fortunately, here the National Trust and Wight Conservation, amongst others, do not allow the use of this chemical and cowpats on our downlands can be seen to be full of small holes where there is insect life helping to return the material to the soil.
Not all bats hang upside down. There is a bat hibernation site at Shide Chalkpit. Recently we found Long-Eared and Natterer’s bat tucked away in tiny hollows inside the aging brickwork enjoying the steady temperature away from winter draughts there. This and other sites have had an entrance grill installed to prevent misuse and disturbance, to which bats are very sensitive. It is illegal to disturb roosting or hibernating bats, unless under licence.
Most woodland bats are very quiet on detectors, they cannot “shout” like Noctules mimicking Swifts in the open air above the forest canopy because all the leaves, branches and vegetation would give too many echo-location returns. The new technology allowed Ian Davidson-Watts to net and safely fit a tiny temporary radio tag to the lactating female Bechstein’s pictured on this page leading to the discovery of a roost in an ancient Ash branch at Chillingwood when she was tracked returning to her young.
Similar woodlands will be surveyed in 2006 when a separate study elsewhere of Serotines is planned. This involves catching them in specially shaped soft deep nets on a long pole as they emerge from their roost at dusk. With licensed tagging it may reveal whether they are permanent residents or cross water to go to and from the mainland, or even the continent.
The best time to see bats is at dawn when they gather together on return to the roost and swarm outside in a small whirlwind before going in, hence the all-nighter at the castle. Also in Carisbrooke, at The Pond, many Daubentons can be seen in the pub’s floodlighting zooming low over the water seizing insects with their feet – the cumulative sound on the group’s several detectors is wonderful. We would not have known about the Parti-Coloured Bats if they had not got into distress and been taken to the IW Bat Hospital, another source of information now that Graham Street’s regular talks to schools and societies has raised public awareness, (both recovered and were released).
As well as enjoying the romance of being outdoors in historic or natural locations as summer nights fall one finds being a member of the Bat Group becomes more interesting each year.