Bats

photo by Ian Davidson-Watts

Wight Conservation commissioned Ian Davidson-Watts, one of the UK’s leading bat experts, to carry out bat surveys at our properties - Wroxall Copse, Chillingwood, Coombe Plantation, Rowborough and Rowlands

The results are spectacular and firmly establish the Isle of Wight and Wight Conservation as of international importance for bats. More remarkably, the Coombe Plantation survey results challenges much of the conventional thinking on bat distribution and habitats

Ian surveyed Wroxall Copse on the 27th June and 19th September 2003, Chillingwood on 23rd July 2005, Coombe Plantation on 19th July 2005, Rowborough 1st June 2006 and Rowlands 5th August 2006. The table below gives an overview of his principal recordings.

Ian Davidson-Watts’ surveys at Wroxall, Chillingwood and Coombe Plantation have produced startling results, especially for the presence of the Bechstein’s and Barbastelle bats. His 2006 surveys at Rowborough and Rowlands Woods were even more spectacular and, in his opinion, have established Wight Conservation as of international importance for bats.

The Chillingwood survey was notable for a juvenile and its lactating female Bechstein’s, one of a very few recordings ever of breeding Bechstein’s in the UK.  Coombe Plantation was notable because no fewer than 9 different species were caught and positively identified within only four hours.  At Rowborough four of the five adult female Barbastelles were pregnant and by a remarkable feet of detection the roost was traced to an area of New Barn Down.  It was the second only colony to be located on the Isle of Wight and less than 15 colonies are known within the UK.  Both Bechstein’s and Barbastelles were identified at Rowlands Wood and both species were traced back to their roosts.

Extracts from Ian Davidson-Watts’ surveys are reproduced below:

WROXALL COPSE

Both surveys of Wroxall Copse have revealed the presence of two of Europe’s rarest bats, the Barbastelle bat and Bechstein’s bat.  Both of these species are listed on Annex II of the European Habitats Directive providing these bats the highest levels of protection in Europe and the UK.  Indeed only four of the UK’s 16 resident bat species are listed on this part of the Directive.  Wroxall Copse is clearly important to male Bechstein’s bats throughout the summer and autumn and is possibly an important mating area.  It is highly likely that the predominantly tree dwelling Bechstein’s bats roost in some of the old trees within the Copse.  Very little is known about male Bechstein’s bats, however research in Germany has shown that they often roost alone and remain in discreet areas for a large proportion of the year.

Initial views on Wroxall Copse suggested that the wood might support some tree roosting bats particularly given the nature of some of the veteran trees within it.  However, the Copse’s open, northerly aspect and woodland connectivity in the general area overall, it was considered that the Copse would be of low value to bats.  As a feeding area for bats the surveys appear to support the view that the Copse is of low value, at least to a wide range of bats, or bats that are easier to detect such as Pipistrelles and Noctules and Serotines.  However, as a roosting and mating area the Copse may support some of the rarest tree roosting bats in Europe.

CHILLINGWOOD

This ancient woodland is part of a wider network of woodlands in the north east of the Isle of Wight, which includes the Briddlesford Copse complex.  The first breeding colony of Bechstein’s bats on the Island was discovered in Briddlesford Copse in 2000.  The Chillingwood survey has revealed a juvenile and a lactating female using the woodland, that may be part of the Briddlesford colony or possibly a second colony or sub colony (metapopulation).  This is quite an exciting find as there are currently very few records of breeding Bechstein’s bats in the UK and only one other on the Isle of Wight.  Four Bechstein’s bats were recorded/captured during just one night’s survey, indicating a strong presence in Chillingwood for foraging and/or roosting.

COOMBE PLANTATION

Coombe Plantation is very different type of woodland situated in west Wight, this wood is much younger c. 100 years old, but part of a very large complex range of woodland types.  Little proactive (e.g. surveying) bat work has been done in the woodlands on the west side of the Island.  Due to the relatively young age of this wood, it was expected that the diversity in bat species using it for either feeding, commuting or roosting would be low.  However within 4 hours of the survey commencing, a total of nine species of bat had been recorded, including the very rare Bechstein’s bat and the rare Barbastelle bat. Only one Bechstein’s bat was caught however, a male, which may have been roosting solitarily in this wood or a nearby woodland.  The ride through the center of the woodland appeared to be particularly good for a range of feeding bats, especially for Pipistrelle bats, but also for the Barbastelle bat.  Unfortunately this species was not captured and therefore this bats breeding status remains unknown (i.e. were they breeding females?).  Breeding bats were captured at Coombe Plantation however, including the Whiskered bat (Myotis mystacinus) and Brandt’s bat (Myotis brandti), and the Natterer’s bat (Myotis nattereri), three bat species equally associated with trees and buildings for roosting.

Although at an early stage in determining what type of woodlands are important for rare tree dwelling bats, these surveys, combined with information from Wroxall Copse and Briddlesford Copse appear to suggest that any type of woodland may support male bats of these rare species.  They also suggest that only large ancient woodlands or smaller ancient woodlands that are part of a larger complex of woodlands support breeding populations of these species.  Further data is needed to test this hypothesis and surveys of Rowborough and Rowlands woods planned for 2006 should provide more clarity.

ROWBOROUGH

Following the capture of a pregnant barbastelle bat, a radio-transmitter was attached to her back in an attempt to discover her roosting location and possibly a maternity roost. Searches for the released bat were made to track down her roost the following day, but despite an extensive search on foot and by vehicle the tagged bat was not located. On the 5th June an aerial search was conducted using a light aircraft. The signal from the tagged bat was quickly identified and the tagged bat was located in an area of Newbarn Down.

The high numbers of barbastelle bats caught in this woodland clearly highlights its importance as a feeding/commuting area for these rare woodland bat species. The Brighstone Forest complex of woods may be particularly significant for these bats and allow them to safely commute to feeding areas at either end of the chalk ridge. Chalk grassland restoration works involving the removal of woodland areas will need to consider the connective importance to these bats species.

It would appear that a breeding colony is likely to roost in the Newbarn Down area, although this was not confirmed on the ground. Other studies of the roosting habitats of this species (Davidson-Watts, unpublished data – Mottisfont, Hampshire 2006) showed that a breeding colony of up to 50 bats uses over 36 maternity roost sites within 1 km square area.

This area appears to support a lower diversity of bats, just three species were recorded. However these results were from just one night of survey effort and a greater level of effort, particularly at other times of the year may be more revealing. Notwithstanding the low diversity of bats here, the discovering of the barbastelle bats makes this area of international significance. This Newbarn roost area is the second only colony to be located on the Isle of Wight and less than 15 colonies are known within the UK

ROWLANDS

The male juvenile Bechstein’s bat caught was fitted with a transmitter in an attempt to locate its roosting site. The following day after a short search its signal was located in the southern side of Chillingwood. Its roost was located in a rot hole in an ash tree. An emergence count using infrared cameras revealed 11 bats emerging.

The female barbastelle bat caught was also fitted with a transmitter. Her roost was located at East Ashey farm in small copse. Due to access not being granted from the landowners, the type of tree roost or the number of bats could not be established; however the bat used this site for at least 7 days indicating that this was an important site.

This ancient woodland is part of a wider network of woodlands in the NorthEast of the Isle of Wight, which includes the Briddlesford Copse/Combely Great wood complex. In 2005 Bechstein’s bats were also discovered in Chillingwood which is linked to Rowlands wood and the Briddlesford complex. The results of this survey confirm the high importance of all these woodlands to breeding Bechstein’s bats. Bechstein’s were also caught in Combely Great wood during summer 2006.

The location of the breeding roost in Chillingwood is of major significance and demonstrates the importance of the whole area to these woodland specialists. However, despite the increased level of recorded Bechstein’s bats during these surveys, it is not possible to clarify whether the bats of Chillingwood and Rowlands woods are directly connected to the colony occupying Briddlesford Copse. Bats of this species have now been located in all the major woodlands in this area and DNA samples from all bats captured have been taken. Analysis of these DNA data should be revealing in understanding the relationships between the bats captured; however funding is currently not available to undertake these analyses.

Although clearly important to Bechstein’s bats, Rowlands also appears to support the foraging requirements of barbastelle bats. The lactating female caught and tagged was roosting over 2 km away in relatively isolated and small woodland. Both these species are known to roost in the same woodlands and it is possible that barbastelle bats could also roost in Rowlands or Chillingwood. The presence of both breeding Annex II species is of international significance and the SAC designation of Briddlesford should be reconsidered to include these areas.

Other bats were also captured, including both soprano and common pipistrelle bats, and the noctule bat, another tree roosting specialist.

Fortunately, without any special effort, our normal conservation works both protect and improve habitat for bats.  Veteran trees and standing deadwood, with old woodpecker holes, rot holes and hollow branches, are ideal for the Bechstein’s, Barbastelle and other woodlands bat species.  At Wroxall Cross Farm, the house and the large extensive old farm buildings of stone with slate tiled roofs are ideal.  There is a pond in Coombe Plantation and a small brook borders Chillingwood – both woods are damp and warm, which encourages intense bat activity in warm summer evenings.  Our rock and chalk quarry faces provide further roosting areas..

Our exceptional bat distribution and abundance, just on their own, puts Wight Conservation on the international ecological map.  As the result of the surveys, and in conjunction with further successes recorded at The People’s Trust for Endangered Species’ Briddlesford, we have decided to extend the surveys to the rest of our in-hand woods over the next two years.

Rew Farm, which we purchased in 2006, is known to contain many bats and it would be surprising if a number of important species were not found in the ancient woodland, Rew Copse. It is, however, going to be more difficult to survey due to access difficulties and Ian Davidson-Watts might well wait until we have undertaken some management.