Creating a landscape for bats

A ranger measures a bat’s stretched out wing by torchlight as part of a survey project

This SITA grant funded 2 year project began in 2013 and focuses on the following two National Trust properties, known for their excellent bat populations.

Drovers Estate (near Singleton)

 
We already know that 300 or more bats use tunnels in the Drovers area to hibernate during the winter months, but we have no real idea of where all these bats go during the spring and summer months in order to breed and raise the next generation.
 

Slindon Estate

 
Slindon Estate has a good mix of farmland, woodland, veteran trees, hedgerows and old houses that make it an ideal spot for bats to roost and feed. As the landowner of a large proportion of the buildings in the wider estate and the village, the National Trust can ensure that any building works are sensitive to bats. In one cottage, near Northwood, 60 plus breeding serotine bats have been counted emerging at dusk for the last 2 years
 

The project purpose

 
The main purposes of the project are to establish what bats we have, find out where they go to feed and roost and what can be done to make conditions even better for them.  Using a variety of technology such as radio tagging and harp traps as well as a lot of volunteer man power.  The project is well under way and providing some very interesting results.
 

How does it work?

 

Radio tracking and data logging programme

 
Consultant ecologist and bat expert Daniel Whitby is leading a team of novice volunteers and bat specialists in a bat radio tracking and data logging programme during the summer months, at Slindon and the surrounding countryside. The proposal is to discover where the bats go to feed and to establish where the roosting sites are, both in domestic dwellings and woodland.
Using a combination of harp traps and pole and nets tiny radio transmitters (tags) can be successfully attached to various species of bat to monitor their habits for up to 2 weeks at a time. The tags weigh as little as 0.2g. The bats usually lose the tags during grooming or as they enter buildings. Already, numerous night time surveys have been performed to find and track the tagged bats and to log sights and sounds of bats on a data logger later to be mapped.
 

Harp Traps

 
Bat calls are played to attract bats to a trap, which is made up of a number of nylon lines that catch the bats and funnel them down to a canvas collecting bag. It is designed so not to cause injury to the bats and allow them to be handled by trained and licenced professionals. Social calls are selected depending upon which species you are trying to attract. From the collecting bag the bats can be weighed, sexed and tagged if appropriate. A tagged bat must be of sufficient weight to be able to carry the extra weight and not pregnant. A lactating bat can lead back to maternity roosts, which can be used year after year.
 

Results so far

 
  • Two new serotine bat roots have been found in non National Trust buildings.
  • A fifth colony of barbastelle bats, in the whole of Sussex,  has been found. These bats are internationally protected.
  • A previously unknown breeding colony of brown long-eared bats was found in a tree at Slindon.
  • Data logging has begun the process of mapping the habitual feeding flight lines, which has contributed to identifying Rows barn as suitable location to improve for bats

Planned improvements to Rows Barn for bats

Rows barn, originally part of the Courthill farm tenancy, has been ear marked to undergo improvements for use by bats. We know from visual surveys and the data logging results that bats feed in the barn and have regular flight lines that pass the vicinity, but at present they don’t use it as a roost or for hibernation.
 
Work to improve conditions for bats include:
 
  • Monitoring humidity and temperature to establish the current climate state. The results will influence what is required to make it more desirable to bats.
  • Change the corrugated asbestos roof to clay tiles, with a felt lining which is ideal for pipistrele bats.
  • Creation of a loft space,which tend to be favoured by brown long-eared bats
  • New doors to regulate the fluctuating atmospheric conditions within the barn.