Bats

Advanced Bat Survey Techniques [ABST] Surveys involve the temporary capture of bats on-site through the use of mist nets and harp traps. Capturing bats in this manner enables the bat to be examined in hand for the purpose of confirming the species, sex, reproductive status and age. Depending on the scope of the project, in some instances, it may be necessary for captured bats to be fitted with a radio tag. 

This allows individuals to be tracked across the landscape to their roosts, foraging grounds and to pin­ point their flight routes. The use of ABST is an efficient way to provide robust, detailed and accurate survey data to support planning applications, inform European Protected Species Mitigation Licences (EPSML) and to tailor mitigation/ habitat creation and enhancement measures, increasing the likelihood that these will be correctly sited and effective.

ABST Survey should be considered when it is necessary to confirm Bat roost locations in woodlands and/or to confirm if cryptic species (those that are difficult to identify using sonogram e.g.) are present on-site: 

• Myotis spp. or Barbastelle) are present on-site 
• To determine how Bats are utilising a site (roosting, commuting and foraging) 
• To assess the home range of Bats 
• To confirm/negate likely severance impacts 
• To determine whether Bats from a roost are also using an alternative roost within their range 
• To inform the appropriate siting of replacement roosts (optimising the likelihood of their colonisation) 
• To inform the locations of woodland planting corridors/other green infrastructure.

The use of ABST presents a number of advantages to the client over standard Bat survey methods. They can often provide a more cost effective and efficient approach to the gathering of data, particularly when complex mitigation measures are required involving multiple Bat species. 

Furthermore, when providing alternative Roost sites, depending on the rarity of the Bat species using the Roost, and the type of Roost to be lost, proof of occupation (prior to the removal of any existing Roost) is sometimes required. This can result in costly delays to a scheme. A thorough understanding of flight paths, foraging areas and Roost requirements facilitates the design of appropriately sited, species specific mitigation measures, that are more likely to be colonised quickly by the resident Bat population. 

The use of radio tracking as a survey methodology can also provide cost savings to the client, on the basis that the level of manpower required to gather sufficient evidence to inform large or complex schemes, is often reduced. Following trapping, Bats can be tracked to Roosts for up to tens days, when the tag is active. This approach can capture the usage of multiple Roosts by an individual/colony of Bats. In addition, the used of triangulation methods enables surveyors to cover greater distances within the tracking period of up to 10 square kilometres.

The use of ABST is also beneficial when detailed survey data is required for high impact or contentious schemes, or when there is the risk that the scheme maybe subject to a public enquiry.