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Bats surveys

Bats surveys
Surveys can be undertaken to determine presence/absence of bats at a given site or to assess the status of a known bat roost on your farm.

Surveys are undertaken between April and September, preferably between June and August. However, inspections of potential roost sites, eg buildings and trees, can be undertaken in the winter months. If this is the case, further surveys would be required the following spring.

Bats are identified with the use of a bat detector and for most surveys a frequency-division type detector would be used.

A number of different survey methods are used. The methods used on your farm will be dependent on the survey aims and what you want to find out. If you would like to know which methods will be used on your farm, please ask the Ecologist working on your land. In addition if you like to see a copy of your survey proposal, please ask for a copy.

These are

  • Dusk emergence surveys/manual activity surveys
  • Dawn re-entry survey
  • Inspection survey

Please see the section below on the types of surveys that are undertaken.

bat roostAbsence/presence surveys (Activity surveys)
The survey would normally involve undertaking 2 - 3 surveys at night. These would be evenly spaced (eg every 2 or 3 weeks). The survey would usually involve using the dusk emergence and/or dawn re-entry survey methods. An inspection survey may be undertaken at potential bat roosts (although this will depend on the survey aims).

The survey would start at sunset and would last for 2- 3 hours. These types of surveys can only be undertaken between April and September as bats will be hibernating between October and March.

Assessment of known bat roosts (Activity surveys)
The survey would involve standing outside the known bat roost approx 15 minutes before sunset for up to 2 hours. The length of time spent surveying would depend on the likely species to be present. For example, some species only emerge when it is dark (eg 1 hour after sunset) and will not emerge any earlier. Bats would be identified with the use of a bat detector.

The status of the roost would be assessed by the number of bats present or an internal inspection. These surveys would be undertaken between April and September.

bat roostInspections of potential bat roosts
This type of survey would involve inspecting the building, tree or other structure for droppings and other signs (scratch marks, urine staining). This type of survey can be undertaken at any time of year. It would be normal practice for follow-up dusk emergence and/or dawn re-entry surveys to be undertaken if signs of bats were found (or if there was any doubt).

The amount of survey effort would depend on the survey aims and objectives and as a guide, it would be expected that 2 – 3 dusk and/or dawn surveys would be undertaken.

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