Bat Surveys

Arbeco  »  Ecology Services  »  Bat Surveys

  • © Arbeco Ltd.
  • © Arbeco Ltd.
  • © Arbeco Ltd.
  • © Arbeco Ltd.
  • © Arbeco Ltd.
  • © Arbeco Ltd.
  • © Arbeco Ltd.
  • © Arbeco Ltd.
  • © Arbeco Ltd.


There are 18 bat species in the UK, 17 of which are known to breed here.

Our resident breeding species are Alcathoe bat, barbastelle, Bechstein’s bat, Brandt’s bat, brown long-eared bat, common pipistrelle, Daubenton’s bat, greater horseshoe bat, grey long-eared bat, Leisler’s bat, lesser horseshoe bat, Nathusius’ pipistrelle, Natterer’s bat, noctule, serotine, soprano pipistrelle, and whiskered bat.

Bats are largely nocturnal, sheltering during the day and emerging at night to forage for insects. They rely on shelter, water and insects to survive. They are generally active from late March to mid October, hibernating from late October to mid-March.

Bats roost in a variety of places, depending on species and time of year. Roosts include trees, buildings, bridges, caves, mines as well as other built structures.

Bats breed in autumn prior to hibernation in winter, but females do not become pregnant until the weather gets warmer in spring. Once pregnant, females gather together in maternity roosts in early summer to have their young, normally producing a single offspring per year.

Bats are very sensitive to disturbance during the maternity season, May to August, and may abandon their young if they are disturbed. Once born, the young are suckled by their mothers for around 4-5 weeks until they are old enough to fly and forage for themselves.

  • © Arbeco Ltd.
  • © Arbeco Ltd.
  • © Arbeco Ltd.
  • © Arbeco Ltd.
  • Trapping for bats in woodland © Arbeco Ltd.


Bat surveys start with an initial inspection of trees, buildings or structures that could be adversely impacted by a proposed development. The inspection involves searching for evidence of bats including live bats, droppings or feeding remains. This type of survey can be carried out at any time of year.

If suitable habitat is present on site then further surveys would usually be carried out in suitable weather conditions during a bat’s active season (May to September), to determine the number of bats present, the species and the roosting locations.

Different survey types include emergence surveys (carried out at dusk), or re-entry surveys (carried out at dawn). The surveys are conducted by fully trained ecologists using a range of survey equipment including electronic bat detectors, automated static bat detectors and infrared cameras to determine the presence/likely absence of bats as well as their roost locations and behaviour.

The Arbeco team are also fully trained in carrying out radio-tracking surveys for bats.

Bat Survey Calendar

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Automated logger/bat detector survey                        
Catching surveys for active bats (commuting/foraging)        
Inspection of bird and bat boxes                        
Inspection of buildings and structures for roosts                        
Manual bat detector surveys for commuting and foraging                        
Manual bat detector surveys for dusk/dawn emergence/re-entry                  
Mating roost/autumn swarming surveys            
Radio-tracking surveys      
Tree surveys for active bats (bat emergence or re-entry surveys)                        
Tree surveys for bat roosting features                        
Winter hibernation surveys including underground sites                        
Survey not possible
Sub-optimal survey period
Recommended survey period

Tree climbing surveys

Ground-based surveys are often inadequate when it comes to determining whether bats are roosting within a tree.

Tree climbing surveys, sometimes known as aerial inspection surveys, allow a closer view of any potential roosting features.

This type of survey may avoid the need for costly dusk and dawn emergence surveys, and can be carried out at any times of year meaning delays are rarely imposed by survey timings.

Bat tree climbing surveys are highly specialist. Arbeco staff are experienced in both ground-based and tree-climbing surveys for bats.

  • Radio Tracking Radio Tracking © Arbeco Ltd.
  • Trapping for bats in woodland Trapping for bats in woodland © Arbeco Ltd.


Often the best development option is to preserve existing bat roosts and habitats. If this is not possible, and a development activity is likely to result in an adverse impact on bats and their roosts, then a European Protected Species mitigation licence would be required in order to legally carry out the work.

When a development involves the removal of trees with bat roosts or features with bat roost potential, Arbeco has fully trained tree surgeons with experience of soft-felling that can carry out the work with our bat ecologists.

Protected Species

Ecology Consultancy