In a bid to protect natural habitats and encourage biodiversity, bat surveys are most commonly ordered at this time of year by local authorities considering planning applications.
Here at Syntegra Group, we understand that the need for further bat surveys may cause worry and lead to further questions.
To ease your concerns, our ecology team have produced this short guide to hopefully answer any queries you may have and also ensure a better understanding of the next steps.
Below are the most commonly asked questions that we receive after undertaking surveys and issuing the Preliminary Roost Assessment (PRA).
Q1. When is the active bat survey season?
The active bat survey season as outlined within The Bat Conservation Trust’s Survey Guidelines 2018, runs May to September.
May to August is noted as the OPTIMAL Survey season with September as SUB-OPTIMAL. For roosts with low potential, you require one survey during the optimal season; for moderate you require two surveys, with at least one survey during the optimal season; for high/confirmed presence, you require three surveys, with at least two during the optimal season.
Q2. What does sub-optimal survey season and optimal mean?
Bats’ lifecycles determine when a roost is likely to be used. During May to August, this is when bats are most active, depending on weather and temperature conditions. Maternity roosts form during the months of May. This, however, differs between species, so for example, long-eared and serotine maternity roosts form throughout May, with a tendency for mid to late May.
Towards the end of August, adult bats start to leave summer and maternity roosts and head to swarming/mating roosts. Sub-optimal surveys are helpful especially if your building/structures hold the potential for use. As in BCT guidelines, only one survey (if building is moderate, high or confirmed) is suitable to be undertaken during the sub-optimal season which is September.
Q3. Why do I need further surveys? Can’t these be conditioned?
So, a PRA Survey looks for confirmed presence of bats along with the potential to host roosting bats. By potential, this means if there is suitable space and access for a bat(s). Pipistrelle bats can fit into a hole/gap/crack that is 20mm in size, so a lifted roof tile or gaps in your soffits could be hosting a bat.
Unfortunately, a daytime bat inspection alone cannot determine likely absence of roosting bats and the only way to be sure is by coming back and looking when bats emerge or return to roosts. Bats are a material consideration for planning, therefore the council need to understand all matters prior to making a decision, so all details on the types of roosts (if roost found) need to be presented along with the mitigation measures that will be in place and the replacement roosts.
Q4. Why are bats protected?
Bats have been on a steady decline for decades and therefore need our protection. The reason for their decline is cumulative, a loss of habitat, increased use of pesticides, habitat fragmentation, loss of suitable roosting locations and an increase in light pollution.
In Britain, all bat species and their roosts are legally protected, by both domestic and international legislation. This means you may be committing a criminal offence under the Wildlife and Countryside Act 1981 if you:
- Deliberately take, injure or kill a wild bat;
- Intentionally or recklessly disturb a bat in its roost or deliberately disturb a group of bats;
- Damage or destroy a place used by bats for breeding or resting (roosts) (even if bats are not occupying the roost at the time);
- Intentionally or recklessly obstruct access to a bat roost.
Additionally, The Conservation of Habitats and Species Regulations 2017 (as amended) make it an offence to:
- Deliberately capture or kill a bat;
- Deliberately disturb a bat;
- Damage or destroy a breeding site or a resting place of a bat.
Q5. Can I just do the surveys in one week?
In line with the BCT guidelines, a suitable spacing between the surveys is required. Essentially, the larger the spacing between the surveys the better, however, BCT recommends two weeks as a minimum.
If your building/structure, has a confirmed roost, to avoid an objection/further information request by Natural England that will decide on your EPS License, a survey during the peak breeding season is required (ideally mid-June).
If your site has the potential for, or has a likely maternity roost, this is the best time to capture peak numbers within the maternity roost, followed by a mid to late August survey depending on the species to determine the number of juvenile bats.
Q6. I know I have bats, can’t I just put up a bat box or give them a new roost?
Natural England or the Council will not approve or allow for this approach. The surveys we undertake build up a picture of the bats using the site, so how they are using the building/structure, numbers, and access/emergence points. By understanding how and when the bats are using your building will determine the mitigation measures. For example, if the bats are using your building in the summer, they often will use different locations depending on their microclimatic conditions (smart right?!). So early season, they can be located on the western/southern sides and move to east/north locations during the hotter summer months.
Q7. How many types of roosts are there and why my house?
Bats can roost within buildings year-round depending on the species and what your building has for them. Having a roost in your structure/building means that you have a healthy ecosystem with everything bats require!
Bats’ lifecycle starting with winter has them in hibernation roosts. Normally they prefer steady microclimatic conditions with moisture and north facing (too much sun in this case is not a good thing when you want stable temps).
In the spring bats emerge, start feeding and enter spring/transitional roosts; these tend to be southern and westerly facing, again, depending on temperatures.
In the summer, females move into maternity roosts, which depending on the species can vary in size; pipistrelles can have 100s! For a good maternity roost, bats need to have the space to move around to adjust their microclimatic needs. Males move into summer roosts, which tend to be individual, or depending on the species, can have multiple individuals.
You tend to find that the males move around again depending on their microclimatic needs, if it’s hot they tend to re-roost on eastern/northern sides, and cooler days move into western/southern locations.
Towards August, adult bats start swarming, where males ‘sing’ to their mates and try to entice females into mating roosts. There is one more temporary roost that are also important for bats – feeding perches or night hang up roost. These are used by bats when out in the evening, important, as they help when the weather turns or after they have gorged themselves on insects and need a rest to help build fat reserves.
Q8 – What does a dusk/dawn bat survey entail?
In line with BCT guidelines we have to ensure the building has proper coverage, the potential to host bats and their location(s) will determine the number of surveyors. Surveyors arrive on site for a dusk, 20 minutes prior to sunset and remain on site depending on activity and the species for 1.5-2-hours post sunset.
For a dawn, it is in reverse, the surveyors arrive 2 hours prior to sunrise and remain on site for 15 minutes post sunrise. Surveyors come with a bat detector which converts the ultrasonic frequencies into auditable sounds that we record and also use on site to determine the species. Surveyors will be in position to observe potential roosting features and look for bats returning to or exiting roosts. Once all surveys are complete, we will write up a report along with any detailed bat mitigation measures.
Q9 – So how long will this take?
If we find potential or confirmed presence of roosting bats, we will tailor a work programme in line with best practice. For example, if we do the initial PRA survey in April, then we would aim to get your first survey in for May. Please note May can be unsettled and cooler so it’s not normally possible to do one on the 1st of May but we will always watch long range forecasts and keep you informed.
It is important to also realise that weather plays a factor – yes, the optimal season starts in May, however, in 2021, we had a lot of storms and rain resulting in roosts forming in June compared to previous years.
If we suspect a maternity roost, or the initial survey does find bats present, then to ensure that there are no objections by the council ecologist we recommend the second survey for peak season, which is mid-June. Again, I understand the frustrations for this length between surveys, but we want to ensure no objections, it is also worth noting Natural England who approves any EPS License that could be required, also support this approach, and can request for this peak season survey delaying your works further.
If a maternity roost is found, then we will do the last survey in late August to capture numbers of juvenile bats, a requirement by Natural England. If low numbers of bats are found by the peak season survey, then a follow up survey in 2-3 weeks is acceptable.
Q10 – Its August and my survey has found bats or potential, what now?
We will, of course, work to get as many surveys completed in line with best practice. Normally, we recommend one survey in August and then a September survey. If high potential or confirmed presence of roosting bats is found, then really, we have missed the peak season, so there will be a need to do a further survey the following year. If your PRA survey has found moderate potential then we will carry one survey out in August and then in September, if no roosts are found then your bat report will be produced and ready to support your planning application.
Q11- Why can’t we just do a bat mitigation plan?
This is not a welcomed approach by most councils given that bats are a material consideration for planning. The council and council ecologist will want to have all the information to hand to inform their decision under the Habitat Regulations. In the event that the council ecologist will allow for a BMP, we will produce an Outline BMP, that is then updated once all the surveys are completed. The OBMP will detail the likely species on the site, any surveys to date, and the proposed new roosts and mitigation measures that will be required for the works.
Q12- So your surveys found a roost, what is next?
If a roost is present, then the council ecologist will expect a bat mitigation plan that will detail the avoidance and mitigation measures along with the compensatory measures – so what roosting features we will incorporate into the building if there is to be damage or destruction of the roost. After planning permission is obtained, we will apply to Natural England for the relevant European Protected Species Licence (EPSL). Please note that EPSL can only be applied for after planning permission is granted, as Natural England will not accept a EPSL without the approved notice.
For all queries relating to ecology, biodiversity and bat surveys specifically, please get in touch with us today to discuss your project and next steps.