what You need to Know About Bat Survey Season

The bat survey season is an important part of development planning across Scotland. Because bats are protected species, certain projects require specialist surveys to understand how bats are using a building, tree, or landscape. These surveys can only be completed at specific times of year. Knowing the timetable in advance helps clients avoid delays and plan projects with confidence.

This guide explains the Scottish bat survey season, when different types of surveys can be carried out, and the key deadlines that clients should keep in mind.

When the survey season begins and ends

The main bat survey season runs from 1 May to 30 September each year. This period covers warmer months when bats are active and predictable, which means surveys can gather reliable information.

Surveys cannot be carried out during the winter because bats are largely inactive and their behaviour would not provide accurate results.

Understanding preliminary and activity surveys

Bat surveys generally happen in two stages:

Stage 1 surveys

These take place early in a project. A specialist assesses the building or trees for features that bats might use. Stage 1 surveys can happen at various times of year.

Stage 2 or “bat activity” surveys

These must take place during the active season only, between May and September. Activity surveys involve observing bats at dusk or dawn to understand how they are using a site.

Key deadline: at least one activity survey before the end of August

To collect dependable information, at least one bat activity survey must be completed before the end of August. Surveys carried out in September are still valid but cannot be used to replace all earlier work. September surveys help confirm late-season activity but should not be relied upon as the main evidence on their own.

Clients planning work in autumn or winter should ensure activity surveys are booked early so this deadline is not missed.

Three-week spacing between surveys

Activity surveys must be spaced out to capture a clear picture of how bats are using an area. Clients should allow at least three weeks between each survey. This spacing ensures that results reflect consistent patterns rather than short-term changes in weather or behaviour.

For projects that require more than one activity survey, planning early in the season is essential.

Why timing matters

Accurate survey information helps development projects move forward smoothly. When surveys miss the correct seasonal window, work may need to be postponed until the next year. Early planning avoids delays and ensures that conservation responsibilities are fully met.

If clients are unsure whether their project needs bat surveys, a specialist assessment can provide clarity at an early stage.

Planning ahead

The best approach is to contact an ecologist well before May. Early conversations allow survey programmes to be booked in advance, reducing the risk of seasonal deadlines causing delays. It also ensures enough time is available for follow-up surveys if the first results indicate further work is needed.

Understanding the survey season makes it easier for clients to manage timelines and meet legal responsibilities while protecting Scotland’s wildlife.

References

Bat Conservation Trust 2023. Bat Surveys for Professional Ecologists. Bat Conservation Trust, London.
NatureScot 2020. Bats: Licensing and Guidance. NatureScot, Inverness.
Scottish Government 2019. Wildlife Crime and Protected Species. Scottish Government, Edinburgh.