Taking a bat inventory

Bat colony validation protocol

In order to validate the presence of a bat colony, it is possible to rely on certain indicators such as noise (scratching sounds or vocalizations) and feces (which is called guano and is similar to mouse feces, but longer and more slender and segmented).

However, the best way to confirm the presence of bats is to observe their emergence at dusk. To do this, the first step is to locate their entry and exit points. These are often found where walls meet the roof, in dormers, or above window frames. The following is the best method for spotting these openings.

  1. Openings can be identified by examining the site during the day. They are often indicated by the presence of excrement on the walls.
  2. If the entrances are hard to locate (which is often the case), it can be useful to dedicate an evening to locating them before proceeding with the bat count. The best conditions for observing bats are warm evenings without wind or rain.
  3. On the evening of the observation, observers should ideally be placed at each corner of the building, each observing one side, so that the entire surface is monitored. Each participant should be equipped with a flashlight or a headlamp; however, these should never be pointed directly at the bats’ exit location.
  4. If there is an insufficient number of participants or if the building is too large or irregularly shaped, place people at angles around the building or spread them out so that the entire surface of the building can be monitored.
  5. Once an opening is identified, efforts can be concentrated on another part of the building. If you are alone, you will have to observe the entire building; therefore, the observation process will take longer. Proceed in a systematic way by observing one side or section at a time.


Protocol for counting bats 

  1. Performing a bat count is essential to assessing the size of the maternity colony.

For best results, it is best to conduct counts on warm nights when it is not windy or raining.

  1. Counts can be performed during two summer periods. The first is from mid-June to early July. This is called the pre-volant period, when the young bats have not yet begun to fly. The second period is from mid-July to early August. These dates may vary by location; in some regions, many of the young have left the maternity colony by early August. If you are only able to complete one count per year, ensure it is always done during the same period. To obtain the best possible assessment of the number of bats in a maternity colony, bat counts should be done on two nights, only a few days apart. It should be noted that bats do not leave at the same time every night. Also, a certain number of bats may opt to stay inside for various reasons (to remain with the young, for example). Performing two separate counts on two different evenings will provide a more accurate picture of the number of bats in the colony. However, even if you can only perform one count, that data is still valuable! Please note that the count should be recorded even if no bats are observed. This information is useful for monitoring bat populations.
  2. Before beginning your count, complete Section A of the form (see below). Next, transcribe your results in the online form at batwatch.ca
  3. Once on site, find the previously identified openings. At sunset, place two people at each opening. Bats generally begin to emerge about 30 minutes after sunset, but 45 or even 60 minutes may pass before they appear, so it is important to be patient. Both observers are responsible for counting all the bats that emerge from their assigned opening. If more than one opening is used by the bats, place one observer at each opening and make a note of this in the “Comments” section of the form.
  4. For better viewing, observers should be placed slightly diagonally, 10 to 15 metres from the opening.

Shine a flashlight a little to the side of or below the opening so as not to disturb the bats.

Very bright, direct light may prevent the bats from emerging. It is important to remain very attentive and keep your eyes on the opening so as to see every bat that emerges. Depending on the location of the opening, it may be difficult to observe every bat that comes out.

  1. Count all the bats that emerge through your assigned opening. It is important to avoid counting bats that are simply flying around near the opening of the maternity colony, since they may be from a different site.
  2. If a few bats (2 or 3) return to the roost while others continue to emerge, continue the count. Should it become too difficult to follow the comings and goings of the bats, or should too many bats re-enter the opening, stop the count and take note of the time.
  3. If no bats return to the roost, stop the count approximately 30 minutes after the last bat has emerged.

If possible, take note of the time at which the last bat emerged. Write down the time and temperature at the end of the count.

  1. Write down the results of the count. Note the name of each observer and the number of bats counted by each. If bats emerged through more than one opening, make a note of this. Assign a number to each opening and indicate which observer was assigned to it. Add up the counts from each opening to obtain the total number of bats. If more than one observer was placed at each opening, mark down the number counted by each observer. The count for that opening will be the average of all the counts.

Next, transcribe your results in the online form:


  1. You may discover new openings during the count. It is important that these be noted on the form and, if necessary, identified on a diagram.
  2. You can attach a diagram or photos of the openings and/or of the maternity colony.



  1. Ministère des forêts, de la faune et des parcs. Juillet 2014. Protocole de validation
    d’une colonie de chauves-souris. 1p.
  2. Chauves-souris aux abris. Avril 2017. Protocole pour un décompte de chauve-souris dans une maternité. 4p.