A short introduction to our standard methods
The methodology requires three simple steps:
Locate and describe the roost site
Count the number of bats at this roost
Provide the information via the online form at the bottom of this page or send us an e-mail
Counts should be done during daytime and begin after 09:00 and end before 16:30, when bat activity is low.
Exact Method: This method should be used for small roosts (300 or less) where individuals can be easily counted. Counts should be first conducted on individual branches to create a tree total and then summing bats across all trees.
Estimation Method: If there are too many bats to count each and every bat, one can use an estimation method.
a. Branch Estimates: Identify all the major branches on the tree that have bats on them. Pick a branch that has an average number of bats on it (i.e., don't pick one that has just a few, or the branch that has the most). Count the number of bats on this branch and multiply that number by the total number of branches that are occupied by bats.
You can make this estimate more precise by counting a few branches and taking the average, and also by ensuring that the branches are of roughly equal length.
Additionally you could count the actual number of bats on branches where they are sparse, and then use the estimation methods for the heavily populated branches.
b. Tree Estimates: Where the roost is spread out across many trees (as most of the time), one can count the number of bats on a tree and then multiply by the number of trees. You can increase the accuracy by following the same suggestions as above.
Camera Methods (if appropriate equipment is available): For extremely large or inaccessible colonies, camera counts may be helpful to monitor bats during emergence from the roost. We are currently developing a computer vision method using deep learning to identify bats from videos of camera pointed at the sky. We do not recommend this method yet as it is still under development.
Avoiding Roost Disturbance
It is important that the the researcher does not disturb the bats at their roost during the counts. One should avoid activities such as clapping hands, talking too loud, or trying to touch bats, which may disturb the bats (and screw your count, as they might then fly up). In many colonies bats also react strongly if you carry something that looks like a gun or catapult in your hand (such as an umbrella).
There are many other studies that can be done at the roost site, and much depends on the time and inclination of the participant. Some of the possible topics worth studying include monitoring roosts for sex ratios, reproductive status, threats, social behavior, sleeping activity, social structure, foraging activity, diet, movement between trees/roosts, direction that bats fly at sunset, etc. Feel free to contact us for details if you are interested in such additional aspects! Take lots of pictures!
Data and Ownership
The data collected will be analyzed for patterns and changes in populations, and relevant outcomes will be published online. The summary information, but not the details of each site, will also be available at any time on this page: Monitoring Results.
The network will regularly update the count data on this website, so as to distribute the information to the scientific community and also inform policy.
The data collected belong to the researchers who collect the data and should be available for view through this website. Thus, the individual volunteers may use their site data to publish in any way they wish.
We encourage all volunteers to make their data open access, but researchers and third-parties that may wish to use data collected by other monitoring volunteers MUST ask for permission to use the data for each site.