Microbats and Time of Night

What is the best time of night for microbats?

We have analysed a lot of Anabat data since our last update for the Batting4Bayside project. With the help of many of you, we have also collected a lot more data.

So far this project has collected over 12,000 data files for analysis, about one third of which has not yet been analysed. Of the two thirds that has been analysed, roughly 2,500 files contain recognisable bat calls.

One of the questions we had about our microbats relates to when they are most likely to be out and about.

Preliminary results suggest that most of the locally common bats, such as Gould's Wattled Bat, prefer the first part of the night. However one species, the White Striped Freetail (Austronomus australis) appears to prefer the middle of the night.
Percent of records per bat species throughout the night, as at 1 Feb 2015 

Much of the data we have collected is limited to the first couple of hours after sunset, and would therefore bias these results. However this bias makes the different profile of the White-striped Freetail more remarkable.

As this project continues we will be gathering more whole-of-night data. It will be interesting to see how this analysis changes as our dataset becomes more complete.

In case you were wondering, this analysis deals with the differing length of the night during the year by calculating sunset and sunrise times, and converting the time of the bat call to a percentage of the time between sunset and sunrise. So in the chart above, 0 means sunset, 100 is sunrise, and 50 is midway between the two.

We still have a lot of data collection and analysis to do. If you'd like to join our growing band of helpers, please contact us and let us know your interests.