Ku-ring-gai Flying-fox Reserve Bat Counts

Bat Count Results

Data from the regular monthly counts conducted at Ku-ring-gai Flying-Fox Reserve, Gordon, by volunteers can be accessed below. Select the start and end dates for the time period you wish to view and click on the "Display" button. The graph and descriptive statistics will then be updated. The default display is all dates. There is a link at the bottom of the page to download the displayed data as a comma delimited ASCII file. This can then be viewed using Microsoft Excel or your favourite text editor.

How many flying-foxes are in a camp?

The number of flying-foxes roosting in a camp site is estimated by counting the animals as they fly out at night to forage for food. Fly-out usually begins about 20 minutes after sunset, although weather conditions can cause variations. Each person involved uses a mechanical (click) counter to record the number of flying-foxes, ten at a time, passing their field of vision. Two counters stand some distance from each other - far enough away not to hear the other persons clicker - at each exit point being used by the flying-foxes. Practiced counters consistently produce comparable counts, however there can be variations between individuals so counts at each exit point are averaged. By combining the counts from each flight path an estimate of total numbers of flying-foxes in the camp can be recorded.

Fluctuations in the size of a camp can vary week by week, month by month or in some cases from one night to the next. These fluctuations are a reflection of the nomadic nature of grey-headed flying-foxes. A camp site has been likened to a railway station where lots of people arrive and depart. Similarly, we know from radio-tracking research that flying-foxes move from one camp to another and back again. All the flying-fox camps are linked into one population. Numbers in a particular camp are influenced by food availability and the requirements of mating and raising young. Flying-foxes are not known to undertake regular seasonable mass migrations as many other animal species do, however, when there is abundant flowering of eucalypts in a particular area, then several hundred thousand may congregate to feed. This may account for 20 - 50% of the grey-headed flying-fox population.

The regular monthly counts conducted at Ku-ring-gai Flying-Fox Reserve, Gordon, contribute to our understanding of the grey-headed flying-fox population in Australia as a whole. Since 1998 annual National Counts of grey-headed flying-foxes have been undertaken throughout their range - along the eastern coast of Australia, from Queensland to Victoria. These National Counts take place over the same two successive nights and involve over 600 volunteer counters. The counts have been important in helping to have the grey-headed flying-fox listed as a Vulnerable Species in 2001 by both the NSW and Victorian State and also the Federal Government. It is important that these National Counts continue so that scientists can monitor these important animals survival status. National Count population estimates for the numbers of grey-headed flying-foxes over the last 5 years are as follows.

Count	Estimate	Camps Surveyed
July 1998	400,000	85
April 1999	355,000	103
April 2001	320,000	152
April 2003	435,000	197
April 2004	425,000	212

For a full description of how these counts were undertaken and detailed findings see the series of reports by Dr Peggy Eby listed on the bat references webpage.

Last modified by Marjorie Beck on 2010/03/15.