Fairfax Media contacted a bat expert in effort to find out more about the species and what could be leading them to set up camp in Far South Coast towns.

While the huge colony of bats at the Water Gardens in Batemans Bay is causing much consternation in the community, how the bats came to choose that location and how long they will stick around in such numbers is a bit of a mystery.

Let’s look at the numbers. There were understood to be around 400,000 grey-headed flying fox on the East Coast of Australia when the species was listed as vulnerable by the Environment Protection and Biodiversity Conservation Act.

The bats are also protected under NSW Threatened Species Conservation Act as their numbers have declined by an estimated 30 per cent over a 10 year period, with loss of habitat understood to be the main cause of that decline.

Big numbers of the bats are forced into urban areas where there is shelter and quite often a good food source from both native and fruit trees.

So where to the bats roost during the day and why do they choose those locations? There was a comprehensive honours paper done in 2005 that identified the factors that bats need for a camp including the presence of fresh water, suitable trees to roost and obviously a reliable food source nearby.

There are 250 recognised grey-headed flying fox camps on the East Coast, where the bats roost during daylight hours to rest, socialize, breed and nurse their young. Some of these are occupied and some unoccupied. 

Right now is peak breeding season for grey-headed flying foxes with mating or conception taking place this month with the females usually reaching their trimester of pregnancy in August and then giving birth in September.

Every three months a national survey of these camps takes place with volunteers counting the numbers at each location in each state and territory. Most importantly these bats are highly migratory and will travel anywhere from Melbourne to Rockhampton depending on food availability. 

On the Far South Coast, known flying fox camps are at the Water Gardens in Batemans Bay and also at Moruya Heads, Glebe Park in Bega and also at Pambula.

There is a recognised camp at Narooma at the suitably named Flying Fox Road, but this camp has not been occupied since 2012, according to the survey.

The flowering spotted gums are attracting the flying foxes to the forest around Narooma and the Far South Coast, but the bats are know to travel anywhere between 20km and 50km a night to forage.

So the bats feeding in Narooma could be part of the camps at Moruya Heads, which is 22km away as the bat flies, or even Bega.

How the long the bat numbers will stay in urban locations such as the Water Gardens in Batemans Bay is not known as the bats could decided to up and move to a new food source anywhere in Australia at any time.

Find out more about the grey-headed flying fox here

And whether bat dispersal even works remains in question. 

Councillor Peter Schwartz provided a document entitled: “Review of past flying-fox dispersal actions between 1990-2013. Prepared by Billie Roberts and Peggy Eby June 2013”, which reads:

To understand the utility of dispersals as a management tool to resolve conflict between humans and flying-foxes, the outcomes of 17 recent camp dispersal attempts were systematically reviewed.

The review identified a set of common outcomes of camp dispersals that should guide their use in Australia. A further observation was that the outcomes of dispersals are often not known for several years.

In all cases, dispersed animals did not abandon the local area. In 16 of the 17 cases, dispersals did not reduce the number of flying-foxes in a local area.

Dispersed animals did not move far (in approx. 63 per cent of cases the animals only moved <600m from the original site, contingent on the distribution of available vegetation). In 85 per cent of cases, new camps were established nearby.

In all cases, it was not possible to predict where replacement camps would form. Conflict was often not resolved. In 71 per cent of cases conflict was still being reported either at the original site or within the local area years after the initial dispersal actions.

Repeat dispersal actions were generally required (all cases except extensive vegetation removal).

The financial costs of all dispersal attempts were high ranging from tens of thousands of dollars for vegetation removal to hundreds of thousands for active dispersals (e.g. using noise, smoke etc).

There were a few exceptions to these patterns, but they only occurred when there were abundant financial and human resources (e.g. RBG Melbourne and RBG Sydney) and/or specific landscape characteristics (e.g., isolation from neighbours (Batchelor, NT) or habitat link to ‘acceptable’ location (RBG Melbourne)).