Bat Management in East Gippsland
Two significant populations of cave bat species are found in East Gippsland. A third was discovered in the 1960s but disappeared as a cave species almost immediately. The Common Bent-wing Bat (Miniopteris schreibersii) is the most abundant species with a population in excess of 100,000. One maternity cave supports 60 - 70,000 females every summer. Adult males, non-breeding females and immatures occupy many caves, mine shafts, bridge culverts and buildings throughout Gippsland during the warmer months. They all move to overwintering caves during the winter. Where the majority of the Common Bent-wing Bat population overwinters is still a mystery.
The second species is the Eastern Horseshoe Bat (Rhinolophus megaphyllus) which is generally more sedentary although it is known to be capable of long distance movements. Three maternity colonies are known, the largest containing possibly up to 5,000 females and the other two, several hundreds combined. Eastern Horseshoe Bats occupy the same cave or local caves all year around.
The third species, the Large-footed Myotis (Myotis adversus) was known from only two caves in Gippsland but scientific collecting and disturbance led to an early demise of breeding populations. No subsequent breeding site has been found for this species. It does not rely solely on caves.
Cave bats are protected by the Wildlife Act 1975 and the Flora and Fauna Guarantee Act 1988. They are listed as 'vulnerable' (a category of threatened wildlife) because of their colonial breeding behavior. Their listing under the FFG Act has led to commencement of the determination of their critical habitat which will ultimately strengthen protection.
Cave management in relation to cave fauna, particularly bats, is generally unknown. A number of caves in the Buchan area contain unique invertebrate species and it is likely that undescribed species remain. The general lack of interest in Victorian cave fauna is perhaps highlighted by the first correct identification of the Common Bent-wing Bat and the Eastern Horseshoe Bat in 1953.
Perhaps the most comprehensive records of the distribution of cave bats comes from the work of Elery Hamilton-Smith in the 1960s.
Little attention has been given to the continued survival of bat populations since their discovery even though it is likely that at least one of the species has declined in numbers.
Threats to Cave Bats
The paucity of information makes it difficult to understand what the original populations were like. However, the reports of early observers suggest that the bats were more widespread than they are today.
Several threats have been identified affecting cave bats in Victoria:
- Protecting some important karst features within caves led to their gating with solid wooden doors. At least two significant bat habitats were lost this way
- Disturbance to maternity caves led to the cessation of breeding at one Eastern Horseshoe Bat maternity cave for a period of perhaps several years
- Ongoing disturbance to the Common Bent-wing Bat maternity colony is suspected of causing significant juvenile mortality
In February of this year an intruder into the breeding chamber, accompanied by a kerosene lantern, despite warning signs, was concerned to find 200 dead and dying young bats within a square metre of the cave floor. His concern for their welfare led him into our clutches bearing the forlorn young.
On one occasion, empty shotgun cartridges were discovered near the entrance.
Disturbance to overwintering caves may have had fatal consequences that we aren't fully aware of because we cannot locate them any more. Perhaps they are secreted in more remote locations.
Disturbance to summer roosts is best illustrated by the example of our research for a suitable cave for public education. A bat population was found not too far from the tourists. However, on the eve of the inaugural event it was discovered that the bats had moved out. Regular visits to this cave by various groups, sometimes up to 16 at once, in the preceding months had no doubt a significant impact.
Upgraded protection resolved the problem immediately.
Pollution and forest clearing may also have impacted on cave bat populations.
Cave Bat Management
Four important issues were identified and the programs installed simultaneously, and given equal priority.
- A monitoring program was designed to determine the current usage of caves by bats
- In order for staff and others involved in the monitoring program to correctly identify species and to understand the behavior of cave bats, it was necessary to instigate staff training agenda.
- It was also important to lift the profile of cave bats via a community education program.
- To immediately ensure better protection of known significant caves such as maternity and overwintering sites.
The Monitoring Program
From the work of Elery Hamilton-Smith and others, summarised in a report by Geoff Miller, 1985; a chart of all bat caves was drawn up and a schedule of visits were implemented.
The objectives were:
- to determine usage and for what purpose
- to record populations and period of use
- to identify roosts within caves
- to monitor the effects of recreation on bats
Techniques for monitoring varies according to the time of the visit and information required.
Inspection of overwintering caves involves going in quietly in the morning after a cold night and making direct visual observations. Monitoring of maternity caves and summer roosts are carried out from the entrance. Trapping, using harp traps, allows a small sample of the population to be analysed. An ultrasonic detector is also used to aid in identification. Aspects such as sex, reproductive status age and condition of the bats can be obtained from trapping. Captured bats are also banded to assist in studying their movements. A cave bat data card is being tried.
Several key staff were identified for involvement in the monitoring program. The agenda was:
- A general introduction to bat ecology and behavior and how to relate the activity to research and management
- Techniques for trapping, banding, identification, direct observations, correct handling and use of ultrasonic detectors
- Using bats as an interpretive subject
- The use of artificial hollows or bat houses
- Cave protection
So far three such programs have been run with an average attendance of 12, including some non staff participants. The venue has been the Rotamah Island bird observatory on the southern shores of the Gippsland Lakes. The course runs overnight and this site gives participants the opportunity of handling several other species of forest dependant bats which enhances participants identification skills. Bats are also abundant on Rotamah island with one trap yielding over 200 bats of 8 species in a single catch.
Going Batty program
Aims of the program
- To promote a positive image of bats
- Increase participants awareness and knowledge of habitat requirements, life cycles, adoptions and behavior of bats in general
- Promote DCNR's relationship with the public due to the increased understanding of the cave bat monitoring program
- Promote awareness and understanding of why bats and birds are banded, and how the public can assist in retrieving bands
- Promote awareness and understanding of signs in caves explaining the need not to disturb overwintering or breeding bats
- Target audience: families, casual cave users
- Group size: A maximum of 20
- Timing: Weekly during January from 8pm to approx 10pm
- Preceding each session a harp trap was erected at the front of the cave entrance.
- An introductory session covered such topics as:
- Why people had attended, and what did they know already about bats
- Basic bat taxonomy
- Geology/age of cave
- Yearly cycle of male and female bent-wing bats
- Purpose of cave bat monitoring program
- At approximately 8.45pm the group would approach the cave and around the entrance of the cave, 5-10 metres from the harp trap. Here they experienced the sunset and exit of bats leaving the cave. They were invited to participate in a count of the bats leaving the cave.
- Once several (5-10) bats have been caught, they were removed from the trap into a calico bag and the trap removed from the cave entrance. People witnessed the remainder of the bats exit. This was generally 9.20pm or 9.25pm and to some extent determined by darkness (i.e. too dark to count)
- The captive bats were then processed and shown to the group. Participants were encouraged to handle a bat
Protecting Important Bat Sites
- Interpretive signs have been erected, 2 maternity caves, 1 overwintering cave
- Caving groups notified of restrictions
- Private landowners notified and asked to co-operate
- Increased ranger patrols
- Disguising access routes to some caves
Evaluation of Programs
- The monitoring program is still in its infancy. We are still at the stage of determining which caves should be included on the schedule. In some cases our visits have related little usage of former bat caves. These are given a low priority so our limited resources can be directed in the right areas. Publicity given to the monitoring program has encouraged others to participate directly or to provide additional information. Some problems associated with the monitoring program have involved the allocation of staff to carry out the surveys during a period of peak workload. A conflict of priority exists.
- The training of staff and others is ongoing but we now have a core group with the skills and confidence to undertake solo surveys including handling bats and to be able to talk to the public about bats. The long term effectiveness of the training program is now reliant on the staff themselves to continue involvement and retain/enhance their skills.
- Community education. The public interest in 'Going Batty' and in wanting to learn about and experience bats was demonstrated by the enormous number of people wanting to attend sessions. Each session was more than fully booked with a waiting list. The range and depth of participants questions was encouraging and gratifying. It was a very, very valuable and successful activity and is self-funding. Future recommendations are: to continue a session per week, find an alternative cave to the one currently being used to minimise disturbance, and to develop interpretive materials.
- The signposting of caves has led to a decrease in human disturbance. This is further strengthened by the combination and the co-operation of landowners, if the caves are private, notifying caving groups and increased ranger patrols.