The Latest on the Bat Action Plan, Bent-wing bat taxonomy, and Lyssavirus
Introduction
I was invited to speak on the bats of the southeast (SE) of South Australia as part of this session on site specific issues. Because this conference has as its focus matters relating to caves and karst, and since only two of the 17 bat species in the region are cave dwelling bats, I thought it would be useful also, to give a brief update on some current issues relating to Australian cave bats (Miniopterus taxonomy, the forthcoming Bat Action Plan and Australian Bat Lyssavirus).
Bats of the SE
Key points I wish to make in this section are:
- that the SE has a rich bat fauna when compared with other regions in the State,
- that broad scale habitat modification in the SE represents a serious conservation threat for bats,
- that very little is known about the natural history of most of the bats species in the region,
- that the southern bentwing bat is uniquely vulnerable because of its reliance on a small number of caves for its survival, and
- that the currently used estimate of population size for the southern bentwing bat at Naracoorte is not based on reliable measurement and could be very misleading.
The South East
Laut et al (1977) have divided South Australia into eight environmental provinces based on both biotic and abiotic factors (Fig 1) For the purpose of this paper, I have followed their definition of the SE, that is, Province 1. The SE region defined this way includes parts of the Naracoorte Coast and Murray Darling Basin Bioregions (Thackway and Cresswell, 1995).
Figure 1 Environmental Provinces of South Australia (Laut et al 1977)
The bats of the SE
Twenty-five bats species occur or are confidently expected to occur in South Australia. It should be noted that very little systematic bat survey work had been undertaken in South Australia until about fifteen years ago. The species inventory and distributional information to that time was largely due to the accumulation of opportunistic collecting. Over the last 15 years, a series of bioregional flora and fauna surveys have been conducted by the Department of Environment, Heritage and Aboriginal Affairs and the South Australian Museum, and while the survey effort on bats during these expeditions has been inconsistent, the surveys have added considerably to our knowledge of bats, especially in the northern part of the State. Several smaller localised surveys throughout the State have been conducted by the SA Museum. This history of bat survey work has meant that we can only estimate what species were present and in what relative abundance, in most regions of the State before the impact of European settlement. Even today, our knowledge of species composition and status in many areas is incomplete. This is certainly true of the SE.
In preparing a list of bats species for the SE, I have drawn upon SA Museum data, recent survey work in Victoria conducted by the Arthur Rylah Institute (ARI) and from field work by a former NPWS ranger, Dennis Matthews. Two species, Mormopterus sp 2 and Falsistrellus tasmaniensis have not yet been recorded in South Australia although the recent ARI survey found them in Victoria, near Edenhope (less than 30km from the SA border) and in the Lower Glenelg National Park, again less than 30 km from the SA border. I consider it most likely both species occur in SE because the vegetation types in which they were collected in Victoria also occur in nearby South Australia. No specimens of Saccolaimus flaviventris have been collected in the SE however the species has been spotlighted near Piccaninnie Ponds (Dennis Matthews pers comm).
Table 1 shows the list of bat species known (or confidently expected) to be present in each of the eight environmental provinces. Of these 25 species, four belonging to the genus Mormopterus (freetailed bats of the family Molossidae) have yet to be formally described as species although all have been treated as species for some time (Adams et al 1988; Churchill 1998). The SE environmental province has the highest bat diversity with 17 species.
TABLE 1 Bat species occurring in the eight environmental provinces (SE =province 1)
The list shows that two flying fox species have been recorded in the SE. Pteropus scapulatus (little red flying fox) has only been recorded six times in South Australia over the last century and is not considered a normal inhabitant of the State (Reardon and Flavel 1991); it is widely distributed elsewhere in northern Australia (Churchill, 1998). Equally, P. poliocephalus (grey-headed flying fox) is known from only a few records in SA, all of which are from Mt Gambier, Kalangadoo and Kingston and observed in the summer of 1997/8. The usual distribution of this species is coastal from about Melbourne, north to near Rockhampton. Populations of this species are known to seasonally travel large distances in search of their diet of eucalypt blossoms (Eby, 1991) and exceptional movements beyond normal range have been recorded when abnormal timing of flowering results from droughts caused by El Nino. The observations in the SE coincided with the effects of El Nino. Grey-headed flying foxes were not recorded this past summer, 1998/9. Neither flying fox species is therefore a usual inhabitant of South Australia and thus of no special conservation concern in the state at the present time.
The remaining 15 bat species are insectivorous. Two, Miniopterus schreibersii (southern bentwing bat), and Myotis macropus (southern large-footed bat) are mainly obligate cave dwellers in the SE, while the rest are dependent upon trees (hollows, bark ) for roosting sites. Four of the insectivorous species (M.schreibersii, N.gouldi, F.tasmaniensis and Mormopterus sp 2) are present in South Australia only in the SE province where they are at the south-western extremity of their Australian distribution (Churchill 1998).
Conservation status
Of the 15 insectivorous species occurring in the SE, none are placed in threatened categories at the national level, but M. macropus is categorised as Lower Risk (near threatened) while M. schreibersii (southern form = Naracoorte/Warrnambool population) is Lower Risk (conservation dependent) (Baker et al. 1999). At the South Australian state level, S. flaviventris, M. macropus M. schreibersii, F. tasmaniensis , N. gouldi and Mormopterus sp 2 are vulnerable.
Conservation concerns for bats - habitat destruction and modification
The landscape of the SE region has undergone extensive modification over the last 150 years. Native vegetation in particular has suffered to the extent that only about 10% remains (Croft et al. 1999). Many plant communities including shrublands, heathlands and some tall forests have completely disappeared from the region. Of the native vegetation remaining, about 30% is "protected" in government conservation reserves or under private Heritage Agreements, and another 5% is under protection in Forestry SA reserves (Croft et al.1999).
Drainage of surface waters in the SE has significantly reduced the area of wetlands, altered the water table and altered the vegetation composition. Grazing and other agricultural activities have also added to fragmentation and alteration of native habitats. A summary of the environmental changes and a list of major conservation threats is given in the 'Biodiversity Plan for the south east of South Australia' (Croft et al 1999). The Plan makes recommendations for the protection of native habitats as well as threatened fauna - the only mention of bats however is to say that they were present in the region.
Native vegetation clearance, especially of old, hollow-bearing trees still continues. It is difficult to obtain details of native vegetation clearance from the Native Vegetation Council, the body responsible for allowing vegetation clearance. My inquiries to get details for this paper yielded only general figures for the State, and only for the year previous to this. We do know that the State Government, through Primary Industries, SA, has cleared thousands of mature trees in the last five years - mainly in preparation to plant pine. The expansion of vineyards in the SE has led to applications for the clearance of mature Eucalyptus camaldulensis, an important hollow bearing species.
I believe that it is reasonable to deduce that the number available natural roosting sites for hollow roosting bats in the SE has diminished by 50-80% since European settlement. The reduction of available roosts results not only because hollow-bearing trees have been cut down, but also because there is strong competition for those hollows that remain. It is probable that birds and other mammal species such as dasyurids and possums may dominate in competition for larger hollows. Introduced honey bees also compete for hollows.
Added to the loss of roosting sites, are the probable effects of vegetation modification on insects, the food of bats. It seems likely that insect diversity has reduced with the loss of food plant diversity, and that the abundance of some insect species has been reduced through the loss of surface waters and the use of pesticides. Pesticides were directly responsible for killing several million bats from a single cave population of Mexican freetail bats in the USA. The literature from overseas show that pesticides, particularly organochlorines, not only kill insects, the diet of bats, but kill the bats themselves. Herbicides and insecticides are widely used in the SE in forestry and agriculture. Although over 100 papers on the effects of pesticides on bats have been published overseas, only two small studies on the effects of pesticides on Australian bats have ever been published.
While we have no evidence for the extinction of any tree-roosting bat species from the SE, the weight of probabilities suggest that population sizes for most species must have declined significantly. The actions recommended in Biodiversity Plan (Croft et al 1999) for native vegetation protection, may be the only practical approach in the short term to help conserve present bat populations. Nonetheless, considerably more field work is required just to understand what are the habitat requirements for each of the bat species, and to make some realistic assessment of their respective conservation status in the region.
Cave-roosting bats
Myotis macropus
Of the two cave dwelling bats, M. macropus is the lesser known (at least in the SE). I know of only one cave on the South Australian portion of the Lower Glenelg River which purportedly contains M. macropus. On the three occasions that I have visited this cave, I have only observed M. schreibersii as being present.
Recent studies in Victoria near Lake Eildon (Caddle, 1998) have shown that individuals of M. macropus can fly to feeding areas some 22 km from their roost site. They normally forage over fresh water streams and lakes, flying low to the water and feeding mainly on aquatic insects. Fish scales have been reported in the faeces of pregnant and lactating females. It is indeed possible that the many open sinkholes and ponds in the Mount Gambier region are frequented by M. macropus. I am uncertain of the true conservation status of M. macropus in the SE.
Miniopterus schreibersii
In the Action Plan for Australian Bats (Baker et al. 1999), the populations of M. schreibersii from South Australia to just west of Melbourne are considered to form a separate taxon (referred to as the southern bentwing bat) (current research suggests that this taxon is a distinct species). The southern bentwing bat is categorised under International Union for the Conservation of Nature (IUCN) criteria as 'Lower Risk, conservation dependent', that is, the taxon should remain secure as long as there is continuing conservation management. What is the current conservation management and what do we really know of the conservation status of this taxon?
In South Australia, the southern bentwing bat is reliant upon about twenty caves for its survival. Bat Cave at Naracoorte is the major (if not the only) maternity cave. Adult and yearlings gather in Bat Cave in spring causing a rise in cave temperature and humidity such that conditions are suitable for the birth and rearing of the season's new young. In late summer and autumn, most of the bats leave Bat Cave and over-winter in caves in the SE and probably western Victoria. The wintering caves are an important link in the life history of the southern bentwing bat. Some 20 caves in SA are known to have been used as wintering caves by bats. Only a small number of these caves are on NPWS reserves and thus afforded some protection. Several wintering caves on private land have been filled in or have been used as refuse pits. Many of the wintering caves are used by recreational cavers during the winter months - disturbance of wintering bats can be fatal for the bats. I see wintering caves as a very vulnerable link in the survival of southern bentwing bats.
The current status of the southern bentwing bat is unclear. The peak colony size of Bat Cave in the summer of 1963/4 was estimated as 100 000 - 200 000 individuals (including the newborn) (Dwyer and Hamilton-Smith, 1965). This estimate was based on determining the number of pups (baby bats) per square foot (density) multiplied by the total area of bats roosting in the cave. Population numbers were also estimated using mark-recapture method (Lincoln index) - these two methods yielded similar estimates (Hamilton-Smith communicated at the ACKMA conference). These estimates made in the 1960s are the earliest reliable estimates of the peak population size in Bat Cave and represent the only real reference point we have to assess the status of the population.
It is alarming to me that over recent years, the figure given for the peak population size in Bat Cave has steadily risen despite the fact that there have been no properly conducted counts since the late 1960s. An interesting phenomenon has occurred - it seems that the high end of the 1960s estimate range, that is 200 000, became established as THE figure, and then this number subsequently became the low end of a new range. This leap-frogging of population estimates over the years has resulted in current NPWS brochures saying that the peak population in Bat Cave "may exceed 300 000 bats". Such a trend would suggest that the population is in good health. There is absolutely no real basis for this estimate of peak population size.
The possibilty is that the true colony size at the time of the 1963/4 census, may have been closer to 100 000. Population monitoring has been conducted on a qualitative basis from year to year by rangers who have to make a judgment, based on memory, whether the colony size is more or less than that of the previous year. I contend that the colony could have been decreasing in size by 2000 per year for decades without being noticed at the current level of observation.
This is an important colony, and following the change in annual aggregation count is probably the best way to monitor the health of the whole southern bentwing bat population. I believe that it is imperative that a reliable method be developed to estimate the population size from year to year. If the method relies upon human operators, then the method must be so well defined that it will yield consistent results independent of the operator. It may be preferable to take human error out of the equation by developing electronic counting methods (infra-red counting beams, passive infra-red detectors and radar have been suggested as potential candidates for the job).
Protection of Bat Cave has been a key plank in the management strategy of the southern bent wing bat by the current NPWS regime at Naracoorte - Brian Clark and his team are to be commended for their strict enforcement of limiting access into Bat Cave, only to persons with bona fide purposes. I suggest that reliable yearly population counts be added to the management strategy so trends in population can be monitored. The fact that most of the population gathers at Bat Cave every year means that monitoring of the population at large can be achieved just by monitoring Bat Cave. The long-term protection of wintering caves must also be included as a management goal. Further actions for the conservation of the southern bentwing bat are given in the Action Plan for Australian Bats (Baker et al. 1999).
In summary
The SE region contains a rich diversity of bats in comparison to other regions of South Australia. More survey work is required to confirm the presence of F. tasmaniensis and Mormopterus sp 2 in the region, and to establish the current distribution and habitat requirements of all bat species. The southern bentwing bat is soon likely to be elevated to full species status - it then will have a unique place amongst the bat species in South Australia since it has a comparatively small distribution that is centred on the SE. I recommend that annual monitoring of peak population size in Bat Cave be added to the management strategy for southern bentwing bats, and that ways of protecting wintering caves over the long-term be investigated.
References
Adams, M., Reardon, T.R. Baverstock, P.R. and Watts, C.H.S.1988 Electrophoretic resolution of species boundaries in Australian Microchiroptera. IV. The Molossidae (Chiroptera). Australian Journal of Biological Science 41:315-326.
Baker, B., Duncan, A.and Montgomery, 1999 DRAFT An Action Plan for Australian Bats. Environment Australia
Caddle, C. 1998 Roost selection by the large-footed bat, Myotis adversus in southern Australia. Honours thesis , Melbourne University.
Croft, T., Carruthers, S., Possingham, H. and Inns, B. 1999 DRAFT Biodiversity Plan for the south east of South Australia. Department for Environment, Heritage and Aboriginal Affairs.
Churchill, S. 1998 Australian bats. Reed New Holland, Sydney. 230pp
Dwyer, P.D. and Hamilton-Smith, E. 1965 Breeding caves and maternity colonies of the bent-winged bat in south-eastern Australia. Helictite 4(1): 3-21.
Eby, P. 1991 Seasonal movements of grey-headed flying foxes Pteropus poliocephalus (Chiroptera:Pteropodidae) from two maternity camps in northern New South Wales. Wildlife Research 18:547-559.
Laut, P., Heyligers, P.C., Keig, Gael, Loffler, E., Margules, C., Scott, R.M. and Sullivan, M.E. 1977, Environments of South Australia, Province 1, South East. Division of Land Use Research, CSIRO, Australia.
Reardon,T.B. and Flavel, S.C. 1991 A guide to the bats of South Australia. South Australian Museum, Adelaide.
Thackway, R and Cresswell, I.D. (eds.) 1995 An Interim Biogeograghic Regionalisation for Australia: a framework for establishing the national system of reserves, Version 4.0. ANCA, Canberra.
Some bat news
Miniopterus taxonomy
The genus Miniopterus (bentwing bats) has a wide distribution extending from Europe through Africa and Asia to Australia. The taxonomy of the genus has undergone many revisions yet it remains in confusion. Australo-Papuan forms have also been subject to differing treatments and in particular, the Naracoorte/Warrnambool population has been variously treated as a population or full species. Linda Reinhold (Qld Forestry), Marcia Lara (Uni of Qld) and I, have been re-examining the species level taxonomy of Australo-Papuan Miniopterus using a combination of approaches, namely morphology, allozyme electrophoresis and DNA sequencing. Our results, soon to be published, have clarified the number of species in the region.
Of particular interest to Australian biologists will be our findings on M.schreibersii in Australia. DNA sequencing shows that true schreibersii from Europe is unrelated to the Australian 'schreibersii'. In addition, our data show that Australian 'schreibersii' is a complex of three species, the Naracoorte/Warrnambool population (to be named), M.oceanensis distributed along the eastern seaboard of Australia, and M. orianae from WA/NT.
The Action Plan for Australian Bats
The Action Plan for Australian Bats has been long in the making. After nearly five years and several revisions, Environment Australia expect that the Plan will be released in July/August 1999. The Plan recognises 90 taxa, each of which has been assigned a conservation category according to the criteria set down by the IUCN. Recovery outlines have been prepared for all threatened taxa.
Cave-roosting bats make up one third of all bats in Australia. The following table lists all the taxa which are either obligate or facultative cave dwellers, together with their conservation category.
Of the 31 cave dwelling bats one is classified as Critically Endangered, three as Endangered and one as Vulnerable. Of particular interest to some will the decision to downgrade the conservation status of the Ghost bat Macroderma gigas to Lower Risk (near threatened) - under previous treatments, this species was classified as Endangered.
The two following points from the Plan reflect key issues facing bat managers and biologists;
"Thus, almost half of all bat species are of some conservation concern or the knowledge is lacking to determine their conservation status".
Nearly one third of Australian bat species require taxonomic reappraisal.
I thank Barry Baker from Environment Australia for permission to discuss the 1999 draft of the Action Plan for Australian Bats at this conference.
Australian Bat Lyssavirus
I had put this item on the list of news items in the hope that by this conference some new information about some recent developments might come to hand.
The background is thus - the discovery of Australian Bat Lyssavirus and the subsequent two fatalities. Australian Bat Lyssavirus (ABL) is a virus closely related to the virus that causes classic rabies. ABL was first discovered in 1996 and is responsible now for two human deaths in Australia. Studies since then have shown that four species of flying fox (Pteropus species) and one species of insectivorous bat (Saccolaimus flaviventris) carry the virus although probably less than 10% of individuals for each species are carriers. It is not known whether ABL is a newly arrived virus or whether it has always been naturally occurring in Australia.
Scores of insectivorous bats, representing many species have been tested for ABL in the last two years and until early 1999 none, other than S. flaviventris, had been confirmed as carrying the virus. In early 1999 however, unofficial reports began circulating that ABL had been isolated from two long-eared bats (Nyctophilus, species not determined) from NSW, and from a single lesser long-eared bat (N.geoffroyi) from SA. These reports were particularly disturbing since long-eared bats are perhaps the most abundant and widespread bat species in Australia, and are common inhabitants of houses. If ABL was confirmed as present in long-eared bats then it suggested that ABL was likely to be carried by more species, including cave bats. (Note: bat researchers may inadvertently contribute to the spread of viruses across species because standard bat traps catch many bat species at the same time, thereby presenting the opportunity for contact between tree dwelling and cave bats that otherwise would never come together).
Naturally this development was of some importance to those of us involved with bat research (or indeed those who might encounter bats as part of their caving activities). If these reports were confirmed it would lead to a reassessment of the risk associated with working with or encountering bats. I have tried to find out for this conference, whether the results have been confirmed or rejected but no-one is giving anything away!
In fact it has been very difficult to get any information at all. The Australian Animal Health Laboratories (AAHL) in Geelong are the main testing facility for ABL. I know that the earlier positive results were based on the less reliable method of Polymerase Chain Reaction - false positives are possible. The person responsible for the diagnostic work was not prepared to discuss the issue with me (it is now late June, no answer yet).
Further background and relatively recent developments can be found at a number of websites (just search using 'Lyssavirus').