Microchiropteran Bat Survey of Dalton Park

(Oolong Sanctuary) March 2007.

Eastern Horseshoe Bat (Rhinolophus megaphyllus)
Photo:Michael Pennay NSW Department of Environment and Conservation PO Box 733, Queanbeyan, NSW 2620

Introduction:

A survey for microchiropteran bats was undertaken at ‘Dalton Park’ which forms part of Oolong Sanctuary at Dalton (near Gunning) in the South Eastern Highlands Bioregion of New South Wales on the 17^th of March 2007. The survey was undertaken at the request of the owner Mr Gianni D’Addario to gather information on the biological significance of the Oolong Sanctuary a regional private conservation reserve. The survey forms one of many such projects undertaken on Oolong Sanctuary– for more details visit the Oolong sanctuary website projects page at projects.html

Sites:

The survey was undertaken within the ‘Natural Habitat’ section of Dalton Park (152 Ha.), approximately 700m asl. A general inspection of the area was undertaken by vehicle and on foot including accessible mines and adits and watercourses. In addition to an inspection of mines and adits two specific sites were surveyed in the evening using the methods detailed below. These were the dam located below one of the old mine exits (position N,11 in figure 1) and remnant vegetation corridor along Bush’s Road (P,7-11 in Figure 1). The vegetation surrounding the dam site was dominated by open Red Stringybark (Eucalyptus macrorhyncha) regrowth with a shrubby understorey dominated by Sifton Bush (Cassinia arcuata) approximately 50 metres downslope from a large disused gold mine. The vegetation on Bush’s road was a narrow linear strip of good quality Whitebox ,Yellow box woodland, adjoining paddocks containing isolated large remnant (living and dead) Yellowbox (Eucalyptus melliodora) trees.

Figure 1: Map of Dalton Park, Oolong Sanctuary.

Methods:

Mine inspections: several disused mines on Dalton Park were inspected for the presence of bats during the day. Where safe mines were entered and inspected with a 12v spotlight for roosting bats, where access was not safe mines were assessed from the entrance for general suitability as roosting sites and signs of occupation such as scats, bones or audible bat noises.

Mist Netting; Two 18 meter mist nets were placed over the Dam site in a ‘y’ formation to catch bats in the evening as they flew in to drink and forage over water.

Ultrasonic detection; One Anabat detector connected to a laptop computer was used to record bats at both the dam site and along Bush’s Road.

An example of an ultrasonic bat call recorded using the Anabat detector. This bat was calling at about 40 kilohertz, double the maximum limit of our hearing (around 20 kilohertz). Most bats call at different frequencies or in different ways and records of their calls can be used to identify which species are flying around – without having to catch them. This call is particularly interesting. It shows the normal 'pulse' the bat was emitting to navigate (much like a sonar), and also a 'feeding buzz' (seen in the centre) where the bat has intensified its call to 'home in' on a prey item; then carried on again.

Results:

Unfortunately early in the evening of the 17 ^th of March an easterly change brought a drop in temperature and moist winds to the survey area. This weather was not ideal for bat survey in general and particularly mist netting as the nets are easily blown around in the wind and bat activity is reduced. Despite less than ideal conditions six bat species were observed flying in the early evening including one species listed as threatened in NSW (Large Bentwing Bat). Amongst the species observed were two cave dependent species (Large Bentwing Bat and Eastern Horshoe Bat) indicating that the disused mines on Dalton Park form habitat for these species. Neither cave dependent species were observed in large numbers, suggesting the disused mines form supplementary habitat for small numbers of these bats rather than core habitat for large colonies. Most bats observed were hollow roosting bats, the vegetation corridor along Bush’s Road and mature paddock trees adjacent to the road providing exceptional habitat for hollow roosting microbats.

Species detected during the survey

Discussion:

The majority of species detected at Dalton Park were typical of species expected in tableland woodlands of south-eastern Australia where suitable hollows can be found. The two cave dependent species (Miniopterus and Rhinolophus) were less usual and almost certainly use the disused mines on the property for roosting. This was supported by the visual inspection of the mines which found that several of the mines contained suitable bat habitat despite no roosting bats being found. Both species were recorded ultrasonically and the bentwing bat observed at the dam, but neither was found in large numbers. The mines did not appear to be used by large colonies of these species but by a small number of individuals, perhaps as supplementary habitat to major colonies elsewhere such as Wee Jasper. Nevertheless Dalton Park may form an important ‘stepping stone’ for these species between the coast and tablelands. Both of the forest bat species are tiny bats weighing between 3 and 7 grams (less than 1/3 the weight of a mouse), they roost in tree hollows and feed on small insects such as mosquitos and midges. These two species were the most common species observed at Dalton Park, along with Gould’s wattled bat which is a larger species weighing between 10-20 grams. Gould’s wattled bats often emerge earlier than other bats and their silhouettes can often be seen against the fading light sky at dusk. They also roost in tree hollows and feed on insects such as moths.

a) Gould’s wattled bat. b) White striped mastiff bat Photos:M.Pennay

The White-striped mastiff bat was heard and seen by spotlight, it is a relatively large bat with distinctive white markings where the wing joins the body. It typically flies high above the treetops and has a distinctive echolocation call that falls into the hearing range of many people. It feeds on moths and beetles. Other bats not found on Dalton Park but expected in the habitat are Long-eared bats Nyctophilus gouldi and Nyctophilus geoffroyi, and Chocolate Wattled Bat Chalinolobus morio. These species are also common residents of tableland woodlands and would likely occur in the area despite not being detected in this survey.

Conclusion:

Dalton Park and Oolong Sanctuary provides habitat for numerous hollow dependent and two cave dependent bat species. As such Oolong Sanctuary forms a regionally important habitat linkage between other natural areas. The management of the area as a conservation reserve is highly commended for this reason. Of particular note is the presence of disused mines used by cave dependent species and the Yellowbox remnants used by hollow dependent species.

Note on other significant sightings:

During the inspection of Dalton Park, babblers were noted nesting at a dam in the northeast of the property (E,18 Figure 1). These may have been Grey-crowned Babbler which is listed as a threatened species in NSW, or Whitebrowed Babblers, identification was not certain at the time. Regardless of the species the presence of babblers is uncommon in the region according to the Atlas of NSW Wildlife, and it is recommended an ornithologist visit the site and confirm which babbler species is nesting at the dam.