Byron Flora and Fauna Study 1999 - Byron Shire Council

A GREENPRINT FOR A SUSTAINABLE FUTURE
Little Bentwing-bat Miniopterus australis
Regional distribution and abundance. The Little Bentwing-bat is relatively common and widespread in coastal areas of northeastern
New South Wales with a concentration of records in areas of high rainfall (NSW National Parks and Wildlife Service 1994, Parnaby
in prep., ANSWW database). Elsewhere in the region it is less common, with a sparse and patchy distribution mainly confined to mid
and low elevations (ANSWW database). It reaches the southern limit of its distribution in the Hunter River area (NSW National Parks
and Wildlife Service 1994).
General ecology (habitat, shelter, diet, territory, breeding, movements). The species occurs in a very wide range of habitats from
coastal mangroves and heathlands to subtropical rainforests. However, although recorded from a variety of dry forest types, it appears
to be most strongly associated with rainforest and wet sclerophyll vegetation (NSW National Parks and Wildlife Service 1994,
Parnaby in prep.).
It forages mostly below, but sometimes above, the canopy of forest and woodland, including rainforest, swamp sclerophyll forest and
dry sclerophyll forest, and also over open spaces such as estuaries (Dwyer 1968, Parnaby in prep., D. Milledge unpubl. data). The
species appears to be active and forage longer into winter than the Common Bentwing-bat (Dwyer 1968). The diet is poorly known
but is thought to be composed mainly of small flying insects.
The Little Bentwing-bat is known to roost in caves including sea caves, old mine shafts and tunnels, and occasionally in old railway
tunnels, storm-water drains, culverts and buildings (Dwyer 1968, Gilmore and Parnaby 1994, NSW National Parks and Wildlife
Service 1995). It has also been recorded roosting in large hollow trees (e.g. Schulz 1996). Most roost sites are closely associated with
dense vegetation such as rainforest, wet sclerophyll forest and coastal shrubland (Dwyer 1968, Gilmore and Parnaby 1994, Parnaby
in prep.). Roost site selection varies seasonally depending on factors such as climate and breeding requirements (Dwyer 1968). In
New South Wales, the Little Bentwing-bat shares maternity roosts with the Common Bentwing-bat, with the only confirmed maternity
colony in the Willi Willi Caves system near Kempsey (Dwyer 1968, Parnaby in prep.), although others are suspected to the north
and south (Parnaby in prep.). It has been suggested that the Little Bentwing-bat depends on large concentrations of the latter species
to create the warmth necessary for development of its young (Dwyer 1968).
Most individuals recorded in northeastern NSW probably originate from the Willi Willi Caves or from breeding sites in southeastern
Queensland (Dwyer 1968, CSIRO Division of Wildlife and Ecology 1996). Movements of up to 60 km have been recorded between
roosts and the maximum distance travelled between sites in one night is 32 km (Dwyer 1968).
Conservation status and threatening processes. The Little Bentwing-bat is listed on Schedule 2 of the TSC Act, 1995 as Vulnerable.
The original reasons for its listing as an endangered species were ‘population reduced, but suspected to be stable; concentrates;
threatening processes severe; ecological specialist’ (NSW Scientific Committee).
The major threat to the species in NSW appears to be the loss of food resources at critical times such as when the population is clustered about
breeding sites in spring and summer (Dwyer 1968, Parnaby in prep.). The availability of food resources in traditional winter foraging areas may
also be vital in sustaining population levels. Likely causes of losses of food resources are difficult to identify when the diet is so poorly known, but
it can be expected that if the availability of flying insects associated with the forest canopy and understorey is substantially reduced by clearing or
simplification of the forest structure through logging, grazing and burning, then this would have a significant impact.
Other threats are human disturbance at roost sites and changes to the microclimate in the vicinity of roost sites (Dwyer 1968, Parnaby
in prep.). The loss of any roost sites could be strategically significant to the species because of its complex social structure and annual
pattern of movements.
Any decrease in the numbers of the Common Bentwing-bat may adversely affect the Little Bentwing-bat because of its apparent
dependence on a high density of the former at its maternity colonies.
Local distribution and abundance. The Little Bentwing-bat is a common species throughout Byron Shire. It was the most widely
recorded of all microchiropteran bat species during the bat call survey (Appendix 10), occurring from the coast to the hinterland at
roughly equal detection frequencies. Almost twice as many record locations were obtained in the survey compared with the next most
commonly recorded species, the Common Bentwing Bat.
It has also been among the most commonly detected species in other bat surveys in the Shire, being reported from a wide variety of
habitats (ie. CSIRO Division of Wildlife and Ecology 1996, Hoye 1993, 1995, Milledge and McKinley 1992).
Local ecology and conservation significance of the study area. Probably the most important habitats for the Little Bentwing-bat in
Byron Shire are the more extensive rainforests and wet sclerophyll forests of the hinterland, and the rainforests, wet sclerophyll, moist
sclerophyll and swamp sclerophyll forests of the coast. It has also been recorded over shrublands, heathlands and major streams with
well-developed riparian vegetation as well as about remnant rainforest patches and artificial habitats such as sewage treatment works
and urbanised areas with bright light sources.
No confirmed roost sites of this species are known from the Shire, although a possible roost has been reported from Whian Whian
State Forest near the Shire’s western boundary (R. Kooyman, NSW State Forests, unpubl. data). However, there are known roost
sites in adjacent Ballina and Lismore Shires (CSIRO Division of Wildlife and Ecology 1996, H. Parnaby pers. comm.) where many of
the Little Bentwing-bats occurring in Byron Shire may roost.
Some large tracts of habitat are protected in Mt Jerusalem National Park and Inner Pocket and Billinudgel Nature Reserves and
smaller areas in Snow’s Gully, Brunswick Heads, Tyagarah and Broken Heads Nature Reserves. However, even larger areas of suitable
habitat occur on private lands bordering the National Parks, Nature Reserves and State Forests in the Shire’s north-western sector
and in the Goonengerry, Marshalls Ridges, lower Brunswick River, West Brunswick, Tyagarah, Belongil Creek, Skinners Shoot, Tallow
Creek and Broken Head areas. All these areas are likely to provide high quality over-wintering foraging habitat for the species because
of the availability of potential food resources at this time, particularly coastal areas where a sequence of tree and shrub flowering
attracts high densities of flying insects (Gilmore et al. 1986, Milledge 1991). These areas may be important in maintaining the
numbers of colonies breeding in southeastern Queensland, from where local individuals are presumed to disperse (CSIRO Division
of Wildlife and Ecology 1996).
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