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The remarkable “Adaptable Bat”: a challenge to ecological concepts in the management of Australian forest bats

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Abstract

The scientific merit of two opposing themes toward the conservation of Australian forest dwelling microchiroptera over the past four decades is reviewed. The initial theme throughout the 1960's and 1970's was of a vulnerable and threatened bat fauna - a contemporary view for which there is strong evidence. An opposing view, here termed the Adaptable Bat syndrome, emerged in the 1980's. Rather than being of conservation concern, bats were portrayed as resilient, adaptable ecological generalists that could not “reasonably” be considered at risk from human impacts. The Adaptable Bat is an unsophisticated perspective that has been utilised as an ideological counter-attack against societal concern with escalating environmental destruction. This perspective was adopted by some management agencies and many bat workers. It is a modified off-shoot of a more general assertion of the infinite resilience of nature and represents a societal mind set that can be described as the utilitarian ideology, i.e. the dominance of resource utilisation above all other considerations. The chances of the long-term survival of bat fauna in forests used by the logging industry appear to be bleak because the ideology of the Adaptable Bat has dominated the agenda of biological assessments of the management, threat status and general biology of Australian bats for nearly 20 years. Perhaps the most significant lesson from the Adaptable Bat syndrome is that, like many issues in environmental management, the conservation of Australia's forest bats has everything to do with cultural, political and corporate influences, and very little to do with biological “facts”.
Introduction
This chapter examines the attitudes, arguments and
assumptions about the biology, management and
conservation status of the Australian bat fauna held
by many conservation planners, managers, bureaucrats
and industry lobbyists, fauna consultants and some
biologists. Two diametrically opposed general attitudes
toward the conservation management of Australian forest
dwelling microchiroptera are evident over the past four
decades. The dominant theme throughout the 1960s and
1970s was of a vulnerable and threatened bat fauna a
contemporary view for which there is mounting evidence.
An opposing view arose and increased in momentum
throughout the 1980s: rather than being of conservation
concern, most forest dwelling bats were portrayed as
resilient, adaptable generalists that could not “reasonably”
be considered at risk from human impacts. Bats were said
to be opportunistic dietary generalists, habitat generalists
and were claimed to be highly adaptable in their selection
of daytime roost sites. It was asserted that bats, as a group,
were not a threatened component of the forest fauna
and it was claimed that bats were coping well with the
extensive environmental changes arising from European
settlement. This theme dominated a burgeoning new
literature; the “grey” literature of unpublished commercial
environmental impact assessment reports and has become
increasingly prevalent in the scientific literature.
In the remainder of this chapter, the prevalent view of
a generalist and adaptable bat fauna will be referred to
as the “Adaptable Bat” syndrome. We argue that such
an attitude is a syndrome because the main arguments
invoked in support are to an extent inter-linked and
self-reinforcing, and the evidence for each is weak or
non-existent. Though a dominant attitude over the past
15 years, it should be emphasized that an alternative view
has run parallel, that forest bat species as a group are
vulnerable and under threat from factors such as intensive
forestry activities, land clearing and urban expansion.
Much of our assessment of the Adaptable Bat syndrome
is drawn from extensive discussions over the past two
decades with a wide range of bat biologists, land managers,
bureaucrats and industry lobbyists, together with
experience over the past 20 years as fauna consultants
specialising in assessment of environmental impacts upon
bats, primarily in NSW and Victoria.
The focus is largely on south-eastern Australia, as this is
where the majority of debate about the impacts of forestry
and other industries upon the microbat population has
occurred. Only the microchiroptera are discussed, as the
megachiroptera, specifically the flying foxes (Pteropus spp.)
have been subjected to a separate and totally different
set of commercial and cultural pressures (Eby and
The remarkable “Adaptable Bat”: a challenge to
ecological concepts in the management of
Australian forest bats
Harry Parnaby1 and Elery Hamilton-Smith2
1Honorary Research Associate, Mammal Section, Australian Museum, 6 College St., Sydney, 2000
2Chair, IUCN/WCPA Task Force on Cave and Karst Protection; Professor School of Environmental and
Information Sciences, Charles Sturt University, Albury NSW
ABSTRACT
The scientific merit of two opposing themes toward the conservation of Australian forest dwelling
microchiroptera over the past four decades is reviewed. The initial theme throughout the 1960’s
and 1970’s was of a vulnerable and threatened bat fauna – a contemporary view for which there is
strong evidence. An opposing view, here termed the Adaptable Bat syndrome, emerged in the 1980’s.
Rather than being of conservation concern, bats were portrayed as resilient, adaptable ecological
generalists that could not “reasonably” be considered at risk from human impacts. The Adaptable
Bat is an unsophisticated perspective that has been utilised as an ideological counter-attack against
societal concern with escalating environmental destruction. This perspective was adopted by some
management agencies and many bat workers. It is a modified off-shoot of a more general assertion
of the infinite resilience of nature and represents a societal mind set that can be described as the
utilitarian ideology, i.e. the dominance of resource utilisation above all other considerations.
The chances of the long-term survival of bat fauna in forests used by the logging industry appear to be
bleak because the ideology of the Adaptable Bat has dominated the agenda of biological assessments
of the management, threat status and general biology of Australian bats for nearly 20 years. Perhaps
the most significant lesson from the Adaptable Bat syndrome is that, like many issues in environmental
management, the conservation of Australia’s forest bats has everything to do with cultural, political and
corporate influences, and very little to do with biological “facts”.
Key words: Australian forest bats, microchiroptera, management, Adaptable Bat, utilitarian ideology, forest ecology,
timber industry, forestry profession.
Pp 81 - 93 in the Conservation of Australia’s Forest Fauna (second edition) 2004, edited by Daniel Lunney.
Royal Zoological Society of New South Wales, Mosman, NSW, Australia.
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82 Conserving Australia’s Forest Fauna
Lunney 2002). We have not attempted a comprehensive
literature review but have deliberately focused on citing
literature from the 1970s and 1980s where appropriate, to
emphasise that information was often available to enable
the formulation of alternative views to the Adaptable Bat,
had social and political forces been different. In particular,
we refrain from citation of the “grey” literature as this is
generally not open to public scrutiny and would tend to
disguise principles in debate about detail.
The Bionomics of Australian Forest
Bats
It is first necessary to describe some key characteristics of
microchiroptera which shape, or even dictate, the ways
in which bats relate to their environment. Although this
description must be generalised, it must be emphasised
that the microchiroptera as a taxon exhibit remarkable
diversity, much of which still remains to be discovered.
Perhaps the most basic element is that most microchiroptera,
particularly in temperate regions, are not homeothermic,
that is, they lack the physiological controls to maintain a
stable body temperature and metabolic rate. This means
that they must constantly seek out habitats that enable
them to establish their body temperature at the level
required by their metabolic state at various points in their
annual and daily life cycle (Lyman 1970, Hill and Smith
1984: 78-86). The actual physiological patterns and the
strategies utilised vary widely from species to species, and
there is all too little research so that we just do not know
enough to describe the thermoregulatory process in any
Australian temperate zone species. Hence, we do not
understand how and why these bats select their preferred
roosting habitat at specific times of the year.
It has not been possible to identify the types of tree hollows
required by a particular species, how many are used in a
local area, the spatial arrangements of roosting and foraging
areas and how these might vary at different times of the year.
The difficulties of identifying the key resources for mobile
fauna such as bats, presents a major management challenge.
However, it has long been recognised that Australian forest-
dwelling insectivorous bats consist of a diverse assemblage of
species that differ markedly in size and morphology (Wood
Jones 1928; Troughton 1940). There were reasonable
grounds for assuming that species have equally diverse
ecological requirements.
For example, species exhibit a wide range of foraging
strategies as observed in the field (O’Neill and Taylor 1986)
and inferred from predictions based on wing morphology
(Dwyer 1965) and were shown to have equally varied
echolocation call designs (e.g. Woodside and Taylor 1985).
Further, ecological requirements were known to vary in
different parts of a species’ geographic range, during different
seasons, or with changes in climatic conditions, as shown
for the Bent-wing Bat Miniopterus schreibersii in NSW (e.g.
Dwyer 1966). Clearly, there is a reasonable expectation that
different species had specialist requirements, as suggested
by studies of bat community structure in Western Australia
(McKenzie and Rolf 1986). The bat fauna was obviously not
a homogenous group in relation to ecological requirements.
Obviously, flight is a characteristic not shared by other
mammals and provides bats with a remarkable capacity
for mobility. This has often been cited as conferring
advantages over other fauna, as it has the potential to
increase access to dispersed food and roosting resources
(Law 1996; Fenton 1997). Burbidge and McKenzie (1989)
cited these factors in accounting for the lack of extinctions
of Western Australian bats compared to other vertebrates
in that State. Lumsden et al. (1995) considered that
mobility, colonial roosting and interspecific tolerance
were factors that prevented regional extinctions of bats in
a fragmented rural landscape in northern Victoria.
Although mobility has been invoked as a possible
contributing factor to buffer bat species from decline, it
also conveys vulnerability. Foraging areas are likely to be
dispersed and could be in different habitats to day roost
sites. The spatial arrangements of foraging areas and roost
sites are difficult to define and are generally unknown.
Such areas can only be identified with significant research
effort. The viability of roost sites could be jeopardized
if foraging areas within range of roosts are degraded
or destroyed. Movements between roost site and
foraging areas might also be disrupted by destruction or
modification of intervening habitat.
Several studies indicate that vertebrate abundance and
species number are highest in areas of high-quality habitat,
that is, in structurally and floristically complex forest,
often on high-nutrient soils. This has been demonstrated
in south-eastern NSW for arboreal mammals (Braithwaite
1984), ground mammals (Cork and Catling 1996) and
birds (Recher et al. 1991). Recher et al. (1991) described
patterns of distribution of bird species in south-eastern
NSW. They found that in addition to a group of usually
abundant and widely distributed habitat generalists, some
uncommon bird species also occurred in all habitats, but
a preponderance of such species occurred on sites with
the greatest structural and floristic complexity and high
productivity. The limited available evidence suggests that
bat communities might show a similar response to habitat
complexity and forest productivity. Richards (1994) found
relationships between increased bat species number, foliar
potassium content, basal area of understorey vegetation
and number of canopy trees at a range of sites in the forests
of north-east and south-east NSW. However, although
sufficiently detailed studies have not been undertaken to
confirm this pattern for bats, it is anticipated as a general
pattern for the distribution of vertebrates and arthropods
(Recher et al. 1996). The highest number of bat species
often coincides with the most intensive areas of human
settlement, and are also the regions with the most
intensive forestry and agricultural activities, such as the
coastal districts of northern NSW.
Several aspects of bat biology have been identified that
predispose bat populations to being particularly vulnerable
to human-induced or other impacts. Bat populations are
unlikely to recover from rapid population decline as they
generally have low reproductive rates, long generation
times, and high juvenile mortality. Consequently, bat
populations are unable to survive elevated mortality rates
or factors that reduce the size of a population (Hall and
Parnaby and Hamilton-Smith
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Conserving Australia’s Forest Fauna
Woodside 1989; Pierson 1998). Further, insectivorous bats
are vulnerable to pesticide poisoning. The combination of
a high rate of food intake due to relatively high metabolic
rates, comparative longevity, and fat storage for torpor,
makes bats susceptible to accumulation of pesticide
poisons in body fat (Dunsmore et al. 1974).
A further research problem is that we have only recently
started to come to grips with the complex speciation of
bats and to develop an adequate taxonomy. As a simple
example, what was in the 1960s generally considered a single
species, Eptesicus (Vespadelus) pumilus, is now recognised as
comprising at least nine species (Duncan et al. 1999). Many
other genera have similarly been revised, or are in the process
of revision, and further species are regularly added to the
Australian fauna. This means that many historic accounts
can only be considered unclear and so valid comparisons
over time cannot be made, and even in any one study, what
appears as a single species may not have been so.
This means that although there is no evidence of extinction
of bat species on the Australian mainland, it is usually not
acknowledged that there is effectively no information about
the bat species present at the time of European settlement.
There is thus no evidence of species extinctions, because there
is effectively no evidence. Declines of other mammal species
have been documented from specimens collected by early
naturalists, and by assistance from the intimate knowledge
of Aboriginal Australians (e.g. Krefft 1866; Burbidge et al.
1988). In marked contrast, very few specimens of bats
were obtained by early collectors and many Aboriginal
communities did not appear to recognise different species of
bats other than “big batand “little bat” (Tunbridge 1991),
and were not able to provide the same level of assistance in
obtaining bat specimens compared to other mammal species
(Krefft 1866). A further consideration is that many of the
well-documented extinctions or dramatic range contractions
of mammals following European settlement are of species
that are morphologically very distinctive. In marked
contrast, many bat species are superficially similar and
are currently difficult to distinguish morphologically. The
taxonomy of Australian bats is still far from resolved. Under
these circumstances, it is most unlikely that extinctions or
dramatic contractions in geographic range could have been
detected (Parnaby 1991).
The Conservation Tradition and
Australian forest bats
Although there has long been a concern for the
conservation of biota, the contemporary perspective
on biodiversity management has been developed and
formalised at the international level, and in turn by
virtually all governments. In relation to bats, the major
international initiatives have arisen from the Chiroptera
Specialist Group of the IUCN Species Survival
Commission with the extremely proactive support of
the NGO Bat Conservation International. In particular,
identification of threats and development of action plans
including microchiroptera have been developed at the
world and Australian levels (Hutson et al. 2001; Duncan
et al. 1999). Although indeed valuable, the Australian
report has been criticised on the basis that it focuses
on threatened species but gives too little attention to
threatening processes (Lunney et al. 2003). The same
is true of the world document and both are therefore
too broadly generalised to provide much of value to our
understandings of threatening processes.
Initial concern for bat conservation in Australia centred
on a small number of cave dwelling species, which were
the only microchiropteran species that had been studied.
The vulnerability of the cave-dwelling species to human
disturbance from visitation, or destruction or modification
of cave roosts had been clearly demonstrated during the
1960s and 1970s for all of the limited number of species
that had been studied. The vulnerability of subterranean
roosting bats to disturbance at roost sites has long been
recognised (Dwyer 1963; Hamilton-Smith 1968). Large
numbers of individuals can be concentrated at relatively
few roosting sites, and in some cases a significant proportion
of a regional population can be concentrated in one cave
roost (Dwyer 1966). Disturbance or destruction of such
sites can have a major impact on an entire population.
Subterranean roosting species are especially vulnerable
to disturbance of maternity colonies during spring and
summer, or when dependent young have not yet learned
to fly, and during winter when bats are torpid (Hamilton-
Smith 1974; CLMC 1992). Further, it is thought that
only a limited number of caves are suitable as roost sites,
and their destruction or modification could be highly
detrimental to the survival of regional populations.
One of the major lessons of the research on these bats
was that a detailed knowledge of the physiology and
consequent environmental relationships of each species
is vital to the development of effective survival planning.
Another was the fundamental importance of microclimatic
and microhabitat analysis in the development of such
plans. Regrettably, this has not been properly recognised
in most studies of forest bats.
Bats are a vulnerable and threatened group of forest
fauna. The most relevant broad threats to forest-dwelling
species are habitat destruction and modification and
poisoning from accumulation of pesticides in body tissues.
Other issues identified include a lack of public education
(e.g. Woodside 1990), and the very serious lack of
biological information (Richards and Hall 1998) including
taxonomic uncertainty (Parnaby 1991).
It has also been acknowledged for more than 30 years that
forestry activities pose a significant threat to bat populations
(e.g. Cowley 1971; Routley and Routley 1975; Hamilton-
Smith 1980; Law 1996; Recher 1996; Richards and Hall
1998). More recently, several authors consider that regional
extinctions of hollow-dependent fauna such as bats are
likely to result from forestry disturbances (Lunney and
Barker 1986; Lunney et al. 1988; Norton and Kirkpatrick
1995; Recher 1996). Bats are likely to either rely on old-
growth forest or have populations that are centred on forest
with old-growth attributes (Scotts 1991; Recher 1996). It is
also likely that old-growth forest elements such as hollows
in old trees, and arthropod food resources from invertebrate
communities associated with old-growth attributes, such as
large logs and large trees (Recher et al. 1996), will prove to
be critical for some bat species.
Adaptable bat
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84 Conserving Australia’s Forest Fauna
A reliance on old growth elements renders bats vulnerable
because of the long lead times – at least several centuries
– required for formation of critical old growth resources, and
the fact that old growth elements are being rapidly destroyed
over most of the Continent. The long time horizons
spanning hundreds of years required for regeneration of
critical resources for bats means that from a management
perspective, such resources are effectively finite in terms of
the short logging rotations and working life of managers. For
example, the formation of both large hollows (Mackowski
1984) and well-developed understorey plants (Mueck et al.
1996) can take hundreds of years and the replacement of
decayed logs on the forest floor can take over 1500 years
(Recher 1996). Recovery of the full range of structural
diversity, and therefore the full range of potential foraging
substrates for bats, of clear-felled sites of old-growth forest
would take 1500 to 2500 years, that is, several generations
of the overstorey trees (Norton and May 1994).
The combined impacts of forestry operations is reduction
of quantity, availability and suitability of foraging habitat,
food resources and roosting resources for fauna, such
as most bat species, that are dependent on old-growth
attributes (Lunney et al. 1988; Kirkpatrick et al. 1990;
Scotts 1991; Norton and Kirkpatrick 1995; Recher 1996).
This arises from the modification of forest by simplifying
forest structural and floristic complexity (RAC 1992;
Mueck and Peacock 1992; Recher 1996), disruption of
ecosystem processes (Norton and Kirkpatrick 1995), and
adverse effects arising from the fragmentation of forest
landscapes (Recher and Lim 1990).
Further dimensions of the problem arise from studies
suggesting that hollow-utilising bat species are likely to
require multiple roost trees in close proximity and are
known to frequently change roost sites between different
trees (e.g. Lunney et al. 1988; Lumsden et al. 1994; Lumsden
and Bennett 2000). This is a common characteristic of the
hollow-utilising bat fauna in other continents (Lewis 1995),
and appears to be essential as a means of predator avoidance,
for reduction of parasite loads, and as a response to altered
social or climatic conditions (Lewis 1995). It is also likely
to reflect the continuing search for the right microclimatic
conditions at specific times. Radiotracking studies have
found that individuals often change roost sites, daily or
every few days, and it has been suggested that an individual
is likely to show fidelity to an area containing a number of
alternative roost trees, rather than to a single roost site.
These conclusions have been reached by Lunney et al. (1988)
for Gould’s Long-eared Bat Nyctophilus gouldi in forest on the
south coast of NSW; Taylor and Savva (1988) for four species
in forest in Tasmania; Lunney et al. (1995) for the Northern
Long-eared Bat Nyctophilus bifax in littoral rainforest in
northern NSW; and by Lumsden et al. (1994) for the Lesser
Long-eared Bat Nyctophilus geoffroyi and Gould’s Wattled Bat
Chalinolobus gouldii in northern Victoria.
Alternate roost sites used on consecutive nights are
typically within a few hundred metres of one another.
Taylor and Savva (1988) found that distances between
roosts used over a period of several days by four Tasmanian
species averaged about 500 m and ranged from 80m to
1.4km for 10 roost sites. The majority of movements
reported for Gould’s Long-eared Bat by Lunney et al.
(1988) were less than about 500 m for both males and
females. Lumsden et al. (1994) found that, for both the
Lesser Long-eared Bat and Gould’s Wattled Bat, about
70% of all roost relocations were within 300 m of the
initial roost and, for both species, a significant proportion
of movements were less than 100 m. Consequently,
removal of hollow-bearing trees could have a dramatic
impact on local populations, even if the hollows destroyed
were not in use at the time of felling.
Radiotracking studies have found that roost hollows are
preferentially selected in the largest available trees by
all species which have been studied, e.g. Goulds Long-
eared Bat (Lunney et al. 1988), Chocolate Wattled Bat
Chalinolobus morio (Lunney et al. 1985), Goulds Wattled
Bat and the Lesser Long-eared Bat (Lumsden et al. 1994)
and the Forest Bat Vespadelus pumilus (Law and Anderson
2000). Significantly, all species have wide distributions,
are regarded as common, have been presumed to be
ecological generalists and would not be considered as
threatened even though large, hollow-bearing trees
are a threatened resource throughout most Australian
landscapes. These species have not been cited as being
of “conservation concern and even include species that
have been considered to be of least conservation concern
(e.g. the Lesser Long-eared Bat), yet all are clearly
vulnerable to decline or elimination of roost sites.
Although the foraging ecology of Australian forest bat
species is poorly known, an indication of the likely
complexity of foraging patterns and requirements of
species can be gauged from detailed studies of northern
hemisphere temperate zone insectivorous bat species.
It has been suggested (e.g. Kunz 1974) that bats could
adjust their nightly foraging distances from the roost of
large colonies to reduce competition for food resources
via greater dispersal of individuals than occurs in smaller
colonies. Kunz (loc. cit.) suggested that adult females
foraging further from maternity roosts during the period
when young begin to fly could also reduce competition.
Adams (1995) demonstrated that adult Little Brown Bats
Myotis lucifugus shifted foraging activity from less cluttered
microhabitats when young to more cluttered microhabitats
when they became old enough to undertake foraging
flights. Racey and Swift (1985) found that the foraging
ability and feeding efficiency of newly volant young is
significantly less than that of adults. Young initially foraged
within 100m of the roost, and progressively increased
foraging distance and foraging time, which reached
distances of adults (about 5km) after about two weeks
(Racey and Swift 1985). Other mechanisms that would
reduce intraspecific competition for food resources include
dispersal of individuals to numerous smaller colonies
during seasons of reduced insect availability (Kunz 1974).
This has been documented for the Large Bentwing Bat in
NSW (Dwyer 1966). The increased energy demands on
adult females throughout pregnancy and lactation can
decrease foraging distances from the roost (e.g. Racey and
Swift 1985). Daily energy requirements for females at peak
lactation have been estimated to be double that of early
lactation for some species (Kurta et al. 1989). Foraging time
Parnaby and Hamilton-Smith
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Conserving Australia’s Forest Fauna
has been observed to decrease during late pregnancy, when
the increased body weight of gravid females is thought to
constrain flying ability and the energetic rewards of feeding
(Kurta et al. 1989). Adam et al. (1994) found that foraging
distances of the endangered Virginia Big-eared Bat Plecotus
townsendii were most restricted during pregnancy, and the
maximum distance observed of females from the maternity
roost was about half that of males (3.6km compared to
maximum male distance of 8.4km).
Although some genera (e.g., Miniopterus, Tadarida) appear
to cover a much larger foraging range, the evidence
cited immediately above suggests that many of the
vespertilionid bats of our temperate forests may well need
to find the necessary food within a relatively small radius
from their roost.
Introducing the Adaptable Bat
concept
The belief that our forest bats, as a group, are an adaptable,
resilient component of the mammal fauna gathered
momentum throughout the 1980s, despite mounting
scientific evidence to the contrary. In particular, there was
a growing conviction that as a whole, the bat fauna could
not seriously be considered to be threatened and that there
were very few, if any, threatened bat species in south-eastern
Australia. We suggest that the rise of the Adaptable Bat
parallels the emergence of forest bat conservation as an
issue of public concern around the mid 1980s, by which
time it had to be addressed by forest managers, e.g. the Eden
EIS prepared for the Forestry Commission of NSW (Smith
1986). The Adaptable Bat gained substantial impetus in
NSW following the Endangered Fauna (Interim Protection)
Act, 1991. In 1992, nearly half of the State’s bat fauna
was listed as threatened, and bats comprised about one
tenth of all extant vertebrate species listed as threatened
in NSW (Lunney et al. 2000). The Act, and its successor,
the Threatened Species Conservation Act 1995 (TSC Act),
which incorporated the listing of threatened species made
in 1992 into its schedules of Endangered and Vulnerable
species, imposed a legal requirement to evaluate impacts of
a wide range of development proposals on threatened bats.
This brought bats into the direct focus of a range of industry
groups additional to the logging industry, particularly
coastal housing construction, rural land clearing, highway
construction and mining operations along with a host of
minor industries.
The fact that a wide range of bat specialists contributed
to the species assessment process for the Act and that a
large proportion of bat species were considered at risk is
a clear statement that the bat fauna was considered to be
far from resilient and adaptable. Vested financial interests
in tandem with those who were ideologically opposed to
“environmentalism” mounted a major counter-offensive
against the view that much of our fauna, including bats,
were threatened by human activities. In this respect,
the “Common” Bentwing Bat came in for special
attention from fauna consultants in NSW (Parnaby
1996). A mythology arose that had the effect of trying to
marginalise concern about its conservation by claiming
that it was abundant, had a distribution that spanned half
the globe from Australia to Europe, was found in urban
Sydney, and had no special requirements for protection of
foraging habitat. Although the scientific literature clearly
demonstrated the vulnerability of this species, it was used
as a lever in an attempt to discredit the entire species
threat assessment process undertaken for the TSC Act.
The general arguments used in support of the Adaptable
Bat, are outlined below and are discussed in detail in later
sections. One argument is that no bat species is known
to have become extinct since European settlement.
The implication, usually not stated, is that if bats have
escaped the levels of extinction documented for others
mammal groups such as rodents, bandicoots and small
macropods, then they are over the “extinction hurdle”
and are therefore somehow secure. Further implicit in
this argument is the misconception that the worst threats
from European settlement occurred early in the history
of settlement, and that if the bat fauna is secure now, it
must somehow be secure into the future! But as has been
already demonstrated, we just do not know how many
species really existed in the past.
It is often claimed that bats are highly adaptable in
selection of daytime roost sites and did not have specific
roost requirements because of the diverse array of daytime
roost sites in which individuals of a species were found,
which often included buildings. For example, in relation
to roost site selection:
“Bats are generally quite adaptable when looking for a
place to roost and they are found in a large variety of
situations including caves, tree hollows, under bark,
buildings, old mine shafts, and bird’s nests. (DCFL
1988, pg 33)
“The majority of the remaining microchiropteran
bat species recorded in the TMA [Tenterfield
Management Area] are considered generally to rely
on tree-hollows for roost sites, although many species
also shelter under exfoliating bark, or in a variety of
sites, including buildings, rock crevices, Sugar Glider
nests, birds nests, and “the exhaust pipe of a tractor”
(Chalinolobus gouldii Dixon 1989). Thus, for several
species, roost site choice appears to be opportunistic,
and timber harvesting may not be of particular
consequence.” (Fanning 1995, p 86)
Most south-eastern Australian species have been found
in a wide range of vegetation types, which has been
interpreted as proof that nearly all are habitat “generalists”,
i.e. they do not have specific habitat requirements. This
view is articulated by Richards (1995, pg. 40):
“In general the bat fauna could be grouped into
species that were generalists and found in many
habitats, or specialists that were restricted to just a
few. This is a pattern that is expected throughout
south-eastern Australia....
Bat species were viewed as opportunistic dietary
generalists, i.e., with very few exceptions species were not
considered to have specific dietary requirements. This
view prevailed, despite the lack of properly designed and
sufficiently detailed dietary studies for any species that
would enable dietary specialisation to be detected.
Adaptable bat
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86 Conserving Australia’s Forest Fauna
Assessing and Comparing the
Adaptable Bat concept
Despite the high level of uncertainly associated with the lack
of key ecological data required for effective management of
each bat species, the Adaptable Bat concept, if accepted,
has very specific management implications. If it is accepted
that bats are adaptable generalists, it follows that no specific
management actions are required, beyond retention of
a few hollow bearing trees and riparian habitat belts,
both of which will already be required either for erosion
control or arboreal birds or mammals. For example, if
bats are adaptable, opportunistic feeders, they will prey
on pretty well any insects that are available and protective
measures for feeding resources are not required. Thus,
fauna prescriptions for logging publicly owned native
forest in NSW contain no specific measures for protection
of foraging resources for bats, with the exception of very
limited areas for the Large-footed Myotis Myotis macropus
and Golden-tipped Bat Kerivoula papuensis (see logging
prescriptions for NSW public forest areas in Forestry and
National Park Act 1998 Annexure B). If bats are habitat
generalists, high quality habitat can be destroyed, and bats
are expected to be able to survive quite well on adjacent
low quality habitat. Logging prescriptions have generally
not addressed the needs of virtually the entire bat fauna,
both in NSW and elsewhere in Australia.
If the adaptable bat concept were proven accurate, it would
mean that there was little or no conservation issue and the
widespread concern about future prospects for the Australian
bat fauna would be unwarranted. On the other hand, if it is
incorrect, then it may in the long run prove to have been
a very costly error. So, each of the major expressions of
adaptability will now be analysed and evaluated.
Habitat Selection and Adaptability
Despite the claims for the adaptable bat, there is currently
no evidence that bats are habitat generalists. The wide
range of vegetation types in which many bat species
have been recorded (see the species accounts of Strahan
1983; 1995) is cited to support the view that many, and
perhaps the majority, of species are therefore habitat
generalists. There are many flaws in this argument, a
fundamental one being that such categories, whether
rigorously defined botanically or not, are more correctly
termed biotopes and there is no particular reason why
bat species will necessarily respond to this demarcation
The Political Economy of the Adaptable Bat
The extent to which the adaptable bat concept is clearly an advantageous one, at least in the short and
mid term, to the forest industry (and some others) needs at least some assessment here in helping
us to understand how the concept has evolved.
Current environmental policies demand that those seeking to undertake major industrial, resource
harvesting, construction or other major projects must undertake and make available to scrutiny an
‘independent’ environmental impact assessment. This sets up a process where scientists are expected
to provide ‘answers’ to any questions about the environmental impact of the project concerned. This
is indeed a problematic policy. First, the emphasis is upon ‘answers’ rather than defining the many
questions that demand continuing inquiry throughout the life of the project (cf. Feinsinger 2001).
More importantly, the scientists are engaged and paid (often as little as possible) by the proponents of
the development, and this inevitably generates a working relationship within which the scientists feel
an obligation to the proponent. This means that they might do what they can to satisfy the proponent,
but there are even more subtle effects. They certainly try to avoid being the messenger bearing bad
news, because although such messengers are not shot, they might face a significant threat of failing to
gain further contracts. Moreover, they are aware that their assessment must be supported by strongly
developed, even incontrovertible, evidence.
In the case of bats, there is generally little research evidence to provide such an assessment of any
one bat species in any one specific part of its range. So, they might say there is no evidence, they might
manage to even avoid the bat question, or they might resort to the adaptable bat.
This has happened widely enough that, as pointed out elsewhere in this chapter, it has acquired a
hegemonic authority, that is, it has become a dominant set of beliefs and practices that is widely
agreed and even has the appearance of common-sense reality (Williams 1983). It is not a deliberate
conspiracy, but arises out of a complex intellectual process, aspects of which have been briefly
summarized above as they have related to this concept.
Another dimension of the problem is the ‘economic fundamentalism’ of modern developed nations,
which is particularly marked in Australia, and leads politicians (and the administration) to be unwilling
to accept barriers to economic growth and development. Thus, even many of those employed in
agencies that operate on a mandate of environmental and biodiversity protection fail to challenge the
‘adaptable bat’ (or similar heresies).
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of the environment. Bats need a specific diversity of
microhabitats to meet their physiological needs, and
broad range biotopic classifications provide no relevant
information on this question.
Dietary Requirements and Adaptability
Claims that most species are “dietary generalists”,
“generalist feeders” or feed opportunistically” are
an important part of the concept of the Adaptable
Bat. In the management context, these claims have
an unequivocal meaning: it is implied that they
will eat pretty well anything on offer, and so no
specific conservation measures are required to protect
food resources.
The issue of diet specificity might appear to be
straightforward, but in fact this is a confused and
complex issue. The issue is confused because these terms,
while appearing self evident, are actually vague and open
ended. The clear implication is that such species do not
have a selective (i.e. specialist) diet. However, a species
can be a dietary specialist, yet feed opportunistically. For
example, a species could be a beetle specialist, meaning
that it preferentially feeds on beetles, even though other
insect orders might be more readily available in its foraging
areas, yet will opportunistically feed on whatever family
of beetles are encountered. Alternatively, a species could
feed selectively on a particular size range of insects but
take a wide range of insect orders in proportion to their
availability. Such a species has a selective (specialist) diet
on the basis of prey size, but is opportunistic in terms
of insect taxa eaten. In a broad sense, a species can be
said to be a selective feeder if it preferentially takes prey
items in a different proportion to what is available – if
the taxa in the diet occur in the same proportion as the
food available, it is not a selective feeder.
The usual basis of the claim of opportunistic dietary
generalist is that Australian dietary studies, limited
though they are, have found a wide range of invertebrate
orders in the stomachs or faeces. The classic study of
Vestjens and Hall (1977) has been widely cited in such
a context. They studied stomach contents of museum
preserved specimens and found that a range of insect
taxa were present in most of the species studied. The
problem here is that the very research design is generalist
and so will inevitably produce a generalist result.
Hall and Woodside (1989: 878) summarise the prevalent
view that insectivorous bats have a generalist diet.
Referring to overseas studies they state:
“Many bats specialize in certain prey taxa (Ross
1967; Black 1974; Belwood and Fenton 1976;
Belwood and Fullard 1984) or prey size (Belwood
and Fullard 1984), while other bats (or the same
bats at other times) are opportunistic (Fenton and
Morris 1976; Anthony and Kunz 1977; Bell 1980). In
Australia, there are very few specialist feeders among
the vespertilionids. Robson (1984) showed that
Myotis adversus tends toward a fish eating diet and
D.P. Woodside, K.J. Hews-Taylor and S.K. Churchill
(unpublished observations) note that Kerivoula
papuensis specializes in orb-weaving spiders.”
In our view Hall and Woodside accurately reflect the
dominant view of that time. The concept that Australian
bats were predominantly dietary generalists is all the more
remarkable given the fact that, not only were the dietary
requirements of virtually all Australian microchiroptera
unknown, but that it was acknowledged that dietary
selectivity could occur not only from specialization on
invertebrate taxa, but also on prey size. Despite this, the
only test of specialization that is applied is the restricted
test of specialization based on prey taxa.
The classic study of O’Neill and Taylor (1989), probably
the most detailed yet on the diet of Australian bat
assemblages, has evidently been widely interpreted as
support that most forest bat species are likely to be
opportunistic generalists, largely because these are the
claims made by those authors. However, their study
actually provides evidence that 3 of the 8 species studied
were dietary specialists in terms of preferentially selecting
insect orders. Further, they provide evidence that most
of the 8 species preferentially selected prey species on
the basis of size – larger bats selected larger sized prey.
The pattern of selectivity of prey size was even more
specific – a given sized bat species preferentially selected
smaller sized beetles than moths. Their paper illustrates
the confusion and contradictory evidence that typified
discussions of dietary selectivity.
A current Asian research study measures the percentage
of recorded occurrences and of volume in stomach
contents for each of the relevant taxonomic orders. This
has again demonstrated that most species are either
specialists in beetles and some other chitinous insects (e.g.,
cockroaches) or in moths and other soft-bodied species.
Further, the extent to which a bat falls into either of these
categories is clearly related to patterns of dentition and this
in turn sets constraints upon prey size. The major surprise
of the study was the discovery of a vespertilionid bat which
is predominantly vegetarian and feeds almost exclusively
on a single plant species – a classic demonstration of
the dangers of generalized assumptions and of dietary
specialization (Wai Wai Myint, in progress).
Roost Selection and Adaptability
The most important argument to support the claim that
bats are very versatile in roost selection and have generalist
roost requirements is the wide range of situations used as
daytime roost sites by individuals of a particular species.
Observations which are inferred or stated as indicative of
bats having adaptable roost requirements include the range
of roost situations reported for individuals of a particular
species, e.g. under loose bark, in buildings, under bridges,
under stones. The premise of underlying adaptability is
seriously flawed partly because it is based on a perception
of roost utilisation which does not acknowledge the
complexities of the situation, and also because the context
of the observations is not fully considered.
Roost requirements of many species are known to differ
among the sex and age classes, and to vary according to
different physiological demands induced by reproductive
condition, seasonal climatic differences and different
weather conditions, all underlain by the problems of body
Adaptable bat
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88 Conserving Australia’s Forest Fauna
temperature regulation. This is illustrated by Lumsden
et al. (1994) for the Lesser Long-eared Bat, a common
species previously thought to be highly adaptable (e.g.
Maddock 1983). They found that although some
individuals, particularly males, roost in a range of relatively
unprotected sites such as in fence posts, buildings and
under slabs of bark in disturbed agricultural areas, all
maternity roosts were located in cavities in the largest
available trees in forest areas.
Further, because we are dealing with the widespread
problem of body temperature through one strategy or
another, it is instructive to make a comparison from the
intensive ecological studies on cave-dwelling bats. Bats
not only select very different caves at different seasons and
differing physiological conditions, but they select an even
wider diversity of specific roost sites within any one cave.
Major Environmental Change and
Adaptability
The presence of bat species in highly modified landscapes
is often invoked as proof, or at least a strong indication,
that bats must have adapted well to the large scale changes
that followed European settlement. The three types of
landscape typically discussed are landscapes degraded by
agriculture, logged public forests, and urban areas.
Some bat species still persist in highly modified landscapes,
where 70% or more of the native vegetation has been
destroyed by agriculture. This has been interpreted as
evidence that bat species have adapted to such changes
but perhaps more relevant, implicit in such claims is
the assumption that, to all intents and purposes, these
species will remain a permanent part of these landscapes
and are over any “extinction hurdle”. These claims are
premature. Populations might currently be stable, yet
unlike populations in a less disturbed environment, be
unable to sustain foraging activity during the increased
pressures resulting from environmental changes, such as
climatic extremes, perhaps in combination with other
factors such as fire and drought. Such extremes might
occur only over a time scale of decades or centuries and
would not be detected by short-term research programs,
even if they were to be implemented, that rarely exceed a
few years’ duration.
A wide range of bat species have been reported roosting
in buildings in Australian urban areas, and this includes
maternity colonies of some species, e.g. Goulds Wattled
Bat in Melbourne (Dixon and Huxley 1989). The fact that
bats roost in buildings in urban landscapes is often cited
as the ultimate proof of the adaptability of the bat fauna.
These claims and assumptions are unjustified because
they have been made in a near vacuum of understanding
about the ecological nature of urban occupation by bats,
and because they are an oversimplification as the context
of such occupation is unknown for most species.
For example, the presence of colonies of the Large Bentwing
Bat in buildings in urban Sydney has often been invoked to
discredit the perceived vulnerability of this species. However,
a recent assessment of this species (Hoye and Spence 2003)
supports the need for caution in interpreting the presence
of such species in urban environments. They conclude that
the species appears to have significantly declined and the
pattern of roost utilisation has altered over the past two
decades. Whereas year-round occupation was documented
in the past, the species is now evidently absent over the
summer months. Maximum colony numbers 20 years ago
are double the maximum now recorded. Although the
exact cause of decline is unknown they found that winter
mortality rates from collisions with vehicles is thought to
place significant pressure on urban bats, in contrast to bats
sampled in rural areas.
A related issue that has added to the perception that bats
are highly adaptable is the presence of a diverse urban bat
fauna in Europe, which not only has a long history of close
human settlement and highly modified landscapes but many
bat species appear to be largely reliant on human structures
(including buildings) for daytime roosts (Stebbings 1988).
However, the progressive renovation of old buildings and
construction of modern buildings has often resulted in
‘bat-proofing’, and there has been a drastic decline in many
of these populations (Stebbings 1988, Hutson et al. 2001).
For a similar reason, combining both renovation and the
fact that most building stock is relatively recent, Australia
has never had a large number of urban bat colonies. In
many recent European studies, urbanization is recognized
as a threat to the survival of bat species (e.g. Yalden and
Morris 1975; Roer 1980), as is the destruction of “natural”
landscapes and habitat (Schober and Grimmberger 1993).
Clearly, there are serious difficulties with asserting that
bats are highly adaptable simply because of the presence of
some species in urban areas. It is certainly true that some
buildings may provide very appropriate microhabitats for
some bats, but this is really of very limited value at the
species population level. One cannot cite the occasional
use of an urban habitat as any evidence of adaptability,
especially when one sees how any one bat species only
selects a very specific habitat, e.g., the preference of
Tadarida to roost against sun-heated metal.
Finally, let us consider the impacts of timber harvesting,
particularly contemporary clear-felling. The persistence
of bat species in forest areas which have a long history
of logging is often either implied or invoked as proof
that such species are not adversely impacted by logging
operations or, alternatively, as proof that they can survive
current logging regimes. Further, it is often inferred that
such species will be able to survive in logged forest in
perpetuity. These claims are flawed for many reasons.
Such claims are generally based either on animals
captured in bat traps, or recordings of echolocation calls,
neither of which provide information about the activity of
the bats during capture or recording, nor about the extent
of survival. Obviously, the significance of records of a
species from sites in logged forest cannot be interpreted
without a detailed knowledge of the ecology of the species
involved, and at the very least, on being able to determine
the activity of the individuals in logged forest. These
arguments also ignore the dynamic and highly complex
long-term changes induced in forest ecosystems by human
activities, many of which will not become apparent for
decades or centuries.
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Summarising the Adaptable Bat
The Adaptable Bat, though breathtakingly vacuous,
has been a truly adaptable, resilient and successful
piece of propaganda and it is informative to examine
its construction. The usual claims cited to justify the
assertion of adaptability dietary, habitat and roost
generalists- have several important characters in common.
The simplicity of each claim belies a much more complex
situation, an appreciation of which reveals that each claim
is quite misleading. The “evidencecited in support has
considerable logical appeal and the whole matter appears
to be self-evidently true. In fact, the appeal to common-
sense is a normal element of intellectual hegemony, even
though common-sense is well-known to be anti-scientific.
Each claim appears to be clear-cut but in fact is based
on a concept that is vague and open-ended or even
demonstrably false. Thus the Adaptable Bat relies on
coarse and biologically inappropriate interpretation of key
terms, e.g. to qualify as a habitat specialist, a species is only
to be found in one or two “habitats” and habitat is defined
in terms of a broad vegetation type.
The arguments reviewed above either do not support
the perception of the Adaptable Bat, are too limited to
shed any light either way, or contradict it. Thus, there is
little or no support for the view that bats are adaptable
and are not an extinction prone group, nor is there any
convincing evidence that they are therefore not likely to
be adversely impacted by the massive inroads of modern
civilisation. In particular, there certainly does not seem to
be any convincing scientific basis for adopting this as the
default view, let alone allowing it to be a continuing, and
often dominant, hegemony.
Nevertheless, one of the more powerful dynamics in
the manufacture of the Adaptable Bat syndrome is not
reflected in the written word but in the strong psychological
impact of constant aggressive assertions of adaptability
during meetings, workshops and conversations between
bat consultants and government and industry operatives.
During such interactions, the non-compliant consultant,
or the misguided bat specialist, is left with absolutely
no doubt about what is considered to be acceptable,
balanced and reasonable – and this just happens to be the
Adaptable Bat! Consequently, if you advance a contrary
view to the Adaptable Bat syndrome, you are seen as being
unreasonable, unrealistic, extreme, and generally unsuitable
you will not be asked back! If you persist in your point
of view throughout the meeting, you are seen as being
unnecessarily negative and disruptive, and a general irritant.
Such people are likely to be abruptly reprimanded with the
self-righteous impatience of those who know better.
Consultants and bat specialists alike quickly develop
an intuitive understanding about the boundaries of
“acceptable” ideas – and this is not likely to include
anything that will be unacceptable to powerful vested
financial interests. This does not imply that bat specialists
and consultants are necessarily prostituting themselves,
as the limits of respectable thought are probably largely
unconsciously absorbed. We suggest that an additional
important dynamic is the general lack of assertiveness,
or confidence that we have witnessed in many specialist
participants in land management procedures. Some
specialists feel that they have no right to hinder
economically important projects, on the grounds of
adverse impacts on bat species. It’s as though they feel
that they have not been sanctioned by society to present
their real perspective of likely impacts, but rather, must go
through a more limited charade. Too often, we have been
involved in impact assessment procedures where the idea
that the proposeddevelopment should not go ahead,
isn’t even on the agenda.
A central issue is the dominance of the utilitarian ideology
in the subculture of several key professions, industries and
government agencies involved with resource management.
For example, the Australian forestry profession continues
to be criticised for failing to adequately embrace changing
community values in regard to non-timber values of
public forests, for example, by treating fauna conservation
as a constraint on wood production (Routley and
Routley 1975; French 1983; Shaw 1983; Recher 1986;
Lindenmayer and Franklin 1997).
On reviewing the core research strategies, the essential
concepts were well in place in the Australian and overseas
literature on temperate zone insectivorous bats by the mid
1980s that would have enabled the formulation of robust
alternatives to the Adaptable Bat. In particular, the view
that hollow-utilising forest bats were a vulnerable group that
could be expected to have specific ecological requirements
and that faced impending threats from habitat destruction
and modification was certainly a view expressed at the time,
e.g. ABRG (1985) and Ahern (1982).
Specifically, the potential threat from loss of roost sites in
hollows in old trees should have been apparent. The logic
behind the idea that a hollow-utilising species such as the
Lesser Long-eared Bat could be regarded as an adaptable
generalist that does not have specific roost requirements
simply because individuals have been found in a diverse
range of daytime roost sites has always evaded us. A tree
hollow has a microclimate, as does a cave, and it is a
simple step from the demonstrated specific microclimate
required for maternity colonies demonstrated for cave
roosting species, to a scenario of specific requirements
for say, a maternity colony in a tree hollow. Consequently,
that a hollow-roosting species might have specific hollow
requirements, at least at some stage in the reproductive
cycle, would hardly have been a novel concept. Tree
hollow microclimate in eucalypts was examined by Calder
(Calder et. al. 1983). The long time periods required for the
formation of hollows in eucalypts and the severe problems
resulting from hollow loss from logging operations was
demonstrated by Mackowski (1984) and identified
specifically in relation to bats by Cowley (1971).
In relation to diet, perhaps Australian workers were
unduly influenced by the idea that insectivorous bats were
opportunistic generalists (e.g. the review of Fenton 1982).
However, the concept that Australian insectivorous bats
potentially include a range of species that were dietary
specialists, species that were generalists and species that
were opportunistic generalists but were dietary specialists
during some seasons had a reasonable foundation:
diet was poorly known for virtually all species, and the
Adaptable bat
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90 Conserving Australia’s Forest Fauna
overseas literature clearly indicated that this issue was
unresolved. At the very least, one would have thought
that a more appropriate Australian response would have
been to consider the issue as unresolved.
It is significant that the legacy of a vulnerable and potentially
threatened bat fauna that dominated the views of Australian
cave bat workers in the 1960s and 1970s did not appear to
transfer to hollow-utilising bats as a dominant view during
the 1980s, despite the increasing environmental concerns
being expressed by the broader community. Perhaps it did
transfer initially, but was remolded by a broader counter-
attack against environmental concerns and the resulting
demands for “precautionary use”. Perhaps people were
influenced by the Big Country Mystic: for example, even
if old trees with hollows were being rapidly eliminated over
large areas, both from rural die-back, land clearing and
intensive forestry, there was probably a view that there were
plenty more “elsewhere” in this vast country, despite the fact
that only some 5% of the Australian land mass is forested.
Whatever the reasons, by the close of the 1990s, the
Adaptable Bat was still very much alive, was creeping into
the scientific literature, especially from authors employed by
publicly funded forestry authorities, and continues to distort
public debate about bat conservation and management.
Even more pervasively, it distorts research strategies and
methodology. Many of the claims invoked to support
the Adaptable Bat can be found in the environmental
assessment literature, appropriately modified for other
fauna groups.
It could even be argued that the Australian Federal
Government’s Bat Action Plan (Duncan et al. 1999) is also
the result of similar pressures, given the small proportion of
species listed as threatened compared with a much higher
proportion of the fauna that might be expected given a
less politically influenced assessment process. A panel of
bat experts convened by Environment Australia settled on
a threatened status for 18 Australian bat species (Parnaby
2000). The final list determined by a sub-committee was 9
species. A cynic could match an industry pressure group for
each species dropped from the initial 18, e.g. the Ghost Bat
Macroderma gigas and Orange Horseshoe Bat Rhinonicteris
aurantius with the mining industry that was reworking old
adits across northern Australia; the Western Falsistrelle
Falsisrellus mackenziei with the politically sensitive logging
industry in Western Australia; the Spectacled Flying Fox
Pteropus conspicillatus with North Queensland orchardists
and perhaps the Eastern Little Mastiff-bat Mormopterus
norfolkensis with coastal urban expansion in NSW. A
conspicuous example is the extraordinary omission of
the Ghost Bat, recognised as vulnerable for nearly four
decades, and the nonsensical reasons given to justify its
demotion from the threatened fauna list. Of course, there
may have been other motivations, for example, a desire
to ensure that the lists of Federally recognised threatened
species were kept low, e.g., not higher than about 10% of
the relevant faunal group.
This chapter has been considerably reduced from a
previous and fully documented draft out of some sympathy
for the reader. But the evidence for our arguments in this
paper is overwhelming. If we are to achieve adequate
conservation strategies and programs, and to genuinely
meet our obligations under such international agreements
as the 1992 Convention on Biological Diversity, then
we must develop a much more rigorous and searching
approach to the problem.
Acknowledgements
The formative stages of this chapter were enhanced
by valued discussions of a range of issues with Alex
(Sandy) Gilmore, Chris Corben, Dan Lunney,
Glenn Hoye, Dave Milledge and Les Hall and with
many other Australian bat workers over the past
few decades.
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... A central theme to emerge from our assessment is the need for a re-appraisal of the management of bats of the Pilliga forests, a point that also applies to all the hollow-dependent fauna of inland hardwood forests and woodlands. In our opinion, attitudes toward the four broad issues discussed in this paper have largely reflected cultural, political and corporate influences (see Parnaby and Smith 2004). Our aim in this paper was to emphasis the need for a re-evaluation of the ecological basis for the management of bats, as well as the trees upon which they depend. ...
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Four issues influencing the management of hollow-dependent bats are examined for the Pilliga forests of inland NSW. These are: I) the longevity of eucalypts and implications for the strategies for retaining hollow trees; 2) the condition of the forests and woodlands of the Pilliga at the time of European settlement, focusing on densities of hollow trees; 3) the impact of fire and climate change on loss of tree hollows; and 4) the implications of recent ecological research on perceptions of the vulnerability of hollow-using bats. We argue the need for an urgent reevaluation of these issues. Average tree longevity is likely to be much greater than previously acknowledged, the pre-European Pilliga was a forest with hollow-bearing tree densities approximating those of coastal and montane forests, rather than being an open woodland; and fire will significantly reduce the numbers of hollow trees. Consequently, hollow-using bats in the Pilliga are more vulnerable than previously realised, and densities of hollow-bearing trees need to be quantified across tenures. We suggest that densities of hollow-bearing trees to be retained under current logging prescriptions need to be revised upwards. A cross-tenure approach to management is needed, given that the Pilliga forests are about evenly divided between forest managed by DECCW and by Forests NSW, i.e. the difference between conservation and commercial priorities.We conclude that the protection of remaining hollow-bearing trees is the only effective option for managing the hollow-dependent bats in the Pilliga.We predict that local extinctions of a range of hollow-using bat species will occur without active management and monitoring to protect the remaining hollow-bearing trees, and the intermediate-aged, hollowrecruit trees, from logging and fire.
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... Ball et al., 1999;Whitford, 2002;Whitford and Stoneman, 2004). The lag times thus make bats vulnerable, given the short logging rotations prevalent in Australia (Parnaby and Hamilton-Smith, 2004). Consequently, many bat species may be negatively impacted by the removal of large and older trees during logging, which leads to a reduction in the number of suitable roost sites and possibly render roost sites in remaining trees suboptimal (Goldingay, 2009). ...
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... Habitat loss is often considered to be a main factor contributing to the decline of fauna, including bats, in an area despite continued provision of food and water (Catterall & Kingston 1993;Barclay & Brigham 1996;Holmes 1996;Kunz & Lumsden 2003;Racey & Entwistle 2003;Parnaby & Hamilton-Smith 2004). Almost two-thirds of the roost trees used by the white-striped freetail bat were found on public or Crown land, emphasizing the importance of retaining mature habitat trees on public areas. ...
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Insectivorous bats make a significant contribution to mammalian diversity in central Australia, with 12 known extant species; however, little is known about their habitat preferences and how these interact with temporal patterns in their abundance and activity. Although most species forage widely and in a variety of habitats, we expected that woodlands associated with ephemeral rivers would constitute high-value habitat for bats because they provide tree hollows, suitable structural habitat for foraging, and canopies rich in invertebrate biomass. The aim of this research was to establish whether riparian woodlands were a focus of bat activity and to identify patterns in habitat use and whether these changed through time. We investigated the activity of bats in riparian woodlands and neighbouring vegetation over 2 years. Bat activity was higher in riparian woodland than in nearby vegetation, and this difference was most significant during a hot and dry summer. At the species level, body size and foraging guild were important factors explaining differences in activity, with larger ‘open space’ species more active in riparian woodland than adjacent habitat. In contrast, we did not detect significant differences in the activity of smaller vespertilionid species between habitats. Coinciding with patterns in invertebrate activity, bat activity was highest in summer and lowest in winter. Within river channels, canopy cover was important in explaining patterns in bat activity. There was also a significant location effect, with bat activity in some river systems much higher than in others. We propose that this is related to both regional variability in rainfall and productivity, in addition to topography. Our findings demonstrate the importance of riparian woodlands to bats in an arid environment, particularly during low-resource periods, and suggest that bats may be affected by future climate changes and degradation from fire impacts.
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I examined the habitat use patterns of an Arizona insectivorous bat community using ultrasonic sensing equipment which allowed field identification of bat species based on their echolocation calls. Response to prey patchiness by the species encountered was tested using ultraviolet lights to attract swarms of insects. No partitioning of habitat or time was observed, there being a high degree of species overlap, and many species of bats appeared to be positively associated. All species responded to light-induced prey patches on at least some occasions. Analysis of prey populations indicated that food, though abundant, was extremely patchy in distribution, both spatially and temporally. These data indicate a bat community in which species are highly adapted to an abundant, but patchy food source.
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The echolocation calls of fourteen species of insectivorous bats were recorded and analysed to obtain a suit of call descriptors for use in field identification of bats. Measurements relating to frequency and duration of the calls can be used to discriminate species only when a large number of calls are sampled and when mean values for each measurements and species are used. Some overlap between calls of certain species leads to considerable ambiguity in identification. Clarification is possible, however, when both the pattern of frequency change over time for each call and the pattern of pulses in each call sequence are also considered. All FM-bats are similar in that the bandwidth of their calls typically spans one octave. Similarities in a whole suite of call characteristics occur among bats of different taxonomic groups and are more likely to represent ecological relationships among species than phylogenetic ones.
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The Australian bat fauna includes 52 described species. Further taxonomic clarification is desirable in several genera. Although the historical zoogeography and evolution may be inferred, no fossil evidence has yet been recorded. With the exception of the Bent-winged Bat, Miniopterus schreibersii, and the flying foxes, Pteropus spp., little is known of the biology of Australian species.
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The ecological impacts on eucalypt forest biodiversity resulting from integrated forestry harvesting in E Australia are discussed. Forest allocation and management options for mitigating these impacts are outlined. Logging and associated activities, such as roading and the use of prescribed fire have significant impacts on biodiversity in many ways at various spatial and temporal scales. Impacts may be positive, negative or indeterminate in the way they change the distribution, abundance and likelihood of persistence of species, assemblages of species and other components of forest biodiversity. The new National Forest policy offers a framework for a move towards ecologically sustainable forestry. It outlines an approach based on a dedicated system of reserves that are to be representative, comprehensive and adequate, and complemented by improved off-reserve management. The protection of unreserved forest ecosystems with known or likely conservation value appears essential as they will provide the major options for reservation in at least the short-medium term. Significant reductions in logging quotas and major changes to current codes of forest practice are required if stated biodiversity conservation goals are to be achieved. -from Authors
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Movements and day roosts of the Chocolate Wattled Bat Chalinolobus morio were studied in Mumbulla State Forest near Bega on the south coast of New South Wales from 1981-1984. Part of the forest had been intensively logged since 1979, leaving a patchwork of alternate logged and unlogged coupes of 10-20 ha each. This part of the forest contained the major part of the study area. The location of roosts and the movements of bats were estimated from (a) recapture data of 11 bats from among the 88 which had been caught, banded and released, (b) reports by logging crews, and (c) radio emissions from transmitters fitted to 3 bats. Trapping data alone greatly underestimated distances moved by this species. Radio-tracking revealed that C. morio can fly rapidly through several kilometres of forest and so make use of widespread resources. It was concluded that the assessment of habitat preferences of this species should incorporate resources within at least 5 km from the site of capture. All three bats caught in logged forest flew 5 km to roost in unlogged forest, and the two identified roosts were in exceptionally large trees. The authors concluded that to conserve C. morio in a forest to be logged requires the retention of some trees in a range of age classes to replace existing roost trees when they die and fall, as well as the retention of areas of forest in a permanently unlogged state.
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Discusses forest biodiversity conservation in New South Wales from a national and international perspective. The conservation status of temperate eucalypt forests in Australia is little different from that globally despite the fact that this continent was only recently occupied by Europeans. Approximately half of the continent's forests have been cleared or severely modified since 1788 and rates of deforestation remain high. The forest conservation reserve system is not currently representative of the full range of biodiversity. Many impacts related to forestry are significantly detrimental since they can 1) destroy and modify complex forest landscapes and ecosystems; 2) destroy and modify the natural environmental heterogeneity of forest ecosystems; 3) destroy, prevent or hinder ecological processes that are the basis for species' persistence and evolution; 4) destroy or significantly modify the habitat of species; and 5) destroy individual organisms and significantly modify populations and assemblages of species. Many forestry impacts on biodiversity may be irreversible or effectively irreversible and the harvesting of many old growth eucalypt forest ecosystem in NSW does non appear to be ecologically sustainable. Essential components of a move towards sustainability include the establishment of a comprehensive conservation reserve network centred on old-growth forest ecosystems on productive sites, enhanced off-reserve codes of forest practice on both public and private lands; an ecologically-conservative approach to forest management; and development of a systematic ecological monitoring programme across the forest estate. -from Authors
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All species and most individuals were concentrated in minor portions of the forest (63% of animals in 9% of total area felled). An index of foliage nutrient concentration of eucalypt communities appeared to be the major determinant of density and species richness of animals. The richest communities (in terms of nutrients and fauna) were mainly confined to the most fertile soils derived from Devonian intrusive rocks. Findings emphasise the conflict existing between the habitat requirements of the fauna and human requirements of the same forest lands for either intensive wood production or for farmland.-from Author