CASE STUDY — EXAMPLES OF TRENDS IN SIGNIFICANT SPECIES AND COMMUNITIES — SOUTH AUSTRALIA
Status of the greater bilby (Macrotis lagotis) within the Arid
Recovery Reserve
Description
Arid Recovery is an ecosystem restoration program in the far north of South Australia.
Now in its tenth year, the program is based around a 60 km2 reserve from which all feral
cats, rabbits and foxes have been eradicated. An additional 26 km2 has recently been
fenced and introduced species are being eradicated.
The reserve has created an area of complete protection allowing the regeneration of native
flora and fauna and the successful re-introduction of four locally extinct mammal species,
one of which is the greater bilby (Macrotis lagotis).
Figure 1. Location of Arid recovery Site in Northern South Australia
The greater bilby is a burrowing, nocturnal bandicoot that digs extensively for the seeds,
bulbs and invertebrates that constitute its diet. The greater bilby has been successfully reintroduced to some areas and islands within its former range where feral cats and foxes are
absent, intensively controlled or eradicated (e.g. Thistle Island in South Australia). Reintroductions into inland arid zone areas have proved more difficult due to the problems of
controlling and excluding introduced predators from a large area without the use of
peninsulas or costly fences. A trial re-introduction into Watarrka National Park in the
Northern Territory failed due to high levels of predation (Southgate pers comm). Reintroduction research on bilbies in arid inland Australia has focused on spinifex deserts
(e.g. Southgate 1990) and the potential success of bilby re-introductions into the chenopod
shrublands and Acacia dunes of the southern arid zone was largely unknown.
Greater bilbies were known to previously inhabit the Arid Recovery area because subfossil material was collected 30 km from the reserve and local pastoralists remember
‘pinkies’, a colloquial name for bilbies, in the local sand dunes until the 1930s.
Significance
The greater bilby has declined since European settlement and although still found in the
arid interior of the Northern Territory, Western Australia and Queensland, the species now
occupies only 20 per cent of its former range (Pavey 2004). Current classifications list the
bilby as vulnerable to extinction (Pavey 2004) and it is suggested that the bilby may still
be in decline. Southgate et al. (1994) suggest that a combination of changing fire regimes,
increased predation through the introduction of feral cats and foxes and degraded habitat
caused by rabbits and stock was responsible for their historical decline.
Data and information
Bilbies are monitored at Arid Recovery through track transects, burrow monitoring, and
quarterly capture using hand nets. Six track transects ranging from 3-10 km in length are
conducted quarterly within the reserve and eight transects are conducted on the outside of
the reserve. Between 20 and 30 bilby burrows are monitored annually for activity and 10
bilbies are captured by hand each quarter to compare body condition and reproductive
output. Radio-tracking has also been conducted following internal and external bilby
releases to gather information on survival, home range and habitat usage.
A number of research projects have contributed significant knowledge to the recovery
effort. Key recent research at Arid Recovery includes: research on survival, ecology and
reintroduction protocol (Moseby and O’Donnell 2000); foraging behaviour and influence
of bilbies on the seed bank (James 2004, Newell 2004, James and Eldridge 2007), predator
awareness training (Cameron 2005) and external bilby release (Cunningham 2004,
Hill 2004).
Management requirements and issues
Predation by feral cats and foxes is the main threat to the long-term survival of the greater
bilby at Arid Recovery. The success of the greater bilby reintroduction at Arid Recovery is
largely dependant on the ongoing exclusion or intensive management of such predators.
Other issues are intra-specific competition for resources within the Arid Recovery
Reserve. With the absence of natural predation and limited opportunities for dispersal,
animals inside fenced reserves will eventually become limited by resources. Significant
population crashes of burrowing bettongs and brush-tailed bettongs have been experienced
recently at other reserves in South Australia and Western Australia. Thus, ensuring the
long term survival of bilbies in the arid zone should include protection of un-fenced large
wild populations.
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ASSESSMENT OF AUSTRALIA’S TERRESTRIAL BIODIVERSITY 2008
The long term impacts of restricting this wide-ranging and dispersing species in relatively
small exclosures or ‘islands’ are unknown but large scale dispersal and movements may
be important ecological processes that can only occur naturally in large tracts of available
habitat.
Management actions and responses
The Arid Recovery Reserve has provided greater bilbies access to 52 km2 of feral cat and
fox-free land through the use of a 1.8 metre high exclusion fence. Nine (5 female and 4
male) greater bilbies from the Monarto Zoo captive breeding facility were released into
the Main Exclosure of the Arid Recovery Reserve in April 2000. In 2003, a further eight
(4 males and 4 female) bilbies from Monarto were released into the Northern Expansion,
while in 2004 15 (4 female and 11 male) bilbies from Thistle Island (SA) were released
into the Northern Expansion and a further 10 were released from Monarto into the
Northern Expansion in 2005. The total number of animals released to date is 42 (18 female
and 24 male).
Arid Recovery is now attempting to support a sustainable population of greater bilbies in
several ways by:

gradually expanding the Reserve to 119 km2 to facilitate dispersal and support a
genetically viable population. A large reserve also increases the chance of patchy
rainfall events falling inside the reserve, producing the ephemeral growth preferred by
bilbies in their diet

reintroducing natural predators back into the environment (e.g. woma pythons) so that
overpopulation may be controlled and a more balanced ecosystem produced

installing one-way gates to allow natural dispersal of bilbies outside the Reserve. In
2007 Arid Recovery tested four different one-way gate designs that would allow bilbies
to disperse outside the reserve when numbers in the reserve are high, but would prevent
any animals, including rabbits and feral predators, from invading. This would also
contribute to our long-term goal of establishing viable populations of threatened species
populations (i.e. bilbies) outside of the fenced reserve system

establishing a population of wild bilbies outside the reserve. In 2004 12 bilbies were
released outside the Arid Recovery Reserve to determine if bilbies would survive in the
wild. Unfortunately the majority of these were taken by feral cats within one month of
release. However, some bilbies survived and bred over the following year, suggesting
that some bilbies are able to survive in the presence of feral cats and foxes. The
question then becomes ‘can bilbies learn to avoid feral cats and foxes?’ Subsequent
research at Arid Recovery has identified that bilbies respond to predator-awareness
training with trained bilbies exhibiting a heightened sense of awareness and responding
to cat odour by moving burrows (Cameron 2005). Ten trained and untrained bilbies
were released outside the reserve in 2007 to determine if survival is greater in bilbies
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that have been given predator awareness training. An intensive control program has
also been undertaken outside the reserve to determine the level of predator control
required for a population of wild bilbies to become established.
Outcomes
Greater bilby numbers have been fluctuating over the years in response to seasonal and
local conditions (see Figure 2). Numbers often appear to be higher during the summer
months and the population is estimated at between 300 and 500 individuals.
70
60
tracks per km
50
Main
40
First
30
Northern
20
10
May-07
Nov-06
May-06
Nov-05
May-05
Nov-04
May-04
Nov-03
May-03
Nov-02
May-02
Nov-01
May-01
Nov-00
May-00
0
Figure 2. Number of greater bilby tracks per kilometre within the Main Exclosure
(10km transect), First Expansion (5.5km transect) and Northern
Expansion (16km transect) of the reserve. (Pink line denotes separation
between different tracking methodologies).
During boom periods many bilbies are seen along the boundary fences, possibly trying to
disperse. The release of the 10 captive-bred animals in 2005 failed possibly also due to
overpopulation and an absence of free territories. The one-way gate trials (designed to
allow bilbies to disperse outside the Reserve during periods of overpopulation) have
identified that bilbies have a clear preference for a particular gate type that is different to
the gates preferred by bettongs. The next stage of the trial is to test the gate types to
determine if they will exclude predators.
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ASSESSMENT OF AUSTRALIA’S TERRESTRIAL BIODIVERSITY 2008
The woma python release in 2007 was unsuccessful due to high predation by Mulga
Snakes. Future research will look into using wild-caught woma pythons and also other
potential natural predators that could be used to regulate bilby and other mammal
populations in the reserve to create a more naturally functioning ecosystem.
The 2007 external bilby release has so far been very successful with both trained and
untrained bilbies exhibiting high survival rates. The intensive predator control program is
so far controlling feral cat and fox numbers to a level where both trained and untrained
bilbies can survive. However, although pouch young have been recorded, no juvenile
bilbies have been captured to date.
Future scenario
If expansion activities are funded, the greater bilby should eventually have access to more
than 119 km2 of fenced arid zone habitat within the Arid Recovery Reserve. An additional
200 km2 of land adjacent to the Reserve will also be managed for greater bilbies by
controlling feral cats and foxes. If predators can be effectively controlled outside the
Reserve, then more than 300 km2 of land will be available for bilbies supporting up to
1000 individuals. One-way gates and native predators will be used to maintain population
levels, prevent overcrowding and allow natural dispersal. Further research on broad-scale
control of feral cats is urgently needed in order to protect extant bilby populations in the
arid deserts. Arid Recovery is currently comparing aerial baiting with integrated control
methods to develop a strategy for broad-scale control for the protection of threatened
species such as the greater bilby.
Greater bilby – Photo: Hugh McGregor
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References
Cameron A. 2005. A comparison of predator trained and untrained bilbies (Macrotis
lagotis). Arid Recovery Technical Report 2005 (1)
Cunningham L. 2004. A trial re-introduction of the Greater Bilby outside the Arid
Recovery Reserve. Arid Recovery Technical Report 2004 (1)
Hill B. 2004. Outside bilby release. Arid Recovery Technical Report 2004 (3)
James A. 2004. The creation of fertile patches by four ecosystem engineers in an arid
South Australian dunefield. Honours Thesis, UNSW.
James AI and Eldridge DJ. 2007. Reintroduction of fossorial native mammals and
potential impacts on ecosystem processes in an Australian desert landscape, Biological
Conservation , doi:10.1016/j.biocon.2007.04.029
Moseby KE and O'Donnell E. 2003. Reintroduction of the greater bilby, Macrotis lagotis
(Reid) (Marsupialia : Thylacomyidae), to northern South Australia: survival, ecology and
notes on reintroduction protocol. Wildlife Research 30:15-27.
Newell J. 2004. Investigating the effects of ecosystem engineering by reintroduced
Greater Bilbies (Macrotis lagotis) and Burrowing Bettongs (Bettongia lesueur). Poster
presentation, Australasian Wildlife Management Society Conference, Kangaroo Island.
Pavey C. (2004). Recovery plan for the Greater Bilby, Macrotis lagotis, 2005-2010.
Northern Territory Department of Infrastrucutre, Planning and Environment, Darwin.
Southgate RI. 1990. Distribution and abundance of the Greater Bilby, Macrotis lagotis
Reid (Marsupialia:Peramelidae). In ‘Bandicoots and Bilbies’ (Eds J.H. Seebeck,
P.R.Brown, R.I.Wallis and C.M. Kemper) pp 293-302. (Surrey Beaty and Sons: Sydney.)
Southgate RI, Bellchambers K, Romanow K. and Whitfield S. 1994. Re-introduction of
the Greater Bilby, Volume 1 A field guide. Final Report to World Wide Fund for Nature,
Project 95.
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