Reintroduction of macropods (Marsupialia: Macropodoidea) in Australia—A review

Biological Conservation 1992, 62, 189-204

Reintroduction of macropods (Marsupialia: Macropodoidea) in Australia A review Jeff Shortfl S. D. Bradshaw, b Jack Giles, C* R. I. T. Prince d & George R. WilsonC¢ CSIRO Division of Wildlife & Ecology, L M B 4, PO Midland, WA 6056, Australia b Department of Zoology, University of Western Australia, Perth, WA 6009, Australia c New South Wales National Parks and Wildlife Service, PO Box 1967, Hurstville, N S W 2220, Australia d Western Australian Department of Conservation and Land Management, PO Box 51, Wanneroo, WA 6065, Australia (Received 19 August 1991; revised version received 4 November 1991; accepted 21 November 1991)

This paper describes six recent attempts to conserve threatened wallabies (Marsupialia: Macropodoidea) by reintroduction. All ended in failure. We place these attempts within the context of nineteen other reintroductions of macropods known to us. Success of reintroduction of macropods appears to depend critically on control or exclusion of exotic terrestrial predators. Islands without exotic predators support a success rate of reintroductions an order of magnitude higher than that of mainland sites and islands with exotic predators (82% cf. 8%). Reintroductions have generally been poorly monitored and poorly documented. Researchers have often failed to appreciate the enormity of the task of controlling introduced predators (foxes and feral cats and dogs) and herbivores (rabbits), and to make adequate use of existing technology (radiotelemetry), and have been unable to overcome the logistical problems of managing reintroductions far from their research bases. Successes in management and reintroduction of other threatened fauna in Australia suggest that effective control of introduced predators and rabbits using the poison 1080, for which many native species have a high tolerance, may provide an effective means of managing mainland reintroductions.

onslaught of 200 years of European settlement. This period has seen the extinction of six species and the loss from the Australian mainland of a further four species out of a total of 50 (Johnson et al., 1989). One facet of management of threatened species is their reintroduction to parts of their former ranges. However, many past attempts to conserve macropods by reintroduction have failed. Worse than this, they have been poorly documented and few lessons have been learnt from the experience. This paper is an attempt to redress that situation for six recent reintroductions. Reintroduction is defined as 'the intentional movement of an organism into part of its native range from which it has disappeared or become extirpated in historic times as a result of human

INTRODUCTION It is common practice in wildlife management to bury one's failures as quickly and quietly as possible (McNab, 1983). However, the result is often that subsequent generations of wildlife managers repeat the mistakes of the past. One of the most significant problems in the management of Australia's macropods is the maintenance of those remnant colonies that have barely survived the * Present address: Taronga Park Zoo, PO Box 20, Mosman, NSW 2088, Australia. :~ Present address: Bureau of Rural Resources, GPO Box 858, Canberra, ACT 2601, Australia. Biological Conservation 0006-3207/92/$05.00 1992 Elsevier Science Publishers Ltd. 189

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J. Short, S. D. Bradshaw, J. Giles, R, I. T. Prince, G. R. Wilson

activities or natural catastrophe' (IUCN, 1987). We include movements of animals to islands which are within the broad historical range of the species but for which there is no evidence of their former occurrence. There are current plans to reintroduce a number of macropod species to parts of their former range. The justification for this is often aesthetic (restoring ecosystems to their pre-European state), often conservative (spreading the eggs between more baskets), and only occasionally scientific (understanding the complex interactions between the species and its now often much-modified environment). While these proposals are laudable they must be regarded as high-risk. We believe a critical look at past attempts may improve their prospects. We describe six reintroductions of macropods. They are the attempts by researchers at the University of Western Australia to re-establish quokkas Setonix brachyurus and tammar wallabies Macropus eugenii on the coastal plain near Perth in the period 1972-1988; the New South Wales National Parks and Wildlife Service (NSW NPWS) to reintroduce parma wallabies M. parma to Pulbah Island in Lake Macquarie in 1972 and to Robertson in 1988; the Western Australian Department of Fisheries and Wildlife to reintroduce banded hare-wallabies Lagostrophus fasciatus to Dirk Hartog Island in 1974; and the New South Wales Department of Tourism to reintroduce brush-tailed rock-wallabies Petrogale penicillata to Wombeyan Caves in 1980. All these attempts ended in failure. Finally, we provide a brief summary of nineteen other reintroductions of macropods, some successful, some not. F r o m an overview of these twentyfive reintroductions, we suggest recommendations to improve management of future reintroductions.

Fig. I(A). The former (light) and present (dark and arrowed) range of the quokka (a) and brush-tailed rockwallaby (b).

~:.

Fig. I(B). The former (light) and present (dark and arrowed) range of the tammar (a) and parma wallabies (b).

THE SPECIES The quokka is a small wallaby of c. 3 4 kg that occurs in southwestern Australia (Fig. I(A). It can be distinguished in appearance from other wallabies by its short tail, legs, and ears. Its preferred habitat is the dense vegetation surrounding permanent swamps. The major extant populations are on offshore islands: Rottnest and Bald Islands off the southwest coast. It persists in large numbers on Rottnest despite a harsh, seasonally arid climate, a lack of habitat similar to that

Fig. I(C). The former (light) and present (arrowed) range of the banded hare-wallaby

Reintroduction of macropods in Austral& preferred on the mainland, little free water, and the presence of cats Felis catus. Its major period of decline on the mainland was c. 1930s (White, 1952) attributed variously to disease, competition with rabbits Oryctolagus cuniculus, and predation by foxes Vulpes vulpes. It still persists in low numbers at some, mainly coastal, locations within the southwest (Kitchener & Vicker, 1981). The tammar is a medium-sized wallaby growing to c. 5-8 kg that, at the time of European settlement, had a dozen isolated populations: the southwest of Western Australia, the Eyre and Yorke Peninsulas and adjacent coastal areas in South Australia, Kangaroo Island and numerous other island populations off the southern and western coast of Australia (Smith 1983; Copley et al., 1984; Saunders & St John, 1987) (Fig. I(B)). The tammar requires dense low vegetation for daytime shelter and open grassy areas for feeding (Smith, 1983). It is now rare on the mainland and absent from St Francis, St Peter, Thistle, and Flinders Islands where it occurred in historic times (Delroy, 1974; Smith, 1983). Perry (1973) suggested a major collapse of populations of this species in the southwest of Western Australia in the period 1938-1944. Its major decline was apparently somewhat earlier (pre-1920) in South Australia (Wood-Jones, 1924). The parma wallaby is a small wallaby of c. 45 kg. Its optimal habitat is wet sclerophyll forests with a thick, shrubby understorey and occasional grassy patches (Maynes, 1983) in eastern Australia (Fig. I(B)). It was believed to be extinct in its native range until its rediscovery near Gosford, New South Wales in 1967. An irony was that it had been successfully introduced to Kawau Island in New Zealand in about 1868 and was being vigorously controlled there in the 1960s as a pest of

191

regrowing pine plantations (Wodzicki & Flux, 1967a). Surveys of its former range in New South Wales subsequently revealed that it was still present in the northern half of its former range but was absent from the southern half (Maynes, 1977). The banded hare-wallaby is a species of c. 23 kg that occurred in a broad arc across southwestern Australia until at least 1906 (Kitchener & Vicker, 1981) (Fig. I(C)). It is now extinct on mainland Australia and occurs only on Bernier and Dorre Islands off Shark Bay (Short & Turner, 1992). Gilbert (in Gould, 1863) reported that it was found only 'in densely thick scrubs, on flats and on the edges of swamps, where the small brush Melaleuca grows so thickly, that it is almost impossible for a man to force his way through'. The brush-tailed rock-wallaby is a wallaby of c. 6-8 kg that inhabits cliffs, boulder piles, and scree slopes throughout much of the more rugged parts of eastern Australia (Fig. I(A)). Its habitat requirements, diet, and status have been the subject of recent studies (Short, 1982, 1989; Short & Milkovits, 1990). It has declined from a substantial part of its former range, particularly from Victoria and from southern and western New South Wales. THE REINTRODUCTIONS Q u o k k a s to J a n d a k o t

Over 670 quokkas were reintroduced to the 254-ha field station of the University of Western Australia at Jandakot over the period 1972-1988 (see Table 1). All animals came from Rottnest Island 18 km off Perth, some via a captive breeding colony at the University.

Table 1. Number of quokkas introduced, population estimates of quokkas from trapping, and number of foxes and cats shot or poisoned at the University of Western Australia's field station at Jandakot, WA Trapping of 'resident' quokkas at Jandakot was generally in April of each year; reintroductions were generally in the latter half of the year

Species

Year

Total

1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 Quokka Number introduced Population estimate Fox Cat *Tracks observed.

22

45

27

No records No records

58

69

47 73 2

125 129 1 6

58 54 99 74 123 101 5 * >1 4 * 2

62 46 101 4 1 2 3

7 673 68 1

54 3

16 6

9 1 2

2

>28 >20

192

J. Short, S. D. Bradshaw, J. Giles, R. I. T. Prince, G. R. Wilson

The field station is on the Swan coastal plain in the southern suburbs of Perth 25 km from the city centre. The area is predominantly a low woodland dominated by Banksia spp. Several swamps (often dry) have a dense and continuous vegetation cover of the reed Baumea articulata, and are surrounded by a woodland of Melaleuca rhaphiophylla, Eucalyptus rudis, and Banksia littoralis (Algar, 1986). The swamps (primarily the 25-ha Lake Banganup) became the primary foci of quokka activity. Algar (1986) reported that 87 of the 91 quokkas captured over a two-month period in 1981 in a trapping programme that extended across the reserve were located in and around this lake. Management of the field station consisted of the erection and maintenance of a fox- and rabbitproof fence around the perimeter; control of rabbits by shooting, poisoning, and fumigation of warrens; poisoning and shooting of foxes, cats and dogs that entered the reserve; initial restocking of the existing population of western grey kangaroos Macropus fuliginosus and introduction of euros M. robustus to the reserve; subsequent culling of western grey kangaroos when pasture appeared overgrazed; and the provision of grassed lawns to provide an additional food source for the quokkas (Algar (1986) and unpublished annual reports of the field station). The reserve was surrounded by a 1-8-m chainlink wire fence buried 15 cm in the ground and with three barbed wire strands offset at 45 ° . Wire netting (90 cm) was attached to the outer base of the fence (laid horizontally a few centimetres beneath the surface of the soil). The middle barbed wire and, in 1979, a second barbed wire were electrified. The fence apparently has never been an effective barrier against foxes or cats. Trapping over the period 1978-1988 gave an estimate of average minimum population numbers of quokkas on the reserve of 72. An average of 55 animals per annum were introduced over the period 1972-1983 (Table 1). Reintroductions were approximately six months prior to trapping censuses each year. The population fell to c. nine in 1988 in the absence of restocking over the previous five years. Quokkas had failed to establish successfully. Declines in population numbers occurred despite reasonable fecundity (69% of 485 females trapped between 1978 and 1988 carried pouch young), some recruitment (22.8% (range 0-46%) of animals captured each year were born in situ), survival of at least some animals for periods from three to nine years after reintroduc-

tion or birth /n situ, and body conditions of individuals better than that of the source population on Rottnest. Major declines in number were not related to periods of drought. For example, the known population in 1982 declined from 62 animals in April to 17 in October. Rainfall for the six- and 12-month periods prior to October 1982 was 80% and 96% of the long-term average, respectively. Algar (1986) attributed the failure of the quokka to establish successfully (despite annual additions of animals over 11 years) to overgrazing by rabbits and the other species of macropods. We view overgrazing as a contributory factor but would suggest that direct predation from foxes and cats is a more plausible explanation. It is more consistent with the observed fecundity, recruitment and condition of individuals reported in the annual reports of the field station, and the consistent presence of foxes and cats (mean 4.4 shot or poisoned per annum between 1977 and 1988 (Table 1)). It is likely that intense grazing pressure by rabbits and other macropods might increase the susceptibility of quokkas to predation by forcing them to feed further from the protective cover of dense vegetation around the swamp. Other factors considered as potential contributors to the failure of the quokkas to establish were incidence of Salmonella infection, reintroduction of inappropriate age/sex classes, and behavioural problems associated with reintroducing naive captive-I~red animals. However, attempts to modify subsequent reintroductions to account for these factors (e.g. screening animals for exotic strains of Salmonella, reintroducing younger and wildcaught animals) appear to have had little effect on survival. Tammar wallabies to Jandakot

Eighty-five tammars were reintroduced to the University of Western Australia's field station between 1971 and 1981. Six animals, probably originating from nearby Garden Island, 18 km to the west, were introduced in 1971. At least three tammars were recorded as killed by foxes in 1972. A further 60 were reintroduced to the field station in 1975, and in early 1981 a further 19 animals (10 male, 9 female) were introduced. The last group came from Garden Island and were initially quarantined in yards at the Zoology Department of the University in Perth to check for infection

Reintroduction of macropods in Australia with Salmonella. Animals were reported to have lost condition during this period. In 1981-82 there were two sightings and three deaths recorded in the reserve. There were no sightings of tammars .or records of their death after 1982. The population had failed to establish. The exact fate of the tammars is unknown but the most likely explanation is that they were killed by foxes and cats. Parma wallabies to Pulbah Island in Lake Macquarie

In 1972 the NSW NPWS were faced with a dilemma. Parma wallabies had only recently been rediscovered in their former range, 35 years after any previous sighting. Their precise distribution and abundance were largely unknown. They were listed by the I U C N Red Data Book as rare. However, New Zealand authorities were attempting to eliminate an introduced population of this species from Kawau Island because it prevented the establishment of pine plantations. The Kawau wallabies, only recently identified as parmas, were possibly the only secure population of this species. It was against this background that the NSW NPWS decided to establish a colony of the wallabies on Pulbah Island. Pulbah Island in Lake Macquarie has an area of 0.64 km 2 and is 1.0 km from the mainland. A primary reason for its choice was that it was free of foxes. It had been used previously and unsuccessfully as the site in which to establish a population of the rapidly diminishing bridled nail-tail wallaby Onychogalea unguifera (see Table 2). It was acquired as a nature reserve by NSW NPWS in 1970. Twenty-four wallabies from Kawau Island were caught by a professional trapper, airlifted to Sydney, and taken by truck and boat to Pulbah Island in March 1972. They were transported in cardboard boxes (120 x 30 x 30 cm) with plywood tops, with two animals in each box separated by a partition. Total travel time from Kawau to Pulbah was approximately three days. Twelve other animals from a captive colony at Taronga Park Zoo in Sydney, that originated from Kawau Island, were taken to Pulbah at the same time. They were transported in hessian sacks suspended from the interior roof of vehicles. All animals of both groups survived the translocation. One of the zoo animals appeared sick on arrival and so was not released. The New Zealand animals were released into a

193

0.4-ha yard (with a 1.3-m high fence of plastic sheeting), the zoo animals into a separate smaller yard. Several animals immediately escaped by jumping the fence. The zoo animals were transferred to the major yard one week after translocation. Food (carrots, pellets) and water were provided. The parmas were maintained in this yard for six weeks then released to the island proper. Rangers visiting the island 10 weeks later (July) saw no wallabies or evidence of their presence, although a regular visitor to the island reported seeing two or three in the previous week. No signs of wallabies were found by rangers in September or December despite a search of the entire island by a line of 40 people walking abreast. A variety of explanations were offered for the complete and immediate loss of the wallabies but the exact cause remains a mystery. The island had a high rate of visitation by picnickers, fishermen, and their dogs. Two carcases were found apparently badly mutilated by dogs. Another wallaby was seen killed by a visitor's dog. In addition, a team of workers cleared the noxious weeds lantana Lantana camara and bitou bush Chrysanthemoides monilifera from a small area of the island each day, thereby removing some of the wallabies' cover close to the enclosure. However, as the rest of the island had a dense understorey of native scrub, this seems unlikely to have had an adverse effect on the wallabies. It seems likely that the uncontrolled presence of dogs on the island was the primary cause of the demise of the parmas. Parma wallabies to Robertson

Conservationist and businessman Peter Pigott set up a captive breeding population of parma wallabies on his property at Mt Wilson 90 km west of Sydney during the early 1970s when they were believed to be at considerable risk. He imported 30 animals from Kawau Island. This founding population grew to 3 0 0 4 0 0 by 1987. Management at this site included their confinement to a fox-proof enclosure of approximately 10 ha, and the provision of supplementary food and water. A release site was chosen near Robertson in the southern part of the former range of the species 200 km south of the nearest extant wild population. The site was chosen because of its disturbed vegetation which provided dense cover alongside grassy areas likely to provide food. The land was

194

J. S h o r t , S. D. B r a d s h a w , J. Giles, R. I. T. P r i n c e , G. R. W i l s o n

Table 2. Reintroductions of maeropods to Australian islands Most are translocations to islands within the broad historical range of the species but where the species did not occur at the time of European settlement

Species

Year(s) of reintroduction

Site

Number reintroduced

Survival

Factors limiting success of reintroduction

Source

Tammar wallaby

1905

Greenly Island, SA (128 ha)

?

85 years +

None limiting survival, overgrazing reported

Mitchell & Behrndt (1947), Robinson (1980)

Tammar wallaby

1968

Granite Island, SA (c. 25 ha)

12

22 years +

None limiting survival, overgrazing reported

Tsatsarouis & Savarton (1986)

Burrowing bettong

1924-26

Kangaroo island, SA (112 000 ha)

2+2

No

?

Finlayson (1958)

Bridled nail-tail wallaby

Late 1930s

Pulbah Island, NSW (64 ha)

?

No

?

Harper (1945), Ride (1970)

Western grey kangaroo

< 1948

Woody Island, WA (240 ha)

?

42 years +

None limiting survival, overgrazing reported

GoodseU et al. (1976), D. McKenzie (pers. comm.)

Black-flanked rock-wallaby

1960

South Pearson 5 Island, SA (60 ha)

30 years +

None

Thomas & Delroy (1971), Robinson (1980)

Black-flanked rock-wallaby

1974-75

Thistle Island SA (3 925 ha)

5+10

6 years +

Suitable rock habitat

Hewett (1980)

Black-flanked rock-wallaby

1975

Wedge Island, SA (974 ha)

11

5 years +

Suitable rock habitat

Hewett (1980)

Parma wallaby

1972

Pulbah Island, NSW (64 ha)

35

c. 4 months

Dogs, disturbance

This paper

Banded hare-wallaby

1974

Dirk Hartog Island, 11 WA (62 000 ha)

3 years +

?Goats, sheep, drought, cats

This paper

Brush-tailed bettong

1979

Bird Club Island, SA (8 ha)

6

1 animal > 1 year, others c. 6 months

Dogs

Delroy et al. (1986), Nelson et al. (1990)

Brush-tailed bettong

1980

Island A, SA (17 ha)

7

11 years +, None peak population >65

Delroy et al. (1986), Nelson et al. (1990)

Brush-tailed bettong

1981

St Francis Island, SA (800 ha)

40

1 animal >3 years, most <8 months

Brush tailed bettong

1984

St Francis Island, SA (800 ha)

42

< 1 year

Brush-tailed bettong

1987

St Francis Island, SA (800 ha)

48

< 1 year

Brush-tailed bettong

1982

Bairds Bay Island, SA (13 ha)

10

9 years +, peak population >35

None

Delroy et al. (1986), Nelson et al. (1990)

Brush-tailed bettong

1983

Wedge Island, SA (974 ha)

11

7 years +

None

Delroy et al. (1986), Nelson et al. (1990)

Brush-tailed bettong

1989

St Peter Island SA (3 500 ha)

113

?

?

Nelson et al. (1990)

Unknown, but possibly: Delroy et al. (1986), vegetation unsuitable Nelson et al. (1990) from 50 years of stock (removed 1967), Delroy et al. (1986), competition Nelson et al. (1990) from bandicoots, Delroy et al. (1986), predation from pythons, sea eagles Nelson et al. (1990)

Reintroduction of macropods in Australia controlled by a state government authority, the New South Wales Water Board. The area was baited heavily by the Water Board staff three times in April and May 1988 with meat baits (approx. 250 g containing 3 mg of monosodium fluoroacetate (1080)), distributed in an area of 2 km radius around the release site. An enclosure of 1.5 ha bounded by hessian walls 1.5 m high was constructed to hold the parmas upon release. Forty-seven wallabies were caught by 50 volunteers at the Mt Wilson property on the evening of 8 May. Valium (2.5 mg) was administered to each wallaby on capture. They were held overnight in hessian bags. Eleven animals recently fitted or refitted with radio-collars were given a further dose of valium (0.5 mg) in the morning to reduce the combined stress of being collared and then transported to the release site by either helicopter (39) or vehicle (8). All wallabies were transported in hessian bags. Transport time by helicopter was about 1 h and by vehicle it was 5 h. Total time from capture to release was about 19 h. Animals were translocated on 9 May. An additional animal was caught at 1400 h on 9 May and released at Robertson at 1600 h the same day. Twelve of the 48 wallabies were fitted with radio-collars from four to six weeks before translocation to allow animals to become accustomed to the collars and to allow collection of preliminary data on behaviour and home range before translocation and to provide information on survival after translocation. A number of problems were immediately apparent. The second dose of valium put the wallabies into an excessively deep narcosis. This resulted in one animal suffocating while in transit by helicopter. This wallaby was unconscious on arrival at the release site and did not recover. Another became wet and died from hypothermia on the first night (the ground and vegetation in the release area was damp from recent heavy rains and local flooding and there was a frost overnight). Further, despite attempting to keep details of the release secret, as many as 70 journalists and others were present for the release. This was not conducive to a smooth and calm release and indirectly resulted in the death of at least one further animal (which was pursued into a swamp and drowned). The 45 remaining parmas appeared to establish territories in dense vegetation (mainly tall sedges) within the enclosure, and began to venture beyond

195

the bounds of the enclosure after three days to feed on grasses and carrots to which they were habituated. On 30 May (three weeks after translocation) the heads and thoraxes of two wallabies were found buried by foxes 1-2 km from the enclosure. Twenty-six carcases were recovered in total, 24 of which were buried. Deaths of all wallabies recovered were attributed to foxes. By 7 July no collared wallabies remained alive and by early August probably all wallabies had been taken by foxes. During this period poisoned baits placed around the enclosure were ignored by foxes, probably due to the abundance of live food. Banded hare-wallabies to Dirk Hartog Island Bernier and Dorre Islands (44 and 52 km2 respectively) contain the only remaining populations of the banded hare-wallaby. The adjacent Dirk Hartog Island was viewed as a satisfactory site to reintroduce hare-wallabies, perhaps because of the absence of the introduced red fox so common on the mainland, its similar climate and vegetation to Bernier and Dorre, and its large size (620 km2). Its negative attributes were that it was a pastoral property carrying some 6000 sheep (range 1968-1984:2500-12500 sheep (Payne et al., 1987)), it had large populations of feral goats and cats, and it was relatively inaccessible making regular monitoring visits to the island difficult. In June 1974, 17 banded hare-wallabies (4 adult male, 7 adult female plus 6 pouch-young (5 male, 1 female)) were transferred by boat from the White Beach area of Dorre Island to two small holding yards (20 x 25 m) on Dirk Hartog Island 5 km northwest of the homestead. Total translocation distance was approximately 100 km; maximum time from capture to release was c. 48 h. The population had grown to 25 adults (13 female, 12 male) by October 1975, and 35 adults (18 female, 17 male) by December 1976. Some losses of animals from predation by wedge-tailed eagles Aquila audax occurred. In May 1977 six animals (three females, three males) were transferred to an enclosure of 4 ha located 2 km south of the homestead. No water or supplementary food was provided. In February 1978, 45 000 1080 meat baits were spread by aircraft in an attempt to eliminate feral cats. Rainfall on the night of baiting would probably have leached the poison from the baits (1080 is highly soluble). Further heavy rain (c. 60 mm)

196

J. Short, S. D. Bradshaw, J. Giles, R. I. T. Prince, G. R. Wilson

in the following six weeks would have rendered all remaining baits ineffective. No pre- or post-baiting surveys of the abundance of cats were undertaken. By June 1978 the group in the 4-ha enclosure had raised three young (all male) to independence, and had further young in the pouch. One of the original males had died. An additional two females were added to the group about this time from the other captive colony. Shortly after, several holes were made in the fence of the enclosure to allow the animals to disperse into the area beyond. The released group was supplemented in August by a further two adult females obtained from Dorre Island, and in September by six females and five males from the captive colony. Hence at this time there were 21 adult and independent juveniles that were free-ranging. In June 1979, 13 (eight females, five males) of the 21 were trapped. Five of the females had either pouch-young or evidence of lactation. Animals appeared to be using an area of c. 23 ha of tall, dense Acacia ligulata. Further trapping in September 1980 suggested that only 10 animals remained. This decline was associated with a drought over the summer of 1979-80, which apparently resulted in the loss of perhaps 30-40% of the Acacia shrub cover. This loss was exacerbated by intensive browsing by both goats and sheep. Goats browsed by climbing into the shrubs, often breaking branches. At this point the project was abandoned due to lack of resources and increasing logistic difficulties of getting to the island. The fate of the remaining released animals and animals from the captive colony is unknown. No wallabies have been sighted since that period (T. Wardle, pers. comm.). Brush-tailed rock-wallabies to Wombeyan Caves

Rock-wallabies persisted at Wombeyan Caves until at least 1929 (M. Fleming, pers. comm.) but were not present in 1948 (C. Stiff, pers. comm.). The most likely time for their disappearance from the caves was the early 1930s. Residents of the area during this period (and other nearby limestone cave sites that also had rock-wallabies) claim that introduced rabbits at pre-myxomatosis levels eliminated rock-wallabies through direct competition for food resources during drought. At this time the vegetation would be completely eaten out in dry seasons on the Wombeyan Reserve except for the unpalatable stinging nettles. The hills

at Wombeyan were often bare and red--the soil exposed. Rabbits would dig grasses out by the roots, ringbark shrubs, and nip off the growing tips of shrub and tree seedlings. In the 1930s and 1940s most farm owners in the area spent one-third of the year on rabbit control (MarchAugust), with the produce of rabbits (skins and carcasses) contributing about one-third of farm income at that time. Many properties had as many as four men working full-time on the control of rabbits (M. Fleming, pers. comm.). C. Stiff (pers. comm.) described poisoning 700 rabbits in one night on the grassy fiats at Wombeyan in the late 1940s. A spotlight count of the same area in 1987 yielded only four rabbits. Recent studies examining the decline of rock-wallabies (Kinnear et al., 1988; Short & Milkovits, 1990) have placed more or equal emphasis on the effects of introduced predators (particularly foxes) and/or goats. Four rock-wallabies were introduced to Wombeyan Caves in February 1980 and a further six in January 1981. All came from a population at Jenolan Caves, 55 km to the north. These caves had both a small wild population (<20) and a captive population (c. 40-80) held in an enclosure of several hectares. The reintroduction was carried out by the New South Wales Department of Tourism, which controlled both sites. The primary aim was to provide a feature for tourists (>40 000 in 1985) who visited the guided show caves at Wombeyan. Wallabies were caught within the Jenolan enclosure, placed in individual hessian sacks, and transported to Wombeyan by vehicle (approximate travel time 2 h). The initial two pairs were held in a small enclosure (c. 10 x 10 m) within 50 m of a limestone cliff and arch. They were released after six weeks. One wallaby apparently immediately left the area, being seen several days later at a quarry 2 km downstream of the release site. The remaining three wallabies were sighted near the release site on 16 April 1980, three weeks after release from the enclosure. The additional three pairs were released directly to the site because of the presence of resident animals. Information on the colony is scant for the period up to October 1986. At this time the colony consisted of nine animals: six males and three females. Animals appeared to be confined to a very limited area around the release site (within 500 m), despite suitable habitat extending for some kilometres to the south and west. Guide staff remembered locating at least two carcases of

Reintroduction of macropods Australia Table 3.

Species

Year(s) of reintroduction

197

Reintroductions of macropods to the Australian mainland

Site

Number reintroduced

Survival

Source

Factors limiting success of reintroduction

1911-14

Wilson's Promontory, Victoria

?

?

Quokka

1972-88

Jandakot, WA

c. 700

Some >3 year, ?Foxes most <1 year

This paper, Algar (1986)

Tammar wallaby

1971-82

Jandakot, WA

85

< 2 years

?Foxes

This paper

Brush-tailed bettong

1977

Yendicup Block, Perup, WA

52

13 years +

Foxes (controlled by 1080 baiting in 1979 (twice), 1980 (twice) and 1981 (once))

P. Christensen

Brush-tailed bettong

1982-83

Collie, WA

52

<2 years

Foxes (baited once at release), insufficient ground cover, ? native cats

P. Christensen (pers. comm.)

Brush-tailed bettong

1983

St Johns Brook, Nannup, WA

67

<6 months

Foxes (no 1080 baiting)

P. Christensen (pers. comm.)

Brush-tailed 1980-81 rock-wallaby

Wombeyan

4 + 6

10+ years

?Foxes, cats

This paper

Rufous 1984-85 hare-wallaby

Lake Surprise, NT

12 + 15

c. 16 months

?Drought, cats, dingos

Lundie-Jenkins (1989)

Rufous hare-wallaby

1990

Lake Surprise, NT

11

<4 months

Cats

K. Johnson (pers. comm.)

Parma wallaby

1988

Robertson, NSW

47

<4 months

Foxes

This paper

Red-bellied pademelon

Thylogale billardierii

9

Menkhorst & Mansergh (1977)

(pers. comm.)

Caves, NSW

rock-wallabies from the immediate area of the release site over the years since release. Hence there had been both mortality and recruitment over the six years since the establishment of the colony. However, the founder animals had not been marked so it was not possible to ascertain which animals had been recruited into the population since translocation, apart from one subadult male. Over the next four years there was a gradual loss of animals from the site with no recruitment (Fig. 2). By March 1990 only three animals remained: two males and a female. Females were known to have produced young in 1987 (two of two females caught) and 1989 (the one remaining female observed with a mature joey in the pouch), but none of these animals were recruited into the population. Rock-wallabies have been recorded as living for 12-15 years in captivity (Collins, 1973), so it is possible that many of the animals were the original translocated stock that were dying of old age in the late 1980s.

No management regime was put in place to assist establishment of rock-wallabies after the 1980 release apart from providing food pellets. Cats and foxes were occasionally shot. Rabbits occurred at low densities throughout the 1980s in the area around the release site. However, cats were at high densities in the area, probably attracted by food scraps left by tourists in camping and picnic areas. They were often seen in and around the cliffs and limestone arch used by the rock-wallabies. Foxes were present in the area but not seen as frequently as cats.

Other reintroductions of macropods Table 3 provides a brief summary of nine reintroductions of macropods to mainland Australia, including four described in detail above. The location of each reintroduction is shown in Fig. 3. The only successful reintroduction was of the brush-tailed bettong Bettongia penicillata, which was shifted

J. Short, S. D. Bradshaw, J. Giles, R. 1. T. Prince, G. R. Wilson

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within Perup Nature Reserve. Hence the success rate of mainland reintroductions to date is 11%. Bettongs at Perup were transferred 13 km to the north within the same reserve. There were no obvious barriers to dispersal between source and reintroduction areas. However, bettongs had been absent at the latter site for a period of five years prior to the reintroduction (P. Christensen, pers. comm.). Fox control was implemented during establishment of the bettong population but apparently not thereafter. The Perup area is subject to a burning regime designed to foster regrowth of heartleaf poison Gastrolobium bilobum thicket as a management practice to ensure habitat for tammar wallabies (Christensen & Maisey, 1987). The thickets provide cover and the plants (which contain monosodium fluoroacetate) have an important role in controlling predators. Native herbivores feeding on the plants have a high tolerance but introduced predators feeding on the herbivores die from secondary poisoning. Hence predator numbers remain low. Table 2 provides a similar summary of translocation of macropods to islands; locations are shown in Fig. 3. Most are to offshore islands but Pulbah Island, Island A and Bairds Bay Island are in estuaries or coastal lakes. One reintroduction (St Peter Island) is too recent to make any judgement on its success. Of the remaining 15 it seems that 9 (60%) have been successful in that the populations appear to have established-maintained for >5 years and showing every sign of persisting (tammar wallabies to Greenly and

Fig. 3. The location of reintroductions of macropods listed in Tables 2 and 3. 1, Dirk Hartog Island; 2, Jandakot; 3, Collie, Nannup, Perup; 4, Woody Island; 5, St Peter, St Francis, Bairds Bay Island, and Island A; 6, South Pearson and Greenly Islands; 7, Wedge and Thistle Islands; 8, Kangaroo and Granite Islands; 9, Bird Club Island; 10, Wilson's Promontory; 11, Robertson; 12, Wombeyan Caves; 13, Pulbah Island; 14, Lake Surprise.

Granite Islands, western grey kangaroos to Woody Island, black-flanked rock-wallabies Petrogale lateralis to South Pearson, Thistle and Wedge Islands, brush-tailed bettongs to Island A, Bairds Bay Island, and Wedge Island), All were to islands which have no foxes or cats.

DISCUSSION AND R E C O M M E N D A T I O N S Land use changes in Australia since European settlement have generally benefited the large macropods (kangaroos), but have led to the extinction and decline of the smaller species (wallabies and ratkangaroos). Those of the latter group that persist often do so within a small fraction of their former ranges. Extensive land clearance in some areas (e.g. cereal-growing areas) mean that there is little scope for re-establishing wild self-sustaining populations of macropods. However, over much of Australia, the native vegetation is sufficiently intact for wildlife managers to convince themselves that some small change in management (reduction of grazing pressure by stock, change in fire regimes, control of exotic predators) may allow reestablishment of native mammal populations. Hence reintroduction is an attractive option. Reintroduction as a management strategy for conservation has become increasingly popular since

Reintroduction of macropods in Australia the early 1970s. Our overview of macropod reintroductions reveals a major dichotomy between those to mainland Australia and those to islands. The success rate of island reintroductions (60%) is far greater than that of the mainland (11%). Ironically the successful island reintroductions were all to islands which have no historic record of the occurrence of the reintroduced species although present on the adjacent mainland (strict application of the I U C N definitions given above would result in these being classified as 'introductions' rather than 'reintroductions'). The success of these translocations is mirrored by similar successful introductions of wallabies to islands in New Zealand (Wodzicki & Flux, 1967b) and Hawaii (Kramer, 1971). This dichotomy is even more stark if sites with cursorial predators are compared to those without. Reintroductions to islands and mainland sites with such predators have a success rate of 8%. This compares with the success rate of reintroductions to sites (all islands) without such predators (82%). Hence successful reintroduction requires the absence or effective control of cursorial predators such as foxes and cats. We offer a number of generalisations and recommendations from our overview of the 25 reintroductions. We believe these may assist researchers in planning and implementing future reintroductions.

Planning of reintroductions Clear objectives and appropriate experimental design There can be a variety of reasons for reintroducing populations. The most common is to increase the probability of the long-term survival of the species by creating additional populations. Objectives other than this include providing regular wildlife sightings for tourists (as at Wombeyan), and a teaching facility for students (as at Jandakot). Another objective may be to understand the reason(s) for the former decline of the species across its range. Different objectives may require different methods and different reintroduction sites. If the primary aim is conservation then a site will be chosen where European impacts are minimal (e.g. no stock and with rabbits, foxes, and cats either absent or at low densities). If the primary aim is to understand the cause(s) of decline and extinction then sites with various combinations of these post-European impacts may be required so that

199

their separate and/or synergistic effects may be identified. Whatever the primary objective, an experimental design which incorporates monitoring of both the reintroduced population and an experimental control (preferably the source population) will allow comparison of patterns of mortality, fecundity, condition, recruitment, and dispersal. This should give valuable insight into the reasons for success or failure of the reintroduced population to establish. Two examples where such data would have been useful are the reintroductions of banded hare-wallabies to Dirk Hartog Island and quokkas to Jandakot. In both cases a number of explanations could be given for the failure of the populations to establish. The effect of a severe summer drought, competition from sheep and goats for the reduced food supply due to drought, or predation from cats are all equally plausible explanations for the failure of the reintroduction on Dirk Hartog Island. Similarly, predation by foxes and cats, failure of quokkas to establish effective social units after relocation, and competition from rabbits and kangaroos are possible explanations for the failure of quokkas to establish at Jandakot. In both cases a comparison of population parameters between reintroduced and source populations would have helped adjudicate between alternative explanations. Harvesting theory (e.g. Caughley, 1977) suggests that high levels of predation should increase the availability of food per head for survivors. Hence body condition and reproduction should be enhanced. In contrast, food shortage or a disrupted social system (characterised by high levels of stress within the population) would inevitably be reflected in poor body condition and reproduction.

Long-term commitment to management Often the forces that caused the initial decline of a species at a site will need ongoing management after that species is reintroduced. Hence a longterm commitment to husbandry/management is necessary before embarking on a reintroduction. Such ongoing management is often carried out by different staff from those who carried out the reintroduction. This suggests that there should be broad consultation and agreement between researchers proposing to reintroduce species and managers who may be charged with long-term custodial care of the reintroduced population. An example may be that of researchers introducing a species that may require frequent

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J. Short, S. D. Bradshaw, J. Giles, R. I. T. Prince, G. R. Wilson

(monthly) baiting for predators and then handing this requirement over to management staff when the reintroduced population appears established. If this requirement is not a priority for management or is not adequately resourced then the reintroduction may falter or fail.

Site parameters Choosing a release site The most effective formula for successful reintroduction is likely to be the relocation of wallabies to areas where the impact of European man is least. Often such sites are islands. Most (nine out of ten) successful reintroductions of macropods have been to islands. Similarly reintroductions of koalas Phascolarctos cinereus to Phillip and French Islands in Victoria were so successful that they provided stock for many mainland reintroductions (Warneke, 1978). However, reintroductions of brush-tailed bettongs to St Francis Island, banded hare-wallabies to Dirk Hartog Island, and bridled nail-tail and parma wallabies to Pulbah Island are examples where reintroduced populations on islands continued to be subjected to the effects of man and his introduced species. Trans-fer of macropods to offshore islands adjacent to their former mainland range may produce major changes in vegetation that are often regarded as undesirable (e.g. tammar wallabies to Granite Island (Tsatsarouis & Savarton, 1986) and Greenly Island (Robinson, 1980), and grey kangaroos to Woody Island (Goodsell et al., 1976). Factors influencing choice of sites for mainland reintroduction include: quality of habitat, knowledge of prior occurrence of the species, similarity to site of source population, practicality of predator control, access and facilities, and land tenure. Choice of a site where there is the possibility of several threatened species being re-established may generate substantial economies of scale in management effort. Griffith et al. (1989) emphasised the importance of choosing a high-quality site that falls within the core (cf. periphery) of the species' former range. This core may not be the geographical centre of the species' range but rather the area where it occurs (or occurred) at highest density. If density information is not available then a reasonable first approximation may be the centre of the 'climate space' occupied by the species (see examples for red and grey kangaroos in Caughley et al., 1987: Fig. 4).

Effective predator control or exclusion is essential The most consistent factor limiting the success of reintroductions appears to have been predation. This includes foxes at Robertson, foxes and cats at Jandakot and Wombeyan, foxes, cats, and dingos at Lake Surprise, dogs on Pulbah and Bird Club Islands, and a contributing effect from cats on Dirk Hartog Island. Hence effective control of predation is essential to ensure the success of any reintroduction of wallabies in this size range. This conclusion is reinforced by the successful application of predator control to the management of threatened mammals. Kinnear et al. (1988 and pers. comm.) reported substantial increases in the density of threatened fauna (rock-wallabies, bettongs, and tammars) after effective control of foxes using the poison 1080. Similarly, Friend (1990) successfully reintroduced numbats Myrmecobius fasciatus to Boyagin Nature Reserve in the southwest of Western Australia using a similar intensive programme of fox control. The lack of success of baiting of foxes at Robertson and Jandakot contrasts markedly with these successes. This may have been due largely to less frequent and less systematic baiting, and to the poor timing of baiting relative to local rainfall (e.g. the 753 mm of rain that fell at Robertson in April 1988 would have rendered meat baits ineffective, as 1080 is highly soluble). Baiting regimes for the effective control of exotic predators are still under test. However, some broad generalisations can be made. Regular baiting appears essential. Kinnear et al. (1988) and Friend (1990) baited at monthly intervals; baiting at six-monthly intervals has been used successfully for a reintroduction of numbats of Karroun Hill Nature Reserve, WA (J. A. Friend, pers. comm.). Baiting should take place a sufficient time before reintroduction to ensure that it has been effective. High rates of reinvasion by foxes to poisoned areas may make it necessary to poison substantial buffer zones around reintroduction sites. An effective buffer zone of 20 km (approximately double average dispersal distance) would appear to exceed 92% of cub dispersals (Coman et al., 1991). Aerial baiting may be the most costeffective means of applying meat baits over a large area. Areas of high rainfall (either annual or seasonal) may require delivery of bait in a way that prevents loss of 1080 through leaching. Domestic fowl eggs baited with 1080 rather than conventional meat baits have been used to control

Reintroduction of macropods in Australia foxes during wet winter months in the Western Australian wheatbelt (Kinnear et al., 1988; Friend, 1990). The impervious shell prevents dilution of the poison. Problems may arise in the use of 1080 for the control of introduced predators around settlements and farms where residents may be concerned for the safety of domestic pets or farm dogs, and sites where there are vulnerable native species that might take meat baits. The implication of introduced predators in the failure of reintroductions is now leading to the choice of sites for reintroductions which offer some advantage in predator control (e.g. areas with a high density of the plants Gastrolobium and Oxylobium which are toxic to introduced herbivores and to introduced carnivores through secondary poisoning because they contain 1080 (King, 1981), deserts which may have low densities of foxes (Burrows & Thomson, 1990), and peninsulas where reinvasion after initial poisoning may be minimal and readily controlled (Beckmann, 1990)).

Population parameters Use of captive-bred vs wild-caught stock Successful reintroductions of macropods include those that have used captive-bred stock (e.g. brush-tailed bettongs to South Australian islands: Delroy et al., 1986) and those that have used wild stock (e.g. brush-tailed bettongs to Perup: P. Christensen, pers. comm.). Friend (1990) successfully translocated both captive-bred and wildcaught numbats. Griffith et al. (1989) found that translocations from wild-caught stock were generally more successful (75%) than those from captive-bred stock (38%). Sex-ratio of introduced stock Sex ratios of reintroduced stock have often been biased in favour of females (e.g. quokkas c. 4:1). Survival of males after reintroduction has often been higher than that of females (e.g. quokkas trapped annually at Jandakot generally had a ratio of c. 2 females: 1 male; rock-wallabies at Wombeyan (Fig. 2)). Effect on source populations of taking animals for reintroductions Detailed information on the response of the source population to a 'harvest' for translocation

201

or to establish a captive colony is often lacking. We know of no examples where removal of macropods from relic populations for reintroductions has had a detrimental effect on the source population. This has important implications for the ethics of translocating threatened species to sites that may be suboptimal, as occurs when researchers challenge the threatened species with some level of the agent(s) believed responsible for the species' decline.

Size of release group Increasing the size of starting group should improve the prospects of establishment of a population (e.g. MacArthur & Wilson, 1967). This is borne out by an analysis of 155 translocations (predominantly of game species) by Griffith et al. (1989). They found an asymptotic relationship between number of animals released in a translocation and probability of success of that translocation. Their results suggested an optimum size of release group of c. 20-40 for large mammals, and 80-120 for game birds. There is little evidence from macropods to support an increased probability of successful reintroduction by releasing larger groups. Release groups have varied between four and 125 (Tables 2 and 3). Successful reintroductions have often resulted from the smaller releases. There are examples of macropod populations establishing from a single pair (e.g. brush-tailed rock-wallabies in Hawaii (Kramer, 1971)) when the habitat was suitable. What is obvious is that increasing the size of release group is no substitute for effective identification and management of factors limiting the population (chiefly predation).

Husbandry Pre-release training Observation of parma wallabies at the Robertson reintroduction site suggested that their behavioural responses to exotic predators were naive. This is not surprising given their history of isolation in predator-flee enclosures and on predator-flee islands. Their ability to learn appropriate responses is unknown. Little opportunity exists after reintroduction because all reintroduced stock generally succumb to one or a few predators within several months (e.g. parmas at Robertson and Pulbah Island and rufous hare-wallabies in the Tanami Desert).

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J. Short, S. D. Bradshaw, J. Giles, R. I. T. Prince, G. R. Wilson

Training in predator avoidance for captive-bred stock or stock from islands lacking cursorial predators should be contemplated when reintroducing to mainland sites where they will inevitably come in contact with predators such as foxes and cats. An initial goal may be to put predators and prey together in a non-lethal situation to provide an opportunity for the prey to develop appropriate escape or avoidance responses. This recommendation is consistent with those of Kleiman (1989), who discussed a variety of training programmes for reintroduced mammals. Management .of animals during transport and acclimatisation There have been no reports of death or injury in transport other than that due to the use of valium on parmas. Macropods are transported either in hessian bags, in wooden boxes, or in 'pet packs'. They are caged or bagged individually. Emphasis should be placed on keeping animals cool, quiet, and in darkness or semi-darkness. The use of tranquillisers such as valium may be helpful in some situations. The capture and handling of macropods has been discussed by Poole (1982). Most researchers have attempted to confine animals for periods of weeks or months after translocation when there has been the possibility of animals dispersing widely. It is believed this allows time for animals to familiarise themselves with their new surroundings, establish a social order, and locate food provided. This seems a good idea but there is little evidence to either support or refute this practice.

Monitoring Radio-collaring of animals is essential to understanding post-release events and assessing survival of' the reintroduced population. However, few studies have made effective use of this well-established technique. A comparison between the reintroductions of parmas to Pulbah Island and Robertson provided an excellent example of the value of this technique. Parmas rapidly disappeared after release in both instances. Few carcases were recovered on Pulbah Island and hence the reason or reasons for the failure of this reintroduction remain unclear. Radio-collared carcases were recovered at Robertson, despite being buried, providing an insight into the reason for failure. There have been many reintroductions but few

are adequately documented. The major exception is that of the reintroductions of brush-tailed bettongs to islands off the coast of South Australia (Delroy et al., 1986). This is a major hindrance to the improvement of reintroduction techniques, particularly to mainland Australia. The use of reintroduction as a tool for the conservation of macropods has had a relatively inauspicious beginning. There are lessons that can and should be learnt from past mistakes but even then it may be difficult to increase the success rate of mainland reintroductions greatly without inordinate and long-term management effort. Many threatened species of macropods may be inherently more vulnerable than marsupials such as koalas (Warneke, 1978; Martin & Handasyde, 1990) and numbats (Friend, 1990) that have been successfully re-established in parts of their former ranges. However, substantial advances can be made by using reintroductions as a tool in understanding the reasons for the decline of species, in improving knowledge of the basic ecologies of threatened species, and in improving the application of new management strategies such as predator control.

ACKNOWLEDGEMENTS The authors wish to thank the various State wildlife agencies for permission to relocate animals; the Rottnest Island Board for assistance in removing animals from Rottnest Island; Brian Clay for assistance with tammars and quokkas at Jandakot; guide staff at Wombeyan and Jenolan Caves, particularly Michael Chalker and Ernie Holland for their support; Sir Thomas Wardle for logistic support and encouragement on Dirk Hartog Island; Ron Strahan and Graham Robertson for assistance with the reintroduction to Pulbah Island; Peter Pigott for his assistance with the conservation of parma wallabies generally as well as his specific support for their reintroduction; and Don Tilley, the New South Wales Water Board and the Zoological Parks Board of New South Wales for assistance with the reintroduction of parmas to Robertson. Australian National Parks and Wildlife Service and Dick Smith provided financial support for the reintroduction of parmas to Robertson. We thank Per Christensen and Peter Copley for providing unpublished information. Peter Copley and Ken Johnson critically reviewed an earlier draft of this manuscript.

Reintroduction o f macropods in Australia

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