Jeff Short

MAMMAL DECLINE AND RECOVERY IN AUSTRALIA

Fifty percent of all the mammal species to have become extinct worldwide in the past 200 years have been lost from the Australian fauna giving Australia the worst record for mammal conservation of any country or continent. Sixteen species from a mammal fauna of 245 are believed to be extinct, 26 species now occur only as remnant populations occupying <20% of their former ranges. Offshore islands, tropical Australia, and the mesic fringe of the continent have provided refuges where mammal communities have survived relatively intact. The drier interior regions, which include cereal growing areas, intensive and extensive pastoral areas, and the little-used Triodia deserts, have lost many species. Extinctions and declines have not occurred equally throughout the Australian fauna, but have occurred at a disproportionately higher rate among medium-sized ground-dwelling mammals in the weight range 0.035-5.500 kg. Historically, conservation of mammals has concentrated on protection from hunting and trade, reservation of land as national parks and nature reserves, and faunal surveys to map distribution and abundance. These approaches have been necessary but insufficient to either stabilize the decline of endangered mammals or to promote their recovery. The past 20 years have seen many attempts to conserve endangered mammals, either by evading the presumed cause(s) of extinction or decline by translocation to islands, or by managing these causes within reserves by controlling exotic predators, controlling or excluding exotic herbivores, or applying a particular fire pattern or regime. The most significant successes have come with effective control of exotic predators, either by establishing populations of endangered species on predator-free islands or by the intensive use of 1080 poison to control exotic predators at mainland sites.

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

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.

Kangaroos, their ecology and management in the sheep rangelands of Australia

Preface 1. Introduction to the sheep rangelands Graeme Caughley 2. The environment of the Australian sheep rangelands Graham Robertson, Jeff Short and Greg Wellard 3. The effect of weather on soil moisture and plant growth in the arid zone Greg Wellard 4. Plant dynamics Graham Robertson 5. The diet of herbivores in the sheep rangelands R. D. Barker 6. Factors affecting food intake of rangelands herbivores Jeff Short 7. The mobility and habitat utilisation of kangaroos David Priddel 8. Kangaroo dynamics Peter Bayliss 9. Condition and recruitment of kangaroos Neil Shepherd 10. Ecological relationships Graeme Caughley 11. Options for management of kangaroos Neil Shepherd and Graeme Caughley Indices.

Surplus killing by introduced predators in Australia—evidence for ineffective anti-predator adaptations in native prey species?

Australian examples of surplus killing by mammalian predators were collated. These included surplus killing of native mammals and birds by foxes (Vulpes vulpes) and stock, native mammals and native birds by dingoes (Canis lupus dingo). We found no examples of surplus killing by feral cats (Felis catus). Incidents collated include historical anecdotes of surplus killing by foxes as they colonised the Australian mainland, recent examples where foxes killed threatened native species at sites despite intensive management to exclude foxes, and recent examples of the killing of native species on formerly fox-free islands to which foxes gained entry. Episodes of surplus killings by foxes, other than predation on captive or closely confined animals, appeared different in kind and frequency to those documented for co-evolved predator-prey systems on the large continental landmasses. They did not appear to be uncommon events associated with synchronised births of prey species, unusual or extreme weather that disadvantaged prey species, or seasonal food caching by a predator. Rather, surplus killing events appeared to reflect ineffective anti-predator defences by prey species when encountering a novel and efficient predator to which they have had no evolutionary exposure. We suggest that surplus killing by foxes may have been a feature of, and major contributor to, the rapid mainland extinction or contraction in range of many native species in Australia. In contrast to foxes, examples of surplus killing by dingoes relate mostly to domestic stock (calves and sheep). The arrival of dingoes to the Australian continent preceded that of foxes by 3500-4000 years, but they appear not to have had the dire impact on native mammals that we attribute to foxes. This may be due to fundamental differences in hunting styles and prey size and to their sparse populations in pre-European Australia. Active persecution of non-commensal dingoes by Aborigines, the lack of free-water, and the absence of European rabbits (Oryctolagus cuniculus) as an alternative food supply would have limited their numbers and their impact on native mammals.

The impact of cats and foxes on the small vertebrate fauna of Heirisson Prong, Western Australia. II. A field experiment

The hypothesis that predation by feral cats and introduced foxes reduces population sizes of small, native vertebrates was supported by results of a predator-removal experiment at Heirisson Prong, a semi-arid site in Western Australia. The methods of control used against cats and foxes to protect native mammals reintroduced to Heirisson Prong produced three broad ‘predator zones’: a low-cat and low-fox zone, where foxes were eradicated and spotlight counts of cats declined after intensive cat control; a high-cat and low-fox zone where spotlight counts of cats increased three-fold after foxes were controlled; and a zone where numbers of cats and foxes were not manipulated. Small mammals and reptiles were monitored for one year before and three years after predator control began. Captures of small mammals increased in the low-cat and low-fox zone, but where only foxes were controlled captures of small mammals declined by 80%. In the absence of cat and fox control, captures of small mammals were variable over the sampling period, lower than where both cats and foxes were controlled, yet higher than where only foxes were controlled. The capture success of reptiles did not appear to be related to changes in predator counts. This study presents the first experimental evidence from mainland Australia that feral cats can have a negative impact on populations of small mammals.

The extinction of rat-kangaroos (Marsupialia:Potoroidae) in New South Wales, Australia

Three of five species of rat-kangaroo have declined to extinction within New South Wales since European settlement, and a fourth now occupies less than 2% of the state. This paper provides new evidence on the timing of those extinctions and details the spatial pattern of collapse of their populations. Data come from detailed records of bounty payments paid in districts throughout much of New South Wales for their control as pests of agriculture Nearly 3 million rat-kangaroos were harvested during the period 1883-1920. Rat-kangaroo populations survived the colonization of New South Wales by the European rabbit in the period 18701900, the build up of sheep numbers to a record 55 million in New South Wales in 1892, and the major changes in Vegetation structure and biomass that would have resulted. They also survived the major drought of 1888. The European red fox invaded New South Wales from the south in the late 1890s and occupied the entire state, apart from the far north-east, by 1915. Rat-kangaroo decline is closely associated with the south-north advance of the fox. In the south and central regions, the decline coincided with the drought of 1902. However, in the north, where foxes were yet to arrive, rat-kangaroo populations recovered strongly from that drought, only to collapse 10 years later as foxes advanced into the region.

The Functional Response of Kangaroos, Sheep and Rabbits in an Arid Grazing System

Red kangaroos Macropus rufus, merino sheep Ovis aries and rabbits Oryctolagus cuniculus were studied in grazing trial in the arid zone of W New South Wales. Animals grazed a chenopod shrubland composed of low halophytic bushes of Maireana pyramidata interspersed with a herb layer of annual forbs and grasses. Maximum food intakes of rabbits, kangaroos and sheep during the trial were 68, 62 and 61 g kg-0.75 day-1, respectively. These intakes are similar despite the 30% difference in basal metabolic rates between eutherians and marsupials. All species avoided Maireana but when food was scarce sheep switched to it more strongly than did the other herbivore species. Sheep consumed 20% of their intake as Maireana at a pasture biomass of 250 kg ha-1 compared to only 10% y the other two species at this biomass. Maireana reached 20% of the intake of rabbits and kangaroos at a pasture biomass of 100 kg ha-1. Harvesting efficiencies (ability to maintain food intake at low vegetation biomasses) of kangaroos, sheep and rabbits were considerably higher than that of sheep grazing sown pastures in higher rainfall areas. The three herbivore species appeared equally capable of reducing the pasture to an ungrazable residuum of less than 20 kg ha-1. The relationship between food intake and food availability for each species of herbivore was an asymptotic function, suggesting that this, rather than a linear function, is the typical pattern for most mammalian herbivores

Reintroduction of the burrowing bettong Bettongia lesueur (Marsupialia: Potoroidae) to mainland Australia

The burrowing bettong was successfully reintroduced to the Australian mainland in 1992 after an absence of 50 years. The population, derived from 42 individuals translocated from a remnant population on an offshore island, has persisted for over seven years on the Heirisson Prong peninsula at Shark Bay in Western Australia. It has grown to over 260 individuals that are distributed widely through available habitat. The successful management of exotic European foxes and feral cats proved crucial to the outcome of the reintroduction. Factors contributing to the successful management of predators and to a reduction in their impact included: the choice of a narrow peninsula as the site for reintroduction (permitting cost-effective use of predator-proof fencing); effective baiting (fox and cat) and trapping (cat) strategies; the maintenance of an in situ breeding colony (to provide insurance against major loss of free-range animals to predators); choice of high quality habitat (providing reasonable cover and promoting a high and relatively stable rate of increase for bettongs, even during dry years), and choice of a site that was accessible for regular management visits. An abundance of European rabbits at the reintroduction site appeared not to be a limiting factor. The success of this reintroduction has stimulated a range of other reintroductions of endangered mammals to arid and semi-arid sites across Australia, particularly to peninsulas or other sites where exotic predators can be controlled effectively.

KANGAROOS AND CLIMATE: AN ANALYSIS OF DISTRIBUTION

(1) The distributions of three partially sympatric kangaroo species, Macropus giganteus (Shaw), M. fuliginosus (Desmarest) and M. rufus (Desmarest), were analysed to determine their climatic characteristics. (2) M. giganteus occupies areas only where rainfall either has little seasonal trend or where rainfall in summer exceeds winter rainfall. (3) M. fuliginosus is found in areas of uniform or winter rainfall. (4) Seasonality of rainfall has little influence on the distribution of M. rufus. Instead, its distribution reflects interaction between mean annual precipitation and mean annual temperature. (5) The extent of sympatry and allopatry appears to be determined by the independent reaction of each species to specific and differing climatic stimuli rather than by biological interaction between species.

Reintroduction and establishment of the western barred bandicoot Perameles bougainville (Marsupialia: Peramelidae) at Shark Bay, Western Australia

The western barred bandicoot was reintroduced to the Australian mainland in 1995 after an absence of at least 60 years. The new population was derived from 14 animals, reintroduced to Heirisson Prong from Dorre Island in Shark Bay, Western Australia. Introduced predators (the European red fox and the feral cat) were controlled at the reintroduction site, but European rabbits were not. A large fenced area of natural vegetation within the reintroduction site was used as a secure refuge from mammalian predators. Bandicoots were released from this predator refuge to the 12 km2 conservation site. Dispersal from the point of free release was minimal. The reintroduced population has persisted for 4 years and increased, with at least 175 bandicoots recruited to the population in this time. The recapture rate of marked bandicoots was low, suggesting that adult mortality was high. Reproductive output at Heirisson Prong appeared greater than that of the two surviving wild populations on Bernier and Dorre Islands. Litter size was similar, but there was an extended annual breeding season at the reintroduction site. Body condition of reintroduced and wild bandicoots were similar, although there was some indication that reintroduced males may have been in poorer condition than their island counterparts. The litter size of bandicoots increased with a decrease in rabbit abundance, however, bandicoots were able to reproduce, maintain condition, and sustain recruitment to allow the population to increase despite the presence of rabbits. Two fox incursions occurred during the 4-year period of establishment, and feral cats were present on occasion in low numbers. Feral cats may be responsible for a lower rate of population increase than that observed on predator-free Dorre Island. Ongoing predator control is essential for any mainland reintroduction of bandicoots.