Ecological Restoration of sub-Antarctic Macquarie Island

Springer, K. Ecological Restoration of sub-Antarctic Macquarie Island.

Invasive vertebrate species have had devastating impacts on the flora, fauna and landforms of Macquarie Island over a period of 200 years. Following the successful eradication of weka (Gallirallus australis) by 1989 and feral cats (Felis catus) by 2001, planning for the eradication of ship rats (Rattus rattus), house mice (Mus musculus) and European rabbits (Oryctolagus cuniculus) began in 2004. Funding of AUD$24.7M was secured in 2007 for a multi-year project based on aerial baiting targeting rabbits and rodents followed by ground hunting targeting surviving rabbits. The first aerial baiting attempt in 2010 was abandoned due to unfavourable weather and shipping delays. The degree of non-target seabird species mortality from limited baiting in 2010 lead to a renewed examination of non-target mitigation options. Rabbit Haemorrhagic Disease Virus (RHDV) was introduced in February 2011, to reduce the pre-baiting rabbit population and thus minimise non-target mortality amongst scavenging seabirds. Aerial baiting resumed in May 2011 using four AS350 helicopters and a team of 27 people, and was completed by July 2011. No rodents have been detected post-baiting and the estimated rabbit population of 150,000 has been reduced to fewer than 30 at the conclusion of baiting The rabbit hunting phase commenced in July 2011 using a team of 15 hunters and 12 dogs and is ongoing, with thirteen rabbits accounted for. Hunting and monitoring is expected to take a total of five years post-baiting and will be based on annual progress reviews. A minimum of two years monitoring will be conducted. Rodent detection dogs will deploy in 2013 to assist in determining rodent eradication success.
Six months after baiting, vegetation recovery was already evident and increased burrownesting seabird activity has also been observed in the first breeding season post-baiting.

Macquarie Is. eradication accomplished

Mission Accomplished - Landline - ABC

Ecology of the feral cat on Macquarie Island

Jones, E. (1977). Ecology of the feral cat, Felis catus (L.),(Carnivora: Felidae) on Macquarie Island. Wildlife Research, 4(3), 249-262.

On Macquarie Island from December 1973 to March 1975 the diet of feral domestic cats (Felis catus) was estimated. There was rabbit (Oryctolagus cuniculus) in 82% of faeces and 71% of guts, rabbits under 600 g bodyweight, about 10 weeks old, were 81% of all rabbits eaten. There were Antarctic prion (Pachyptila desolata) and white-headed petrel (Pterodroma lessonii). Cats ate small numbers of rats, mice and wekas and scavenged on dead elephant seals and penguins, especially in winter. Availability of food in winter seemed to be an important factor limiting the population; adult population was estimated to be 250 to 500 and the area of the island is 120 km². Prion and white-headed petrel nest in burrows; there was little or no predation by cats on surface nesters such as albatross, giant petrel, southern skua or southern black-backed gull, or on live penguin.

Macquarie Is. declared rodent and rabbit free

via ABC news

The World Heritage-listed Macquarie Island has been declared free of pests after a near seven-year campaign to eradicate it of rats, rabbits and mice...

Eradication of cats from Macquarie Island

Robinson, S. A., & Copson, G. R. (2014). Eradication of cats (Felis catus) from subantarctic Macquarie Island. Ecological Management & Restoration 15: 34–40. doi: 10.1111/emr.12073.

A feral cat roams among baby penguins on Macquarie Island.
Photo: Geoff Copson/ Tasmanian NPWS

The feral Cat (Felis catus) population on Macquarie Island was targeted for eradication between 1996 and 2002, with 761 cats captured during this period. After 22 years of cat control from 1974 integrated with control programmes for other pests, effort intensified for 2 years before a dedicated eradication programme began in 1998. The primary knock-down for the eradication used cage trapping and shooting, with most surviving cats captured with leg-hold traps. A total of 6298 field days and 216 574 trap nights were recorded in this operation. Factors contributing to the success of the programme included extensive planning, increased staff numbers at critical times, better access to remote areas of the island, introduction of leg-hold traps, sufficient operational funding and good collaboration between government agencies operating on the island. The programme would have benefited from earlier deployment of detector dogs and better posteradication monitoring of a broader range of native species impacted by cats. The successful eradication of cats from Macquarie Island, being the second largest achieved to date, provides valuable experience for cat eradication attempts on other large remote islands. This programme relied on ground-based techniques with minimal use of poisons and provides possible options for sites where broad-scale poisoning, or where aerial distribution of poisons, cannot be used.


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Invasive mammal eradication on Macquarie Island

Springer, K. 2014. Pest Eradication on Macquarie Island. Australia's State of the Islands Report. Pp. 70-80.

Invasive vertebrate species have been present on Macquarie Island for over 200 years, and have had devastating impacts on flora, fauna and landforms. Weka (Gallirallus australis) were successfully eradicated by 1989 and feral cats (Felis catus) by 2001. Planning for the eradication of ship rats (Rattus rattus), house mice (Mus musculus) and European rabbits (Oryctolagus cuniculus) began in 2004. Funding of AUD$24.7M was secured in 2007 for a multi-year project based on aerial baiting that targeted rabbits and rodents, followed by hunting of any surviving rabbits. Following three years of planning, the first aerial baiting attempt in 2010 was abandoned after two months due to unfavourable weather and shipping delays. The degree of non-target seabird species mortality from the limited baiting in 2010 lead to a renewed examination of non-target mitigation options. Rabbit Haemorrhagic Disease Virus (RHDV) was introduced in February 2011, to reduce the pre-baiting rabbit population and thus minimise non-target mortality amongst scavenging seabirds. Aerial baiting resumed in May 2011 using four AS350 helicopters and a team of 27 people, and was completed by July 2011. No rodents have been detected post-baiting and the estimated rabbit population in excess of 150,000 has been reduced to less than an estimated 30 at the conclusion of baiting. Some rabbits were expected to survive baiting, and the hunting phase commenced in July 2011 using a team of 15 hunters and 12 dogs. By December 2011thirteen rabbits had been accounted for. Hunting efforts are ongoing, and together with a monitoring phase are planned to continue for five years. A minimum of two years monitoring for rabbits will be conducted. Continued effort each year will be based on annual progress reviews. Rodent detection dogs will deploy in 2013 to assist in determining rodent eradication success. After one summer since baiting, vegetation recovery is already evident and increased burrow-nesting seabird activity has also been observed in the first breeding season postbaiting.

How the Macquarie Island parakeet became extinct

Taylor, R. H. (1979). How the Macquarie Island parakeet became extinct. New Zealand Journal of Ecology, 2, 42-45.

For 70 years following the discovery of Macquarie Island in 1810 the endemic parakeet Cyanoramphus novaezelandiae erythrotis remained plentiful, despite the introduction of cats (Felis catus) and other predators. The crucial factor in the bird's rapid disappearance between 1881 and 1890 appears to have been the successful liberation of rabbits (Oryctolagus cuniculus) in 1879. This led to great increases of feral cats and introduced wekas (Gallirallus australis) and presumably to greatly intensified predation on parakeets.

Changes in numbers of parakeets, rats,mice, feral rabbits, feral dogs, feral cats and wekas on Macquarie Island 1810-1920. Diagrammatic reconstructionfrom early accounts (Cumpston, 1968). Not to scale.

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Recovery of seabirds to vertebrate management on Macquarie

Brothers, N. & Bone, C. (2008) The response of burrow-nesting petrels and other vulnerable bird species to vertebrate pest management and climate change on sub-Antarctic Macquarie Island. Papers and Proceedings of the Royal Society of Tasmania, 142, 123-148

Pest species management is causing rapid and significant changes to burrow-nesting petrel populations on sub-Antarctic Macquarie Island. The Weka, Gallirallus australis, was eliminated by 1989 and the Feral Cat, Felis catus, eradicated in 2000. The most abundant burrownesting petrel species currently, White-headed Petrels, Pterodroma lessonii, Antarctic Prions, Pachyptila desolata, and Sooty Shearwaters, Puffinus griseus, have yet to increase in numbers, but are expected to do so in the absence of cats. This study found evidence that Grey Petrels, Procellaria cinerea, began breeding again on the island in 1999, after an absence of over 100 years. Blue Petrels, Halobaena caerulea, and Fairy Prions, Pachyptila turtur, were found to be re-colonising Macquarie Island from offshore stacks after a similar absence. South Georgian Diving-Petrels, Pelecanoides georgicus, were also possibly recolonising the island. Despite the presence of Black Rats, Rattus rattus, most of the bird species discussed are considered capable of population increase. If European Rabbits, Oryctolagus cuniculus, are not eliminated or maintained in reduced numbers, some petrel populations will never fully recover. Climate change could have a negative impact on burrow-nesting petrels, and is likely to exacerbate the detrimental effects of the remaining pest species on vulnerable indigenous bird species, compounding the need for remedial action against rabbits in particular. Together with predictions that other petrel species will now return to breed, certain terrestrial bird species, alien to the region, may invade Macquarie Island as a consequence of the combination of pest eradication and changing climatic conditions.


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Ecological restoration on Macquarie island

Copson, G., & Whinam, J. (2001). Review of ecological restoration programme on subantarctic Macquarie Island: pest management progress and future directions. Ecological Management & Restoration, 2(2), 129-138.
The establishment of exotic species of vascular flora and vertebrate fauna on subantarctic Macquarie Island since its discovery in 1810 has resulted in major changes in the biota. A management programme aims to reduce the numbers of exotic plant and animal species and assist with the recovery of pre-existing communities and processes. This paper reviews the integrated vertebrate pests management programme on Macquarie Island since 1974 and outlines future management considerations. As part of this programme, the responses of some native and exotic species of vascular flora and vertebrate fauna were monitored following control of European Rabbit (Oryctolagus cuniculus) numbers. Changes in the vegetation recorded over 10 years showed that approximately half of all the vascular species had benefited from rabbit grazing, including several which formed a major part of the rabbit’s diet. After rabbit control, some adversely affected plants responded rapidly to a reduction in grazing pressure while others will require an almost total cessation of grazing in order to re-establish their former distributions. With the decrease in rabbit numbers it was also necessary to control Feral Cats (Felis catus) due to their increased predation on native burrow-nesting birds. Feral Cat predation on introduced fauna also increased, one result of which was the eradication from the island of the introduced Weka (Gallirallus australis scotti). Reduced rabbit grazing is leading to re-establishment of the native Tall Tussock (Poa foliosa) grassland and with it the spread of the introduced Ship Rat (Rattus rattus). This review indicates that an integrated approach to pest management, with monitoring of the responses of both target and non-target species, is the most effective way to restore pre-existing communities and processes.

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Biology of feral cats on Macquarie

Brothers, N. P., Skira, I. J., & Copson, G. R. (1985). Biology of the feral cat, Felis catus (L.), on Macquarie Island. Wildlife Research, 12(3), 425-436.

A feral cat roams among baby penguins on Macquarie Island.
Photo: Geoff Copson/ Tasmanian NPWS

246 feral cats were shot on Macquarie Island, Australia, between Dec. 1976 and Feb. 1981. The sex ratio ( males : females ) was 1:0.8. The percentages of animals with tabby, orange and black coats were 74, 26 and 2 resp. [sic]. Of the 64 orange cats, 56 were males . The breeding season was Oct.-Mar., with a peak in Nov.-Dec. The number of embryos in the 14 pregnant females averaged 4.7 (range = 1-9). The size of the 23 litters that were observed averaged 3 (range = 1-8). Kitten survival to 6 months of age was estimated to be <43%.

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Controversy on cat's eradication on Macquarie Island: predator or pathogen's release?

Bergstrom D, Lucieer A, Kiefer K, Wasley J, Belbin L, Pedersen T & Chown S (2009). Indirect effects of invasive species removal devastate World Heritage Island. Journal of Applied Ecology, 46: 73-81

A feral cat roams among baby penguins on Macquarie Island.
Photo: Geoff Copson/ Tasmanian NPWS

1. Owing to the detrimental impacts of invasive alien species, their control is often a priority for conservation management. Whereas the potential for unforeseen consequences of management is recognized, their associated complexity and costs are less widely appreciated.

2. We demonstrate that theoretically plausible trophic cascades associated with invasive species removal not only take place in reality, but can also result in rapid and drastic landscape-wide changes to ecosystems.

3. Using a combination of population data from of an invasive herbivore, plot-scale vegetation analyses, and satellite imagery, we show how a management intervention to eradicate a mesopredator has inadvertently and rapidly precipitated landscape-wide change on sub-Antarctic Macquarie Island. This happened despite the eradication being positioned within an integrated pest management framework. Following eradication of cats Felis catus in 2001, rabbit Oryctolagus cuniculus numbers increased substantially although a control action was in place (Myxoma virus), resulting in island-wide ecosystem effects.

http://ingervandyke.com/conservation/

4. Synthesis and applications. Our results highlight an important lesson for conservation agencies working to eradicate invasive species globally; that is, risk assessment of management interventions must explicitly consider and plan for their indirect effects, or face substantial subsequent costs. On Macquarie Island, the cost of further conservation action will exceed AU$24 million.

Dowding, J. E., Murphy, E. C., Springer, K., Peacock, A. J., & Krebs, C. J. (2009). Cats, rabbits, Myxoma virus, and vegetation on Macquarie Island: a comment on Bergstrom et al.(2009). Journal of Applied Ecology, 46(5), 1129-1132.

1. Eradication of a single pest species from a multiply invaded island system may have unpredicted and detrimental impacts.Bergstrom et al. (2009) describe damage to vegetation following an increase in the number of rabbits on Macquarie Island. They propose that the increase in rabbit numbers was caused solely by eradication of cats.

2. However, their modelling is flawed and their conclusion that cats were controlling rabbit numbers is unsupported. We suggest the increase was because of some combination of four factors: reduced releases of Myxoma virus, abundant food after 20 years of vegetation recovery, release from cat predation and climate variability.

3. Recent high numbers of rabbits on Macquarie Island are not unprecedented; vegetation has been damaged in the past but has recovered. Rabbit numbers appear to be in decline again in the absence of both cats and Myxoma releases, suggesting that other factors can contribute to regulation of rabbit numbers in this system.

4. We do not agree with the implication that pest management could have been better integrated. Eradication techniques for rodents and rabbits on an island the size of Macquarie were unavailable when cat eradication was deemed necessary. The benefits to seabirds of cat eradication have been rapid. Our analysis further highlights the complexity of multiply invaded island ecosystems.

Bergstrom, D. M., Lucieer, A., Kiefer, K., Wasley, J., Belbin, L., Pedersen, T. K., & Chown, S. L. (2009). Management implications of the Macquarie Island trophic cascade revisited: a reply to Dowding et al.(2009). Journal of Applied Ecology, 46(5), 1133-1136.

1. The management of non-indigenous species is not without its complications. In Bergstrom et al.’s (2009) study, we demonstrated that feral cats Felis catus on sub-Antarctic Macquarie Island were exerting top-down control on the feral rabbit Oryctolagus cuniculus population, and that the eradication of the cats led to a substantial increase in rabbit numbers and an associated trophic cascade.

2. Dowding et al. (2009) claim our modelling was flawed for various reasons, but primarily that a reduction in the application of the rabbit control agent, Myxoma virus, coinciding with cat removal, was a major driver of rabbit population release.

3. We explore this proposition (as well as others) by examining rates of Myxoma viral release between 1991 and 2006 (with an attenuation factor for the years, 2003–2006) in association with presence/absence of cats against two estimates of rabbit population size. Myxoma viral release was a significant factor in the lower estimates of rabbit population, but the effect was small, and was not significant for higher rabbit population estimates. By contrast, the presence or absence of cats remained highly significant for both estimates.

4.Synthesis and applications. We re-affirm our position that top-down control of rabbit numbers by cats, prior to their eradication, was occurring on Macquarie Island. Nonetheless, we agree with Dowding et al. (2009) that systems with multiple invasive species represent complex situations that require careful scrutiny. Such scrutiny should occur in advance of, during, and following management interventions.

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Cat diet on several sub-Antarctic islands

Kerguelen
Pontier, D., L. Say, F. Debias, J. Bried, J. Thioulouse, T. Micol & E. Natoli. 2002. The diet of feral cats (Felis catus L.) at five sites on the Grande Terre, Kerguelen archipelago. Polar Biology, 25: 833–837
Assessing the impact (direct or indirect) of introduced predator species on native seabird populations is a clear management priority, particularly so in the simple sub-Antarctic ecosystems where these effects may be dramatic. We evaluated the diet of introduced feral cats (Felis catus L.) on the Grande Terre, Kerguelen archipelago, by analysing 149 scats from 5 sites. Overall, rabbits (Oryctolagus cuniculus) were the primary prey (72.6%), followed by house mice (Mus musculus) (11.6%) and birds (all species confounded, 14.9%). However, the proportions of the three prey species varied among sites, reflecting the spreading pattern of cats onto the Grande Terre. Birds were consumed much less frequently in this study (7.3%, all sites pooled but one) compared to a 1976 study in the same area (66.3%), suggesting that cats had a strong impact on the native avifauna

Marion
van Aarde, R.J. 1980. The diet and feeding behaviour of feral cats, Felis catus at Marion Island. South African Journal of Wildlife Research, 10:123-128.

Analyses of prey remains (n = 1 224) and stomach contents (n = 125) of feral domestic cats at Marion Island indicated that these exotic predators mainly feed on nocturnal burrow­ing petrels (fam. Procellariidae). Seasonality in their diet is discussed and predation rate on the various prey species seems to be a factor of availability rather than selection. An estimate of predation rate based on the energy requirements of the cat population and the caloric content of their most im­portant prey species suggested that a single cat kills approximately 213 petrels per year.

Auckland
Harper, G.A. 2010. Diet of feral cats on subantarctic Auckland Island. New Zealand Journal of Ecology, 34(2): 259-261
Feral cats were trapped and cat scats collected at Port Ross, Auckland Island, during two weeks in winter 2007. Eleven cats were caught and 40 scats collected, including from upland tussock areas. Cats’ diet predominantly consisted of birds (77.5% occurrence in scats) and mice (52.5% occurrence). The cats were relatively heavy and in good condition compared with other feral cats in New Zealand populations.

Macquarie
Jones, E. (1984). The feral cat on Macquarie Island. Tasmanian Naturalist, 79: 16-17

Domestic cats must have been taken to Macquarie Island soon after its discovery in 1810; feral cats were reported on the Island by 1820 (Debenham 1945). No records are available on the activities of these cats for the next 70 years, but the role of the feral cat as a predator of burrow-nesting petrels was then recognised by visitors to Macquarie Island such as Hamilton (1894), Burton (1900) and Mawson (1916) (the latter two in Cumpston 1968).
During 1974 I studied the diet of feral cats on Macquarie Island by a combination of scat and gut analysis, in an effort to determine their present ecological impact on the Island's fauna.

The percentage frequencies of the major food items found in 756 cat scats are presented in Table 1.

TABLE 1. Occurrence of major food items in 756 cat scats.

Food Item	Number of Seats	Percentage Frequency
Rabbit	619	81.9
Prion	220	29.1
White-headed Petrel	120	15.9
Mouse	33	4.4
Penguin	25	3.3
Rat	20	2.6
Weka	15	2.0

These results clearty indicate that rabbits, Antarctic Prions and White-headed Petrels were the major dietary items; other foods were less frequently eaten. The analysis of the gut contents of an additional 41 adult cats confirmed this finding but also indicated a seasonal change of diet during winter when less common food items such as wekas were eaten, and scavenging on dead elephant seals and penguins took place. Also, by the measurement of bone fragments it was found that 58% of the rabbits eaten weighed 200 - 300g, 23% weighed 300 - 600g, 8% weighed 600 - 1300g, and 11% weighed more than 1300g.

Cats were sighted and seats collected from all parts of the Island but densities were highest in areas of greatest prey abundance. It was estimated that in 1974 there were between 250 - 500 adult cats present and those cats collected were similar in size (mean weight of males 4518g; mean weight of females 2844g) to common domestic cats.

The ecological impact that these cats are now having on the fauna of Macquarie Island is difficult to assess, due to the other major ecological changes which have also taken place. However thei r depredations may still be affecting the less common species of petrels present.

Since most burrow-nesting petrels are absent from the Island during winter and the young rabbits have grown larger, the total amount of food available to the cats at this time is at a minimum. This winter food stress acts as a yearly limit to the cat population size and also causes the change in diet mentioned earlier. Thus if a major reduction in the rabbit population could be achieved, then this would cause a corresponding reduction in the cat population. The remaining cats would then become major predators of young rabbits in the following spring and summer and suppress the rate of increase of the rabbit population. However if rabbits were eliminated from Macquarie Island, feral cats would become rare.

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Campbell

Dilks, P.J. Observations on the food of feral cats on Campbell Island. New Zealand Journal of Ecology, 2: 64-66. 

Feral cats (Felis catus) are very scarce on Campbell Island (52 S, 169 E). Scats were collected during three summer visits and later examined. Norway rats (Rattus norvegicus) were much the most important prey, although birds and insects were also taken.

Identification of sites of high conservation priority impacted by feral cats in Australia

Dickman, C. R., Denny, E. A., & Buckmaster, T. (2010). Identification of sites of high conservation priority impacted by feral cats. Report to the Department of Environment, Water, Heritage and the Arts, Canberra.

Feral cats (Felis catus) have been recorded throughout the Australian mainland and on many offshore islands. Predation by feral cats has been implicated, together with other factors, in the population declines of many species of native vertebrates. Some of these declines have resulted in the shifting of species’ conservation status to a more endangered level, with several native species having become extinct. Predation by feral cats is classified as a key threatening process by the Australian Government under the Environment Protection and Biodiversity Conservation Act 1999. 

The cryptic nature of the cat, its exploitation of both modified and unmodified habitats, its status as both a pest and a pet species, and the abundance of introduced prey species and supplemental food sources throughout its range, all contribute to the many acknowledged problems associated with the control or eradication of feral cats in Australia. 

In the absence of a single, robust way to measure cat densities and the known difficulties associated with assessing cat impacts at the species level, indirect methods are required to prioritise sites for the implementation of cat control programs. 

This report uses an interactive decision-making tree based on characteristics of prey species to provide a relative measure of probable cat impacts between sites on the Australian mainland and offshore islands. The decision-making tree provides a single score for geographical (IBRA) regions, specific mainland sites and offshore islands that may be used comparatively for the allocation of resources for cat control programs. Although the scores in this report are based only on those species listed in the Australian Government’s Threat Abatement Plan for Predation by Feral Cats (2008), comparative scores can be calculated and allocated for sites that support any species at risk of predation by feral cats and classified as threatened, endangered, or vulnerable at the national, state or local level. Indeed, the decision-making tree also allows non-threatened species to be assessed for their risk of predation from cats, should the need arise to do so.

The interactive decision-making tree provided comparative scores for the potential impact of cats in each IBRA region of Australia. These scores varied from a high of 328 for the South Eastern Highlands IBRA region of eastern Australia, to a low of 24 for the Gawler IBRA region of South Australia and for three other IBRA regions located wholly or largely in Western Australia. However, there were also 9 IBRA regions with no extant TAP-listed species; these consequently received no scores. The decision-making tree also rovided comparative scores for the impact of feral cats in specific sites throughout the mainland and on offshore islands. These scores, based on data provided by land managers or available in the literature, varied from highs of 117 for the Diamantina National Park in Queensland and 108 for the East Gippsland area in Victoria, to a low of 10 for Dirk Hartog Island off the Western Australian coast. Further scores were calculated for sites at which cat control is uncertain (‘data deficient’) and from which cats have been eradicated or never recorded to identify sites that could be potentially impacted by feral cats in future. These scores varied from a high of 201 for sub-Antarctic Macquarie Island to a low of 9 for Boondelbah Island off the coast of New South Wales. 

We conclude that feral cat control on the Australian mainland is a long-term, multifaceted,labour- and resource-intensive venture requiring site-specific control methods that provide systematic and regular downward pressure on feral cat populations. An effective program of management should also include concurrent control of populations of both stray and owned domestic cats. We conclude further that greater 

success in cat control programs will be achieved by targeting specific sites using site-specific control methods. Human activities such as urban and rural development, agriculture and habitat modification favour the establishment and maintenance of feral cats. We recommend that a ‘nil tenure’ approach to cat control, with management activities encompassing public- and privately-owned reserved land as well as adjacent urban, rural and semi-rural developments, is necessary to reduce the feral cat population on the Australian mainland and offshore islands. In the absence of a sustained and integrated approach of this kind, declines and losses of native species are likely to continue.

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