Little recovery of burrowing petrels after cat eradication

Cerfonteyn, M., & Ryan, P. G. 2016. Have burrowing petrels recovered on Marion Island two decades after cats were eradicated? Evidence from sub-Antarctic skua prey remains. Antarctic Science, 1-7.

In the 1980s, penguins dominated the prey remains of sub-Antarctic skuas Stercorarius antarcticus breeding on Marion Island, whereas on neighbouring Prince Edward Island burrowing petrels made up >95% of prey remains in nest middens. This difference resulted at least in part from the impact of introduced cats Felis catus on Marion Island’s burrowing petrel populations. Cats were introduced to Marion Island in 1949, and prior to their eradication in 1991, they killed an estimated 450 000 petrels each year, greatly reducing the densities of petrels breeding on the island. A repeat survey of skua prey remains showed that penguins still dominated the prey of breeding sub-Antarctic skuas on Marion Island in the summer of 2010–11, two decades after cats were eradicated from the island. The proportion of penguin remains decreased slightly compared to 1987–88, but this might be expected given the decreases in penguin numbers on Marion Island over this period. Regurgitated pellets confirmed the dominance of penguin prey on Marion Island. Taken together with the decrease in skua numbers on Marion Island over the last two decades, our results suggest that there has been little recovery in the population of at least summer-breeding burrowing petrels since cats were eradicated.

Modelling eradication of feral cats

Beeton, N. J., McMahon, C. R., Williamson, G. J., Potts, J., Bloomer, J., Bester, M. N., ... & Johnson, C. N. (2015). Using the Spatial Population Abundance Dynamics Engine for conservation management. Methods in Ecology and Evolution.

1. An explicit spatial understanding of population dynamics is often critical for effective management of wild populations. Sophisticated approaches are available to simulate these dynamics, but are largely either spatially homogeneous or agent based, and thus best suited to small spatial or temporal scales. These approaches also often ignore financial decisions crucial to choosing management approaches on the basis of cost-effectiveness.
2. We created a user-friendly and flexible modelling framework for simulating these population issues at large spatial scales – the Spatial Population Abundance Dynamics Engine (SPADE). SPADE is based on the Spatio-Temporal Animal Reduction (STAR) model (McMahon et al. 2010) and uses a reaction–diffusion approach to model population trajectories and a cost-benefit analysis technique to calculate optimal management strategies over long periods and across broad spatial scales. It expands on STAR by incorporating species interactions and multiple concurrent management strategies, and by allowing full user control of functional forms and parameters.
3. We used SPADE to simulate the eradication of feral domestic cats Felis catus on sub-Antarctic Marion Island (Bester et al., South African Journal of Wildlife Research, 32, 2002, 65) and compared modelled outputs to observed data. The parameters of the best-fitting model reflected the conditions of the management programme, and the model successfully simulated the observed movement of the cat population to the southern and eastern portion of the island under hunting pressure. We further demonstrated that none of the management strategies would likely have been successful within a reasonable time frame if performed in isolation.
4. Spatial Population Abundance Dynamics Engine is applicable to a wide range of population management problems and allows easy generation, modification and analysis of management scenarios. It is a useful tool for the planning, evaluation and optimisation of the management of wild populations and can be used without specialised training.

Toxoplasmosis in prey species and consequences for prevalence in feral cats

Afonso, E., Thulliez, P., Pontier, D., & Gilot-Fromont, E. (2007). Toxoplasmosis in prey species and consequences for prevalence in feral cats: not all prey species are equal. Parasitology, 134(14), 1963-1971.

Toxoplasma gondii is largely transmitted to definitive felid hosts through predation. Not all prey species represent identical risks of infection for cats because of differences in prey susceptibility, exposure and/or lifespan. Previously published studies have shown that prevalence in rodent and lagomorph species is positively correlated with body mass. We tested the hypothesis that different prey species have different infection risks by comparing infection dynamics of feral cats at 4 sites in the sub-Antarctic Kerguelen archipelago which differed in prey availability. Cats were trapped from 1994 to 2004 and anti-T. gondii IgG antibodies were detected using the modified agglutination test (1:40). Overall seroprevalence was 51·09%. Antibody prevalence differed between sites, depending on diet and also on sex, after taking into account the effect of age. Males were more often infected than females and the difference between the sexes tended to be more pronounced in the site where more prey species were available. A difference in predation efficiency between male and female cats may explain this result. Overall, our results suggest that the composition of prey items in cat diet influences the risk of T. gondii infection. Prey compositon should therefore be considered important in any understanding of infection dynamics of T. gondii.

Genetic structure of the feral cat on a sub-Antarctic island

Pontier, D., Say, L., Devillard, S., & Bonhomme, F. (2005). Genetic structure of the feral cat (Felis catus L.) introduced 50 years ago to a sub-Antarctic island. Polar Biology, 28(4), 268-275.

Information about the invasion dynamics and demographic status of invasive species is essential to choose the optimal control options of population numbers. While long-term direct demographic and historical records are generally lacking, the analysis of the genetic variability of a current population might supply information about past and current demographic processes. In this study, we analysed the genetic variability of the cat population living on the main island of the Kerguelen archipelago. Genetic diversity was consistent with the introduction of a very small number of individuals followed by a demographic explosion of the cat population. Significant genetic structure among sites (Fst=0.06 ±0.005) and absence of isolation by distance could indicate that the initial phase of fast colonisation is now over. Estimates of individual relatedness indicated a significant kin structure. Overall data suggested that the cat population of the main island has probably reached carrying capacity.

Cat population density in a sub-Antarctic island

Say, L., Gaillard, J. M., & Pontier, D. (2002). Spatio-temporal variation in cat population density in a sub-Antarctic environment. Polar Biology, 25(2), 90-95.

We used the walked-line transect method for estimating the density of cats and coefficients of variation of density estimates in 4 contrasted sites on the main island of Îles Kerguelen between 1998 and 2000. Density estimates varied from 0.44±0.15 cats per km² to 2.42±0.23 cats per km²  according to site and period. Coefficient of variation of density estimates ranged from 11.92% to 34.76%. The line transect method was, therefore, an efficient method for monitoring the density of the cat population in a sub-Antarctic environment characterised by short vegetation. Our results suggest that cat population size at the main island of Îles Kerguelen (the total number of cats expected is around 7,000) is much lower than previously thought.

Parasites in insular and mainland populations of feral cats

Fromont, E., Morvilliers, L., Artois, M., & Pontier, D. (2001). Parasite richness and abundance in insular and mainland feral cats: insularity or density?.Parasitology, 123(02), 143-151.

Hosts living on islands carry few parasite species, and the prevalence and intensity of directly transmitted parasites are often higher in insular than in mainland populations. However, it is unclear whether density or other features of insular populations can be responsible for the pattern observed. We compared the parasite richness, prevalence and intensity of parasites between 2 feral populations of cats living either at low density on an island (Kerguelen) or at high density on the mainland (Lyon). Parasite richness was higher in Lyon than in Kerguelen, where only Toxocara cati was found. T. cati egg prevalence was higher in Kerguelen (71·1%) than in Lyon (58·0%). Because cat density cannot explain this pattern, we propose that the low number of parasite species, the diet and/or immunity of cats act to increase prevalence in Kerguelen. Moreover, prevalence, intensity and variance-to-mean ratio increased with age and body mass in Kerguelen whereas, in Lyon, prevalence decreased with age and body mass. We hypothesize that the pattern of exposure differs between populations, and that density-dependent parasite mortality is lower in Kerguelen than in Lyon. We discuss the consequences concerning the influence of parasites on insular host populations.

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...

An evaluation of the biological control of the feral cat

Howell, P.G. 1984. An evaluation of the biological control of the feral cat Felis catus (Linnaeus, 1758). Acta Zoologica Fennica, 172: 111-113.

Conditions in the population of feral cats on Marion Island, to the southeast of South Africa, approached the optimal for the release of a feline parvovirus for biological control. The introduction of feline panleucopenia virus into the population in 1977 is described, together with the methods used to monitor the effect of the virus. Studies on population density showed a conservatively estimated reduction of 80% over the following 5 years.

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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Cats, mice and climate change impact on Marion island's birds

Huyser, O., Ryan, P. G., & Cooper, J. (2000). Changes in population size, habitat use and breeding biology of lesser sheathbills (Chionis minor) at Marion Island: impacts of cats, mice and climate change?. Biological Conservation, 92(3), 299-310.


Impacts on the native avifauna of sub-Antarctic islands by introduced vertebrates are well documented for species such as burrowing petrels (Procellariidae), but less is known about impacts on surface-nesting species. The sub-Antarctic Prince Edward Islands, comprising Marion and Prince Edward Islands, support an endemic form of lesser sheathbill (Chionis minor). Marked differences have developed over the last 20 years in winter habitat use and population trends of sheathbills between the two islands. Currently birds at Marion forage almost exclusively along the coastline and in penguin colonies during winter, but at Prince Edward they occur at higher densities and forage throughout the coastal plain. Compared to the 1970s, sheathbills at Marion are now less abundant around most of the island, forage proportionally less in the vegetation of the coastal plain, commence breeding with a lower body mass and lay smaller clutches. These changes are likely a result of a decrease in terrestrial macro-invertebrate prey, formerly an important winter food resource for sheathbills at Marion Island. The main biological difference between the two islands is the presence of many more introduced species at Marion, including house mice (Mus musculus) and feral cats (Felis catus) (now eradicated). We suggest that house mice are impacting the sheathbill population by consuming terrestrial macro-invertebrates, and that this impact has been exacerbated by the removal of feral cats, by the massive reduction in burrowing petrels (which promote invertebrate populations through manuring), and by climatic warming (which may be promoting higher densities of mice). This proposed web of interactions between sheathbills, introduced species, invertebrates and burrowing petrels needs to be further investigated, given the likelihood of further climatic change.

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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Population biology of feral cats on Marion Island

Van Aarde, R. J. (1984). Population biology and the control of feral cats on Marion Island. Acta Zoologica Fennica, 172, 107-110.

Predation by feral cats, Felis catus, on burrowing birds of southern temperate and sub-Antarctic islands has resulted in their presence being considered undesirable. Attempts to eradicate or control these cats on Marion Island, a temperate island to the southeast of South Africa, have included the introduction of the host-specific feline panleucopaenia virus during March 1977. Surveys suggest a continued decrease in population size since 1977, the mean cat density being 65% lower in June 1980 than in June 1976.


Bloomer, J. P., & Bester, M. N. (1992). Control of feral cats on sub-Antarctic Marion Island, Indian Ocean. Biological Conservation, 60(3), 211-219.

Since their introduction in 1949, feral cats have caused extensive damage to seabird populations on sub-Antarctic Marion Island, Indian Ocean. This paper reports on the first four years of an eradication programme launced in 1986. Eight hundred and seventy-two cats were shot dead and 80 trapped during 14 725 hours of hunting. Cats sighted per hour of night hunting and kills per hour decreased dramatically. Hunting success (cats killed as a proportion of those seen) decreased. The only reliable indication of the decrease in density as a result of hunting was the decrease in the number of cats seen per hour of night hunting. By the end of the third season it was apparent that hunting alone was no longer removing sufficient animals to maintain the population decline, and trapping was incorporated into the eradication programme.

Breeding of Procellariidae before and after eradication of feral cats at Marion Island

Cooper, J. Marais, A.V.N., Bloomer, J.P. & Bester, M.N. 1995. A success story: breeding of burrowing petrels (Procellariidae) before and after eradication of feral cats Felis catus at sub-Antarctic Marion Island. Marine Ornithology 23: 33-37.

Greatwinged Petrels Pterodroma macroptera and Blue Petrels, Halobaena caerulea bred more successfully alter the eradication in 1991 of feral domestic cats Felis catus at subantarctic Marion Island. The larger Whitechinned Petrel Procellaria aequinoctialis did not show such improvement, although percentage burrow occupancy in the late breeding season increased significantly between 1982/83 and 1988/89 for that species, suggesting decreased cat predation during this period of cat control. Breeding success and burrow density of selected species of burrowing petrels should be monitored to ascertain the rate of recovery of their populations now that Marion Island is cat-free. 

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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Effects of FPL on a feral cat population

van Rensburg P.J.J., Skinner J. D. & van Aarde R. J. (1987) Effects of feline panleucopaenia on the population characteristics of feral cats on Marion Island. Journal of Applied Ecology, 24, 63-73.

(I) This paper evaluates the effects ofthe artificial introduction offcline panleucopaenia (FPL) as a primary control measure ofa feral cat population on the sub-Antarctic Marion Island (46º54'S,37º45'E). 

(2) The population decreased from an estimated 3409 cats in 1977 (introduction of control factor) to 615 (S.E. = 107) cats during 1982, suggesting an annual rate of decrease of 29%. 

(3) Litter size decreased and the age structure changed significantly because ofa decrease in subadult numbers. Age specific mortality rates were higher but followed the same pattern as in 1975 because there were fewer subadults but the same age structure of adults. 

(4) The intrinsic rate ofincrease, as suggested by the survival and fecundity schedules of the: population, was higher in 1975 owing to a greater proportion of adults and a higher fecundity in age class II. 

(5) Antibody titres of FPL were lower in 1982 than in 1978 which illustrates that FPL did affect the cat population but is no longer spreading effectively. FPL was independent of feline herpes (FVR), an endemic disease of the cat population. and FPL was, therefore, directly responsible for the decrease in cat population density. 

(6) During 1982 the cat population showed a decrease of 8% year-I, whieh indicates stabilizing of the negative growth rate. This observation was supported by lower titres of FPL. 

Recovery of seabirds after cat control

Cooper J. & A. Fourie. 1991. Improved breeding success of great-winged petrels Pterodroma macroptera following control of feral cats Felis catus at subantarctic Marion Island. Bird Conservation International, 1:171-175.

A population of feral domestic cats Felis catus has existed at subantarctic Marion Island since 1951. From 1977 to 1990 an ongoing programme has utilized an introduced disease, shooting and gin-trapping in an endeavour to control cat numbers, with the eventual aim of their eradication. Burrowing petrels (Procellariidae) form the majority of the cats' diet. The breeding success of the winter-breeding Great-winged Petrel Pterodroma macroptera has varied between nil and 20.5% in the period from 1979 to 1984, due primarily to cat predation of chicks causing up to 100% mortality. In 1990, by which time cat numbers had been greatly reduced from their 1970s' peak, Great-winged Petrels had a breeding success of 59.6%, with chick mortality being zero. No signs of cat predation were observed. This finding provides good reason to continue the control programme until cats are finally eradicated from Marion Island.

Alien mammals on French subantarctic islands

Chapuis, J. L., Boussès, P., & Barnaud, G. 1994. Alien mammals, impact and management in the French subantarctic islands. Biological Conservation,67(2): 97-104.

The unique plant and animal communities of the French subantarctic islands have been greatly modified by the introduction of mammals since their discovery in 1552 and 1772. Nine species, wild and domestic, thrive due to a lack of competitors, predators and diseases and despite the small number of founders. Herbivores have induced significant changes to the nature and structure of plant communities and carnivores have modified burrowing petrel Procellaridae populations and species diversity.

Introductions are now prohibited. Research programmes have been developed to study the population biology, and measures are being taken to control or eradicate alien species populations. Control programmes are effective for rabbits Oryctolagus cuniculus on the Kerguelen archipelago and cattle on Amsterdam Island. Planned programmes deal with cat, mouflon and sheep in the Kerguelens.