Rat eradication on South Georgia – what a fantastic effort by an NGO on a shoestring budget

I was reading yesterday about New Zealand’s effort to eradicate rats on an off-shore island and remembered the success story from South Georgia on our trip through Antarctica last year. South Georgia is in the southern Atlantic Ocean approximately 1,900km east of the southern end of South America and 1,500km east of the Falkland Islands. It is a British territory, being part of the South Georgia and Sandwich Islands, however, ownership of the islands has long been disputed by Argentina. It was the site for the now famous Ernest Shackleton trans-Antarctic crossing where Shackleton’s ship was lost and his party was stranded on Elephant Island, and Shackleton and five of his crew rowed-sailed a dingy 1,300km in Antarctic seas to arrive at South Georgia, then crossed the mountains of South Georgia to be rescued before returning to Elephant Island to rescue his men.

South Georgia is crescent-shaped with no permanent inhabitants. It is approximately 170km long and 40km at is widest and a total area of 3,756km². The backbone of the island is two mountain ranges – Allardyce and Salvescen, and the highest peak is 2,934m. The north-western side of the island is low-lying and the western side mountainous. The climatic is almost Antarctic, and the island lies within the Antarctic Convergence. There is an abundance of glaciers, most of which are now retreating due to global warming.

South Georgia is home to four penguin species – King Penguin (Aptenodytes patagonica), Macaroni Penguin (Eudyptes chrysolophus), Gentoo Penguin (Pygoscelis papua) and Chinstrap Penguin (Pygoscelis antarctica). In excess of 450,000 pairs King Penguins, 1,000,000 pairs Macaroni Penguins, 105,000 pairs Gentoo Penguins and 13,000 pairs Chinstrap Penguins breed on South Georgia (Burton 2016). South Georgia also supports breeding colonies of the threatened Wandering Albatross (Diomedea exulans), Black-browed Albatross (Thalassarche melanophrys), Southern Giant Petrels (Macronectes giganteus), White-chinned Petrels (Procellaria aequinoctialis) and Cape Petrel (Daption capense) (Burton 2016). A wide variety of other coastal and land birds breed or visit the island, including the endemic South Georgia Pipit (Anthus antarctica), the most southerly songbird.

Brown Rats (Rattus norvegicus), Black Rats (R. rattus) and Mouse mice (Mus musculus) were introduced to South Georgia by sailors and the many ships that visited the island to harvest seals and whales. Black Rats appear not to have survived as none were present in 2010, however, Brown Rats established themselves finding suitable retreats in the thousands of burrows dug by seabirds. There was an abundant supply of food in eating eggs, chicks, carcasses of adult birds and scraps from whaling stations, so Brown Rats flourished.

Brown Rats destroyed entire colonies of birds on the island, with the smaller species; i.e. storm petrels, prions, diving petrels and petrels, being almost wiped out from nesting on the mainland island, and only leaving residual populations on off-shore islands. The South Georgia Pipit also went from being abundant to rarely seen, as its ground-nesting behaviour exposed it and its eggs to rodent predation. In 2007, the South Georgia government acknowledged that rats were a significant problem, but indicated that it was not prepared to do anything about the problem.

South Georgia Heritage Trust

The South Georgia Heritage Trust (SGHT) was formed in Scotland in 2005 to work for the future of the natural environment and cultural heritage of South Georgia. This was a charitable trust formed on the opposite side of the planet, yet it has achieved so much in such a short space in time. The SGHT committed itself to a rat eradication program. This was a bold and audacious decision, given that the government had balked at the idea and the SGHT was new, had few resources, no experience in rat eradication, the terrain was extremely difficult and the island very remote.

Rat eradication

The SGHT used an approach pioneered in New Zealand. The trust used a highly attractive bait to rats which was 100% effective and able to be delivered by helicopter to the home range of every Brown Rat on South Georgia (Martin 2015). The bait was Brodifacoum in a cereal pellet that is bound together so that it was not broken down quickly when it get wet. When one pellet of Brodifacoum was ingested by a rat, it did not feel the effects until it is fatally poisoned.

South Georgia is divided up by glaciers, most of which extend from snow capped high inland areas into the sea. Deeply crevassed glaciers are impassable to rats. Each of the areas between glaciers became a rat baiting zone, and once an area had been baited it was not possible for rats to recolonise the area from adjacent areas. There were 19 rat baiting zones and two house mouse zones. The available information indicated that there were no rats in mouse zones and no mice in the rat zones. Zones varied in size from 4 to 233km² and a trial (Phase 1) was conducted in a zone in 2011 to refine the technique before the rest of the island was baited (Martin 2015).

Loss of some birds during the baiting program was an inescapable consequence, but it was a small cost compared to the potential long-term benefits to seabirds and the environment. There were no native terrestrial mammals, amphibians or reptiles on South Georgia, so the impact on non-target species was confined to some birds. To minimise this impact on birds, baits were spread in autumn and early winter when most of the migratory birds had left the island and baits were designed to be non-attractive to birds, i.e. blue-green colour and large enough so they could not be easily swallowed by small birds.

In Phase 2 the northern and western parts of the island were baited in 2013 and in Phase 3 the southern part of the island was baited in 2015. Three hundred tonnes of bait was deployed over an area of 1,070 km2. Helicopters flew 1,050 hours and used 900 drums of aviation fuel. The eradication program cost £7.5m (Martin 2015).

Has the program been successful? No rats have been observed on South Georgia since the baiting program! The SGHT plans to undertaken a rat monitoring program that will have two elements; a trapping program and two detection dogs trained to locate rats. In January 2017 we saw South Georgia Pipits. This small songbird has already bounced back once predation pressure from rats has been lifted and anecdotal data from temporary island residents is that seabird nesting success has increased.

So what are the implications for Australia?

So what is so impressive about this program? Rats have been eradicated from multiple islands around the world (e.g. Garcia et al. 2002, McMcClelland 2002, Morris 2002), so this is very a positive outcome, but that it was done by a charitable trust for £7.5m is a most impressive feature.

There is a growing list of significant achievements by the not-for-profit sector in the conservation of threatened fauna. In this example, albatross, petrels and a pipit were under significant predation pressure from an invasive introduced predator. Closer to home we see some outstanding results in threatened species conservation and feral animal control being achieved by the not-for-profit Australia Wildlife Conservancy (AWC) and the Bush Heritage Australia. By comparison, governments seem slow to act, their programs are often very expensive, there is often slippage in achieving milestones and their programs are not always effective.

Perhaps it is time for more similar bold and audacious programs in Australia. We have recently seen the New Zealand Prime Minister announce that NZ will implement programs to eradicate rats, possums and stoats from New Zealand by 2050 – Predator Free New Zealand. Very clearly this is one of the most ambitious conservation projects attempted on a large scale anywhere in the world.

What are we doing in Western Australia? A quick review would indicate the number of species on the threatened species lists has continued to increase, the ranking of many species on these lists is increasing and there has been little reduction in the abundance of feral and invasive species. We have seen the Cane Toad recently invade WA and significantly impact on vertebrate fauna in the Kimberley with the likelihood it could reach the Pilbara in the not to distance future. On the brighter side, AWC has now fenced and excluded predators from 7,800ha of some of the best habitat in the mid-west and is progressively reintroducing Bilby, Numbats, Western Barred Bandicoots, Shark Bay Mouse, Red-tailed Phascogale, Greater Stick-nest Rats, Banded Hare-wallaby and Chuditch to the enclosure on a budget far less than would have been the case had it been a government initiative.

AWC  announced a bold and audacious program to establish a 65,000ha feral cat free area at Newhaven in central Australia. It will be the largest feral cat eradication program attempted in Australia. Newhaven will become home to Mala, Central Rock Rats and Golden Bandicoots.

Surely, we should be expecting a lot more of our State and Commonwealth government conservation agencies in threatened species conservation and feral animal control. It is acknowledged that there has been some positive improvements since the Commonwealth government appointed a Threatened Species Commissioner, and there is evidence of some small advances for some species, but it is really too early to judge. At a state level, it appears it is a business as usual program, even though the Department of Biodiversity, Conservation and Attractions has had access to significantly increased resources for threatened species conservation from environmental offsets. The only substantive and comparable state government conservation programs are the rangelands restoration program at Lorna Glen (Martuwa) that is funded from the Gorgon Gas offset funds and the Dirk Hartog Island ecological restoration. Brushtail Possums and Bilbies have been established outside a feral predator-free enclosure at Lorna Glen, and Golden Bandicoot and Boodies have been established inside the fence. It is much too early to comment on the success or otherwise of the Dirk Hartog Island ecological restoration program, as the Minister only recently announced $22.5m being allocated to the reintroduction of native animals program. The Department has other projects on a much smaller scale such as the Perup sanctuary, but with a mission to protect and conserve WA’s native fauna and an overall budget of in excess of $300m, one must seriously question whether the Department has been effective in its use of the available resources to protect and conserve the 49 critically endangered, 47 endangered and 149 vulnerable threatened fauna species plus the 203 species on the Department’s priority species fauna list (2017 figures). One might also question the Department’s commitment to threatened species conservation, when the only reason one of its big-ticket flagship projects at Lorna Glen exists is because of industry offset funds.

If a charitable trust can eradicate rats from a very remote island with an inhospitable environment of very high conservation value for £7.5m, then surely we can do much more in reducing the number of feral and pest species and improve the ecosystems for threatened species in Australia.

References

Burton, R. 2016. South Georgia. Government of South Georgia and the South Sandwich Islands, South Georgia.

Garcia, M. A., C. E. Diez, and A. O. Alvarez. 2002. The eradication of Rattus rattus from Monito Island, West Indies. Pages 116-119 in C. R. Veitch and M. N. Clout, editors. Turning the Tide: The Eradication of Invasive Species. Invasive Species Specialist Group, IUCN, Auckland, New Zealand.

Martin, T. 2015. Reclaiming South Georgia. South Georgia Heritage Trust, Scotland.

McMcClelland, P. J. 2002. Eradication of Pacific rats (Rattus exulans) from Whenua Hou Nature Reserve (Codfish Island), Putauhinu and Rarotoka Islands, New Zealand. Pages 173-181 in C. R. Veitch and M. N. Clout, editors. Turning the Tide: Te Eradication of Invasive Species. Invasive Species Specialist Group, IUCN, Auckland, New Zealand.

Morris, K. D. 2002. The eradication of the black rat (Rattus rattus) on Barrow and adjacent islands off the north-west coast of Western Australia. Pages 119-225 in C. R. Veitch and M. N. Clout, editors. Turning the Tide: The Eradication of Invasive Species. Invasive Species Specialist Group, IUCN, Auckland, New Zealand, Auckland.