Rat begone Record eradication effort rids subAntarctic island of invasive rodents

first_img Oli Prince The island of South Georgia in the southern Atlantic Ocean is free of rats and mice after the world’s largest rodent eradication effort to date. A monitoring survey found no evidence that any rodents remained on the island, the South Georgia Heritage Trust (SGHT) in Dundee, U.K., announced at a press conference in London today.The charity had dropped about 300 metric tons of poisoned bait on the island over the course of several years to kill the pests, which threatened native birds. Conservationists have applauded the results, and say that ongoing vigilance will be necessary to ensure that the work is not undone. “It’s really exciting to have it official that South Georgia is rodent-free,” says Clare Stringer in Sandy, U.K., head of international species recovery at the Royal Society for the Protection of Birds, who was not involved in the project. “It’s what we were all hoping for.” Country * Afghanistan Aland Islands Albania Algeria Andorra Angola Anguilla Antarctica Antigua and Barbuda Argentina Armenia Aruba Australia Austria Azerbaijan Bahamas Bahrain Bangladesh Barbados Belarus Belgium Belize Benin Bermuda Bhutan Bolivia, Plurinational State of Bonaire, Sint Eustatius and Saba Bosnia and Herzegovina Botswana Bouvet Island Brazil British Indian Ocean Territory Brunei Darussalam Bulgaria Burkina Faso Burundi Cambodia Cameroon Canada Cape Verde Cayman Islands Central African Republic Chad Chile China Christmas Island Cocos (Keeling) Islands Colombia Comoros Congo Congo, the Democratic Republic of the Cook Islands Costa Rica Cote d’Ivoire Croatia Cuba Curaçao Cyprus Czech Republic Denmark Djibouti Dominica Dominican Republic Ecuador Egypt El Salvador Equatorial Guinea Eritrea Estonia Ethiopia Falkland Islands (Malvinas) Faroe Islands Fiji Finland France French Guiana French Polynesia French Southern Territories Gabon Gambia Georgia Germany Ghana Gibraltar Greece Greenland Grenada Guadeloupe Guatemala Guernsey Guinea Guinea-Bissau Guyana Haiti Heard Island and McDonald Islands Holy See (Vatican City State) Honduras Hungary Iceland India Indonesia Iran, Islamic Republic of Iraq Ireland Isle of Man Israel Italy Jamaica Japan Jersey Jordan Kazakhstan Kenya Kiribati Korea, Democratic People’s Republic of Korea, Republic of Kuwait Kyrgyzstan Lao People’s Democratic Republic Latvia Lebanon Lesotho Liberia Libyan Arab Jamahiriya Liechtenstein Lithuania Luxembourg Macao Macedonia, the former Yugoslav Republic of Madagascar Malawi Malaysia Maldives Mali Malta Martinique Mauritania Mauritius Mayotte Mexico Moldova, Republic of Monaco Mongolia Montenegro Montserrat Morocco Mozambique Myanmar Namibia Nauru Nepal Netherlands New Caledonia New Zealand Nicaragua Niger Nigeria Niue Norfolk Island Norway Oman Pakistan Palestine Panama Papua New Guinea Paraguay Peru Philippines Pitcairn Poland Portugal Qatar Reunion Romania Russian Federation Rwanda Saint Barthélemy Saint Helena, Ascension and Tristan da Cunha Saint Kitts and Nevis Saint Lucia Saint Martin (French part) Saint Pierre and Miquelon Saint Vincent and the Grenadines Samoa San Marino Sao Tome and Principe Saudi Arabia Senegal Serbia Seychelles Sierra Leone Singapore Sint Maarten (Dutch part) Slovakia Slovenia Solomon Islands Somalia South Africa South Georgia and the South Sandwich Islands South Sudan Spain Sri Lanka Sudan Suriname Svalbard and Jan Mayen Swaziland Sweden Switzerland Syrian Arab Republic Taiwan Tajikistan Tanzania, United Republic of Thailand Timor-Leste Togo Tokelau Tonga Trinidad and Tobago Tunisia Turkey Turkmenistan Turks and Caicos Islands Tuvalu Uganda Ukraine United Arab Emirates United Kingdom United States Uruguay Uzbekistan Vanuatu Venezuela, Bolivarian Republic of Vietnam Virgin Islands, British Wallis and Futuna Western Sahara Yemen Zambia Zimbabwe Email Rodents were carried to South Georgia, a British overseas territory with no permanent inhabitants, in the 18th century by sealing and whaling ships. They soon wrought havoc on the island’s bird population, eating eggs and attacking chicks. In response, in 2011 SGHT began an ambitious £10 million elimination project, dropping bait from helicopters in a rodent-infested part of the island. The group followed up with two additional seasons of treatment in 2013 and 2015 that covered the remaining areas inhabited by rodents.The stepwise strategy was possible, says Mike Richardson, chair of the SGHT Habitat Restoration Project Steering Committee, because the island’s glaciers act as natural barriers between areas of the island home to rats and mice, so a treated region was unlikely to become reinfested between treatments. The project ultimately covered an area of more than 100,000 hectares across the 170-kilometer-long island—several times larger than any previous island elimination efforts.Baiting finished in 2015, but a declaration of success had to wait for another 2.5 years. It is difficult to immediately conclude that rodents have been eradicated because survivors can be hard to find, says SGHT project director Dickie Hall. But a couple years later, failure is easier to spot: The rodents reproduce quickly, and even a few survivors can lead to a population boom.  Hall’s team began a final survey of the island in late 2017, setting up and monitoring devices designed to detect any remaining rodents. The devices included so-called chewsticks, on which hungry rodents leave telltale toothmarks, as well as camera traps and tracking tunnels containing ink that mice and rats walk through, leaving behind footprints. The team was also accompanied by three dogs specially trained to sniff out rodents (and ignore the smell of the thousands of seals and penguins present on the island). After 6 months of searching—including 2420 kilometers of walking by the dogs—the team found no evidence of any rats or mice.Richardson says that although they “can’t prove a negative,” all signs point toward a complete elimination of rodents from South Georgia. And although SGHT has yet to conduct a comprehensive survey of the birdlife—it’s next on the agenda—Hall says that since finishing the baiting they have seen an “explosion” in the bird population, including that of the South Georgia pipit and South Georgia pintail, two species found only on the island.Preventing reinfestationJames Russell, a conservation biologist at The University of Auckland in New Zealand, says now that the eradication of rodents from South Georgia is complete, strict biosecurity measures will be vital to ensure that they do not return. “Rats will continue to try and spread around the world and we can be confident that they will come, but … we can stop them,” he says.Richardson agrees: SGHT has made a series of recommendations to the government of South Georgia and the South Sandwich Isles regarding biosecurity, he says, but it is “the government’s responsibility to effect tight biosecurity measures from now on.” He says it is gratifying to see at least one of these suggestions is already being piloted: Rodent detection dogs are inspecting vessels leaving the Falkland Islands for South Georgia, in an effort to sniff out any stowaways.The success on South Georgia could also have lessons for other regions looking to eliminate rodents. New Zealand, for example, is aiming to eradicate all major mammalian predators by 2050, but has much larger islands. Russell says the South Georgia project’s “stepwise” approach could make New Zealand’s goal “more technically feasible”: The country could eliminate predators from multiple isolated regions over time, rather than trying to do whole islands at once.But using the strategy in areas heavily populated by people will raise a host of additional considerations, including people’s acceptance of poisonous baits, Stringer notes. But, “Now that we’ve seen South Georgia succeed with such a huge area,” she says, “well, anything’s possible.” By Matt WarrenMay. 8, 2018 , 7:01 PMcenter_img A sniffer dog team helps survey the island of South Georgia, which has been declared rodent-free. Rat begone: Record eradication effort rids sub-Antarctic island of invasive rodents Click to view the privacy policy. 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