Gough Island, a rugged volcanic island in the South Atlantic Ocean, has been described as one of the most important seabird nesting sites in the world. The island is home to more than eight million birds from at least 24 different species, including the Atlantic Yellow-nosed Albatross, Atlantic Petrel, and the Critically Endangered Tristan Albatross. But many of the birds which nest there, including the iconic Tristan Albatross, are under threat from introduced* House Mice.
The mice were accidentally introduced by sailors during the 19th century. With no predators to control them and able to exploit any available food source they have exploded in numbers. They have also evolved into so-called ‘super mice’ – 50% larger than ‘normal’ House mice. Video cameras placed by conservationists trying to understand seabird mortality on the island have revealed that these large mice have been eating the flesh of live seabird chicks. Tristan albatross chicks are around 300 times the weight of the mice, but they don’t appear to recognise the threat posed to them, and the open wounds have frequently lead to the chick’s deaths.
Film footage has revealed what happens in the narrow burrows the albatrosses are using. Groups of up to nine mice attack the birds, and in the case of chicks can eat them alive. The situation is so severe that just 21% of Tristan albatross chicks fledged during the 2017/18 breeding season. A study from 2018 found that the mice are responsible for over two million fewer seabird chicks and eggs on the island each year.
The RSPB and Tristan da Cunha Government have developed an ambitious programme of conservation action. Based on methods developed primarily in New Zealand but now widely used across the world to restore island ecosystems, rodenticide bait will be spread across Gough Island, eradicating the mice and restoring Gough to its natural state.
The operation is planned to go ahead in 2020, but this month new video footage has been released which for the first time shows that the mice are now attacking adult albatrosses as well. Such attacks are only known from one other island in the world.
Albatrosses mate for life, producing just one egg every other year. The Tristan Albatross has already declined significantly because of drowning associated with longlining, a form of industrialised fishing where lines up to 100km long baited with hooks are paid out behind a ship attracting huge numbers of seabirds. Under a red list compiled by the International Union for Conservation of Nature, 15 out of 22 albatross species are considered endangered with human activity the cause. The loss of adult Tristan Albatross to mice will compound and accelerate this tragedy.
Chris Jones, Senior Gough Field Assistant said, ‘We have known for more than a decade that the mice on Gough Island attack and kill seabird chicks. While this is already of great concern, attacks on adults, which can produce dozens of chicks in their lifetime, could be devastating for the populations’ chances of survival. survival of these long-lived seabirds. It’s a terrible development, and these gentle giants could now be lost even more rapidly than we first predicted.”
The Gough Island Restoration is a globally important partnership programme – partner and funder support is vital. Thanks to generous donations from individuals and funders over £5million has already been raised.
However, there is a funding gap and support is still urgently needed. To equip this major operation for success in 2020 a further £2million is still being sought. The money will be used to purchase final pieces of equipment, including bait and specialist aviculture facilities, and to secure highly experienced staff and helicopter contracts.
*An introduced species (also known as an alien species, exotic species, foreign species, non-indigenous species, or non-native species) is a species of animal or plant that has been moved by human activity, either deliberately (often linked with agriculture or pest control) or accidentally (perhaps hidden away in plant material or on ships or in boat ballast water), and is now living outside its original range.
Species might be introduced to a localised area, or to a whole country. Introduced species that become established and then spread beyond the place of introduction are termed invasive species.
Invasive species are among the leading threats to native wildlife. Approximately 42 percent of threatened or endangered species are at risk due to invasive species. In 2016 the European Group on Biological Invasions (NEOBIOTA) warned that the EU harbours up to 1,800 different Invasive Alien Species.
Amongst the world’s most harmful animal introductions are House mice, Black Rats, Zebra mussels, Cane Toads, and the domestic cat. Introduced plants wreaking havoc on habitats around the world include Japanese Knotweed, Gamba Grass, Prickly Pear, and the Kudzu Vine.