Above picture: A badly wounded Grey-headed Albatross chick that will not survive the onslaught by Marion Island’s introduced House Mice, 17 March 2024; photograph by Michelle Risi
Attacks by introduced House Mice Mus musculus on Marion Island’s beleaguered breeding albatrosses were first reported in 2003 – and have continued every breeding season when checks have been made. First recorded on downy chicks, in recent years depredations by the mice have commenced on adult birds incubating or brooding chicks. Last year’s report of the first observations of adult Wandering Albatrosses Diomedea exulans succumbing to attacks by mice was a further wake-up call, given the bird’s Vulnerable conservation status and that Marion supports a quarter of the world’s population of this iconic species. Also, the loss of an adult of a long-lived and slow breeding species such as an albatross is far more of a conservation concern than is the loss of a chick. Observations of mouse attacks on two albatross species made last and this month during their current 2023/24 breeding seasons clearly show there will no respite for the island’s four species of breeding albatrosses.
This season, mouse attacks have commenced again on Marion’s eponymously named Grey-headed Albatross Ridge. On 17 March, island researcher Michelle Risi came across the severely wounded Grey-headed Albatross Thalassarche chrysostoma chick pictured above on a marked nest in one of the big colony’s long-term study clusters of breeding birds. This, and another wounded chick seen on the same day, are the first mouse attacks recorded on this Endangered albatross for the current breeding season. The chick had been videoed in full health a few days previously on 27 February. The next nest check takes place later this month, but the chick is not expected to be alive by then. Eight chick carcasses were also counted at the time, all showing signs of having been scavenged by mice, which, in all likelihood, had commenced feeding on them while they were still alive, leading to their deaths.
Mouse attack! A Wandering Albatross with a fresh wound continues to tend its chick, 28 March 2024; photograph by Michelle Risi
The attacks by mice have not stopped with the Grey-headed Albatross. On 28 March, Michelle was in the north of the island near Cape Davis conducting nest checks on Wandering Albatrosses when she came across and photographed a wounded male bird brooding its downy chick. Fortunately (so far) the chick had not been attacked by mice. The locality was not that far from where the dead adult Wanderers had been seen in April last year. Whereas the brooding bird will be relieved by its partner, and if still alive, hopefully have an opportunity to recover and heal while at sea, it seems likely the breeding attempt will fail, even if the adult escapes death.
The same Wandering Albatross displays its wound, 28 March 2024; photograph by Michelle Risi
Along with the adults, Wandering Albatross chicks are not being spared. On 03 April, Chris Jones discovered two brooded chicks that showed signs of mice attacks in the Macaroni Bay long-term study colony. These are the first seen for the 2023/24 season; sadly, more are to be expected.
Two different Wandering Albatross chicks being brooded by their banded parents show clear signs of wounds inflicted by mice, -03 April 2024; photographs by Chris Jones
The continued attacks by mice on Marion Island’s threatened albatrosses are of deep concern. Every chick or adult lost to mice is hugely upsetting, most especially for those who witness the results of attacks in the field – and then, after recording them, have to just walk away, leaving the birds to their grisly fates. It is these feelings that keep all the team members of the Mouse-Free Marion Project fully committed to seeing the end of the island’s mouse plague. You can show your own concern and become a part of the Project by Sponsoring a Hectare (at R 1000/ha) or more and being listed on the MFM website’s Honour Roll, along with over 2500 others. Sponsorships of more than a single hectare are regularly being made, with so far the largest being of 500 ha, representing half a million Rands. The team (and more importantly Marion’s albatrosses) will thank you!
John Cooper, News Correspondent, Mouse-Free Marion Project and Chris Jones & Michelle Risi, Marine Apex Predator Research Unit, Nelson Mandela University, 09 April 2024
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At risk to mice. Grey-headed Albatrosses breed on a Marion Island cliff; photograph by John Dickens and poster design by Michelle Risi
The Mouse-Free Marion Project is a registered non-profit company (No. 2020/922433/08) in South Africa, established to eradicate the invasive albatross-killing mice on Marion Island in the Southern Ocean. The project was initiated by BirdLife South Africa and the South African Department of Forestry, Fisheries and the Environment. Upon successful completion, the project will restore the critical breeding habitat of over two million seabirds, many globally threatened, and improve the island’s resilience to a warming climate. For more information or to support the project please visit mousefreemarion.org.
