Above Picture: The Goney Plain Wandering Albatross chick attacked by mice; photograph by Lucy Smyth
South Africa’s sub-Antarctic Marion Island in the southern Indian Ocean is one of only three known islands where introduced House Mice Mus musculus are known to have taken to attacking and killing seabirds – the other two being Gough in the South Atlantic and Midway in the North Pacific. The similarity between these three islands is that mice are their sole introduced predator, with no rats Rattus spp. or feral cats Felis catus being present. Attacks by mice were first observed on Marion in 2003, with chicks of the threatened Wandering Albatross Diomedea exulans (categorized globally as Vulnerable) being the target, putting a quarter of the species’ world population at serious risk. Since then, the three other albatross species and the petrel assemblage that breed on the island have all been affected, including attacks directed at adults for some of them. As a consequence, the Mouse-Free Marion Project is working towards eradicating the island’s mice in 2024 by an aerial drop of rodenticide bait.
Researchers based on the island have continued to record mouse attacks on birds since the first observations were made in 2003. The most recent are of two downy Wandering Albatross chicks showing wounds on their flanks caused by mouse attacks.
The first wounded Wandering Albatross chick was photographed on 25 May 2022 by ornithological field assistants Andile Mdluli and Samuel Peta along the east coast near Ship’s Cove. The downy chick showed a wound on its right flank. On a return visit on 2 June the chick was no longer alive and its corpse was being scavenged by a Brown Skua Catharacta antarctica.
The second bird was photographed with a wound on its right flank (see feature picture above) on 26 May 2022 by ornithological field assistant Lucy Smyth in the Goney Plain long-term monitoring colony for Wanderers, which I with colleagues set up in the mid-1980s, one of three on Marion’s east coast. On a return visit to the colony on 14 June the chick was no longer present, so it is near certain it died due to being attacked by mice.
Now that the brood/guard stage for Wandering Albatrosses is past, and the chicks are largely on their own, it is to be expected that more chicks will succumb to mice made hungry by dwindling resources in the winter months. Monitoring in the three study colonies will continue at regular intervals throughout the rest of the current breeding season to enable a more accurate assessment of mortality due to mice. However, these two observations confirm that mouse attacks on Wandering Albatross chicks are still continuing since being first observed nearly 20 years ago and supports the necessity of removing the mice from Marion Island as soon as is feasible.
The continuation of long-term monitoring of Wandering Albatrosses and other seabird species at Marion Island is made possible through the support of the Department of Science and Innovation through the National Research Foundation (PIs: Dr Maëlle Connan and Prof. Peter Ryan; SANAP Project “Avian Scavengers as Indicators of Recovery of an Island Biota”) and the Department of Forestry, Fisheries and the Environment (PI: Dr Azwianewi Makhado).
With thanks to Maëlle Connan, Marine Apex Predator Research Unit, Nelson Mandela University, South Africa and Azwianewi Makhado, South African Department of Forestry, Fisheries and the Environment.
John Cooper, News Correspondent, Mouse-Free Marion Project, 28 June 2022
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