Above picture: A House Mouse on Marion Island; photograph by Ben Dilley
This is the third in a series on Marion Island’s introduced House Mice Mus musculus. It covers biological research conducted from 1975 until 1995, when a workshop was held to consider the desirability of their eradication. The first in the planned four-part series dealt with the island’s discovery in 1773 and showed that the mice were already on the island by 1818, thought to have been introduced inadvertently by sealers. The second part considered the period from the annexation of the island by South Africa in 1948 up to the publication of the first scientific paper about the mice in 1974. The fourth and concluding part in the series will look at research conducted since 1995 to the present day that has taken a more conservation-driven approach.
Research conducted on Marion Island’s alien mice over the 20-year period considered here was mainly of an academic nature. Two significant studies led to the awarding of masters degrees to postgraduate students of the University of Pretoria’s Mammal Research Institute: the late James Gleeson in 1981 and Donald Matthewson in 1993, the latter supervised by the late Rudi van Aarde who earlier had conducted research on the island’s feral cats Felis catus, now thankfully extirpated. Both James and Donald studied aspects of the mice’s ecology and population biology, including habitat use, seasonal variations in density, breeding and diet. An important finding was the mice’s reliance on invertebrates year-round with plant material more evident in the diet during summer. Only a little avian material was found in stomachs, thought to have come from scavenged burrowing petrel carcasses. There was no evidence of predation on birds, it not being thought likely by James Gleeson in the early 1980s.
In 1994 Silvia Kirkman (née Mecenero) studied the population biology of Marion’s mice as a Zoology Honours project at the University of Pretoria. This was a desktop exercise and she did not undertake field work on the island, instead using data collected by James Gleeson in 1979/80 and Donald Matthewson in 1991/92 and in 1992/93. Other research on mice conducted during the period included aspects of energy metabolism and impact on invertebrates, especially on the larvae of the flightless moth Pringeophaga marioni, by David Rowe-Rowe and colleagues and on the mice’s role in ecosystem functioning by Jan Crafford. An important study in the first half of the 1990s by Steven Chown and Valdon Smith looked at the effect of global warming on mouse-plant-invertebrate interactions on Marion Island, gaining an understanding by comparing their findings with those from nearby and mouse-free Prince Edward Island. With the end of Marion’s feral cat population in 1991 after a long campaign, House Mice had become the sole introduced mammal remaining on Marion Island.
In 1992 I attended a SCAR/IUCN workshop in France that looked at progress in the conservation of sub-Antarctic islands, including Marion. I was given the task of summarizing the workshop’s recommendations relating to introduced biota. Looking back, I see I had little to say on House Mice, concentrating rather on the larger introduced mammals as targets for eradication. The workshop’s overall recommendations also made no mention of mice.
After a sabbatical in 1994 when I briefly visited New Zealand’s sub-Antarctic Enderby Island, where its introduced House Mice had been eradicated in the previous year, I returned enthused about the possibility of seeing the end of Marion’s mice. With Steven Chown, I motivated and co-led a two-day workshop in February 1995 at the University of Pretoria that looked at the impact of the mice on Marion Island and the desirability of their eradication. The workshop concluded that eradication was both feasible and desirable but noted “considerable management research” would be required first, suggesting a five-year programme to address identified gaps in knowledge. Lastly, the workshop recommended the formation of a working group on mice under the auspices of the South African Government’s then Prince Edward Island Management Committee. Such a working group did not transpire; what did take place over the next 28 years that has led to the Mouse-Free Marion Project will be covered in the fourth part of this series on Marion’s mice.
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John Cooper, News Correspondent, Mouse-Free Marion Project, 22 August 2023
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.