Five cats released on treeless Marion Island killed 450,000 seabirds a year

AI digestMimile.ai EditorialAugust 23, 2026 at 12:28 PM

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Five cats released on treeless Marion Island killed 450,000 seabirds a year

Five domestic cats introduced to Marion Island in 1949 to control mice multiplied to 3,400 by 1977 and killed an estimated 450,000 seabirds annually. South African authorities launched an eradication program in 1977 using feline panleukopenia virus, hunting, trapping, and poisoning, removing the last cat in July 1991. The island's mouse population then surged 430% over the next 20 years, prompting a planned $25 million Mouse-Free Marion project.

Key Facts

Five domestic cats were introduced to Marion Island in 1949 to control mice at a meteorological station.
By 1977 the island's cat population had reached approximately 3,400, according to scientific reports.
In the 1970s cats on Marion Island killed an average of 450,000 seabirds per year, based on research published in Polar Biology and Antarctic Science.
The common diving petrel was wiped out on Marion Island and was not seen again until 2015, 24 years after the last cat was removed.
South Africa launched an eradication program in 1977 that included releasing 96 cats infected with feline panleukopenia, reducing the cat population by 50% within 18 months.

The Cat Eradication Program

South African authorities began a comprehensive eradication program on Marion Island in 1977. Ninety-six cats carrying the feline panleukopenia virus were released on the island, and the infectious disease cut the cat population by 50% within 18 months. Night hunting, trapping, and poisoning were used against the remaining cats, reducing their number to 600 by 1982. The last cat was captured in July 1991, ending a 42-year process and making Marion Island the largest island from which cats have been completely eradicated.

Mouse Population Surge

After the cats were removed, the island's mouse population increased by 430% over the following 20 years. Herbivorous mice were found to attack live albatross chicks directly. A $25 million project called Mouse-Free Marion is planned to eliminate the mouse infestation on the island.

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Five cats released on treeless Marion Island killed 450,000 seabirds a year

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Five cats released on treeless Marion Island killed 450,000 seabirds a year

Key Facts

The Cat Eradication Program

Mouse Population Surge

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