Cats Brought to Marion Island in 1949 to Kill Rats Instead Devastated Seabird Populations

The island's lack of trees — its vegetation consisting only of moss and grass clumps — made burrow-nesting seabirds easy targets. The cats eventually stopped hunting rats and turned to storm petrels returning to their underground nests at night. Research published in Polar Biology and Antarctic Science found that during the 1970s, the cats killed an average of 450,000 seabirds per year.

The predation completely disrupted the island's species balance: the common diving petrel disappeared entirely from Marion Island. The species was only seen again in 2015, 24 years after the last cat was captured, in a one-hectare area at Goodhope Bay. Even 20 years after the cats were removed, nest density had only recovered by 56%.