From the referenced paper:
Between December 1976 and February 1981, 246 cats were collected. Overall sex ratio was in favour of males 1:0.8, and coat colour was tabby (74%), orange (26%) and black (2%). The breeding season extended from October to March with the peak in November-December. Mean number of embryos was 4.7 per female and evidence of females producing two litters was found. Mortality in kittens increased as they grew older, with litters of kittens greater than 1.8 kg containing two or fewer animals. Most cats lived in herbfield or tussock grassland, with very few if any in feldmark. The total population was estimated at between 169 and 252 adult cats. Observations of an adult male showed that its home range covered 41 ha, but this appeared not to be maintained during winter. It's daytime activity varied greatly, much time being spent foraging for food.
Domestic cats Felis catus (L.) were feral on Macquarie Island by 1820, only 10 years after the island was discovered by sealers. Their presence was soon noted by early naturalists. Depredations by cats greatly reduced the numbers of burrow-nesting petrels and, together with the weka Gallirallus australis, cats were probably responsible for the extinction of the endemic parakeet Cyanoramphus novaezelandiae erythrotis and banded rail Rallus phillippensis before 1900. Feral cats are common on several other subantarctic islands and have been intensively studied; the only previous study on Macquarie Island was on diet. This study reports on other aspects of the biology of the feral cat on Macquarie Island.