In 1949, five domestic cats Felis catus were introduced to sub-Antarctic Marion Island (29, 000 ha; 46°54'S, 37°45'E; South Africa) as pets. By 1977 their number had grown to a round 3,400. They had caused extensive damage to nesting seabird populations; the extirpation by 1965 of the common diving petrel Pelecanoides urinatrix is attributed to cat predation. This paper summarises initial biocontrol efforts and the first four years of an intensive eradication programme from August 1986 to April 1990.
In 1977, as the cat population density was high, biological control via introduction of the viral disease, feline panleucopaenia, was considered the most efficient and cost effective method to employ. After its introduction, cat numbers decreased from an estimated 3,405 in 1977 to 615 (±107) in 1982 but evidence suggested that the disease was becoming less effective as the rate of decline was slowing. However, at these reduced densities hunting was considered perhaps a feasible method of removal.
A full-scale hunting effort was initiated in the austral spring of 1986. Trapping was also incorporated in the winter of 1989 and the following year when it became apparent that hunting alone was not removing sufficient animals to maintain the population decline.
From August 1986 to April 1990, 872 cats were shot and 80 trapped over 14,725 hours of hunting. Night hunting (by spotlight) proved far more efficient than day hunting, as the cats were found to be largely nocturnal.
As the programme progressed, cats seen during night hunting and kills per hour greatly decreased as cat numbers declined. Hunting success (cats killed as a proportion of those seen) also decreased. Thus whilst the programme succeeded in greatly reducing the cat population, removal of the last individuals became increasingly difficult. Attempted eradication is ongoing.
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