Until recently most attention was paid to the island's goat population, but now pigs are the first priority.
Hunting would therefore have less of an impact on goat populations if hunters avoided killing females.
Instead, the finding shows that goat populations must have already been interbreeding during the early migration into Europe.
However, their numbers are few when compared with the goat population.
The main impact of the goat population was before this collapse, about the turn of the 19th/20th century.
Feral goat populations appear to be small and isolated in Victoria.
Britain's goat population is on the up.there are now more than a hundred thousand kept in this country.
In 1964, although the goat population had declined to around 18 animals, many ticks were found at the island.
One major threat to the species is the feral goat population.
Officials are unsure why the goat population has declined in the Black Hills.