A study has revealed there are more than 2.5 million feral goats in western New South Wales, Australia.
The Western Catchment Management Authority (CMA) says a study has shown the number of goats has doubled since 2000.
The operations manager, Russell Grant, says controlling the pests and the damage they cause to pasture and native scrub is the top priority of the CMA, which will release a management strategy later this year.
He says it is yet to be determined why the population has exploded.
"One theory is that a larger take of billy goats through the feral harvest industry," he said.
Billy goats cause some mortality within goat populations, so removing a lot more of the billy goat may increase the survival of younger goats, something like that but otherwise we don't understand."
The CMA commissioned the Department of Primary Industries to analyse goat populations in the region, with the current number expected to double again during the next decade.
Mr Grant says goat numbers were previously stable.
"Goat numbers fluctuated but stayed fairly consistent, probably at about a million or so goats from about 1992 to 2000, and despite the drought and harvesting operations over the last 10 years, goat numbers have effectively doubled," he said.