The premise that there were cougars in Western Australia was widely believed during the 1970s. There are several theories as to how they were introduced. The most popular theory was that United States servicemen brought four cougar kittens to Western Australia during World War II; they eventually grew too big for captivity and were released—two at Fremantle and two at Bunbury. Another theory is that cougars escaped from a traveling circus that was involved in an accident between Bridgetown and Nannup around 1961. The circus theory has often been referenced to support the allegation that cougars were responsible for the deaths of around 2000 sheep in the Duranillin area in the late 1970s.