As this article states, "figures show the trend has increased in Australia due to an oversupply of single women aged 40 to 54 compared with men in the same age bracket".
Interesting that these independent older women are still called "cougars" Down Under. The term sounds so American, and I'd imagine that some people are not happy with yet another example of US style "cultural imperialism". Maybe one day we'll use the name of a local marsupial instead!