Researchers believe imported cats and foxes are the primary cause of the high rate of mammal extinction that has been sweeping Australia.

A recent study showed a whopping 10 percent of the land mammal species native to Australia have been wiped out since European settlers first arrived in 1788, the Associated Press reported. These mammals include the Tasmanian tiger and various species of mice and wallabies. Today, about 21 percent of Australia's remaining native species are considered to be threatened.

"The extent of the problem has been largely unappreciated until recently because much of the loss involves small, nocturnal, shy species with [little] public profile - few Australians know of these species, let alone have seen them, so their loss has been largely unappreciated by the community," conservation biologist John Woinarski, who led the research, told the BBC.

A team of researchers set out to find the cause of this devastating extinction rate and determine what threats are being imposed on existing species. They pinpointed a correlation between the introduction of the feral cat and red fox, both of which were brought over by European settlers. Both of these species thrived on the continent and quickly took over the land, the AP reported.

"We knew it was bad, but I think our tallies were much worse than previously thought," Woinarski told the AP. "The fact that we're losing such a large proportion of our species is a problem of international importance."

The team observed seven species that were once widespread across Australia now only exist on islands that have yet to be touched by the influences of the invasive animals. They also found many of the species that have been locally killed off are smaller animals that are easy prey for foxes and cats.

Other human activities also may be contributing to the loss of species. In the past it was common practice for indigenous Australians to set small fires to burn away flammable dry brush. A recent decline in that practice is believed to be causing natural wildfires to be more frequent and widespread, the AP reported.

The findings were published in a recent edition of the Proceedings of the National Academy of Sciences.