AT DUSK, the dry savannah of the Kimberley was once alive with the scuttling and foraging of the burrowing bettong, a marsupial whose ''countless numbers'' were marvelled at by early surveyors.

Along with many species of quolls, bandicoots, possums and marsupial rats, the bettongs had thrived for millions of years in northern Australia, surviving ice ages, surging sea levels and human hunters.

Into oblivion . . . some of the disappearing native mammals: (clockwise from above) burrowing bettong, a possum, northern brown bandicoot and northern quoll.

But many of these natives are unlikely to survive another decade or two, according to a new report which reveals an abrupt, stunning plunge towards mass extinction in the past few years.

At the 136 sites across northern Australia that have been repeatedly surveyed since 2001, the mammal populations have dropped by an average of 75 per cent. The number of sites classified as ''empty'' of mammal activity rose from 13 per cent in 1996 to 55 per cent in 2009.