The mystery of Australia's small mammal declines

Across the top end of Australia, from Cape York to the Kimberly Mountains, populations of smaller marsupials and native rodents are collapsing.  What's going on?

  Tapping into traditional knowledge to help solve a mystery (photo by Ian Morris)

Tapping into traditional knowledge to help solve a mystery (photo by Ian Morris)

Several studies in recent years have documented the declines.  A few have shown major changes in a single location, such as Kakadu National Park.  Others have compiled scattered information over a much broader area; one innovative study used interviews with Aboriginal communities to piece together evidence (find study here).

The bottom line: many species that used to be common have become vanishingly rare, or have geographic ranges that are collapsing. 

What is causing all this?  No one is sure.  Some suspect it could be severe overgrazing by livestock, especially during droughts.  During such times the vegetation can become badly damaged--as we're seeing at present in many areas

Others think altered fire regimes are the cause.  And yet others suspect predation by feral cats, with a possible role for lethal cane toads for certain predatory mammals.

Whatever the cause, this might be a new biodiversity crisis for the Land Down Under, which has already lost more native mammal species than any other continent.