Cats threaten native mammal survival in our tropical savannas

(Phys.org) —Australia's tropical mammals are in trouble, with a quarter of species suffering serious decline since 1970, and the devastation evident in iconic areas such as Kakadu National Park.

A team led by University of Queensland researcher Dr Diana Fisher blames the bulk of the decline on feral cats, and highlights savanna management as a likely key to tropical mammal survival.

Dr Fisher, from UQ's School of Biological Sciences, said the international team of collaborators from universities and conservation agencies looked at the characteristics of threatened marsupials and their habitats throughout Australia.

"We found that disappearing tropical mammals are small, with an average weight of about a kilogram— the size of prey that cats hunt," Dr Fisher said.

"Declining species live in dry savanna grassland and woodland, which is widespread across northern Australia.

"Small mammals are increasingly exposed to predators in our tropical savannas because of very frequent fires and grazing, which removes vegetation and fallen timber that they rely on for shelter."

Dr Fisher said the removal of shelter exposed small mammals such as northern quolls to feral predators.

"Rainforest species are generally safe because they are in dense, intact vegetation," she said.

Dr Fisher said foxes had wiped out larger species in exposed and damaged habitats in southern Australia, but didn't thrive in tropical areas.

But feral cats had been established in the tropics for 100 years.

Declining tropical Australian mammals identified by the Dr Fisher's Australian Centre for Ecological Analysis and Synthesis research group included northern quolls, northern brush-tailed phascogales and brush-tailed rabbit rats.

The research is published online in an Early View in Global Ecology and Bio-geography.