Urban backyards are an important habitat as part of wider efforts to protect native animals, conservationists have said.

Ian Darbyshire from the Foundation for National Parks and Wildlife said Adelaide Hills residents, for example, could do simple things to help preserve the region's southern brown bandicoot population, which is in decline.

"Plant some native species — keep your own pets under control, talk to your neighbours [and] see if they will do the same," he said.

"[People can] create some corridors throughout the Mount Lofty Ranges [Adelaide Hills] so the animals can move around, mate, meet and spread the gene pool around."

Mr Darbyshire said today, designated as Threatened Species Day, was a chance to remind people Australia had a very poor past record on native mammal protection.

Since European settlement at least 30 native species had become extinct — nearly half of them in the past half century, environmentalists said.

Feral threat to bandicoots

Among southern brown bandicoots, almost 50 per cent fell victim to feral animals or pet cats before they could reach maturity.

Mr Darbyshire said there had been a dramatic decline in bandicoot numbers.

"The bandicoot used to spread all the way down the east coast of Australia," he said.

"It's now really under threat in the Mount Lofty Ranges — there are just isolated communities left and there is a community also on Kangaroo Island.

"It's quite sad that we have got to that point ... if we don't help them and we don't change some of our practices to help them survive, we won't have them."

Many young bandicoots become prey for feral animals or pets. ( Supplied: Pierre Pouliquin )

Volunteers have been working across 19 Adelaide Hills properties to create a wildlife corridor to help support southern brown bandicoots.

Mr Darbyshire said native animals played an important environmental role in the Hills.

"The bandicoot is important because it spreads helpful fungi around the undergrowth and forests of the Mount Lofty Ranges," he said.

"So these animals have their place, they are useful and we should do what we can to help them survive."