Scientists working to boost the population of Tasmanian devils have made a key discovery which could result in better survival rates for devils released into the wild.

The researchers found that the longer a Tasmanian devil had spent in captivity, the greater the chance of the animal being hit by a car after being released.

Reviewing the survival rates of 50 devils released at two Tasmanian sites in 2015 and 2016, the researchers found 19 were killed by vehicles within six weeks of release.

The biggest killer of Tasmanian devils after the devil facial tumour disease is collisions with vehicles. With dozens of captive-bred animals being released each year, identifying and releasing "street-wise" animals will make a big difference to the endangered species' prospects.

Sydney University population biologist Carolyn Hogg said the study took into account a range of factors including a devil's age, sex and its type of captive existence – roaming free on an island or living at a zoo.

"The only thing that came out as being a contributing factor to being hit by a vehicle was the number of generations in captivity," Dr Hogg said. "It had a much stronger effect than sex, age and release site."

The results, published in the journal Scientific Reports, found devils that spent no more than one generation in captivity fared better in the wild than those in captivity for several generations.

The number of Tasmanian devils held in captivity as part of an insurance population is now about 700. The average time in captivity amongst the insurance population is two generations.

Dr Hogg said the findings would inform future decision making as to which devil to release into the wild.

"It will assist us in making better informed decisions by allowing us to select the animals that we think will have a greater chance of success," she said.

Conservation breeding programs will seek to limit the captive period.

The research adds to a growing body of work that suggests captivity reduces an animal's "street smarts" and ability to be predator aware once released.

Such results are changing the way threatened species are managed in captivity. At Zoos Victoria, endangered helmeted honeyeaters get predator training prior to being released to the wild. This involves exposing them to goshawks about six times a week.

Tasmanian devils are considered vulnerable to being killed by vehicles as they are nocturnal, scavenge on roadkill and travel long distances.  

The devil facial tumour disease, the greatest threat to devils, was first documented in north-east Tasmania in 1996. Then there were tens of thousands of devils living in Tasmania. In the years since, between 90 per cent and 95 per cent of devils have disappeared. Just a few thousand remain and the species was listed by the federal government as endangered in 2009.

The highly infectious cancer known as devil facial tumour disease kills devils within three to five months of the facial tumours first appearing.