Since 1996, the invariably fatal, contagious devil facial tumour disease has been infecting devils in Tasmania, more than halving the wild devil population.

Experts are warning the officially endangered species could be extinct by 2020.

A program working against the devils' extinction is breeding cancer-free, insurance populations at eight sites on the Australian mainland.

Taronga Western Plains Zoo in Dubbo confirmed yesterday at least five joeys had been born to two of the 12 wild Tasmanian devils delivered in December last year.

Senior keeper David Schaap said the zoo's first joeys appeared to be about 100 days old.

''This is a huge success,'' Mr Schaap said..

''The mainland of Australia is basically working as a disease quarantine station working to keep the species ticking over in case the worst occurs and they become extinct.

''To breed these devils is the most valuable thing we can do for devils as a species.''

The devils spend four months in the pouch, then five months being suckled by the mother in a den, who will also feed them bits of wallaby.

Sydney's Taronga Zoo has also bred this year its first two Tasmanian devil joeys under the insurance population program.

The Australian Reptile Park, at Gosford on the Central Coast, has reared 18 Tasmanian devil joeys this year.

Last year, in its first year of the program, the park bred eight devils.

There are five other mainland zoos trying to breed wild Tasmanian devils under the program, in South Australia, Queensland and Victoria.

The aim is to breed a healthy population of devils on the mainland that can then be reintroduced back into the wild in Tasmania once the risk of the disease has diminished.

Tasmanian devils weigh between 10kg and 15kg and were named devils by early European settlers because they produce a fierce screech and can be bad-tempered. AAP