One in five Tasmanian devils released into the wild last week to boost the endangered species' numbers have been killed on the state's roads.
Twenty devils raised by the Save the Tasmanian Devil Program (STDP) were released into Narawntapu National Park on September 25.
Four animals appear to have already ended up as road kill.
The STDP aims to create an "insurance population" of devils to offset the damage wrought by the devastating devil facial tumour disease.
Organisers are urging motorists to take extra care when driving at dawn and dusk to prevent any more deaths.
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Sixteen devils remain part of a trial on immunisation against the facial tumour disease.
Efforts to save the species began after Tasmanian devils were photographed in northeast Tasmania in 1996 with large tumours on their faces.
Ten years later, there was an estimated 90 per cent decline in average spotlighting sightings in the region.
While it is difficult to know how big the present population is, STDP believes an insurance population of about 500 breeding animals is needed to maintain the species' genetic diversity over the next 50 years.
The surviving immunised devils have been detected on cameras placed throughout the park and appear to be coping well.
