Tasmanian devils wipe out thousands of penguins on tiny Australian island
An attempt to save the Tasmanian devil by shipping an “insurance population” to a tiny Australian island has come at a “catastrophic” cost to the birdlife there, including the complete elimination of little penguins, according to BirdLife Tasmania.
Maria Island, a 116-square-kilometre island east of Tasmania, was home to 3,000 breeding pairs of little penguins around a decade ago.
Their populations have dwindled since Tasmanian devils were introduced in 2012, but according to BirdLife Tasmania, the most recent survey conducted by the parks department showed penguins had completely disappeared from the island.
Maria Island was intended to safeguard Tasmanian devil numbers by creating a geographically isolated population free from the contagious and deadly devil facial tumour disease.
An initial population of 28 devils released on the island over 2012 and 2013 had grown to an estimated 100 animals by 2016.
Dr Eric Woehler, the convenor of BirdLife Tasmania, said the loss of birdlife was a sad but unsurprising outcome.
“Every time humans have deliberately or accidentally introduced mammals to oceanic islands, there’s always been the same outcome … a catastrophic impact on one or more bird species,” he said.
“Losing 3,000 pairs of penguins from an island that is a national park that should be a refuge for this species basically is a major blow.”
A 2011 report conducted by the Tasmanian Department of Primary Industries, Parks, Water and Environment predicted the introduction of the carnivorous marsupials would have “a negative impact on little penguin and shearwater colonies on Maria Island through devil predation”.
“Penguins in Australia are facing major threats as a result of human activities, pets and feral animals,” said Woehler. “The offshore islands in Bass Strait, like Maria Island, and offshore islands in Victoria and South Australia are really important for the penguins because we generally don’t see the same spectrum of threats on those islands.”
Research last year found Tasmanian devils had also decimated colonies of short-tailed shearwaters on Maria Island.
“Because of their larger size and ability to dig, devils had greater impacts on nesting shearwaters than either cats or possums [which also prey on the birds],” the study found.
Woehler also noted anecdotal evidence of behavioural changes in Cape
Barren geese on Maria Island, which are normally ground-nesting birds. “We’re getting reports of geese trying to nest in trees to avoid devil predation,” he said.
“It’s very clear that the devils have had a catastrophic ecological impact on the bird fauna on Maria Island.”
The rationale a decade ago for putting an insurance population of devils on Maria Island was valid, said Woehler, because at the time the impact of the facial tumour disease was not well understood.
Research published in 2020 found the facial cancer was unlikely to wipe out devil populations because the spread of the disease seems to have slowed.
Maria Island was initially deemed to be an ideal location for the devils, as it has no public vehicles and roads, and also has introduced macropod species the animals could prey on. The island has Tasmanian pademelons, Forester kangaroos and Bennett’s wallabies, whose populations were previously managed by annual culls.
“You have a range of insurance populations around Tasmania and on the mainland of Australia [now]”, said Woehler. “I would argue that the removal of one insurance population will not have any adverse consequences for the devil.”
A Tasmanian government spokesperson said its Save the Tasmanian
Devil program continually monitored and evaluated the devil population and program activities.
“All effective conservation programs are adaptive and the STDP will continue to evolve in line with new knowledge in science and emerging priorities,” the spokesperson said.
“This also applies to Maria Island, where active monitoring and management occurs, and Maria Island remains an important part of the broader devil program to help restore and maintain an enduring and resilient wild devil population in Tasmania.”