Behaviour change in Tasmanian little penguins points to warming sea surface temperatures

The penguins’ annual cycle used to be consistent year on year – they would breed in the summer, mault in the autumn then spend winter at sea before arriving back in spring.

But adjunct researcher at the Institute for Marine and Antarctic Studies, Dr Eric Woehler, said this behaviour had noticeably changed in the last decade.

“Now we have recorded them breeding from winter through to late summer,” Dr Woehler said.

“As water temperatures are warming, that confinement of the breeding season to summer is less constrained.

“Birds have changed their breeding system, which we believe is a function of warmer ocean temperatures bringing changes to food availability. If the water temperature gets too warm, they won’t be able to find food.”

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Penguins in the warmer climate of the mainland – on the coasts of Western Australia, South Australia, Victoria and New South Wales – have traditionally had a longer and more unpredictable breeding period.

Sea surface temperature monitoring by the Bureau of Meteorology and CSIRO from 1950 to 2017 found the waters through the Bass Strait and down Australia’s east coast have warmed the fastest.

The warming heightens the likelihood of marine heatwaves, which can cause die-offs of certain marine species – some of which are relied upon by penguins for food.

They also result in conditions that can cause Pacific Oyster Mortality Syndrome. The POMS outbreak in Tasmania in January 2016 cause severe harm to the oyster industry.

Dr Woehler said it remained an area of intensive study.

“Because this appears to be a relatively recent phenomena, if we were to have this conversation in 10 years time then we would have a better sense of why penguins are behaving in this manner,” he said.