PHILLIP Island’s little penguins’ feeding habits have been scrutinised as part of a new study.

Researchers from Phillip Island Nature Parks and Monash University spent four and a half years studying the penguins’ movements in water using GPSes and Fitbits.

“Penguins spend 80 per cent of their daytime at sea fishing,” said Associate Professor and marine scientist at Phillip Island Nature Parks, Andre Chiaradia.

“But it’s hard to know what happens under the mysterious blue line on the horizon.”

He explained the GPS and Fitbit tracking devices can reconstruct a penguin’s life at sea.

“Penguins are simple creatures, they have two speeds – fast and very fast,” he said.

“We know when they’re feeding because they go very fast when they are diving and searching for food.”

The study found that the penguins extracted around 1300 tonnes of biomass from their coastal ecosystem over two breeding seasons, including 219 tonnes of the commercially important sardine and 215 tonnes of red cod.

Associate Professor Andre explained that by knowing how much food little penguins eat, researchers can protect their food source from overfishing.

The study was published in Functional Ecology and sets a new baseline for long-term monitoring of Bass Strait food webs.