A lack of protection for the little penguin colony on Granite Island has sparked the City of Victor Harbor into action.
Elected members supported a move by councillor Andrew Robertson at their meeting on Monday for the CEO Victoria MacKirdy to write to the Environment and Water Department (DEW), which manages the island, and Planning, Transport and Infrastructure Department (DPTI), which manage the Causeway, about concerns relating to the colony.
A month ago, nine little penguins were killed by a fox on the island in about three days.
Cr Robertson said the council had to do everything possible to prevent "extinction" of the penguin colony on the island.
"According to the monitoring program on Granite Island, there is only one breeding pair on Granite Island," Cr Robertson said.
"If this is true and they are lost to foxes, it will be the end of little penguins on the island.
"It will be an awful shame if they cease to exist, as they have been a major attraction to Victor Harbor. We must step as a council to get serious action from DEW. We need sustainable management for the colony to thrive again.
"We need structures in place to prevent foxes from entering the island. Member for Mayo Rebekha Sharkie has written to the state government on the community concern of the demise of the penguins."
In video footage from June 24, when the first penguin carcass was found, a pair of foxes are seen sniffing in burrows on Granite Island's north shore.
Lower Inman Valley man Stephen Hedges, who monitors the island's little penguin colony for Flinders University studies, spotted a fox while on the island with another volunteer.
"I saw the fox with a penguin. It dropped the penguin in front of me and another guide. I saw it flopping on the ground and the fox next to it, then the fox ran off," he said.
Earlier this month, a DEW spokesperson said they were "confident one of the foxes is likely dead", as one of a series of baits laid by Nationals Parks and Wildlife Service SA had been taken.
The little penguin population has sat at about 30 birds since 2012. In 2006, a fox destroyed 19 birds before it was killed with bait and in 1994, when there was a larger population, 74 penguins were mauled by a single fox.