Sea lion colony confirmed, but work still needed

April 11, 2018, Massey University
Credit: Massey University

While celebrating the Department of Conservation's announcement of a New Zealand sea lion (rāpoka) breeding colony on Stewart Island, a Massey University marine mammal specialist is calling further action to protect the endangered species.

Beginning with a two-person team eight years ago, Massey University's Associate Professor Louise Chilvers has been visiting the island each year to make pup counts.

"Getting up to 55 pups this year was an exciting find for us, but it doesn't make up for the 1500 pups that are no longer born at the Auckland Islands. The main human impact at the Auckland Islands is local fisheries interaction, so the establishment of this new little population away from that interaction is so important for the endangered New Zealand sea ."

"When it comes to the five sea lion species of the world, ours is the least abundant. South American, Californian, and Steller sea lion populations range in the hundreds of thousands, while the New Zealand and Australian barely break 10,000. These pups and colony are extremely special, so hopefully now there will be an increase in efforts to ensure their protection, and that of the others in the south, and that means not only DOC, but all of New Zealand."

"These are our own New Zealand , only found here and they are unique. Take their forest-dwelling for example, none of the other sea lion species around the world do this. The more we know, the more we can do to protect them."

Dr. Chilvers recently returned from undertaking the count on Stewart Island, working with a team of five from the Stewart Island and Southland Department of Conservation areas and Auckland Zoo.

Sea lion pup enjoying a creek in the forest. Credit: Massey University
"Stewart Island is an important place to focus efforts on research to better inform their management, as has been outlined in the DOC Threat Management Plan, but equally sea lion populations around the rest of New Zealand's mainland and the sub-Antarctics are still threatened by human activity."

"Last year we tagged the pup of a female that we tagged as a pup on Stewart Island from five years previously. It was pretty special to see the generations are staying in the area.

"This work is pretty full-on though, and over the eight-day trip we were working very hard. Sea lions can grow to weigh around 400-500 kilograms, as pups at the age we are tagging them they are 30 to 50 kilograms so not an easy task. But we would never have even been there to do the work if it wasn't for the community's help in the beginning."

That community help came in the form of sightings and photos eight years ago. There had been reports of sea lions breeding on Stewart Island, but never any photos to confirm pupping. So information sheets were sent out with hunting block permits for the island because people would often spot the sea lions when hunting or hiking on the island.

"This wasn't intended to be an accurate count because females actually raise pups mostly in the forest, not the beaches like people assume. It's also hard to tell the difference between a juvenile male and an adult female, so we needed to go ourselves – but we could only make the trip if we knew they were there. "In the end, people sent back information about sea lions they saw – and we had three females and five pups reported and shown in one photo, so that gave us all the information we needed to start the counts and research.

"That community engagement was so crucial for us to make a case about heading to Stewart Island and it has resulted in this exciting announcement eight years on of the first New Zealand sea lion colony on the New Zealand mainland in over 150 years."

Explore further: Competition with humans responsible for decline of New Zealand's endangered sea lions, study shows

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