Department of Conservation biodiversity ranger Jim Fyfe said as the marine mammals re-established a population along the Dunedin coast, seeing groups of the social animals at Smaills Beach in October was becoming expected.
"We’ve been watching Smaills for the last few years, saying this is a feature of October for Smaills Beach, that the females turn up here to congregate," Mr Fyfe said.
"It is a really seasonal thing that occurs — a predictable seasonal attendance at Smaills Beach."
Female family lines tended to keep in touch with one another and hang out together, he said.
At least four females with 10-month-old pups from the last breeding season had been seen with their pups at Smaills Beach recently.
Mothers would be socialising their pups.
They might also leave pups at the beach with the group and head off "somewhere else for a bit of ‘me time"’.
"A lot of these females that are now at Smaills Beach have been hanging out for the last month or so at Allans Beach, and they’re sort of moving from Allans Beach to Smaills.
"There’s quite a, it seems, ‘grouping up’ that happens in that process."
At this time of year pregnant females would be thinking about weaning their pups from last year, Mr Fyfe said.
To that end, the group afforded the animals "a bit of safety in numbers".
Smaills Beach was a wide, sandy beach with shallow water out to Bird Island, he said.
It could be that the beach provided a good spot to continue to avoid larger male sea lions.
"What we know about the females is they can usually outswim and outmanoeuvre the bigger males in shallower water and they’ve got a few tricks up their sleeve about shooting around the back of Bird Island and that sort of thing.
"It seems to be quite a strategic site for them to congregate at this time of year."
Mr Fyfe said locals using the beach over winter, particularly those with dogs, needed to be aware that the marine mammals were back.
The signage at the beach was clear, and dog walkers needed to adhere to the rules in place.
Community rangers, a joint Doc and Dunedin City Council initiative, would begin patrols this weekend, providing education to beach-goers, he said.
A sea lion, now known as Mum, gave birth to a pup in Dunedin in 1993.
She was the first sea lion in 150 years to give birth on the mainland.
Since then a population of the nationally vulnerable species has started to grow and more than 20 sea lion pups are born on city beaches each summer.
The threshold for Doc to declare Dunedin a breeding colony is 35 pups a year over five years.
