Doc coastal Otago biodiversity ranger Jim Fyfe said the species’ behaviour continued to change as they made their presence known in the city during this year’s breeding season.
But despite there being several as-yet unaccounted-for mothers, it appeared this breeding season had not been as productive as years past.
At least 25 sea lion pups were believed to have been born this year — up to 10 shy of the base level for the Dunedin population to achieve official "colony" status, Mr Fyfe said.
It was also up to six shy of the record 31 sea lion pups born in Dunedin last year.
"We can’t confirm the total numbers yet, because there’s still females that we know have pups unaccounted for.
"It’s getting harder and harder as we get more and more females and the habits change.
"By this time last year, certainly all the females that had pups had turned up at the [Otago Peninsula] creche.
"But it’s also getting to the point where we’ve got to consider that we might not even find all the females and their pups.
"Maybe we’ve even missed some in the past ... because I’ve been seeing some yearlings around that are untagged.
"And I’m sort of thinking ‘where have you come from?’."
Late last year, before breeding began, Mr Fyfe said he was hopeful a "magic number" of 35 pups could be reached in Dunedin.
A breeding site needs five consecutive years of at least 35 pups being born a year for Doc to declare it a colony — and there are no breeding colonies on the South Island at present.
Dunedin’s annual breeding season pup counts set records in three consecutive years before this year — increasing from a record 20 pups in 2022 to 21 two years ago and 31 pups last year.
And because there were 39 known breeding-age females in the city this year, there were high hopes for the season.
But five mothers had been seen with yearlings — last year’s pups — and appeared not to have had pups.
The large inlets on Otago Peninsula, where the animals were known to creche pups, were only now starting to fill up.
One factor in the animals’ delayed arrival appeared to be a congregation of eight sea lion mothers letting their pups play in the creek there to get them used to "water sports", Mr Fyfe said.
"As the number of females increase, because they are social animals, their social complexity also increases.
"We’re quite privileged to be able to ... see and appreciate behaviour that has, through the rarity of sea lions, not been witnessed in a few hundred years."
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