Department of Conservation biodiversity ranger Jim Fyfe said the department and research group LeopardSeals.org were receiving fewer reports of the large, solitary seals than normal.
There was still a lot to understand about what the animals, more commonly associated with Antarctica, were doing on Otago’s coastline, Mr Fyfe said.
There had been an apparent increase in the number of leopard seals on the region’s beaches over the past dozen years "but this year it seems to have stepped back again a little bit".
"Of course, there’s all the other climate stuff happening, so whether it’s to do with marine climate, or other aspects of what’s happening to our oceans, we don’t know.
"But certainly we think it’s worth monitoring our Antarctic visitors and trying to understand why they’re coming here and what they’re doing while they’re here."
Until 2019, the species was considered a vagrant in New Zealand waters, meaning there were theoretically only 15 individuals in New Zealand in any given year.
Increased sightings contributed to the species that year being granted resident status by the Department of Conservation, which changed its conservation status to naturally uncommon, indicating fewer than 250 individuals were understood to be in New Zealand.
At the time the changed status was said to be due to an increasing frequency of sightings on the mainland, and new evidence that the species was continuously present in New Zealand.
Dunedin leopard seal researcher Giverny Forbes said although this month and next were typically when most reports of the animals were received, August was usually much busier than it had been this year.
Despite two reported sightings, at Long Beach and Aramoana, on the last two days of the month, there had been a noticeable drop in sightings locally.
Researchers were not familiar enough with the animals to know whether the change in reporting was related to the well-being of the population, she said.
If the assumption was the animals that appeared on Otago beaches arrived from Antarctica, then their arrival did "somewhat coincide" with the seasonal expansion of the sea ice down south.
"They’re still just such a mystery and that’s just another really good reason for keeping up monitoring as best we can."
