Research into a small community of New Zealand sea lions on the Otago Peninsula could shed new light on why these critically endangered mammals are doing well there, but fare much worse on the Auckland Islands.
Only about 10,000 New Zealand sea lions have survived, and pup production at the main breeding population in the Auckland Islands has halved since the late 1990s.
These sea lions are endemic and classified as ''nationally critical'' - which is the highest threat status in the New Zealand threat classification system.
But on the Otago Peninsula a small population of females, producing fewer than 10 pups a year, has been growing at the same time the Auckland Islands population has declined.
Niwa marine scientist Dr Jim Roberts, of Wellington, says he and other scientists have been studying the survival, reproductive rate, diet and other biological factors of different colonies, and coming up with answers.
And he paid tribute to continuing Otago sea lion research by Shaun McConkey, a trustee of the New Zealand Sea Lion Trust.
In an interview, Dr Roberts noted that Otago Peninsula sea lions had relatively ready and nearby access to food and faced less competition from fellow sea lions than on the Auckland Islands, although female sea lions had to contend with potential disruption from male sea lions and some human interference.
At Otago, the reproductive rates were higher than at the Auckland Islands, far fewer dying in the first years of life, and females were producing pups at a younger age.
The comparison with Otago sea lions was ''telling us what these sea lions should be capable of'' and indirectly added to understanding the challenges facing all New Zealand sea lions.
Dr Roberts gave a talk yesterday, at the New Zealand Marine Sciences Society conference in Auckland, describing changes in the demographics and biology of sea lions on the Auckland Islands.
Dr Roberts says the recolonisation of Stewart Island and of the Otago Peninsula was ''brilliant'' for the species.
Research was also showing the decline in the number of sea lions at the Auckland Islands was due to several threats, involving ''nutritional stress'' and food shortages as well as deaths resulting from fishing trawl gear.
And bacterial disease had killed hundreds of pups in some years, he said.
