This is the first time, the satellite-linked equipment has been used to study the threatened species on the New Zealand mainland.
The same high-tech gear has earlier been used in the main New Zealand sea lion breeding area, the Auckland Islands, 700km south of Dunedin.
The sea lions were previously common throughout the mainland, but were wiped out there by hunting and commercial sealing by the early 1800s, initially surviving only at the Aucklands.
About 70 of the protected mammals are now based on the Otago Peninsula.
A sea lion matriarch, Mum, and her descendants have since 1994 established the first sea lion breeding colony on the mainland for 200 years.
Early last month, scientists, including University of Otago zoology doctoral student Amelie Auge, glued small depth-time recording devices with satellite-communication transmitters to four of the mammals: Mum's first pup, Katya (14); Katya's daughter Aurora (4), and two of Mum's other daughters, Honey (5) and Leonie (12).
"It's very exciting," Dr Louise Chilvers, a Department of Conservation mammal scientific officer, said.
Scientific data gathered in the pilot study would help improve the conservation management of "one of the least numerous [sea lion] species in the world", she said.
Initial results show greatly superior feeding conditions experienced by Otago Peninsula sea lions by contrast with a much more marginal existence at the Auckland Islands.
From the peninsula, swimming for food is over a relatively short-distance - ranging from a few kilometres to about 24km from the coast - by contrast with the much more demanding 350km return trips undertaken by mothers feeding their young at the Aucklands.
Otago maternal body weights are much higher.
"This reaffirms that Otago is a great area for marine wildlife," Dr Chilvers said.
Surprisingly, big contrasts in feeding behaviour are also emerging among the Otago sea lions.
"I'm sure that this data will leave us with a lot more questions than answers," she added.
