Upbeat scientists on brink of breakthrough using frozen sperm.

Kiwi scientists are confident of cracking one of conservation's biggest riddles — cryopreservation.

Department of Conservation (DoC) experts believe they are close to artificially inseminating a kakapo from frozen sperm and the landmark feat could happen by next summer.

There are just 126 of the critically endangered kakapo. That is up from the mid-1990s when less than 60 birds remained, conservationists fearing New Zealand's vulnerable, flightless parrot might join the dodo in the ranks of extinction.

Help save the kakapo: kakaporecovery. org.nz.

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For years, and with just one isolated success in 2009, Kiwi scientists have been doing painstaking trial-and-error work on the artificial insemination (AI) of kakapo, a species with infrequent breeding patterns and fertility rates down to 40 per cent.

But now a group of DoC scientists believes incremental gains have them at the brink of "the next level" and using frozen sperm to successfully inseminate kakapo for the first time.

In what would be one of the most significant breakthroughs in conservation science, success with frozen AI could guarantee the long-term survival of kakapo and other critically endangered native birds — perhaps even helping species around the world.

Invercargill-based DoC scientist Andrew Digby, who has previously worked for Nasa in mapping exoplanets, is optimistic the landmark kakapo achievement is just around the corner. "We have a chance to do this next year and are looking to bring some people in from overseas to help," Digby told the Herald on Sunday.

"We're probably going to focus on fresh AI but might get the chance to do frozen too.

"It's actually difficult enough from fresh sperm.

"We successfully produced chicks from fresh AI in 2009, but since then, we haven't been able to produce any. Doing the frozen bit is the next level."

It has taken years to figure out how to best preserve kakapo semen because the requirements of cryopreservation differ from species to species. Digby said the need for cryotechnology was to increase the kakapo's poor reproductive odds.

"Kakapo breed infrequently and even then their fertility is very low. A lot of their eggs are infertile, about 50-60 per cent," Digby said.

"Making it even more difficult, the more times they mate, the more infertile their eggs become.

"Part of the AI plan is building a sperm bank because with such low numbers to start with, we need to ensure the birds avoid inbreeding."

Digby said one of the main hurdles with getting frozen AI working was figuring out how to stop, or minimise, the degradation process of the sperm.