Doc installed the gas-powered traps in the Kepler mountains, near Te Anau, late last year, and staff are monitoring its effectiveness against stoats and rats as part of a year-long programme.
Trials are also being carried out in Te Urewera, in the Bay of Plenty, and in the Orongorongo valley, near Wellington.
Doc Te Anau biodiversity programme manager Lindsay Wilson said 20 of the traps had been installed along with infrared cameras, aimed at testing the claim by the New Zealand manufacturer they were 75% more efficient than manual traps.
The trap - dubbed the "Henry" after pioneer conservationist Richard Henry - is mounted 30cm above the ground on a tree and when an animal enters, a CO2-powered piston is triggered which crushes its head.
The body is then dropped to the ground and the trap resets.
Before the trial, native birds, such as the kea and weka, were observed with a disarmed trap and the department was confident the self-setting traps did not pose a risk, Mr Wilson said.
The traps were an exciting pest-control development, as a conventional trap needed checking once a month, and was "effectively out of action" if it caught an animal.
In contrast, the self-setting trap could reset itself a dozen times before requiring checking, resulting in reduced labour and transport costs for the department - and a higher kill rate, he said.
"They are looking good, so far."
Goodnature co-director Robbie Greig, of Wellington, who helped design the trap, said while the self-setting trap at $160 was more expensive than conventional traps, they proved cheaper in the long term.
The operational cost of a Henry trap over 20 years was $320, whereas a conventional trap was $1900 over the same period, he said.
With Doc monitoring about 10,000 stoat traps in the Te Anau area alone, the new traps would cost $3.2 million to operate over 20 years compared with $19 million for conventional traps over the same period.
The company was also working on a self-setting possum trap, and a mechanism for drip-feeding a daily amount of bait on to the traps.
The company had attracted interest from all over the world in the self-setting traps, and from local holiday homeowners, Mr Greig said.
