In August 2022 a male stoat was identified on Chalky Island/Te Kākahu-O-Tamatea in Fiordland, which has been predator-free since 1999.
Select committee documents show from the time the animal was detected to its capture eight months later Doc spent $483,260.
These include costs such as incident management team costs, staff time, conservation dog handlers, helicopter and boat expenses.
The government agency spent just over another $210,000 on ensuring the island was pest free by installing surveillance systems and doing biosecurity planning.
In the documents Doc explained that had the stoat not been caught it could have killed kākāpō chicks, nationally endangered te kākahu skinks and little spotted kiwi chicks.
Auckland University Professor of Conservation Biology, James Russell told RNZ the fact kākāpō had been reintroduced to the island made it a "precious place."
"That isolation that has protected the birds is also what makes some of these operations so expensive such as doing a predator incursion response."
Russell said he supported Doc's decision to spend the money on the stoat eradication.
"We have to decide, do we want to keep investing in this and push through these reinvasions and hopefully work towards a predator free New Zealand or will we just kind of draw the line and say we're not willing to spend any more money on these predator incursion responses."
He said islands around the country had seen similar stoat incursions.
"On Rangitoto and Motutapu Islands in the Hauraki Gulf they had no less than four stoat incursions over a year in 2021."
Russell said the animal could swim or hitchhike on people's boats.
He said half a million dollars sounded like a lot of money but people should remember that Doc managed 33 percent of the country on half a percent of the government's budget.
"When we are looking at some of the challenges and the responsibilities we have to our native birds and reptiles of New Zealand I think we really should feel that Doc's pretty hard done by."
Russell told RNZ with government departments facing restructures they should be trying to help Doc as much as possible.
The Conservation Minister has been approached for comment.
