A note which said "uneducated retard" was added to the bottom of an anonymous letter of concern about the Department of Conservation's use of 1080 poison in Southland.
The Department of Conservation (DoC) won't comment on the letter because it doesn't know who wrote the note at the bottom of a letter, which was left on a vehicle near Te Anau in November 2016.
At the time, tensions were high in the community over the use of 1080.
A copy of the handwritten letter was emailed by DoC to private investigation firm Thompson & Clark for its information and also forwarded to police, documents released by the department show.
DoC was among government agencies using Thompson & Clark for security services at the time.
The email exchanges between DoC staff, released proactively by the department in response to a review into the use of external security companies by government agencies reveal they had an inkling who wrote the letter.
With the subject line "Recognise this hand writing?", the email said "[Name redacted] reckons it's [name redacted] – what do you think? Was on a vehicle left at Rainbow Reach. Got it here on my desk."
The letter writer was angry about what they said was untargeted and inhumane use of 1080 poison.
"I am upset and sickened by the stench of death and I grieve the terrible, unnecessary and indiscriminate killing this Government has endorsed, all in the name of money and politics.
"It is time to use our anger and stop the ecocide," the letter said.
Underneath, in different handwriting are the words "uneducated retard."
A spokeswoman for DoC told the Herald it would not comment on the note at the bottom of the letter because it was not known who wrote the words.
Marion Dawson, who was among those who protested against the use of 1080 in Te Anau in October 2016, said there was a lot of ill-feeling at the time about 1080 drops.
She said the letter probably voiced how many people were feeling at the time.
"DoC weren't listening to the locals."
She objected to people who were concerned by the use of 1080 being characterised as "uneducated retards", saying the community was full of good and educated people.
"The image of anti-1080 people that is being portrayed by mainstream media does really upset me. I'm not a thug, I'm not uneducated."
DoC has borne the brunt of anger about the use of 1080 poison to kill animals that prey on New Zealand's native species.
Staff, contractors and their families have been threatened and equipment used for 1080 drops have been sabotaged in the long-running dispute.
Those opposed to its use say it is a blunt instrument for dealing with pests, killing everything that eats it or eats the carcasses of other animals that have consumed it. They also say it poisons the land and waterways and is inhumane.
The SPCA this week caused controversy when it said it was "deeply concerned" over the use of 1080 because of the level of suffering it caused animals.
In September, anti-1080 protesters laid the carcasses of native birds on the steps of Parliament, claiming they had been killed by the poison. It was later found none of them were.
Last month, the Environmental Protection Agency's annual report into the aerial use of 1080 in 2017 said it was crucial in protecting native species.