She said, despite this, progress had been made.
"We've live captured a feral dog. She has been to the vet and been spayed because obviously we can't release a dog that might make more, microchipped and vaccinated for parvo and she's come back and had some recovery time.
"Today we will release her in the area where the dogs attacked the mob of sheep a few days ago, hoping that she will meet up with the pack again."
Nilsson said the aim of tracking the dog, which they've named Judy, is to get a good understanding of the feral dogs' movements and habits.
"We will be able to tell where they are, how far they travel and more importantly we will be able to see if they are coming close to the property to attack some animals."
The efforts are being supported by the Northland Regional Council and Department of Conservation.
Capturing the dog has proven they're very feral and are not simply wandering domestic dogs, Nilsson said.
"It was quite an unusual experience meeting her. She's completely unresponsive to people, she's petrified of people, she either acts aggressively or completely ignores that you exist, so it's not a dog that you could reboot, so to speak.
"What we're doing has been done in a lot of places, where you put a feral animal with a tracking device on it and use it to track down other animals. They're normally called Judas animals and so because she's a female we've called her Judy."
Nilsson said she was hopeful the mission will be successful and go some way to controlling dogs in the area.
She previously called on the district council to change the bylaw to reclassify the dogs as feral, which would give authorities greater powers to control them.
Work was underway in the background to get this changed but it will likely take a long time to complete, she said.
- RNZ