A four-month-old Labrador puppy called Bruce is fighting for his life after swallowing a suspected death cap mushroom in Griffith on Sunday.
His owner, Ben Jausnik, broke down in tears when describing the puppy's increasingly dire medical battle, saying the vet had told him there was now little more he could do on Thursday.
"He is in really bad shape and I don't know if I can continue... to justify putting him through the pain," Mr Jausnik said, implying he may have to have the dog put down.
Mr Jausnik, who lives in Kambah, was over at his parents house in Griffith when he let Bruce off his lead briefly to stretch his legs while he was parking his car.
"He just stepped around into the neighbours yard and I remember I saw him munching on something and I did note it was some sort of white fungusy thing.
"I didn't think anything of it and he slept through dinner but he had a big day so I thought he was tired," he said.
When Bruce refused to touch his food and was vomiting and had diarrhoea on Monday, however, Mr Jausnik took him to the vet.
"They thought he may have a tummy bug so I took him home and spent the day with him. I took him in on Tuesday and they kept him in but they still weren't too concerned.
"By Tuesday evening though they said he'd gone downhill and on Wednesday morning they said it was getting a lot worse," he said.
The vet suggested Mr Jausnik collect some samples of the mushrooms from the Griffith yard and take them to the Botanic Gardens to get checked out.
"They were from exactly the same vicinity that I saw him hovering over and I didn't see him eating anything else," Mr Jausnik said.
Mycologist, Heino Lepp, who studies fungi at the Botanical Gardens confirmed the samples Mr Jausnik had brought in on Wednesday were death caps.
"Certainly what he brought in were death caps, definitely no doubt about it they have that typically pale yellowy, greeny colour.
"And the symptoms he described were consistent with death caps," Mr Lepp said.
Meanwhile by Wednesday night Bruce was hemorrhaging badly and the vets had him on antibiotics and liver medications in the emergency animal hospital.
"The vet said the amount that Bruce ate would have been two thirds of a cap and he's only just 12 kgs and he just doesn't have enough body weight to be a buffer against the toxins, he said he could get worse," Mr Jausnik said.
The vet has warned him there was little more he could do - a devastating message for Mr Jausnik and his partner.
"We are really cut up," he said.
Mr Lettp said he could remember at least one other inquiry about a dog eating death caps in his years studying mushrooms.
"The thing with dogs and small children is that you never know for sure, but they are very inquisitive and you never know what they pop into their mouth," he said.
Two people died after eating the highly dangerous mushrooms at a New Years Eve meal in 2012, and four Canberrans were hospitalised in April last year after eating death caps.
ACT's chief health officer Paul Kelly has warned that wet weather and cool evening temperatures have prompted early blooms of death cap mushrooms in Canberra in 2015.