Six dogs have been poisoned on Great Barrier Island this year, resulting in one confirmed fatality sparking warnings from local veterinary staff over the containment of pest control baits, and pets.
The cluster of cases represents a significant spike across the island, where domestic pets and working dogs live in proximity to intensive conservation zones.
“There’s six dogs that have been treated this year,” island veterinarian Anne said. “That’s quite a lot, really. Certainly is for me.”
The most recent fatality involved a dog exposed to a highly lethal dual-action bait known commercially as Double Tap, which combines cholecalciferol (an acute dose of Vitamin D3) and diphacinone (a first-generation anticoagulant). Diphacinone bait is dyed bright green.
The dog’s owners noticed the animal was slightly off for about 24 hours before coming home to find it gasping for breath in a state of acute heart failure.
“The dog was actually really struggling, in a really bad way,” Anne said. “The person who brought it in said that she had seen some green granules in the feces. And so, I started treating it.”
Despite receiving immediate out-of-hours care and a dose of activated charcoal to bind the toxins, the animal succumbed to the poison shortly after returning home.
The incident has highlighted the danger of cholecalciferol-based baits, which cause severe hypercalcemia, leading to rapid mineralization of the heart and kidneys.
The product is widely popular because it is marketed as a single-dose killer—rodents only need to eat it once to die. Unlike standard anticoagulants, the cholecalciferol component has no effective antidote.
“Cholecalciferol is a mega-dose of Vitamin D, and it affects the heart. Their heart starts racing. It’s very, very lethal. I’ve had a few that have survived, but I’ve known a few that were poisoned that didn’t get to me and died before they got to me.” Anne explained.
A separate case last month involved a dog brought in with what the owners assumed was a minor, persistent scratch on its lip.
“The owners rang me and said the dog has got a scab on its lip, and it keeps bleeding,” Anne said. “It was brought in, and it was drip, drip, drip. I said there’s no way that’s normal. If you knock a scab off, you might see a little bit of blood, but I strongly suspect this is rat bait poisoning. And they were kind of shocked.”
The blood failed to clot, a classic indicator of the anticoagulant component. While that specific animal survived following an immediate injection and a strict three-week course of oral Vitamin K, Anne warned that many owners remain entirely unaware that their animals have interacted with the bait.
“If your animal is behaving unusually, and you don’t know where they’ve been and what they’ve been doing, you definitely want to get in touch if you see those bright green granules,” Anne said. “Even with slug bait or rat bait, which is often blue as well, you could start seeing it in their feces. If there’s anything like that in the feces, then that is the time to get in touch with somebody.”
Anne warned that a major factor in these fatalities is owners assuming an unwell dog will simply come right on its own, delaying medical attention until it is too late.
“One actually died because I didn’t get to it early enough,” Anne said. “The owners didn’t want to pay an out-of-hours fee to bring it in and were going to wait until Monday, and it never made it to Monday.”
Anne noted that while cases have been spread across the island, the most recent incidents were concentrated in the far north and the Medlands area.
The recent poisonings have renewed long-standing local scrutiny over how toxic baits are distributed throughout the island’s environment. Historically, some conservation operations stapled open plastic bags of poison directly to trees.
Under current New Zealand law it is an offence to deviate from the instructions on a pesticide’s product label. Modern regulations mandate that high-toxicity baits like Double Tap must only be deployed inside secure, covered, and weather-proof bait stations to restrict non-target access and prevent the environmental weathering or washing away of the poison.
While modern operations utilise these dedicated bait stations, one source spoken to by the Barrier Times said they were concerned about how well-meaning landowners might be deploying the bait without an understanding of current best practice.
Despite the severe risk to non-target animals, Anne argues the use of toxins remains a necessary measure if we are to pursue the island’s conservation goals, noting that alternative methods have historically failed to control pest populations.
Accordingly, she says, restricting animals from roaming remains the only definitive safeguard against ingestion.
“Basically, they’re not going to get poisoned if they don’t wander,” Anne said. “To let them wander is going to cause a problem.”
