Tuatara poisoned
Tuatara at a Nelson zoo are thought to have died by eating live insects, such as cockroaches, which had ingested rat poison.
Four tuatara in Natureland’s care have died, including one in each of August 2017, March 2018 and April 2019.
The fourth died in May this year after a burrow it had made collapsed. The tuatara was said to be well in the morning but then died later that day.
Natureland’s acting director, Grant Abel, said its internal review into the reptiles’ deaths showed that varying levels of the poison brodifacoum was found in three tuatara.
Samples from the first tuatara to die were not kept by Massey University and could not be retested for brodifacoum.
Abel said Natureland’s records indicated that the first tuatara to die did show signs of brodifacoum poisoning, such as lesions and bleeding. However, that tuatara was a male known for defending his territory and who often had small scratches, which meant the link was not made to poison at the time.
Brodifacoum is an active ingredient in anticoagulant rat poisons available at hardware stores for rodent control.
Abel said it was ‘‘deeply sad to lose an animal’’.
‘‘Natureland staff acted in the best interests of the tuatara and the loss of these precious animals has grieved everyone at Natureland,’’ he said.
‘‘But one key thing can be learned and shared from this experience: knowledge of the potential impact of secondary poisoning by way of live insects that have been exposed to products such as the anticoagulant toxin, brodifacoum.’’
Tuatara are endemic to New Zealand and are endangered. They are carnivorous, and are often described as a living fossil from the dinosaur age.
Natureland had used the brodifacoum-based poison Pestoff ‘‘in accordance with the product label instructions’’ since 2015.
Abel said the bait was never used inside enclosures, but believed secondary poisoning occurred ‘‘from insects that got into the enclosures after eating some of the Pestoff bait’’.
Natureland had shared the report’s findings with the reptile zookeeping community ‘‘for the benefit of all tuatara in zoological care and for those organisations dealing with vermin control in the wild’’.
He said Natureland ‘‘immediately discontinued’’ the use of Pestoff after receiving the necropsy report and had switched to other vermin control methods, including cockroach control.
Blood tests were being organised for the surviving tuatara to see if they had signs of sub-lethal brodifacoum poisoning.
The review into the tuatara deaths was conducted by the Natureland Wildlife Trust and involved stakeholders including Nga¯ ti Koata, the Department of Conservation (DOC) and the Zoo and Aquarium Association.
More than 18 experts in captive tuatara care and treatment and specialist reptile zookeepers were involved in the review.
Necropsy reports by DOC could not determine how the toxins may have been ingested, saying only that it could have been direct ingestion of poison, or through the diet or ‘‘via rogue insects’’.
Brodifacoum was found in a 2004 DOC study to have the ‘‘highest overall theoretical risk of secondary poisoning’’ out of four anticoagulant poisons tested.
‘‘The loss of these precious animals has grieved everyone at Natureland.’’ Acting director Grant Abel