More than 600,000 animals - from spider monkeys and chimpanzees to reptiles and pigeons - were used for science in the space of two years, new reports show.
And large numbers of those used for research, testing and teaching over 2017 and 2018 died for the purpose.
Just-released data from the Ministry for Primary Industries (MPI) show a total 314,571 animals were used in 2017, and 301,335 in 2018.
While around three quarters endured little to no impact, half of the animals that were manipulated in 2017, along with 35 per cent in 2018, died either before, during or after the process.
Of all of the animals, most were fish or cattle. In 2017, 100,000 fish were used, of which about 18 per cent remained alive afterward. A third were farm animals, although the vast majority of those returned to normal lives afterward.
But for nearly 10,000 in that year, the impact was "high" or "very high". Those most affected included rodents, possums, fish and other species like ferrets and stoats.
Some of that research involved testing 1080 baits containing deer repellent on 60 caged possums. Another bait, Feracol, was used on possums and rats as an alternative to 1080.
There were also cases of calves being disbudded – or having their horn buds removed – without receiving pre-emptive analgesia, and rats having ovaries removed to induce osteoporosis, before being put on a special diet to see if strontium they were fed could be imaged in their bones.
The reports further listed rabbits being used to try and develop a surgically induced model of bladder dysfunction, cows being fistulated, and guinea pigs used to test animal vaccines.
The main reasons for using animals was for veterinary research, basic biological research, and teaching, making up around three quarters. The bulk of groups using them were commercial organisations (40 per cent in 2018), universities (34 per cent) and Crown Research Institutes (13 per cent).
Some of the more unusual subjects listed in the 2018 report included two chinchillas used for teaching, 44 bats used for species conservation, two elephants and three giraffes used for animal husbandry, five chimpanzees used for veterinary research, and four spider monkeys used for basic biological research.
Further details provided to the New Zealand Anti-Vivisection Society (NZAVS) found blood samples were taken from the chimpanzees during a separate procedure, but specifics about the spider monkeys weren't disclosed.
Any research, testing or teaching using animals must be carried out under the Animal Welfare Act.
None can be manipulated without approval from an ethics committee that has to include representatives from the New Zealand Veterinary Association, the SPCA and a local council.
Researchers have to prove they'd tried to address the "three Rs" – replacing animals with alternatives, reducing numbers to the minimum required, and refining procedures to ensure the minimum possible impact.
However, some research meant suffering was unavoidable.
"Efforts to find the most humane methods of pest control, for instance, can carry a relatively high welfare cost," the MPI reports stated.
"As an example, researchers may need to measure the length of time from ingestion of a poison until an animal is unconscious or dead in order to ascertain the efficiency or otherwise of that method of pest control."
Such activities could cause "considerable distress" – and it was those types of issues that ethics committees had to weigh up against the benefits for native wildlife that scientists were trying to protect.
New Zealand is also a member of the Australia New Zealand Council for Care of Animals in Research and Teaching (ANZCCART), an independent body.
NZAVS executive director Tara Jackson said while the reports showed that thousands of animals were still being used in "unacceptable ways", she was encouraged to see reporting rules had changed.
"The new format of these reports now tells us more than we've ever known about how many animals are used in science," she said.
"A wider scope of animals is now captured in the annual statistics including animals purposely bred with compromised welfare and animals who were killed for the purpose of using their tissues."
"These changes haven't come out of nowhere either, they're a result of the hard work of many people behind the scenes, including staff at MPI."