Responses to a survey of monarch butterfly lovers in NZ has indicated a serious problem for the species.

“A significant deterioration in numbers was found, according to the survey respondents,” said Martin Visser on behalf of the Moths and Butterflies of NZ Trust (MBNZT). “We compared the results of this survey undertaken in December 2024 with the results of a similar survey from 2019.”

So loved is the monarch butterfly, a bright reminder that summer is here, that many people up and down the country encourage the colourful butterfly to breed in their garden. Some people go the extra mile and adopt caterpillars from other’s gardens where there are too many of the yellow-and-black, striped larvae.

“We are so worried by the lack of monarchs that we want to reinvigorate interest in tagging and reporting this season,” said Jacqui Knight, founding trustee of the MBNZT.

“We now need reliable, long-term data on adult numbers,” said Professor Myron Zalucki from the University of Queensland who is spearheading the data collection. “That is why the MBNZT is reintroducing tagging or mark-recapture of the overwintering generation. We need the help of people who love the outdoors and love the monarch butterfly to become citizen scientists.”

Tags, lightweight and long-lasting, are carefully placed on a hindwing of the monarch after it emerges from its chrysalis. Each tag has a unique code and a short form of a website and people finding a tagged butterfly can report its code and location. A computer system calculates the distance the monarch has flown and the duration of its journey. This information can then be collated with weather data to get a clearer picture of what is happening.

“The monarchs are known as an indicator species,” said Knight. “What will be affecting the monarchs will probably be affecting our other beautiful butterflies, moths and invertebrates.”

“And when you think that most New Zealand people don’t even know about the beautiful species we do have… it’s a travesty! If you don’t know something exists, how can you help it?”

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