Monarch butterfly tagging

March 2026

A tagged monarch feeding on a zinnia in the butterfly garden in February

The Moths and Butterflies of New Zealand Trust (MBNZT) have used tagging monarch butterflies as a scientific tool for over a decade. It's been used overseas for a lot longer. A light sticker is placed on a new monarch's wing ahead of being released in the autumn.

Tagging has been used to show that in New Zealand there are no distinct migratory routes and whilst some monarchs undertake long and fascinating journeys, most stay close to where they eclosed (emerged from their chrysalis). It's known that in most of temperate New Zealand the last generation of monarchs do not breed until spring - so they are 'overwintering' - but it is poorly understood where exactly they spend the winter.

Whilst breeding may occur year round in sub-tropical Auckland and Northland - emphasis on the may - the monarchs are not active all the time. So where do they go when they are not flying round on sunny days? It's something I've wondered about here in Auckland over the years, but even hours of research have not given me the answers.

A tagged monarch butterfly on ageratum

In some towns and cities on the South Island, such as Christchurch, there are butterfly lovers who actively monitor known overwintering sites, but butterfly numbers can fluctuate year to year. There are no known sites on the North Shore of Auckland. In fact, there are only two known sites in all of Auckland - Blockhouse Bay Recreation Reserve, where there is a dedicated butterfly habitat, and Jellicoe Public Park, Onehunga. Monte Cecilia Park in Hillsborough has been an overwintering site, but there are not consistent sightings. It's incredible that in New Zealand's most populous city, no one knows where the majority of the monarchs go.

One reason might be that overwintering monarchs can be hard to spot. They like tall, oily trees and can look like dead leaves when roosting together. Check out some of the images on the overwintering iNaturalist project. There is also more information on that project page about why monarchs overwinter.

The second reason might be that they are simply not grouping up in warmer parts of the country any more, because it is not cold enough for long enough. I've watched where monarchs go when I've released them and on less pleasant days I've seen them head for next door's tall kanuka or large pohutukawa. I can't see them once they have landed. It would take a few roosting together to spot with binoculars.

A tagged monarch butterfly on tropical milkweed flowers

At the end of February I was lucky enough to spot a tagged monarch in the butterfly garden. This was the first time I've seen a tagged monarch and I can say that it is easy to go through the logging process on mb.org.nz. Just needs a couple of minutes. February is a bit early to establish Auckland overwintering sites, but it is interesting to have proof that monarchs other than ones I have released are coming to the butterfly garden, to be able to track how long they stay in the garden and how far this generation are travelling. I was very excited and imagined monarchs crossing North Shore suburbs. Turns out it is from a house 300m away as the crow (or butterfly) flies! The first week of March I had another tagged monarch from that house in the butterfly garden and it came back again and stayed for hours, so I will have to go and introduce myself to the tagger. It's great to have another butterfly enthusiast so close. It's like the monarchs are networking for us!

Turns out that analysis from reported tag sightings in 2025 show most tagged monarchs turn up less than 100m from their release site, even weeks later, so these butterflies from up the road are already going further than the 2025 median distance. Tagged butterflies were more likely to be seen where there were swan plants (female monarchs) or nectar plants (male monarchs), which are both available in my butterfly garden. However, we do not have the types of trees that monarchs like to overwinter in -either in height or species - but in surrounding properties there is a Norfolk pine, a Scots pine and a pohutukawa, so will the butterflies that become adults this autumn in my garden stay nearby or will they leave to find better shelter?

This helped me decide that I would tag the butterflies that I am currently raising from eggs found in the garden. I am a little nervous - I don't usually handle the butterflies except to stand on my finger to bring them out of caterpillar castles. The tags do not impede the butterflies in any way, so the only danger is from my bungling it. I am a few weeks away from starting as the caterpillars are small, so watch this space.