This is the second in my series exploring the species featured in my 2024 calendar, Wildlife of East Otago.
Kahuku, or monarchs (danaus plexippus) are our largest and most recognisable butterfly here in Aotearoa. They’ve become true ‘kiwiana’ along with jandals, the buzzy bee, and the good old Edmonds Cookery Book.🦋 But do they really belong here?
These butterflies are said to get their common name from European settlers who arrived in North America and were impressed by its striking black and orange wings. They named it in honour of King William III of England, who had a second title as the Prince of Orange1, a feudal state in the South of France from 1163 to 1713.
The existence of their Māori name, kahuku, suggests that this pūrerehua (butterfly) was here prior to European settlers. Kahuku originate in North America and probably flew (or blew) the 13,000km journey over here2 - but wouldn’t have been able to establish a population until their host plants were brought in. For this reason, they’re considered ‘assisted natives’.3 They may have arrived here on their own, but they were reliant on humans introducing their host plant to survive beyond one generation.
A host plant is the plant a butterfly lays its eggs on, and what its caterpillars eat. Often there is a single genus or family of plant the caterpillars will exclusively feed on - like stinging nettles (in the Urtica genus) for admiral butterflies.
Milkweeds are the host plants for kahuku, and the swan plant is the most popular one to grow here in Aotearoa. I remember growing these in primary school, and watching the little caterpillars become not-so-little, then curl up into chrysalises as part of our science corner. These swan plants, originating in South Africa, were probably first brought here accidentally by European settlers in the mid-nineteenth century.4
Tropical milkweed, or swamp milkweed for cooler regions, are also available for New Zealand butterfly lovers - seeds can be bought from suppliers like the Moths & Butterflies NZ Trust. I’ve seen their bold orange and yellow flowers at the Blockhouse Bay Butterfly Habitat in Tāmaki Makaurau/Auckland and hope to grow some in my own garden this summer.
But you can attract kahuku even if you don’t have swan plants in your backyard. Any nectar-rich flowers, preferably grown in clumps of colour, will attract these pūrerehua in. We don’t have many swan plants in our garden, but kahuku have visited our yarrow and dandelion flowers, and seem to love basking at the very tops of our trees.
Like other insects, kahuku are cold-blooded and cannot generate their own body heat. So, in the cooler months they enter diapause and find a cosy evergreen tree to ‘overwinter’ in. I first saw this spectacle at Abberley Park in Ōtautahi/Christchurch. If the weather is warm and sunny enough, you can see the butterflies basking and feeding; in cold and grey weather they will hold tightly on to the tree branches.
You can find a list of common over-wintering sites for the South Island on The Butterfly Musketeers website, which is how I learned about Abberley Park.
While the migratory monarch of North America was recently added to the long list of threatened species5, the ones in Aotearoa are still considered to be of “least concern”.6
I still think they’re worth looking after, though!🦋
Here in the southern hemisphere, the days are getting a teensy bit warmer, and across the country pūrerehua will be emerging from their overwintering sites. They’ll need nectar, safe spots to catch some sun - and, of course, their host plants.
Happy butterfly spotting,
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https://www.monarchwatch.org/read/faq2.htm
https://www.nzbutterflies.org.nz/species-info/monarch/
https://www.nzherald.co.nz/whanganui-chronicle/news/monarch-butterflies-swarm-whanganui-garden-as-warm-weather-settles-in/DKGPCMMLTXLELCS75RVGN3HFPA/
https://www.scoop.co.nz/stories/AK2207/S00427/monarch-butterfly-endangered.htm
https://www.worldwildlife.org/stories/migratory-monarch-butterfly-now-classified-as-endangered
https://www.iucnredlist.org/species/159971/219149911
Will definitely take a look. They are magical indeed...
Thanks for answering many questions I had about the monarchs we see here in Aotearoa. In the US, people plant drifts of milkweed to sustain these beauties. And their migration to Mexico is astonishing!
https://www.worldwildlife.org/magazine/issues/spring-2020/articles/making-a-home-for-monarchs-in-mexico