New Zealand, about the same size as Colorado, tucked away in the south Pacific… a group of islands to the east of Australia. The country has a highly endemic butterfly and moth fauna of nearly 2000 species, with most species being found nowhere else in the world. And yet our understanding of this fauna is in its infancy compared to knowledge of northern hemisphere faunas.
While the butterfly species number less than twenty, we know precious little about the distribution, habitat requirements and conservation needs of most Lepidoptera and the few specialists in the country cannot hope to fill these gaps in a lifetime’s work. Many species are threatened by habitat destruction and change, and by the impact of invasive insects, mammals and weeds.
Most New Zealand citizens are very concerned about the conservation of our larger species: kiwi, kauri, kereru… and of course marine wildlife – but the Monarch Butterfly NZ Trust is concerned about Lepidoptera. The status of our wildlife depends on the effects of climate change, pollution, alien species and land management. Reliable data on trends in the abundance and distribution of our flora and fauna is vital for predicting the impacts of such change, and for developing an appropriate response.
In the late 1960s a team under the direction of Auckland Museum entomologist Keith Wise undertook tagging to learn about their longevity and dispersal in NZ, overwintering habits etc. At the conclusion Keith stated “…the project did not produce the information sought on dispersal of Monarch butterflies…” and that “…no large scale migrations or movements were detected by tagging.”
“The project, had in the main, established that large numbers of Monarch butterflies in the North Island stayed in their home areas both in summer and winter periods, although a small number did make long flights. At the same time the presence of known overwintering colonies was confirmed, particularly one at Tauranga Bay in the far north, but no movements into or out of these were recorded.”
While thousands of Monarchs were seen overwintering at Tauranga Bay in the 1980s, by winter 2005 when entomologist Peter Maddison surveyed the area, a maximum of twenty were there. What has happened to them. In 2010 a group of members visited Tauranga Bay in the middle of winter and only found one Monarch! What is happening?
In 2005 the Monarch Butterfly NZ Trust revived the 1960-70 tagging exercise. In this country milkweed ‘in the wild’ is virtually non-existent but NZ people have grown up with the tradition of buying swan plants in the spring and planting them in their gardens just to witness metamorphosis. The swan plant is a native African milkweed, Gomphocarpus fruticosus and G. physocarpus, and probably arrived in NZ as a weed, coming on ships bringing settlers from Africa. The Monarch is believed to have flown/blown here from North America in the 1800s, and once the swan plant arrived was able to breed. There is probably very little migration; we already know that Monarchs overwinter in parks and reserves as far south as Timaru, Oamaru and Christchurch. But we want to know more!