Monarch’s plunge a global concern
A late burst in the monarch butterfly breeding season has boosted its numbers, but experts are worried by a period when few were seen.
The big drop in the monarch population on the west coast of the United States has also concerned New Zealand butterfly observers.
National Geographic reported the monarch population in America had plunged more than 80 per cent over the past 20 years.
It blamed climate change and the presence of milkweed plants — relatives of New Zealand’s swan plants — with higher than normal levels of cardenolides, a poison absorbed then used by monarchs to deter predators.
Lepidopterist Brian Patrick and Jacqui Knight of the Moths and Butterflies of NZ Trust are appealing for public feedback on any changes in the insect’s behaviour.
In New Zealand, the butterflies are usually seen in backyards from September to March. But monarch numbers were minimal at best leading up to Christmas, Knight said.
After appealing for information last month, she has been buoyed by the feedback, especially a surge in the past week. “But there was this big patch, about eight or nine weeks, when there were no eggs being laid.”
She encouraged people facing a sudden over-run of eggs or caterpillars on their plants not to kill them, but to pass them to others in their community or family to raise, to continue to boost the population.
The trust has set up a Facebook page, Monarch and Milkweed Matchmaking New Zealand, where people can write what they have an excess of, or need, and do an exchange.
While Knight was pleased to hear monarchs were successfully breeding, she was concerned about the eight-week flat period and how it would affect the next season.
She agreed with climate change concerns in North America, and said she couldn’t help but wonder whether the push to become ecofriendly the past few years could be too little too late for the iconic insects.