A late burst in the Monarch butterfly breeding season has seen numbers finally lift, but experts say they’re still worried about the implications of a two-month quiet period.
But it’s what’s happening in the United States, after reports the West Coast Monarch population has plunged a whopping 86% since last year, that has New Zealand butterfly experts concerned.
National Geographic reported the Monarch population had plunged more than 80% over the past 20 years in America.
The magazine put the cause down to humans; climate change and the growing of milkweed plants - relatives of New Zealand’s swan plants - higher than normal toxicity of cardenolides, a poison absorbed then used as a deterrent for predators by the butterfly.
Lepidopterist Brian Patrick says there are now fundamental concerns with the Monarch’s unusual behaviour in New Zealand and the US that could possibly be showing global implications.
Patrick, together with Jacqui Knight, of the Moths and Butterflies of NZ Trust, have appealed for public feedback about any changes in the butterfly's behaviour.
In New Zealand, Monarchs normally flutter about in the backyards of urban Kiwi properties between September and March. However, the number of butterflies seen around the country was minimal at best leading up to Christmas.
Knight told The New Zealand Herald last month they’d seen fewer - if any - Monarch butterflies, and those they were seeing were not laying any eggs.
She has been buoyed by the public's response so far. The feedback showed there had been few sightings until the past week when there had been a sudden surge.
“But there was this big patch, about eight or nine weeks, where there were no eggs being laid.”
Knight didn’t want people who were suddenly experiencing an over-run of eggs or caterpillars on their plants to kill them, but to pass them on to others in their community or family to raise them, to continue to boost the population.
The trust had since set up a Facebook page called Monarch and Milkweed Matchmaking New Zealand, where people can write what they have an excess of, or needed, and do an exchange.
While pleased to hear the Monarchs were successfully breeding, Knight said they were still concerned about the implications of 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 turn to become eco-friendly the past few years could be too little too late for iconic insects.
“I have been aware of concerns for nature or the environment for 40 or 50 years and people are just beginning to change their attitudes now and I think really, I hope it’s not too late ... we have to look after our planet better.”
Patrick said there were still unusually low numbers of Monarchs.
“There’s a few Monarchs around but they still don’t seem to be laying eggs and doing their normal behaviour. We really need the public’s observations because it seems like it’s a global thing.”
While Monarchs are an assisted native, the swan plant is not and was introduced specifically for the butterfly to survive.
“We’re in a unique situation here - swan plants are weeds in North America, whereas in New Zealand they’ve been planted particularly for the Monarch.”
There so far hadn’t been any studies carried out on either the Monarch or the swan plant to be able to monitor the insect's behaviour.
“We just don’t know what’s happening here. There could be something global in the environment that Monarchs are extra sensitive too, we just don’t know.
“What they’re doing could be telling us something fundamentally that’s happening to our environment ... are there too many toxins out there? But it is ironic that a butterfly that is toxic itself could be extra sensitive itself to other toxins.
“Something similar is happening here and around the rest of the world, that sounds like it’s something more fundamental, more global, and therefore more of a worry.”
Knight said pesticides were also an issue, as they were often used by nurseries to help grow baby swan plants to sell.
The best way was for members of the public to just grow a few swan plants themselves, that way pesticides wouldn’t be needed, she said.
People can report sightings of the Monarch butterfuly, or lack of, on their website, mb.org.nz.
