Sitting in the train on the way back home from Sydney I was chatting with my fellow passenger(not in the quiet carriage of course) about family and she told me of her daughter in Mexico and of the Monarch butterflies whose annual migration path had been disturbed by a cyclone.Animal migrations have always been a mystically interesting topic to me so I thought I would find out more.
The annual Monarch butterfly migration is one of nature’s great spectacles and a top attraction for visitors to Mexico’s central highlands. Each year, as many as 60 million to one billion Monarch butterflies travelfrom eastern Canada to the forests of western central Mexico, a journey of more than 4000 kilometres.
According to local legend, the Monarch butterflies arriving in Mexico at this time of the year are believed to be the souls of the deceased returning to earth.
The Monarchs cluster together over winter and, after mating, begin their return migration to the north. While it only takes one generation to travel to Mexico, it takes four generations to make the return trip. On that trip, both milkweed and wildflowers are vital to the Monarch’s survival.
Little did I realise that our n Monarchs are not native, but imposters,arrivingin about 1870. In , the species also makes limited migratory movements in cooler areas.
The monarch butterflies’ host plant, which it relies upon for food and protection in the caterpillar stages, is a milkweed, a group of plants which exudes a milky, latex-like poison when its external skins are penetrated.
There are milkweed species, like the bush banana, in . But the butterfly does not seem to use them. Instead it predominantly uses two species, also imports, from Africa and the Caribbean.
Professor Tim Roberts is the director of the Tom Farrell Institute for the Environment, University of Newcastle