About Western Monarchs
December 2020: Now a Candidate for the Endangered Species Act, but "precluded", waiting their turn behind more than 150 other species of plants, animals and insects ahead of them.
The much-beloved monarch butterfly is in peril. Having plummeted 99% in four decades, less than 2,000 were counted during the annual overwintering count along the California coast in late 2020, down 5 million in the 1980s.
While the population has rebounded to the 200-300k level since then, it's lower than experts think we need to have a sustainable population west of the Rockies.
The primary causes of the decline are (1) loss of breeding and overwintering habitat (2) climate change (3) mass use of herbicides and pesticides
They need our help.
The good news is that if you help the monarchs, you are helping all pollinators.
Overwintering in Pacific Grove, CA - Dec. 2021
Some Monarch Basics
Monarch butterflies spend their summers searching for healthy breeding habitat (milkweed, nectar sources and water), which brings them north and northeast across the US, with four (sometimes five) generations. Monarchs reach as far as British Columbia in the west, and Ontario, Canada in the east.
The first new generation of the year reaches Utah in May, and their newly laid eggs hatch about 30 days later. This 2nd generation of the year stays in Utah, breeding and laying eggs for 3-5 weeks. Generations 3, 4, and sometimes 5 follow.
In August through September, those emerging from chrysalis across the US are the great migrating generation. Instead of breeding, they save their energy and begin the journey of over 3,000 miles which will take them to locations in central Mexico, or 200+ sites along the California coast where they can stay warm enough to survive the winters. They must survive on nectar from pollinator plants they find along the way, living off their own body fat over the winter. Based on data reported, we know that monarchs in Utah go to both overwintering sites - Mexico and California.
Beginning in March, these monarchs breed and start migrating back to the US or inward from the west coast to find fresh milkweed to lay eggs, which become the first new generation of the year. They have now lived 7-9 months; all other generations just 3-5 weeks.
Monarchs undergo a magical transformation called metamorphosis from egg to caterpillar, chrysalis to butterfly. This process can go as quickly as 22 days in the heat of the summer, or take months during the colder seasons. See graphic to the left.
Did you know?
You will commonly hear people referring to "western monarchs" and "eastern monarchs" - but there is only one species: Danaus plexippus. The Rocky Mountains create a natural dividing line separating a smaller quantity out west from the much larger monarch population east of the Rockies. This may be due to better climate for breeding habitat in the east.