Western Monarch Butterflies

Solemn news this week from the Xerces Society: during the 2020 Thanksgiving western monarch count, only 1,914 butterflies were spotted in 250 observation sites.

In 1997, when data collection began, 1.2 million western monarchs were counted in 150 locales in California and Baja California. 

Habitat destruction and lack of access to milkweed plants (the sole source of food for monarch caterpillars) are a factor. The application of pesticides applied on residential and agricultural lands harms the pollinators at every stage of their lives.

According to the Xerces Society, “In 2017, when monarch populations were still in the hundreds of thousands, researchers used Thanksgiving Count data to develop a population viability analysis and posited that the extinction threshold for the western monarch migratory population was 30,000 butterflies. It seems that, unfortunately, this prediction was right. The 30,000-butterfly threshold was reached during the last two years (2018 and 2019), and the population has crashed further this year. We may be witnessing the collapse of the western migration of monarch butterflies. A migration of millions of monarchs reduced to two thousand in a few decades.”

As west coast dwellers, we saw how the 2020 summertime forest fires wreaked havoc. During a visit to Pacific Grove in early November, a volunteer at the butterfly park told us that no monarchs had arrived.  

Pacific Grove’s sanctuary is populated with non-native Australian Eucalyptus, which the monarchs have adapted to. However, before that tree was introduced to California, it is believed that Monterey pines and cypress trees were their roosting choice. The eucalyptus is a highly flammable tree and in fire-prone California, the recommendation to remove them has to be balanced with the critical status of the western monarch butterflies who linger on the finger-like leaves to roost. (The trees originally arrived in California in the 1850’s as seeds carried by Australian gold miners.)

Adult monarchs’ energy needs are met with nectar, which is around 20% sugar and rotting fruit.  Butterflies taste the nectar with their feet before unfurling their proboscis to suck up the nectar. They also puddle on wet soil, drinking moisture and minerals.

The Santa Barbara Botanic Garden has a wonderful tool for seeing metamorphosis via time-lapsed photographs here

Published by Mashabu

Earnest observer of our natural world.

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