One of the most recognizable butterflies on the planet is the monarch butterfly, with its familiar orange wings laced with black lines and bordered with white dots. They are famous for their seasonal migration when millions of monarchs migrate south from the United States and Canada to California and Mexico for the winter.
The butterfly’s colorful, distinctive pattern is a warning to predators that they are foul-tasting and poisonous. The poison comes from their milkweed diet, which is toxic; however, monarchs have evolved to tolerate it and use it to their advantage by storing the toxins in their bodies to make themselves poisonous. Monarchs eat the milkweed during their larval, or caterpillar, stage.
At Bok Tower Gardens, there are several species of native milkweed – Butterfly Milkweed, White Swamp Milkweed, and Sandhill Milkweed – and some non-native species of Milkweed – Tropical/Silky Gold Milkweed (Mexico), Balloon Milkweed (Africa), and Giant Milkweed (Asia).
Although not currently on the Endangered Species List, monarch populations are threatened by habitat loss, genetically modified crops, and weather events during migration.
The monarch population is being weakened by a protozoan parasite called OE (Ophryocitis elektroschirrha) that enters the caterpillar upon ingesting the milkweed and kills them before they can become healthy adults. In 2019, Bok Tower Gardens formed a team to focus on the monarch butterflies. Their mission was to tag monarchs to re-evaluate the butterfly population, track their migration, and collect abdominal samples to examine for OE.
To minimize OE and damage the Monarch population, the Bok Tower Gardens team plans to cut back Tropical Milkweed. The team has theorized this action will reduce the percentage of OE in these plants. They also hope to increase the number of native milkweed plants throughout the Gardens.
Our BTG monarch team will continue their work studying and counting monarch butterflies. Bok Tower Gardens has also joined Monarch Watch, a volunteer-based citizen science organization that tracks the monarch butterfly’s fall migration.
Blog post was written by David Solove, BTG Guest Services Associate with assistance from Elaine Berner, and features photographs from Cassidy Jones, John Guiseppi, and Sarah Lingwall.
