Monarch butterflies putting on a spectacular show in Tucson this fall | Local news

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“Tagging is the only way you can really understand the movements of monarchs in the landscape,” said Billings.

The threats monarchs face

In addition to climate change, the decline in monarchs is also attributed to habitat loss and pesticide use that go hand in hand. Housing estates and agriculture take away space, host plants and food from the monarchs.

“The monarchs don’t have as much food as they used to,” says Tony Palmer, animal keeper for invertebrates at the Arizona-Sonora Desert Museum.

The monarch is culturally and ecologically significant. It fills a unique niche in its ecosystem by eating milkweed, a highly toxic plant that often grows near corn fields and that uses toxins as a defense against predators. To eliminate pests from their crops, many farmers spray their fields with pesticides such as glyphosate and BT. When monarch caterpillars consume BT-contaminated milkweed, they essentially “go to a pulp and die,” Palmer said.

Experts doubt that the monarch will not go away entirely. But its sharp decline in stocks serves as a strong warning as it is widely considered a type of indicator.

“This really dramatic decline in monarch migration is kind of a potential indicator of our larger ecosystem,” said Madsen of Tucson Botanical Gardens. “And if this migration doesn’t go well, there is a very good chance that other insects and organisms with similar life strategies are likely to suffer as well.”

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