Hi all, About a year ago, on January 25, 2024, volunteers stumbled upon a multitude of dead and dying monarch butterflies that were scattered across the lawn of a private property close to the Pacific Grove Monarch Sanctuary in California. While it is normal for them to discover both live and dead monarchs in the area, one troubling sign in this incident was that the butterflies were dying in large numbers: 200 out of 2000 overwintering butterflies were affected. The other sign was that the butterflies were spasming, which is commonly associated with pesticide poisoning (I have seen this happen to a bumblebee before. It is not fun to watch).
To investigate, Pacific Grove staff and partners sent a sample of the dead butterflies to be tested for pesticide residue. The test revealed that the monarchs had indeed been exposed to a variety of pesticides. According to Xerxes Society, each butterfly had on average 7 different pesticides in its body, including three extremely toxic insecticides that were at or close to lethal levels. Further investigation found that it was likely an unreported pesticide application by a local resident or business. Education and awareness raising around pesticide use in California could help prevent further tragic incidents like this one. For example, not everyone knows that even some organic pesticides can be lethal to monarch butterflies. But education is not enough. Establishing social norms around pesticide use could be helpful, with residential property owners putting up signs indicating that they do not use pesticides, and respected leaders in communities establishing new habitats for monarchs. Making the connection between avoiding pesticide use and protecting monarch butterflies could be a compelling narrative for many people. Even when there is only a minority of people avoiding pesticide use, it is worth pointing out that the minority is growing. People will be generally receptive to this idea. One piece of good news to encourage you is that the U.S. Fish and Wildlife Service recently proposed including the monarch butterfly as a threatened species under the Endangered Species Act. This could provide vital protection in addition to behavior-related efforts. To read more about this Xerxes Society story, click here.
To investigate, Pacific Grove staff and partners sent a sample of the dead butterflies to be tested for pesticide residue. The test revealed that the monarchs had indeed been exposed to a variety of pesticides. According to Xerxes Society, each butterfly had on average 7 different pesticides in its body, including three extremely toxic insecticides that were at or close to lethal levels. Further investigation found that it was likely an unreported pesticide application by a local resident or business. Education and awareness raising around pesticide use in California could help prevent further tragic incidents like this one. For example, not everyone knows that even some organic pesticides can be lethal to monarch butterflies. But education is not enough. Establishing social norms around pesticide use could be helpful, with residential property owners putting up signs indicating that they do not use pesticides, and respected leaders in communities establishing new habitats for monarchs. Making the connection between avoiding pesticide use and protecting monarch butterflies could be a compelling narrative for many people. Even when there is only a minority of people avoiding pesticide use, it is worth pointing out that the minority is growing. People will be generally receptive to this idea. One piece of good news to encourage you is that the U.S. Fish and Wildlife Service recently proposed including the monarch butterfly as a threatened species under the Endangered Species Act. This could provide vital protection in addition to behavior-related efforts. To read more about this Xerxes Society story, click here.
