26 February 2024
WICHITA, Kan. (KSNW) — Researchers say the eastern monarch butterfly population that overwinters in Mexico is the second smallest on record, so people can expect to see less this summer.
The total forest area occupied by overwintering monarch colonies is 0.90 hectares, which is a 59.3% decrease from the previous season of 2.21 hectares. The lowest was 0.67 hectares in 2013-14.
The reason for the low population is because of a decline in nectar sources and milkweed.
“The weed part of the name kind of indicating it’s undesirable in crop fields and other types of locations,” Monarch Watch director and senior scientist Dr. Kristen Baum said. “So with advancements in pesticides that have been very effective against milkweed, we’ve lost a lot of milkweed in the U.S. and southern Canada, so the breeding range of monarchs.”
The drought last fall extended from Oklahoma to central Mexico, reducing the sugars in nectar needed to fuel migration and develop fat reserves to get through the winter.
“In other years when there have been dry conditions, it hasn’t covered that full range,” Dr. Baum said. “But this year, challenging conditions the whole way. So not being able to build up those fat reserves that they need to to get through the winter.”
Founding director of Monarch Watch, Orley “Chip” Taylor, says this is unexpected.
“This news is a shock to all who follow monarchs,” Taylor said. “The depth of this decline is beyond our experience, and the implications for the future of the monarch migration are surely of concern. However, populations have been low in the past. This count does not signal the end of the eastern monarch migration.”
“Unexpected that the extent of how low the population was so, knew there was cause for concern especially during the migration, but the extent of it being even more of concern,” Dr. Baum said.
To recover, monarchs will need an abundance of milkweed and nectar sources, and people can plant those habitats. Those things can also benefit others.
“Good monarch’s habitat is good habitat for lots of other pollinators,” Dr. Baum said. “So there’s also lots of bees that are in decline. So a monarch waystation is going to provide lots of good habitat for a lot of our native bee species as well as other wildlife. You know, a lot of our good nectar plants for monarchs also provide seed that quail like.”
Dr. Baum says sharing data and contributing to science is also helpful. Taylor says monarchs are resilient.
“Catastrophic mortality due to extreme weather events is part of their history,” Taylor said. “The numbers have been low many times in the past and have recovered, and they will again.”
Dr. Baum says they will know more about the future of monarchs when the first generation returns to Texas.
“Ideally, they’ll have a big first generation in Texas,” Dr. Baum said. “Now, there’s challenges if it’s too warm or too cold, and that can result in a lower population. So if conditions are good, that could get the population off to a good start. Monarchs have multiple generations, so if the first one is large, that will help the subsequent ones be larger as well.”