SANTA FE, N.M. — If you grew up in New Mexico, you probably remember a time when lots of monarch butterflies wafted through the air in late summer and early fall. These days, they’re a relatively rare sight. Sadly, monarch butterfly populations are under severe stress. They have declined by 85% in the past two decades, prompting the monarch to be considered for protection under the Endangered Species Act.
In Mexican lore, the monarch butterfly holds a mystical power. They were considered the embodiment of heroes and the newly departed dead. The Teotihuacan culture venerated the butterfly in frescos and on palace walls, and Toltec warriors emblazoned them on their breastplates.
It’s easy to understand why. Butterflies are a marvel of natural engineering, transforming from an egg to a caterpillar to the final dramatic emergence from a chrysalis as a fully formed butterfly. Monarchs are particularly impressive as they are the only butterfly known to make a two-way migration, similar to birds. Unlike other butterflies that can overwinter as larvae, pupae or adults, monarchs cannot survive the cold winters in North America. As the days shorten and the nights get colder, the monarchs know it is time to travel south to Mexico or west to California for the winter.
Key to monarchs’ survival and reproduction are milkweed plants. Female monarchs lay their eggs only on milkweed, which the caterpillars need to grow and develop. Milkweed grows across New Mexico and you might even find locally native species in your backyard. Because of the monarch’s dependence on this plant during the breeding season in the spring and summer, protecting it also protects the butterfly.
As part of Los Alamos National Laboratory’s environmental stewardship efforts, a Los Alamos team has been documenting the cycles and seasons of monarch butterflies, and the location of milkweed on laboratory property. These efforts will better inform management decisions if this species is listed under the Endangered Species Act. They were able to document eggs on milkweed in late June and caterpillars enjoying milkweed into September.
There was just one problem – some of the milkweed with eggs was about to be mowed down as part of lab efforts to reduce wildfire danger along evacuation routes in the event of a wildland fire.
The laboratory’s Environmental Stewardship group jumped into action to save monarch eggs that had been deposited on the plants. Working closely with the wildfire management team, they asked if they could preserve the milkweed just long enough to collect the eggs. The wildfire management team agreed and pledged to save a large patch of showy milkweed to use as a seed source for mitigation and restoration projects.
The team collected 23 eggs that mowing operations would otherwise have destroyed. Team members successfully reared all of the caterpillars and released the butterflies with school groups, families and the local environmental education center.
Monarchs spend the summer breeding in North America over three to four generations. During this time, each generation lives about a month. However, the generation that emerges as butterflies from late August to October is different and is arguably the most important. Incredibly, this generation is migratory and will travel thousands of miles to its overwintering grounds in central Mexico or the coast of California – places they have never been before. They will live in Mexico for eight to nine months, then these same butterflies will journey back north in the spring to lay their eggs on emerging milkweed.
So, you can see how milkweed is crucial for monarch butterflies to survive. If you want to help restore the populations of these amazing creatures, plant a butterfly garden to attract monarchs to your yard, and help them during their life cycle and migration. Milkweed, along with spring and fall blooming nectar flowers, helps monarchs and other pollinators, too, as milkweed provides nectar resources to a diverse suite of bees and butterflies. Don’t plant milkweed in areas where you might be grazing cattle or horses, though – it can be poisonous to them.
Fall is the best time to plant milkweed seeds, because the seeds need a period of cold before they will readily germinate. Milkweed seedlings can be planted after the last frost has passed in the spring. Contact local nurseries and ask if they have milkweed seeds and plants, but please plant species of milkweed that are native to New Mexico.
You can register your garden as a monarch waystation with Monarch Watch (https://monarchwatch.org/waystations/).
You can also help researchers by contributing information on monarch sightings, milkweed locations and monarch tagging. Websites include the Southwest Monarch Study (www.swmonarchs.org), the Western Monarch Milkweed Mapper (www.monarchmilkweedmapper.org) and Journey North (https://journeynorth.org/).
If you decide to rear monarch caterpillars as an educational tool or for citizen science, please do so in small numbers. High-density rearing situations may increase parasites and disease. Raise them in areas that receive natural daylight and outdoor temperatures. Also, make sure you have enough milkweed to feed these very hungry caterpillars!
Jenna Stanek is an ecologist with the Environmental Protection and Compliance division at Los Alamos National Laboratory.