Monarch Butterflies in Mexico

Photo © Court Whelan, Ph.D.

Newsworthy, noteworthy, and utterly fascinating. Monarch butterflies routinely make the news—for good reason.

The migration of the monarch butterfly is considered by scientists a unique phenomenon, and one of the largest animal migrations on Earth. However, in recent years, a steady decline in the butterflies’ population numbers has turned global attention on this most famous of insects in a race to save them.

Spending the winter each year in the high-altitude region of the Sierra Madre Oriental and Sierra Madre Occidental mountains, monarch butterflies seek the adequate, steady climate provided by the oyamel forests to undergo a quasi-hibernation each year. Protected from winter storms by large trees in fast pine and fir forests, they have done this for what most scientists agree must be thousands and thousands of years.

Monarch Butterflies in Mexico

Photo © Court Whelan, Ph.D.

One of the largest threats to the monarchs and their migration is the use of herbicides and habitat conversion throughout the Midwest, effectively killing all weeds, including milkweed from agricultural fields. Milkweed is the only plant monarchs use to breed and the only food source for their caterpillars. Through programs like Monarch Watch (University of Kansas) and World Wildlife Fund’s Monarch Squad, milkweeds are being planted more than ever and making a comeback, helping the monarchs recuperate.

The monarchs’ safe haven has also been under siege from environmental and human pressures. While illegal logging has slowed considerably since 2012 thanks to the Mexican authorities and local communities’ efforts, deforestation and forest degradation continues to be an issue in the Monarch Biosphere Reserve. Although these tiny denizens of the Mexican Sierras are hardy and able to withstand subfreezing temperatures more than most butterflies, the severity and frequency of such winter storms has conservation biologists concerned.

Fortunately, there is good news. Monarch colony population numbers have rebounded during the last winter season, with the butterflies occupying nearly 10 acres across multiple colonies in December 2015—up from 1.7 acres in 2013 and 2.8 acres in 2014. Population numbers are estimated by measuring the area of forest they occupy during hibernation. Actual population numbers are just an estimate, but this increase likely translates into tens of millions of more butterflies reaching their overwintering grounds in Mexico last winter. And of course, we hope that trend continues into next year’s Monarch butterfly migration.


The cause of all this? Scientists point their fingers (in a good way) to backyard gardeners, conservationists, and ecotourists who are actively fortifying monarch habitat by creating monarch waystations and planting milkweed to provide food for the butterflies along their migratory path.  While overall habitat loss continues to be perhaps the greatest threat to monarch survival, citizen science that focuses on planting milkweed and using less pesticides have great potential to help monarchs recuperate.

Like all conservation stories of today, good news comes with a reminder that we’re not out of the woods yet.  Monarchs continue to face threats as they travel between Canada, the U.S. and Mexico, including the loss of milkweed habitat, illegal deforestation and a changing climate. Nevertheless, we rejoice with the positive news coming out of Mexico that monarch colony sizes are at a five-year high. For years, we at Natural Habitat Adventures have led ecotourism trips to the kingdom of the monarchs, contributed to research, and spread awareness, and the story of the season is that it is working.

Let’s continue to lift up these little critters so that they can continue to soar the sky for the decades to come.