Migrations: The Monarch Butterfly

Cover photo: © 2017, Mike Bessler, some rights reserved.

Did you know that there is a species of butterfly that migrates south in the winter? Meet the monarch, one of California’s most interesting butterflies.

Cover photo: © 2017, Mike BesslerPhoto Library (Flickr), some rights reserved.

Places to See Monarch Butterflies

Monarch butterflies make an annual migration to warmer temperatures, with some populations traveling as far as 3,000 miles.

Millions of monarch butterflies undergo an annual migration, just as birds migrate south in the winter to escape cold temperatures. Cooling temperatures, shorter days, and the aging of milkweed (the primary source of food for monarch caterpillars) signal to the butterflies that it’s time to begin the journey south. Upon reaching their destinations, the monarchs congregate together and form large clusters on the branches of trees. This allows the insects to retain enough warmth to survive the winter.

You can see this migration in the Bay Area! From mid-October to mid-February, the monarch butterflies overwinter at Lighthouse Field State Beach and Natural Bridges State Beach.

For more information on their migration, check out this Bay Area Naturalist article.

The western population of monarch butterflies has been facing declines over the past 20 years.

In 2018, citizen scientists recorded the lowest numbers of monarch butterflies seen in California for 5 years. According to one source, 1.2 million butterflies were recorded on a California survey two decades ago. In 2018, a survey using almost the same number of locations recorded just 300,000 butterflies.

A recent study conducted by a Cornell University scientist posits that loss of overwintering habitat, the loss of habitat for butterflies to stop during their migration, and the declines of sites with nectar-producing flowers for adults during their migration are the main causes of the monarch butterfly declines.

You can help participate in the counts that help scientists know the status of monarch butterfly populations! For more information, check out the Western Monarch Count’s page on volunteering.

Monarch butterflies are vibrant orange.

Monarch butterflies have unmistakable orange wings, with black veins creating beautiful windows in the color. The caterpillars are just as vibrant, with black, yellow, and white stripes across their bodies.

The viceroy butterfly is a species that mimics, or copies, the physical appearance of monarch butterflies. Can you tell the difference in the photo below?

Image result for viceroy vs monarch
Monarch versus viceroy butterfly; Source: Socratic.org

Monarch caterpillars only eat milkweed.

Milkweed plants are rich in toxic chemicals called cardenolides. Monarch caterpillars, which feed exclusively on milkweed, are able to store the chemicals in their bodies through adulthood, making adult monarch butterflies bitter-tasting and potentially toxic to predators.

Monarch butterflies don’t specialize on one type of plant like the caterpillars do. They will consume nectar from a variety of flowers.

Monarch butterfly males and females look different from one another.

Male monarch butterflies have a small black spot in the middle of their hindwings (their bottom pair of wings). These “spots” are actually areas that emit chemicals for the courtship displays of some butterflies; however, the spots are not known to be important in the courtship displays of monarchs.

Male and Female Monarch Butterfly
Male versus female monarch butterfly; Source: gardenswithwings.com

Cool facts about monarch butterflies:

  • Only one generation of monarch butterfly migrates out of the 4-5 generations of butterflies that live each year. The generation that migrates is termed the “migratory generation”.
  • Monarch butterflies weigh between 0.27 and 0.75 grams. For some perspective, a U.S. quarter weighs 5.67 grams.

Resources to learn more:

Trouble in Paradise: Migrating Monarch Butterflies Face Declines

Cover photo: © Felix, 2011, some rights reserved.

Learn about the Monarch Butterfly, the threats that contribute to their continuing decline, and ways you can help from your own backyard.

Cover photo: © Felix, 2011, Photo Library (Flickr), some rights reserved.

Quick Facts

  • Monarch butterflies make an annual migration to warmer temperatures, with some populations traveling as far as 3,000 miles.
  • Santa Cruz is one of the monarch overwintering sites in California.
  • Monarchs have faced declines over the past 20 years, and 2018 marked the lowest count in 5 years for the California population.
  • Factors such as loss of flowers, degradation of stopover sites along their migration, and the loss of overwintering habitat in Mexico contribute to their decline.

 

It was late December when Dan and I packed up our camera gear and set out for Santa Cruz to see the monarchs. Ever the worry-wart, I anxiously clasped and unclasped my hands the entire one-hour drive over. “What if we missed them?”, I asked, eyes wide with potential disappointment as we wound down Highway 17. It was our first time hearing about the incredible journey of this butterfly, and I was avid about witnessing it for myself despite it being towards the end of their migration.

Racing the sunset, we arrived in the Lighthouse Field parking lot and made our way down a field path leading to a small stand of eucalypts. Rounding the a corner on the trail, we were met with a small cluster of trees dripping in orange. Tiny flutters gave life to the bright masses, which were unmistakably made of hundreds of butterflies.

The Journey South

Most people, myself included, will react in disbelief upon hearing that a delicate orange butterfly migrates thousands of miles to escape cold temperatures. “But migration is for the birds!” they’ll think, when trying to picture an insect achieving such a feat. Sure enough, monarch butterflies are the only known butterfly species to migrate in two directions (north and south), and they happen to overwinter in Santa Cruz, just outside of the Bay Area.

This incredible journey is made by one specific generation of butterflies, termed the “migratory generation”. Cooling temperatures, shorter days, and the aging of milkweed, the primary source of food for monarch caterpillars, signal to the butterflies that it’s time to begin the journey south to escape cold temperatures.

There are two populations of migrating monarchs: one east of the Rocky Mountains, and one west. The eastern population, with individuals from places as far as southern Canada, make their journey down to Mexico where they congregate in the oyamel fir forests. For this population of butterflies, the migration can be as long as 3,000 miles. The western population makes their way over to California’s coast, overwintering in locations from Santa Cruz all the way down to San Diego.

Migration Map Epic Migration
Created by Paul Mirocha for Monarch Watch

Relying on navigational cues such as the Earth’s magnetic field and the position of the sun, the butterflies make their long flight. Upon reaching their destinations, the monarchs congregate together and form large clusters on the branches of trees. This allows the insects to retain enough warmth to survive the winter.

Trouble in Paradise

The Western Monarch Thanksgiving Count is a citizen-science project (a scientific study based on data collected by the public) that stands as the longest-running and most comprehensive count in for the monarchs overwintering in California. Citizen-scientists, biologists, and other professionals join forces for a 3-week long effort to count butterflies at multiple sites.

Monarch Butterfly Count
Xerces Society Western Monarch Thanksgiving Count. 2018. Western Monarch Thanksgiving Count Data, 1997–2017. Available at: http://www.westernmonarchcount.org (For a full list of contributors, see westernmonarchcount.org/about)

But lately, the numbers have been grim. The western population of monarch butterflies has been facing declines over the past 20 years, and 2018 marked the lowest count in 5 years. According to one source, 1.2 million butterflies were recorded on a survey two decades ago. The graph above shows the decreasing numbers, and in 2018 a survey using almost the same number of locations recorded just 300,000 butterflies.

A Complex Decline

Many sources have suggested that the loss of the monarch caterpillar’s only food source, milkweed, has been the major contributor of the monarch decline. However, a recent study on long-term monarch population trends conducted by a Cornell University academic suggest otherwise.

Anurag Agrawal, from Cornell’s Department of Ecology and Evolutionary Biology, wanted to take a closer look at all of the monarch population data. Pulling together multiple data sets, he worked with the intent to identify where the biggest hits to the population occurred along the monarch’s migratory route.

Surprisingly, he found that populations trends appear to be doing the best at points where they are relying on milkweed, meaning that milkweed’s decline may not be the only cause of the monarch population decline. Instead, the problem is happening at points during their migration and in parts of their overwintering sites in Mexico. The degradation of sites that they use to stopover along their migration, the lack of sites with nectar-rich flowers to fuel their migratory journey, and the loss of their overwintering forests in Mexico appear to be the main contributors to population loss.

That’s not to say that planting native milkweeds to help the butterflies will be a vain effort – as providing additional resources to the butterflies can never hurt. However, these efforts can be greatly amplified by other efforts as well. Planting habitats for monarchs to feed in your own backyard, only buying FSC-certified wood (Forest Stewardship Council certification, certifying that the wood has come from a responsibly-managed forest and supply chain), and volunteering for monarch counts are all other ways that we can help.

Public education, in particular, can also work to help the butterflies – for that allows us to approach the complex problem on a unified front. With more people aware, we can work together to save the monarchs before they vanish from our coast.

36851758775_1a136b1162_o.jpg
© 2017, Mike Bessler, Photo Library (Flickr), some rights reserved.

Resources

See Wintering Monarchs at Lighthouse Field State Beach

Santa Cruz, Ca – From mid-October to mid-February, the trees in this park are shelter to thousands of migrating Monarch butterflies. Any other month of the year, this park offers beautiful sunset views and a glimpse at Santa Cruz’s radical surf history.

Species to Look Out For

monarch circle

Monarch Butterfly

About the Park

Santa Cruz, Ca – State Beach

Science Spotlight: Wintering Monarch Butterflies

Just like birds, there is one butterfly that make an annual migration to warmer temperatures. Each year, the monarch butterfly makes its way south to escape freezing temperatures.

Monarchs use environmental cues such as shortened days and colder temperatures to signal that the migration is ready to begin. Two populations of monarch butterflies migrate: one population east of the Rocky Mountains, and one to the west. The eastern population travels all the way down to Central Mexico, with some individuals traveling as far as 3,000 miles.

The western population has an overwintering site right in Santa Cruz at Lighthouse Field State Beach. There, in down the path in an unassuming field, hundreds of monarchs congregate together to stay warm.

Yet this amazing phenomenon faces a sad reality: monarchs have faced declines over the past 20 years, and 2018 marked the lowest count in 5 years for the California population. Factors such as loss of flowers, degradation of stopover sites along their migration, and the loss of overwintering habitat in Mexico contribute to their decline. For more information on the monarch butterfly migration and their decline, check out our article.

Overwintering Monarch Butterflies
© 2011, Photo Library (Flickr), some rights reserved.

Park History

Aside from being an incredible beacon for California natural history, the state beach is home to California’s first surfing museum in the Mark Abbott Memorial Lighthouse.

Visit the Park

Before visiting, please note that the monarch butterflies are only present from mid-October to mid-February.

During your visit, we recommend checking out the monarch butterflies in the grove of trees out in the field. We also recommend stopping by the lighthouse and surfing museum across the street from the parking lot, as well as scenic views of surfers catching waves off the coast.

Here are some helpful resources to help plan your visit:

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Enjoy a Beach Day at Natural Bridges State Beach

Santa Cruz, Ca – Home to thousands of migrating monarch butterflies from mid-October to mid-February, Natural Bridges State Beach offers an amazing view into an important piece of California’s natural history.

Species to Look Out For

About the Park

Santa Cruz, Ca – State Beach

Science Spotlight: State Marine Reserve at Natural Bridges

California was the first state in the nation to implement an expanse of Marine Protected Areas (MPA’s) along its coastline following the California Marine Life Protection Act (MLPA) of 1999. Similar to a National Forest or National Park that protects areas on land, MPA’s work to protect marine areas from the effects of humans. MPA’s work to protect entire habitats from harm – rather than protecting just a single species.

Implemented in September of 2007, Natural Bridges is 1 of 29 protected marine areas along California’s Central Coast, and 1 of 124 areas in the state. It spans 0.25 square miles, spanning 4.1 miles along the shore. Natural Bridges is a State Marine Reserve, meaning that it is restricted from the recreational or commercial removal of all marine resources. The MPA was put in place primarily to protect the intertidal zone of the area.

Park History

Spanish colonization of the Natural Bridges State Beach area brought an era of changing ownership to the land that was once home to the Ohlone Native Americans. From the arrival of the Spanish onwards, the land was a brussel sprout farm, the site of a movie set, and an unfinished housing development. The ownership ceased changing hands in 1933, when the land was purchased by the state of California.

In 1983, the park also set aside the monarch grove as a natural preserve so that the area remains protected for future generations of monarchs and human patrons.

Visit the Park

Recommended Hike: Monarch Trail (0.6 miles)

Please note that there is a $10 vehicle day-use fee. Dogs are not allowed on beaches or trails. Please also note that the monarch butterflies will only be present from mid-October to mid-February.

When visiting during the monarch migration season (mid-October – mid-February), we recommend taking the Monarch Trail to experience the amazing sights of the migrating butterflies. You have the option to connect to the Moore Creek Trail after viewing the monarchs, which ends at the beach.

Here are some helpful resources to help plan your visit:

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