The Science of Sustainability

Natural Bridges State Beach

2531 West Cliff Drive

Santa Cruz, CA 95060

(831) 423-4609

Open 8:00 to sunset

Wi-Fi access available with wireless enabled laptop computers or personal digital assistants (PDAs) to access the Internet. Park visitors will be able to gain Wi-Fi access when they use a wireless device within about 150 to 200 feet of the Visitor Center in the park.

  • Please, do not touch or throw objects at the fragile butterflies.
  • For everyone's enjoyment, no smoking, dogs, bicycles, skates, or skateboards on the  boardwalk.
  • Quiet please. Monarchs and other visitors are relaxing.

There are monarch tours on weekends from mid-October through February.
Celebrate the monarchs' return with the Welcome Back Monarchs Day in October and their departure at the Migration Festival in February.

1a. MonarchIn this oasis between the ocean and the edge of Santa Cruz lies one of the largest monarch butterfly overwintering sites in the western United States. The park also includes large coastal scrub meadows that in spring are filled with native wildflowers.

In 1983, California State Parks made the monarch grove a natural preserve and sanctuary for these fragile world travelers. Monarchs journey as far as 2,000 miles on their paper-thin wings, seeking protected places like this one where they can find food, warmth and shelter. This grove provides the ideal conditions for the butterflies—and for you to see them. Look through the spotting scope to catch a glimpse of the breathtaking sight of hundreds of monarchs clustered together in the canopy.

The park also includes large coastal scrub meadows that in spring are filled with native wildflowers. Moore Creek flows through the meadows and forms wetlands in the sand.

Monarch Life Cycle

Image source: Wikimedia

A female monarch lays hundreds of eggs in her lifetime. She deposits the yellow pinhead-sized eggs on milkweed leaves, the only plant on which the larvae can survive. In three to six days, the eggs hatch into larvae, or caterpillars, less than 1/16th of an inch long.

Each caterpillar spends the next 15 to 20 days eating the milkweed leaves and flowers and increasing its weight by a factor of 2,700! It molts, or sheds, its yellow, black and white-striped skin four times before it reaches its final length of about two inches.

Next, the larvae seek a safe, sturdy place to attach and dangle upside down curled into a "J" shape. After 15 to 20 hours of metamorphosis, the larvae shed their skin to reveal the bright green chrysalis underneath. The caterpillar's tissues break down inside the chrysalis and the body of the mature butterfly forms.


Image source: minuk

After 10 to 15 days, the monarch butterfly emerges and clings to the outside of the chrysalis. Its soft, crumpled wings expand as it pumps fluid them. Over the next few hours, the wings dry and harden until the adult monarch is ready to take flight.

Milkweed and Eucalyptus


Image source: Wikimedia

Milkweed isn't native to the California Central Coast, but it's the only food that monarch larvae eat and the plant they live on for about half the year. You can see a demonstration patch of milkweed near the visitor center and get an up close look at monarch eggs, chrysalids and caterpillars.

There are many species of milkweed, and monarch larvae will eat any of them, but common milkweed (Asclepias syriaca) is the one most people think of when they hear the name. Look for its purple or pink flowers along the edges of lakes, ponds and waterways, and in the forests and prairies of the Midwest. Native Americans ground the seeds into a salve for sores. The seeds have been steeped in boiling water to make a serum for drawing out rattlesnake poison. Be careful if you handle milkweed. The sap can irritate your eyes if you rub them.

Milkweed contains poisons that the monarchs absorb into their bodies. Predators who try to eat monarchs usually spit them out or get sick from the poison. They learn to avoid monarchs after that!

1c. Monarchs and Eucalyptus Trees

The blue gum eucalyptus is so common in California that many people think it is native to the state. This tree, with its distinctive smooth trunk and peeling bark, was introduced from Australia in the 1850s as a lumber crop. The venture proved unsuccessful because the trees produce poor quality lumber. They make excellent overwintering sites for monarchs, however, as do Monterey pines and cypresses.

Eucalyptus can be found in a variety of ecosystems and can successfully out-compete native species for water. Its volatile oils make it good for firewood but also a forest fire danger.

Monarch Migration

Image source: Steve took it

Lots of animals migrate. Some travel a few or a few hundred miles to find food or safe breeding areas. Monarch butterflies travel thousands of miles to find warmer temperatures because they can't survive long periods of cold weather. They migrate to find the conditions they need to survive– trees on which to cluster, food, water and a mild climate. Protective branches overhead shield the monarchs from rain, snow or hail and underbrush provides cover if they fall to the ground. The monarchs find what they need in this park, so they return year after year.

Most migrating animals make the outward and return journey year after year. The butterflies that are here this year are not the same individuals that were here last year. This year's overwintering generation is made up of the great-great-grandchildren of the butterflies that were here last year!

Monarchs east of the Rocky Mountains migrate to the transvolcanic mountains of central Mexico. Most of the monarchs west of the Rocky Mountains fly southwest to the California coast. As the daylight hours shorten in October the butterflies gather here, some from as far away as Montana and Canada. On the way to their winter homes they eat flower nectar in order to build up fat reserves for the coming cold months.

In their overwintering sites, like Natural Bridges, the butterflies cluster together to keep warm. When they hook their legs together into a tight mass, their combined weight helps keep them from being blown away by the wind.

With the warmer, longer days of spring, the monarchs begin their return journey to the milkweed patches where they lay their eggs. They have to time their migration carefully: if they return too early and the milkweed isn't up yet, they will have no place to lay their eggs and the cycle will end.

Scientists speculate about exactly how the butterflies find the same overwintering grounds year after year. Does it have to do with Earth's magnetic field? the position of the Sun? geographic features? The answer could be any one or a combination of these– or something as yet undiscovered.

Monarch Dangers

Monarch butterflies face many dangers, from weather and lack of food, to accidents and being eaten. While the butterflies absorb poisons from the milkweed they eat, but they have other ways to warn off potential predators. Their bright black and orange coloring alerts would-be predators that they contain poisonous chemicals. Some birds, like black-headed grosbeaks, can tolerate eating some of the poison. Other birds, like black-backed orioles, eat just the soft insides of the insects, not the cuticle, which contains the poison. Monarchs can also fall victim to fungi, bacteria, viruses, and parasites.

Image source: Wikipedia

In 1998, the monarch population declined markedly in Santa Cruz County and has been declining ever since. A big reason is habitat loss. As the trees and groves age and thin out, there are fewer branches and leaves for the butterflies to cluster on and shelter among during blustery winter storms.

The culprit in the late 1990s was the El Nino storms that felled many trees. Eucalyptus trees can outgrow their root systems, making them vulnerable to high winds.

Monarch Conservation

Human activity poses the greatest threat to monarch butterflies. Monarchs aren't the only creatures that like beautiful coastal property. Habitat destruction caused by the building of new roads and housing developments or the expansion of farms makes it impossible for monarchs to live in a particular landscape. In Mexico, the high concentration of millions of monarchs in relatively small regions makes them particularly vulnerable, especially since some of the sites contain valuable lumber sources. Logging these areas opens up the forest canopy, providing less protection to the butterflies.

Milkweed is considered a weed by many people and so is often destroyed. Ozone and herbicides are destroying milkweed and the nectar-producing plants that the butterflies need for food. Pesticides kill the insects outright, too.


One way to help out is to volunteer as a docent at the park.

There are two training programs for Natural Bridges each year: September and March on Wednesday evenings and Saturdays during the day. Docents lead monarch and tidepool tours for school groups during the week and the general public on weekends, host the Visitor Center, assist in the bookstore, help with special events, tend the milkweed garden, restore native plants, maintain the aquarium, share with others about the resources and more. Find our more by calling Natural Bridges State Beach at 831-434-4609.

You can help by planting butterfly-friendly plants in your garden and not using pesticides or insecticides. Plant a variety of flowering shrubs that bloom at different times of the year, such as buddleia, sumac, alyssum, primrose, wild bergamot to provide nectar for the butterflies.

Latest Visitor Photos

Join the Natural Bridges State Beach photo group on Flickr to share your photos of this amazing place.

 

Quest Educational Resources

pdf Print Guide - Natural Bridges State Beach ( pdf ) Download a printable version of this Science Hike complete with directions, maps, and photos. kml Natural Bridges State Beach ( kml ) Open this Science Hike in Google Earth by downloading the KML version of this map. pdf Tips to get the kids in your life out into nature ( pdf ) Here is a quick "cheat sheet" of helpful tips to keep "Nature Deficit Disorder" at bay with kids. pdf Designing an Exploration on Google Maps ( pdf ) Like the Explorations on the QUEST site? Use this place-based educational guide for educators and group leaders to create similar science-based maps with youth.

 

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