Monterey Bay is one of the few spots in the world where the monarch butterfly migrates to survive the winter amidst groves of trees that are nestled around the bay. The regional maritime climate protects these delicate insects from frost, while the microclimate provided by stands of eucalyptus, Monterey pine and Monterey cypress trees gives them shelter from wind, the right mixture of sunlight and shade to keep temperatures between their ideal range of 50 to 70 degrees and enough humidity to create drops of dew that the butterflies use as a water source.
Arriving in the fall, the monarchs that overwinter in California are part of the population of western monarch butterflies. These aerial stunt pilots, which land en masse in sheltered groves from Marin County to San Diego, are several generations removed from monarchs that spent the winter here last year. More than 200,000 monarchs migrate to California each year from as far north as British Columbia. Some years, Monterey County is estimated to harbor 35 percent of the western monarch population.
"We have huge clusters in mid-December," said Lori Mannel, director of the Pacific Grove Museum of Natural History. "Then mating begins January through February - right around Valentines Day.
During their courtship dance, males catch females mid-air, then drop to the ground. They spend 30 minutes coupling, after which the male will carry the female up to treetops, where they remain coupled all night long. A male can mate up to three times, but after that he'll die.
Soon after mating, females will take flight in search of milkweed plants, where they will lay a single egg on the underside of a leaf. In a sort of relay race of generations, consecutive cohorts of butterflies will continue the journey north to summer grounds until next fall's lowering sun angle will cause them to head south for the winter once again. Because monarchs require such specific conditions to survive the winter, they exhibit fairly stable site fidelity from year to year. When temperatures drop below 55 degrees, the butterflies will cluster for warmth in branches up to 30 feet above the ground.
Your best bet for viewing butterflies fluttering around is to come in the middle of the day when the sun warms them enough to fly in search of nectar sources. Binoculars are recommended for an unforgettable viewing experience.
Monarch Grove Sanctuary in Pacific Grove
There is a reason Pacific Grove has earned the nickname "Butterfly Town, U.S.A." Several thousand monarchs flock to this town on the Monterey Peninsula each year. The sanctuary is located off Light-house Avenue on Ridge Road, though some years the butterflies have been known to visit Washington Park, with an entrance at Spruce and Alder streets.
"If you haven't been to the sanctuary before, be sure to come when there are docents because they have spotting scopes set up so you can view the butterflies and they can give you lots of information," said Mannel.
The sanctuary is open sunrise to sunset. Entrance is free, but donations are deeply appreciated.
Andrew Molera State Park
The relatively undeveloped state park is another place where monarchs have historically overwintered in Monterey County. Because overnight campsites are available, as well as miles of trails, this site offers a true nature experience.
Andrew Molera State Park is located off Highway 1, about 28 miles south of Monterey.
For day use, the park is open one hour before sunrise and one hour after sunset. There is a walk-in camping area with 24 primitive campsites in a meadow. Registration is first-come, first-serve. Day use fee is $10 per vehicle; Overnight camping fee is $25 per site. For more information, call 667-2315 or see www.parks.ca.gov.
Natural Bridges State Park
The park, at the northern boundary of Santa Cruz, has historically been a great place for butterfly viewing. The site includes a visitor center dedicated to educating the public about the life history and conservation of the monarch, as well as hour-long tours on weekends during the monarch season. To get there, take Swift Avenue West from Highway 1 to the park entrance.
Though full wintering goes through the end of February or early March, in the past few years the butterflies have been leaving the park in January. Park interpreters speculate this is likely due to loss of trees. Park staff and local volunteers are trying to remedy the situation by planting more trees to make a better wind break. If the winter is mild, the butterflies could stay longer and possibly overwinter again.
In recent years, the population has shifted to Lighthouse Field State Park, a half-mile from Natural Bridges on West Cliff Drive. Monarchs at Lighthouse Field can be seen roosting on cypress trees planted within a eucalyptus grove.
The park is open from sunrise to sunset, with visitor center hours 10 a.m. to 4p.m. daily. Public tours on weekends are at 11 a.m. and 2 p.m. as long as the monarchs are there. Binoculars and spotting scopes are available. Day-use fee is $10 per vehicle. For more information, call 423-4609 or see www.santacruzstateparks.org/parks/natbridges.
Fascinating Facts About Monarch Butterflies
· Monarchs have a circadian clock within their antennae that functions as a miniature GPS unit, allowing them to navigate using the position of the sun.
· Glider pilots have observed monarchs flying at aerial heights of a quarter-mile above ground.
· While most generations of monarchs live only a month or less, overwintering monarchs survive for 7-9 months, delaying mating until the weather warms in the spring.
· During mating, males insert a nutrient-rich sperm packet in females that gives them enough energy to make the journey north in search of milkweed plants on which to lay their eggs.
· Milkweed plants contain cardiac glycosides, toxic compounds that growing caterpillars will eat and then store in their bodies. If predators try to eat monarch larvae, these toxins will make them sick.
· After hatching, the weight of the larvae increases 2,700 times in 15 to 20 days as it grows to 2 inches long.
· Another North American butterfly, the Viceroy, has evolved coloration to mimic that of the monarch, fooling predators into thinking that it too contains the toxic compound.
· The city of Pacific Grove passed a city ordinance in 1938, authorizing a fine of $500 for anyone molesting a butterfly in any way. In 1952 the fine was increased to $1,000.
Learn more about the Monterey Bay area at MontereyBayAdventures.com.