Pismo Beach is one of my favorite places in California, and while much of the country shivers through ice and snow, the Monarch butterfly is spending its winter here sheltered in the coast’s eucalyptus groves. We’ve seen these beauties overwintering a few times in Pismo, and were fortunate enough to view them last week during a family visit. Monarchs living in the western US migrate to California in the winter, a different path from the eastern Monarch, which funnels through Texas on its migration into Mexico.
The Monarch’s lifespan is only 2 to 6 weeks long, but they are sexually mature as soon as they emerge from the chrysalis as adults, and there are multiple generations each year. However, the last generation of the season (usually determined by the decline of nectar plants) do not become sexually active when they emerge as adults, but go into reproductive “diapause”, which means that they can’t reproduce. They head for the California coast, and cluster together in the Monterey Pine forests of Pacific Grove, and the Eucalyptus groves of Pismo Beach, Morro Bay and San Luis Obispo. They slow their metabolisms, and have sufficient fat stored that they don’t need to eat over the winter.
Then, when the first warm days of January occur and the Eucalyptus bloom as a food source, they begin to mate and renew the cycle. As we watched two Monarchs on the ground together, the docent explained that the male was trying to pick up the female and carry her to the tops of the trees to mate. It sounded fanciful, but apparently he grabs his intended from the cluster, which causes them to tumble down. If she closes her wings to become more aerodynamic, it means she’s willing to be taken to the top… of the tree. If she flutters her wings and keeps them open, it’s “buzz off, buster”.
After mating, the female takes off inland in search of the milkweed plant to lay some of the 400-500 eggs she will probably lay over her short lifetime. After emerging and eating its own eggshell, the Monarch caterpillar eats milkweed leaves exclusively to incorporate the plant’s toxins into its body. Predators know the Monarch is a poisonous butterfly, and won’t eat it. When the caterpillar is about 2 inches long, it begins the process of turning into a pupa. After 10-12 days in the pupa stage, a damp butterfly emerges, pumps liquid into its wing veins to inflate them, dries, and flies off to feed and mate. This second generation of Monarchs will travel into Oregon, Nevada or Arizona. Third and fourth generation Monarchs will venture even farther afield, until it’s again the end of the season, and they return to the California coast when their ancestors lived and begin another cycle of life.