By Michele Byers
As they alight on seaside goldenrod flowers or roost in Eastern red cedars, monarch butterflies are unmistakable with their brilliant orange and black patterned wings.
Although their flight may seem meandering and subject to the vagaries of wind, monarchs are on an instinct-driven mission right now. These “ultra-marathoners” migrate more than 2,000 miles to the forests of central Mexico. They hold the distance record among migrating insects, and their journey is one of the true wonders of the world.
October is the height of monarch migration, and New Jersey’s coastline is historically a good place to see them. But monarch numbers have declined precipitously due to widespread loss of milkweed plants, whose leaves are the sole food source for monarch caterpillars.
Across the country, the monarch butterfly population is down by more than 95 percent over the past few decades from an estimated 1 billion in the mid-1990s to just 35 million in early 2014. Many wildlife experts believe monarchs deserve protection under the Endangered Species Act.
Cape May is one of the great gathering places along the fall monarch butterfly migration route, just as it is for birds. Waves of butterflies rest and refuel along the tip of the peninsula before hazarding the Delaware Bay crossing.
New Jersey Audubon Society’s Cape May Bird Observatory hosts the Monarch Monitoring Project, an annual nine-week census conducted during the fall migration since 1992.
Throughout September and October, observers make three counts per day along a 5-mile route crossing various coastal habitats. This year, said Mark Garland, communications director, the Monarch Monitoring Project has expanded to include counts at Stone Harbor Point and East Point on the Delaware Bay.
Census results vary tremendously due to yearly weather fluctuations, but trends can be detected due to decades of Cape May Point data. In 1999, observers counted an average of 359.8 butterflies per hour, but only 8.9 butterflies per hour were seen in 2004. So far this fall, Cape May’s average has been 36.7 monarchs per hour, about the same as last year.
The spring migration is very different from fall.
In spring, monarchs travel northward relatively short distances before mating, laying eggs on the underside of milkweed leaves and dying. The eggs hatch, and larvae fatten up on milkweed leaves, ultimately metamorphosing into adult butterflies. The new adults continue the cycle.
It takes about five monarch generations to complete the migration to the northern United States and Canada.
But in the fall, monarchs spend their energy on migration rather than reproduction. A single generation makes the long trip south. The only goal of the great-great-grandchildren of the butterflies that departed from Mexico in spring is to instinctively get back to the endangered forests of Oyamel fir in the mountains above Mexico City, a place their non-migratory parents had never been!
“It’s really remarkable,” said Garland of the migratory monarchs. “There’s some environmental cue that makes them behave entirely differently from previous generations.”
The fall journey to Mexico takes the better part of two months, and, once there, the butterflies roost with hundreds of thousands of others until it’s time to begin the spring migration and reproduction cycle anew. This autumn’s generation of monarchs will have a lifespan of eight or nine months, far longer than the spring and summer generations.
So what can be done help monarch butterflies rebound? You can plant milkweeds and allow meadows to grow up naturally along edges and hedgerows, instead of mowing flat every last patch of vegetation.
Milkweed seeds are available at native plant nurseries, and many schools, businesses and nonprofit organizations sponsor planting programs.
If you spend time on or near Cape May, consider becoming a “monarch ambassador” and help out with butterfly counts and tagging.
To learn more about monarchs and their lifecycle, visit the Monarch Monitoring Project at www.monarchmonitoringproject.com/index.html.
Another great resource is the Monarch Teacher Network at www.eirc.org/programs-services/global-connection/monarch-teacher-network/monarch-workshops/.
Michele Byers is executive director of the New Jersey Conservation Foundation. For more information, contact her at [email protected] or visit NJCF’s website at www.njconservation.org.
