Nature Notes: The Flight of the Monarchs
It’s the season for migrating monarch butterflies. The seabeach goldenrods are blooming, the temperature has been favorably warm, and the wind velocities have been on the low side. Monarchs rest during the night, become active at daybreak, flapping their wings up and down slowly to raise their body temperatures and take off, stopping to feed on asters, goldenrods, and other fall flowers on their way south.
Some of the new adults fresh out of their chrysalises apparently fly all the way to Mexico, others stop somewhere along the way and may reproduce before traveling on. It is a long harrowing flight, but they have a special protection that most butterflies lack. They taste bad. Monarchs fed to toads experimentally are rarely eaten. They are mostly rejected after one bite, and thereafter the toads will not touch them. In fact, they are unpalatable to almost all of the predators that feed on insects and butterflies, including other insects, amphibians, bats, and birds.
They taste bad because the adults, which are nectar and pollen feeders, come from larvae that feed on milkweeds and dogbanes. Those plants produce toxic substances, alkaloids and cardenolides, specifically oleandrin, a cardiac glycoside. The sap containing these poisons is bitter, but somehow the larvae thrive on it, as do a few other insects. Thus, the caterpillars have few natural enemies and when they metamorphose into adults in late summer they carry with them the same bitter tasting chemicals.
For perhaps thousands of years in North America, monarchs have avoided the beaks, jaws, and mandibles of most insect-eating animals based on this one factor. Simultaneously, they have evolved bright orange warning colors, so that they announce their repugnant nature wherever they exist. How else could they fly for thousands of miles in a month or two without being snatched out of the air by a hungry hawk or flycatcher?
The larvae are likewise boldly black-yellow-and-white-banded. They cannot be missed against the dull green of the milkweed plant. The butterfly weed, or orange milkweed, is one of their favorites. Most milkweed flowers are white or pinkish. Could it be that the orange milkweed evolved to save would-be predators from unfruitful visits? They can be seen by sharp-eyed predators from hundreds of yards away.
There is a look-alike butterfly, the viceroy, that is rare on Long Island. It is not bad tasting, but because it mimics the monarch’s colors and pattern, it is avoided by predators, too, especially if the would-be predator has already tasted and rejected a monarch.
The story of the monarch’s amazing flights north and south encompassesmore than one generation of adults and was first described by the late Frederick Urquhart and his wife, Norah, in the late 1930s after the two started attaching tags to the wings of adult monarchs before releasing them in Canada at the start of the fall migration. They tagged hundreds, but only a few tags were reported, the most distant of which came from faraway points south, including Texas, just across the border from Mexico, where many of the butterflies head for the winter.
As a result of their research, Mexico was pinpointed as an overwintering spot for monarchs. Then another lepidopterist, Lincoln Brower, became part of the act, independently, ultimately discovering the piney mountainous area in central Mexico where the monarchs came to rest after their long southward trek. Meanwhile, research taking place on the West Coast showed that there were several overwintering spots for monarchs including Pacific Grove and Santa Barbara, two areas of California where it very rarely snowed or frosted.
Since the work of the Urquarts and Brower, the “hibernaculum” in Mexico has been partially desecrated and the monarch population has plummeted. American populations have suffered from the application of herbicides to kill weeds, including milkweeds that compete with corn and other harvestable produce. More recently, the widespread planting of genetically altered vegetables such as corn, from seeds modified to produce poisonous nicotinoids, has further reduced the monarch and honeybees numbers. Their pollen is poisonous to a host of insects.
Conservation organizations and the United States Fish and Wildlife Service, as well as state and local environmental agencies, have banded together to protect what is left of the American monarch population. There are lots of tagging and monitoring groups and individuals scattered throughout the United States trying to help the monarchs. Planting milkweeds and counting adult monarchs stemming from them is just one of the replenishment methods.
Locally there are several monarch counters and a few taggers. I keep in touch with a few of them. Victorian Bustamante of Montauk not only grows monarchs for Warren’s Nursery, but goes into the field to count them. As of Monday she has counted 32. Last year her tally ending on Nov. 9 was 55. Peter Dermody, a hydrogeologist and geologist, started raising and tagging monarchs several years ago. He has not raised and tagged any for a few years now as their Long Island populations have plummeted.
This year thus far, he estimates that he has seen around 60 adults in August and 25 in September.
Terry Sullivan, a nature photographer and author who is out and about almost on any day when it’s not raining, has seen only a few. He has photographed several adults in the past. He saw three on Sunday and Monday while fishing from the ocean beach in Amagansett. Dai Dayton — the intrepid naturalist, hiker, and head of the Friends of the Long Pond Greenbelt — has only seen five all summer. Jane Ross, who keeps track of many different members of the animal kingdom, has seen several, some of which, she thinks, grew up in fields in the Georgica Pond area.
Jean Held, who lives in Sag Harbor, is a longtime student of darning needles and butterflies. She also had orange milkweed in her yard and some of it was flowering right until the last week in September. She noticed seven monarch butterfly larvae, two of which she took into her house as they were very large and ready to metamorphose. Even though she watched them closely for long times on end, wanting to photograph the conversion from larvae to chrysalis, it happened so quickly she was unable to capture it in step-by-step fashion.
There is a question concerning the fall migration routes of monarchs on Long Island. Those that I have seen on local roads in these last two months have all been flying south, that is, toward the coast. It is along the ocean coast that most migrating monarchs are seen. They are visual migrators: They follow the coast west and then turn south when they reach the city, although some have been seen flying far out at sea. The Atlantic Coast is ideal because of its rich stock of seabeach goldenrods on which to rest and feed.
How they get here from New England is another story. It may be that they island-hop. I have received very few reports of monarchs seen flying over the middle of Long Island Sound, but several observations of them flying along the shores of islands comprising the Long Island-New England archipelago: Nantuckett, Fisher’s, Big Gull, and Plum Islands. A month ago on a Plum Island trip I saw several flying low, all along the island’s coastal edges.
What if our observers all saw the same monarchs only at different times along their migratory route? Then we are left with a grand total of a piddling few. I like to think that they all saw different ones and that the monarch butterfly, at least hereabouts, is on its way to recovery. Then again I tend to be a wishful thinker.
Larry Penny can be reached via email at [email protected].