FORT KNOX, Ky. — Butterflies haven’t arrived at Fort Knox yet.
Referring specifically to the roughly 45 million monarchs that migrate to overwintering sites in Mexico and Southern California every year and then back north in the spring. Biologists here say they are ready for them when they do arrive.
“The primary part of this are the forbs, or wildflowers. They are the key to all this,” said Fort Knox biologist Mike Brandenburg. “One of the things we have to manage is to not let the grasses get too thick, so that they then don’t outcompete the forbs that these species need — not just the monarchs but all pollinators, including bees and beetles.”
Brandenburg said a unique key to attracting monarchs into the area involves cultivating a weed that most people would fight to remove from their lawns and gardens.
“Monarchs rely upon milkweed plants,” said Brandenburg. “That’s where they exclusively lay their eggs, and then the eggs hatch and the little caterpillars start eating that milkweed.”
Brandenburg explained that milkweed is the critical component of a successful monarch migration to areas as far north as Canada that involves four or five generations each year. It’s also critical to their survival against threatening predators since milkweed is poisonous to other species.
Another key to their success includes the monarchs known as the “super generation.”
The eastern population of the super generation, born in late August to early September, flies thousands of miles south to an area in Central Mexico for the winter. While there, they mate and make the long trip back up to the United States in search of egg laying spots. Those eggs make up the first generation of the year.
As monarchs reproduce, each successive generation continues its migratory journey north, although their lifespan is considerably shorter than that of the super generation.
The U.S. Fish & Wildlife Service in August 2021 sounded the alarm on plummeting monarch populations in recent years. According to officials there, “From 1996 to 2020, the eastern monarch population dropped 88 percent, from an estimated 838 million to just under 45 million.
“The monarch butterfly, probably the world’s best-known butterfly, has become the symbol for a whole class of imperiled pollinators.”
Brandenburg said one possible reason for the shrinking numbers of pollinators is a shrinking landscape conducive to their survival and farmers’ repulsion of weeds, like milkweeds.
“Monarchs are dependent upon the milkweed species. That’s where the problems have occurred,” said Brandenburg. “Through a lot of the common agricultural practices these days with pesticides and herbicides that use glyphosates, particularly the milkweed is very susceptible to it.
“That’s part of a problem that’s been identified with the pollinators in general, but specifically the monarch, is the reduction in the amount of milkweed that’s available for that species to reproduce.”
As a result, the Environmental Management Division at Fort Knox employs a comprehensive, strategic and aggressive plan that seeks to maintain a balance of trees, grasses and wildflowers, which all wildlife can thrive in. Part of the monarch plan involves capitalizing on roughly seven different species of milkweed that they cultivate in what Brandenburg calls “pollinator focus areas.”
“Those areas used to be mowed, and it was very expensive to mow all of it, so we took them over,” said Brandenburg. “We saved the installation on mowing, and we gained a habitat benefit there. We have been managing those areas specifically for early successional what we would call ‘prairies’ or ‘barrens’ remnants.”
Within those habitats are some uncommon species of milkweed.
“This effort makes us much more ecologically rich,” said Brandenburg. “We need to be sustainable, so we get the benefits from this ecological diversity to provide for habitats that in a lot of off-post locations are going to be either mowed, or they’re in crops, or they’re in pastures, or in hay production.
“Next to wetlands, those habitats are some of the most endangered areas in Kentucky.”
Brandenburg said while they are doing all that can be done to encourage growth of pollinator species, including the monarchs, more can be done.
“We all need to do what we can before these species become imperiled,” said Brandenburg. “You can go buy you some milkweed seeds, plant it in the backyard, and have and watch monarchs.”