A little over a week ago, my wife and I spotted our first monarch of the spring. The large orange and black butterfly was quite pale suggesting it had lost many of its scales. Since we rarely see a monarch this early in the season, we were hoping its arrival was a harbinger of clouds of monarchs heading to their breeding grounds. Within a few days, I stumbled across a news release that dashed our hopes.
The story reported the results of the annual survey of the numbers of monarchs that reached their wintering grounds situated in the mountainous region of central Mexico. This small area is so critical to the monarch it has been designated the Monarch Butterfly Biosphere Reserve. Each year monarchs from throughout Canada and the United States winter here in very small patches of woodlands. The World Wildlife Fund-Mex National Commission of Protected Natural Areas of Mexico, World Wildlife Alliance-Telmex Telcel Foundations carry out the survey with the assistance of a handful of local communities located near the wintering grounds
Basically, the survey consists of delineating the area occupied by the wintering butterflies. As such, the greater the acreage is an indication that more butterflies survived their fall migration and reached their historical winter home.
During the 2018-19 wintering season surveys indicated wintering migrants occupied an area measuring 15 acres in size. In comparison, researchers found that during the winter of 2019-20 monarchs were using only 7 acres of habitat. This means the monarch population plummeted 53 percent from the previous winter.
For approximately two decades, the monarch population has been on a downhill slide. Realizing the plight of what is arguably our most recognized butterfly, the United States Fish and Wildlife Service, National Wildlife Federation, Xerces Society and a host of other private and governmental organizations have been working hard to determine the cause of the insect’s demise as well as initiating science-based conservation measures to reverse the monarch’s alarming population trend.
This effort has revealed there appear to be a number of factors that are contributing to the monarch’s plight. This list includes destruction of the monarch’s wintering grounds, the widespread use of a herbicide called glyphosate to control weeds, such as milkweed, in or adjacent to croplands, the increased planting of corn and other crops that have been genetically modified to be glycophosate resistant, and changes in land use throughout North America, especially from Texas northward throughout middle America and on into Canada. This is the migration route used by the majority of all monarchs.
Weather also plays a key role in determining the size of the continent’s monarch population. In fact, experts are suggesting that lower than normal temperatures during March and April of 2019 across south Texas played a key role in lowering the numbers of monarchs reaching their wintering grounds this past fall.
The reason for this is extremely few of the monarchs that leave Mexico ever reach their breeding grounds. This is because the monarchs that overwinter in Mexico lay eggs when they reach Texas. The caterpillars that hatch then fly northward. This process is repeated several times before monarchs blanket their breeding grounds in the northern United States and Canada.
The low spring temperatures that dominated the weather in March and April of 2019 retarded normal growth rates of both eggs and caterpillars. This, in turn, manifested itself in fewer adult monarchs reaching their breeding grounds well to the north.
While the reduction in the size of the monarch population this past winter is alarming, monarch experts remain confident that this is but a temporary setback. There are several reasons for this optimism. It appears that conservation efforts have slowed illegal logging in the monarch’s wintering grounds. In addition, countless efforts to restore milkweed (the monarch’s only host plant) throughout the butterfly’s breeding range are enhancing breeding habitat. In addition, the recognition that fall food availability along the monarch’s pathway is scarce has prompted folks throughout Georgia and elsewhere to provide much-needed nectar.
If you enjoy seeing monarchs on your property, join the growing army that is restoring milkweeds and planting fall blooming nectar plants needed by the insects to successfully complete their journey to their winter home south of the border.
Terry Johnson is retired Program Manager of the Georgia Nongame-Endangered Wildlife Program. He has written the informative column ‘Monroe Outdoors’ for the Reporter for many years. His book, “A Journey to Discovery,” is available at The Reporter. Email him at firstname.lastname@example.org.