Monarch Madness
What is orange, painted black, and is always seen around the beginning of fall? If you said jack-o-lantern, try again. It’s the monarch butterfly!
The monarch butterfly (Danaus plexippus) is the charismatic face of all Lepidoptera, the order of animal life that contains all of our extant moths and butterflies. Weighing in at well under 0.1 of an ounce (less than a single sheet of paper), about 3”-4” wide, and boasting a truly vibrant orange color with black borders and white dots, the monarch’s grandeur is unique to all others, with the exception of its Mü̈llerian mimicking relative, the Viceroy butterfly (Limenitis archippus).
While its regal beauty speaks for itself - named for the ‘Prince of Orange’ by early European settlers - the monarch has become a household name for all butterflies because of the truly unbelievable annual migratory journey the species has done for countless years.
Range & Migration
Historically native to both new world continents of North and South America, D. plexippus has since become a solely North American species, diverging into two distinct migrating groups on the continent: the western and eastern populations. Where you find them within this range (most notably the eastern group) depends entirely on where they are at in their migratory journey.
Western populations of monarch butterflies are geographically bounded by the Rocky Mountains, so they breed and live out their lives in this region. Much smaller in numbers and range than their eastern counterparts, this group spends its life solely in the western U.S. and southern Canada and migrates to the California coast for over-wintering.
On the other side of the mighty mountains, the eastern population boasts the bulk of the individual North American monarchs - those of which exhibit the awe-inspiring migration they are so aptly revered for. Leaving in the spring, monarchs depart the microclimate of the oyamel fir forests in central Mexico’s Sierra Madre Oriental Mountains to travel north. They’ll eventually find their way back to the ancestral breeding grounds of the great plains, eastern U.S., and southern Canada. While still not fully understood, it is hypothesized that monarchs can sense the shortening of days and the waning of healthy milkweed as signs of the need to head south.
Through a succession of 4-5 north-migrating generations, the monarch population born to the days of late summer and early fall are called the “super generation”. This group must live up to their name, as they are destined to live eight times longer (eight months) and must travel 10 times farther than their migrating ancestors. Eventually, this single generation will fly, by both pure will and nectar, back home to the cloud forests of central Mexico.
While endemic to NorthAmerica, D. plexippus can be found across both the Atlantic and Pacific, most likely due to being blown there by storms, thermal drafts, or island hopping; its host plant Milkweed (Asclepias spp.) helps to support populations in these usually tropical regions.
Life Cycle
Through a sustained and deeply intimate relationship, monarch butterflies have come to rely on Milkweed plants (Asclepias spp.) to aid in the rearing of their young. While adult butterflies are able to feed on a variety of plant nectar, the young monarch caterpillar must dine solely on the Asclepias to both nourish themselves, and bioaccumulate cardio-toxin. Milkweed contains a potent poison used by the caterpillar to deternagainst would-be predators; a witty defense mechanism, no doubt. It is for this reason that an adult mother butterfly knows instinctively that she must lay her developed eggs on these plants for her species’ continued survival.
After about 2-3 weeks of dining out on the all-you-can-eat milkweed buffet, the caterpillar(s) enter their chrysalis stage, which ends a week or two later, the full metamorphosis of the monarch butterfly life cycle. Breaking open from the cocoon is a fully formed monarch, ready for travel.
Upon emerging from its cocoon, the butterfly must journey on. For those that were born to the broods migrating north, adult life will only last about four weeks. In this time they will breed, lay their clutch, and die - pollinating milkweed along the way.
For those born in the northern extensions of their range and in the last parts of summer, sexual maturity will be delayed, and the journey home to the ancestral homelands of central Mexico and coastal California will be undertaken. In March, this super generation that is now 7-8 months old will leave Mexico for the migration back north. This great generation, like so many before them, will ultimately reproduce and die soon after.
Threats & Conservation
“Habitat loss is widely considered to be the most impactful factor when it comes to the suppression and ultimate extinction of species. ”
Once plentiful, the monarch is now facing immense pressures from the both expanding and developing population of humans. Loss of habitat, pesticide use, and climate change are all to blame for the drastic reduction in observed populations of the western and eastern monarchs.
Large areas, once rich in milkweed species of all kinds, have now been turned into areas where only monoculture agriculture crops can be found. Mowing of roadsides and herbicide use have both reduced the amount of milkweed for caterpillar consumption. Deforestation of the fir forests for timber and development has disrupted their overwintering sanctuaries, which are much needed for their survival.
Habitat loss is widely considered to be the most impactful factor when it comes to the suppression and ultimate extinction of species.
Conservation efforts for the monarch butterfly are underway, and you can play a part. The seemingly simple act of native gardening, city rewilding, and planting milkweed can have a great impact on the monarch populations. By creating more habitat for this special species, we can hope to see their migration year after year.
Learn more about the large-scale work being done to protect our monarchs.
By Dylan Hackett, Nursery and Greenhouse Manager
In 2019, Dylan started work at Reflection Riding as an educator, teaching the community aspects of ecology and the flora and fauna around them. Dylan now serves as Nursery Manager, facilitating the propagation of hundreds of species of native plants endemic to the region. Dylan’s work brings him great joy, especially working with community members to learn about environmental stewardship and sending them home with the power of a little bit of good in their hands.