Nine-Minute Naturalist: Monarch Migration
Filed under: Nine-Minute Naturalist
by Josh Palumbo, Forest Management Coordinator
I welcome you to The Nature Foundation at Wintergreen’s attempt to bring some nature and knowledge into your home. The Nine Minute Naturalist borrows from NPR’s lovely 90-Second Naturalist podcast. Since we all have a bit more time on our hands, the goal is to take something that is happening out in our environment and stimulate your brain for roughly nine minutes. Don’t let something as “minor” as a quarantine to keep you from learning. I hope you enjoy!
One of the year’s most fascinating natural phenomena is the monarch migration. The fact that the entire population of one of our continent’s most beloved creatures overwinters in about 15 acres in Mexico and requires one specific plant to complete its lifecycle highlights the fragility of the monarch’s existence. This Nine Minute Naturalist will focus on what a complex life the monarch leads.
The first migration for monarchs begins and ends at two winter sanctuaries, The Cerro Pelon and Piedra Herrada. The monarchs leave their overwinter homes in late February and head north until early April. The females will lay eggs as they work their way north and then die ending migration one.
Migration two begins after generation two monarchs reach adulthood around late April/early May and will soon set off on their way northward. They will cease their northward journey by early June when they reach regions containing milkwood plants. Females lay eggs thus starting a new generation that will move in the opposite direction of the previous two generations.
Migration three begins the change in direction. Directional migration halts from early June to late July during which travel and reproduction are done on a local level. Movement during this time tends to go south/southwest but is much less defined than any other migration.
By the first week in August, the northern most monarchs (50 degrees north around Winnipeg) begin their legendary southward journey that will continue until early December. Migration four is a defined and well-known migration and is the longest in duration and length. This migration differs in that the monarchs do not mate and reproduce on their long southward journey.
Each generation tends to take 25-50 days from egg through pupation. Temperature is the greatest variable that dictates development time as well as reproduction success. Foul weather in the spring and fall tends to play a huge factor in population growth or crash. A survey done this past winter at the overwinter site in Mexico revealed a 53% decrease in the monarch population. The cause of the sudden decrease is attributed to poor weather during the spring and fall migrations. Loss of breeding habitat due to overuse of herbicide in industrial farming greatly decreases the amount of milkweed available to monarchs and thus aids to lower the population. The current populace is believed to be below the extinction threshold and has been nominated for protection under the Endangered Species Act.
I still get excited each time I see the monarchs migrating in both spring and fall. One easy way to facilitate monarch population growth is to manage your landscape for milkweed. Wintergreen’s landscape is full of milkweed varieties that need to be a focal point of each yard at Wintergreen. Over the next month, monarch volume will increase throughout the Blue Ridge migration route. Make sure you appreciate this yearly phenomena!