Each winter, pollinator enthusiasts anxiously await monarch population numbers as eastern populations overwinter in the forests of Mexico.

This winter, we have some less than ideal news as monarch overwintering numbers dropped by more than 50 percent from the 2018-19 season --- going from 6.05 hectares of overwintering area covered last year to 2.83 hectares in the 2019-20 winter season.

Graphic about monarch populations

A lack of host milkweed plants for monarchs to lay their eggs on and for their caterpillars to eat, pesticide use, not enough native habitat for adult monarchs to feed on during their journeys north and south --- so many factors come into play as to why monarch butterfly populations have dwindled almost 90 percent in the past 30 years. Chip Taylor, director of the University of Kansas Monarch Watch program predicted that 2019-20 populations would be down, and he was right. (Read his blog here)

To summarize, he said that monarchs moved too far north too quickly last spring, encountering cool temperatures and inhibiting growth of the first population of caterpillars. That inhibited growth continued throughout the rest of the monarch generations going north, creating a late migration south as well.

In addition, monarch populations seemed to be low in Iowa and western portions of the upper Midwest throughout the season. The temperatures in the summer of 2019 were average, but temperatures slightly above average --- such as what happened in 2018 --- help monarch populations to really boom.

A Texas drought also seems to have impacted monarch populations during migration, because nectar was in short supply as monarch butterflies flew south to Mexico for the winter.

(Read "How Do Monarchs Find Their Way South?")

Not all monarch butterflies overwinter in Mexico. There is a population of monarch butterflies on the west coast, and news surrounding those monarchs is not positive either. This smaller population of monarchs migrate south to overwinter on the Baja Peninsula, and the Xerces Society has found that the west coast population has declined 99.4 percent since the 1980s. In the 1980s, western monarch populations were estimated at 4.5 million, but the 2018 monarch butterfly count only reported 28,429 butterflies. That means for every 160 monarch butterflies in the 1980s, there is only one today.

Spring migration for monarch butterflies has begun for 2020. For the main continental population, it will take four-six generations of monarchs to reach their northern-most territories in Iowa, Minnesota and even into Canada before the last generation heads back south to overwinter again in Mexico.

(Find out more about the majestic monarch's magnificent life cycle)

We can all help those generations.

  1. Plant natives! There are plenty of milkweed varieties, read about them here, that are beneficial and also beautiful in landscaping.
  2. Cut down on pesticide use. Neonictinoids are considered harmful to pollinators, and many other chemicals that have widespread usage are not only deadly to bugs people don't want around but they are deadly to everything. That means chemicals that kill mosquitoes also kill pollinating bees, butterflies, moths, beetles, ants and other beneficial insects.
  3. Get involved. Monarch Watch is asking for citizen scientists to keep track of monarch butterfly numbers throughout the country to help more accurately identify populations. You can sign up to count butterflies in your own community. Find out more about that here.
  4. Advocate. Make sure to talk to your friends, your neighbors, your family about the importance of pollinators and taking small steps in our own yards that will help bring back our populations.

Learn more about pollinators inside Pollinator Paradise at the Dickinson County Nature Center!

 

 

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2 Comments

  1. AmyT on May 2, 2019 at 9:56 am

    Hi, thank you for this article. I am confused that this was written in March 2018 but it talks about winter 2018/19 population—should it instead say winter 2017/18?



    • kiley on May 2, 2019 at 10:08 am

      The original post was written in 2018 and then was re-written and updated with the 2018-19 numbers in March 2019, so it is the accurate 2018-19 numbers 🙂 Sorry for the confusion!