New Year’s Count Of Western Monarchs Tracks Population Decline During Overwintering Season

By Isis Howard on March 2, 2022.

Western Monarch population experiences seasonal winter decline, but remains higher than previous years.

The Western Monarch New Year’s Count serves as a follow-up to the annual Thanksgiving Count to help scientists better understand how the western monarch population changes throughout the overwintering season.

This winter, Xerces scientists and volunteers recorded a 38% decline through the observation period, within the range of a 36-49% seasonal decline observed over the previous six winters. The overall western monarch population remains higher than in previous years.

Although it is difficult to distinguish the exact reasons for winter declines, we suspect it’s likely due to a combination of factors: mortality from winter storms, predation, other causes of mortality, and butterflies leaving the overwintering sites.

Now in its sixth year, the New Year’s Count provides additional information on the status of the migratory monarch population in the West. While the Thanksgiving Count remains the height of the annual monitoring efforts, the New Year’s Count, which runs for two weeks surrounding the New Year’s holiday, continues to gain momentum among volunteers.

Despite a general uptick in the western monarch population this year, monitoring efforts reveal that the migratory population of western monarchs has undergone a dramatic decline estimated more than 95% in the western U.S. since the 1980s… Read More Here!