The Xerces Society recently announced its final Western Monarch Thanksgiving Count numbers for overwintering monarch butterflies and the news is cause for celebration – 247,237 monarch butterflies (Danaus plexippus) were observed across western overwintering sites, more than a 100-fold increase from last year’s count. Although this is good news, the population is still more than 95% below what it was in the 1980s, when monarchs were observed in the low millions.
The Western Monarch Thanksgiving Count is a volunteer-driven community science program organized by the Xerces Society and the count’s co-founder, Mia Monroe, to count overwintering monarchs. It occurs near the Thanksgiving holiday each year, with this year’s count running from November 13 to December 5, 2021. The count collects data on the status of the migratory western monarch population each fall using a standard protocol to estimate the number of monarchs clustered at overwintering sites. A second count centers around the New Year’s holiday each year; those numbers will be released in February.
Some researchers have suggested theories that include resident monarchs and/or an influx of eastern monarchs could be responsible for this year’s increase. According to the Xerces Society, “It is unlikely that there is a single cause or definitive explanation for such a complex migratory journey and for a single year’s increase.” Modeling and analysis of this year’s data is currently underway, however, it may take several years of Thanksgiving Counts to understand this year’s increase in context.
In North America, there are two distinct migratory populations of monarchs separated by the Rocky Mountains: a western population that overwinters in California; and an eastern population that overwinters in high-elevation oyamel fir (Abies religiosa) forests in central Mexico. The monarchs that we observe in Arkansas are considered part of the eastern migratory population. Arkansas lies within the spring breeding area and is a critical part of the migratory flyway of the monarch. Learn more about monarchs in our blog posts “Wings of Hope: Monarch and Pollinator Conservation in Arkansas” and “The Multifaceted Migration of the Monarch Butterfly.”
The population decline hasn’t just happened in the western monarch population – the eastern migratory population is estimated to have declined 70% since monitoring it began in the 1990s. World Wildlife Fund-Mexico usually announces the size of the eastern monarch’s overwintering population each February.
Despite the specific cause(s) for this year’s uptick in the size of the overwintering western monarch population, we can find hope in the results. The value of conservation efforts, along with awareness of the monarch’s plight, has never been more important to the recovery of the monarch butterfly.
Learn more about the 2021 Western Monarch Thanksgiving Count’s results at https://www.xerces.org/blog/western-monarch-thanksgiving-count-tallies-nearly-250000-butterflies.
The Xerces Society for Invertebrate Conservation is an international nonprofit organization that protects the natural world through the conservation of invertebrates and their habitats. The organization’s name comes from the now-extinct Xerces blue butterfly (Glaucopsyche xerces), the first butterfly known to go extinct in North America as a result of human activities.
Photos:
Top — Monarch butterfly (Danaus plexippus). Photo by Samantha Scheiman.
Main — Monarch butterfly (Danaus plexippus). Photo by David Arbour.
Sources
The Western Monarch Thanksgiving Count is a volunteer-driven community science program organized by the Xerces Society and the count’s co-founder, Mia Monroe, to count overwintering monarchs. It occurs near the Thanksgiving holiday each year, with this year’s count running from November 13 to December 5, 2021. The count collects data on the status of the migratory western monarch population each fall using a standard protocol to estimate the number of monarchs clustered at overwintering sites. A second count centers around the New Year’s holiday each year; those numbers will be released in February.Some researchers have suggested theories that include resident monarchs and/or an influx of eastern monarchs could be responsible for this year’s increase. According to the Xerces Society, “It is unlikely that there is a single cause or definitive explanation for such a complex migratory journey and for a single year’s increase.” Modeling and analysis of this year’s data is currently underway, however, it may take several years of Thanksgiving Counts to understand this year’s increase in context.
In North America, there are two distinct migratory populations of monarchs separated by the Rocky Mountains: a western population that overwinters in California; and an eastern population that overwinters in high-elevation oyamel fir (Abies religiosa) forests in central Mexico. The monarchs that we observe in Arkansas are considered part of the eastern migratory population. Arkansas lies within the spring breeding area and is a critical part of the migratory flyway of the monarch. Learn more about monarchs in our blog posts “Wings of Hope: Monarch and Pollinator Conservation in Arkansas” and “The Multifaceted Migration of the Monarch Butterfly.”
The population decline hasn’t just happened in the western monarch population – the eastern migratory population is estimated to have declined 70% since monitoring it began in the 1990s. World Wildlife Fund-Mexico usually announces the size of the eastern monarch’s overwintering population each February.
Despite the specific cause(s) for this year’s uptick in the size of the overwintering western monarch population, we can find hope in the results. The value of conservation efforts, along with awareness of the monarch’s plight, has never been more important to the recovery of the monarch butterfly.
Learn more about the 2021 Western Monarch Thanksgiving Count’s results at https://www.xerces.org/blog/western-monarch-thanksgiving-count-tallies-nearly-250000-butterflies.
The Xerces Society for Invertebrate Conservation is an international nonprofit organization that protects the natural world through the conservation of invertebrates and their habitats. The organization’s name comes from the now-extinct Xerces blue butterfly (Glaucopsyche xerces), the first butterfly known to go extinct in North America as a result of human activities.
Photos:
Top — Monarch butterfly (Danaus plexippus). Photo by Samantha Scheiman.
Main — Monarch butterfly (Danaus plexippus). Photo by David Arbour.
Sources