Details

Autor(en) / Beteiligte

• Culbertson, Katherine A.
• Garland, Mark S.
• Walton, Richard K.
• Zemaitis, Louise
• Pocius, Victoria M.

Titel

Long‐term monitoring indicates shifting fall migration timing in monarch butterflies (Danaus plexippus)

Ist Teil von

• Global change biology, 2022-02, Vol.28 (3), p.727-738

Ort / Verlag

England: Blackwell Publishing Ltd

Erscheinungsjahr

2022

Link zum Volltext

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• Eastern North American monarch butterflies (Danaus plexippus) embark on a yearly migration between summer breeding grounds in the northern United States and southern Canada and overwintering sites in central Mexico, traveling up to 4300 km. This annual multi‐generational migration cycle, like many seasonal natural phenomena, may be impacted by recent changes in climate and habitat. We investigated long‐term trends in monarch abundance and fall migration timing over a 29‐year period in Cape May, New Jersey, using data collected from daily population surveys designed to track patterns of occurrence during the fall migration period through Cape May (1 Sept–31 Oct). Between 1992 and 2020, the migration midpoint, average peak migration day and first peak migration day shifted between 16 and 19 days later in the season, an average of approximately six days per decade. This observed shift in migration timing is correlated with increasing temperatures in September and October in northeastern monarch breeding grounds over the study period. Our data do not demonstrate a significant directional trend in monarch abundance over the study period, yet population data collected at overwintering sites in Mexico indicate a substantial decline over the same period. Further postponement of fall migration may lead to lower migration success and exacerbate the overall decline of this iconic species. Every fall, monarch butterflies travel up to 4300 km from the northern edge of their breeding range to overwintering sites in Mexico (red diamond). Over the past 29 years, migratory monarchs observed in Cape May, New Jersey (blue diamond) have delayed fall migration by 2 weeks (black trendline). This parallels increasing fall temperatures in the source region for the population (approximated by the blue box), especially the average minimum temperature during September and October (blue trendline).