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Rains greet monarchs this 2023-2024 overwintering season

Year to year variation and conditions associated with the El Niño-Southern Oscillation raise questions and concerns about the monarchs' future and how best to conserve this migratory marvel.

January 03, 2024

Isabel Ramírez

During 2023, Mexico experienced changes in normal temperature and precipitation patterns associated with the El Niño-Southern Oscillation. The summer was very dry, with exceptional droughts in the central-western part of the country followed by constant rainfall in November as shown in Mexico's drought monitor map.

In the colonies at Sierra Chincua, the average temperature during November was 8.4°C, one degree higher than the average for the last 15 years for this month. Most striking was rainfall of 102 mm in November alone – equivalent to 20% of the accumulated rainfall so far this year! In field visits to Chincua and El Rosario on December 5 and 11, conditions were still cloudy and humid, with few flowering plants in and around the colonies, despite the humidity. The butterflies were not yet consolidated.

A recent study by Hobson et al. 2023 involving MBF board members Chip Taylor and Isabel Ramírez shows that when droughts occur at high latitudes in the monarch’s range, migrating butterflies can recover their lipid reserves by feeding in the Mexican territory along their route. But what if drought conditions extend along the Mexican migratory route and there is not enough nectar available around the overwintering sites? These are some of the questions we are pondering. We still have much to learn to ensure effective conservation actions!

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