New research shows that higher temperatures may increase the harm caused by the parasite Ophryocystis elektroscirrha. The study reports infections have more than tripled since 2002 and found that monarchs exposed to elevated temperatures were 22% less tolerant of infection. The parasite can reduce wingspan, lower weight and shorten adult lifespan, and it can affect migration.
Researchers raised both parasite-exposed and uninfected monarchs on nonnative tropical milkweed or native swamp milkweed under ambient or elevated, fluctuating temperatures in the field. They expected fewer infections in hotter treatments and more protection from the toxic tropical milkweed, but those expectations did not hold.
Warmer temperatures eliminated the protective effect of tropical milkweed. The team also found that plant toxins were slightly higher in warmth, and strong toxins can slow development or be excreted, which may remove protection.
Difficult words
- parasite — a small organism that lives on hosts
- infection — when a disease organism enters a hostinfections
- tolerant — able to endure harm or difficult conditions
- migration — seasonal long-distance movement of animals
- toxin — a harmful chemical produced by plants or animalstoxins
- elevated — higher than normal in level or amount
- eliminate — to remove or get rid of somethingeliminated
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- How could lower tolerance to infection affect monarch migration?
- Would you plant native swamp milkweed or nonnative tropical milkweed for monarchs? Explain your choice.
- The article says strong toxins can slow development or be excreted. Why might this remove protection for monarchs?
Related articles
Electric car batteries can power homes and cut costs
A University of Michigan study finds that using electric vehicle batteries to power homes (vehicle-to-home, V2H) can save owners thousands of dollars and reduce greenhouse gas emissions. Results differ across regions and the technology is still being tested.
Women, Forests and COP30: RADD's Forest Immersion in Cameroon
During COP30 in Belém (10–21 November 2025) RADD held a forest immersion on 17 November 2025 in Cameroon. The event connected women, local forest knowledge and global climate debates and included training, planting and exchanges.
Wildfire smoke in late pregnancy linked to higher autism risk
A study of more than 200,000 births in Southern California found that exposure to wildfire smoke during the third trimester was associated with higher autism diagnoses by age five. Researchers say the results are not conclusive and need more study.