Researchers report that higher temperatures can make monarch butterflies less able to cope with a parasite. The study found infections have more than tripled since 2002 and that monarchs exposed to warmer conditions were less tolerant of infection.
People plant milkweed to help monarchs, but many use nonnative tropical milkweed. Tropical milkweed can grow year-round and may cause butterflies to skip migration, giving parasites more time. Earlier lab work used constant high heat, but the new study exposed butterflies to natural, fluctuating temperatures in the field to test effects on infection and plant toxicity.
Difficult words
- parasite — an organism that lives on or in another
- tolerate — to accept or handle a problem or damagetolerant
- migration — regular long distance movement of animals
- nonnative — not originally from a local area or region
- fluctuate — to change up and down or move between valuesfluctuating
- toxicity — how poisonous a substance or plant is
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- Do people in your area plant milkweed? Why or why not?
- What could gardeners do to help reduce parasite problems for monarchs?
- How might changing temperatures affect animals you know about?
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