News Animals

Warm autumns could be a driver in monarch butterflies’ decline

In lab tests, higher temps ended monarchs’ reproductive pause during migration

An image of a monarch butterfly on bright flowers

Eastern monarch butterflies fly thousands of kilometers to overwintering sites. In spring, they lay their eggs on milkweed, seen here.

By Jude Coleman

Toastier fall weather might cause migrating monarch butterflies to wing it and change their flight plans, starting the countdown toward death. 

Eastern monarchs captured during their autumn migration and exposed to warm temperatures in the lab came out of their usual reproductive hiatus, evolutionary biologist Ken Fedorka and colleagues report August 12 in Royal Society Open Science.