According to an article that appeared in the magazine Wildlife (published by the National Wild Federation), a study conducted on Iowa’s Camp Dodge military installation, revealed that monarchs are beginning their fall migration later in the year.
According to Montana State ecologist Diane Bebinski, the study found that monarchs are departing their fall migration an average of nine days later than they did in 2003. The results are based on the arrival and departure dates of monarchs recorded from 2003 and 2019. It should be noted that the time of milkweed flowering and monarch spring arrival dates did not change during the study.
Basbinski, the lead author of a report on the study, “This longer breeding season could have benefits and it could also have costs.” On the downside, researchers theorize that the butterfly’s later departure time could possibly harm monarch populations by exposing the butterflies to an increase in late season predators and parasites that attack monarch eggs.
It will be interesting to see if similar studies in other parts of the monarch’s range are also delaying the time they leave for Mexico each year.






