Q. On Saturday, Oct. 28, there was an interesting article that discussed how the the first freeze date was occurring later each year. It also made the point that this was somehow causing Monarch butterflies to die during their migration to Mexico. I had heard that the first Monarch to leave never makes it to Mexico. What is correct? – Mike
A. We contacted Monarch Watch at The University of Kansas to find out. Angie Babbit, communications coordinator, responded in two parts:
On Saturday, Oct. 28, there was an interesting article that discussed how the the first freeze date was occurring later each year. It also made the point that this was somehow causing Monarch butterflies to die during their migration to Mexico.
"The article says, 'Clusters of late-emerging monarch butterflies are being found farther north than normal for this time of year, and are unlikely to survive their migration to Mexico.'
"If one were to assume that late emergence of monarchs is detrimental to the population, then the above statement sounds tragic. However, late emergence is a beneficial, adaptive reproductive strategy, and it happens every year. We call those that remain behind 'stragglers.'
"If all monarchs emerged at the exact same time and migrated to Mexico together, the lack of diversity in the strategy would not accommodate any catastrophe. That would indeed be tragic. The annual loss of stragglers is upsetting to those who do not understand that loss of life is part of the natural cycle of insect biology.
"It is possible that conditions were so favorable for monarch reproduction this year that we witnessed more late emerging monarchs than we have for a while. Those late monarchs would not have been witnessed if there was an early freeze -- they would have died as eggs or caterpillars -- but they would still have been produced in proportion to the quality of earlier reproductive conditions.
"Temperature is one of several complex migration cues, and further reading can be found here:
"Higher temperatures in the fall could potentially override the other cues. I would predict this to be the case at lower latitudes, where we may already be seeing migrants coming out of reproductive diapause when they reach unseasonably warm southern Mississippi and Louisiana.
"This deserves further study."
I had heard that the first Monarch to leave never makes it to Mexico. That is why there is an interest in developing butterfly friendly habitats to allow the species to reproduce along the route. What is correct?
"There are millions of monarchs in the United States in the fall.
"Simultaneously, starting a northern latitudes, a high percentage of them are receiving the same cues to migrate rather than develop reproductively and remain residential. So, there is not a single monarch that is first to depart, and there are always some that miss the boat. Those that do not receive the cues to migrate are going to either freeze or become reproductive residents in freeze-free subtropical climates. Fall migrants have not developed sexual reproductive capacity, and do not reproduce until the spring.
"We advocate for habitat restoration because of habitat loss due to development, mowing practices, and changes in agricultural practices and land use.
"Certainly, climate plays a large role in the success of monarchs.
"Favorable wind, temperature and humidity will promote monarch health and reproductive success and will influence flight speed and trajectories. The monarch is an indicator species, and should be observed closely for impacts of climate on their migration."