New research provides scientists with details about the migratory patterns of monarch butterflies and their endangered habitats.
The Monarch butterfly (or Danaus plexippus) is a popular creature worldwide. Perhaps the most recognized and quintessential butterfly, the Monarch can be found as far south as Mexico and as far north as Canada. In fact, each year millions of these creatures begin their migration from Mexico to the great white north, breeding and laying eggs as they go. Most of these butterflies will stay in the southern and central areas of the United States, laying their eggs on milkweed plants. Some aspiring generations of Monarchs will travel all the way to Canada to reproduce.
In recent years, the milkweed population of the United States and Canada has been damaged, creating problems for this amazing Monarch migration. In fact, the International Union for the Conservation of Nature (IUCN) has declared this migration “threatened” due to milkweed destruction, and Canada has had the Monarch butterfly on their list of species of “special concern” since 1997.
To find out more about this species and why they migrate the way they do, new research is being conducted by the University of Guelph, led by Prof. Ryan Norris, Department of Integrative Biology, former graduate student Nathan Miller, and Environment Canada. Their research shows how these Monarchs recolonize even the northern most reaches of their breeding grounds. With this information, Norris´ team hopes to preserve the species as well as protect their food, habitats, and breeding grounds.
This information is critical in helping researchers understand why the Monarch migrate this way and furthermore, how well they will be able to withstand environmental changes, such as habitat loss.
“It wasn´t clear where these individuals were born and how long they lived,” Norris said. “One possibility was that some monarchs that reach places like southern Ontario could have migrated all the way from Mexico.”
To unravel this mystery, Miller sampled Monarch species from 44 sites across Ontario, Canada and the northern US. He then analyzed chemical markers, or stable isotopes, as well as wing wear to determine the birthplace of each butterfly. This research showed the team that as much as ten percent of the test subjects in the northern breeding range had traveled directly from Mexico. This is no easy feat for any living creature, and the results of the finding were nothing less than extraordinary to the team.
“This is an incredible journey from an animal this size, especially if you consider that these butterflies are little more than eight months old and have travelled thousands of kilometers over their lifetime,” Miller said.
The other 90 percent of Monarchs studied by researchers were first-generation butterflies born that spring while their parents were en route to the north. While researchers had previously thought the most fertile area for Monarchs was the southern area of the United States, the new evidence suggests that many of the butterflies had been born further north, in the central US.
“Linking these periods of the breeding cycle provides us key information for conservation and identifies highly productive regions that fuel the migration further north,” said Norris.
Norris and Miller´s team published their results in the journal PLoS One.
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