Nature's Tiniest Jet-Setters

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"Monarch in flight" by Dwight Sipler/FLICKR (cropped and used under CC BY 2.0)

Every winter in Chicago, I wish I were a Canada Goose. Not because of their overall majesty and awesomeness. It is because, quite frankly, who wouldn’t want to pack up and get out of town when the temperatures plummet relentlessly below freezing for four months straight? If you ask me, these geese have a brilliant strategy.

This may turn out to be another case of “the grass is always greener on the other side.” However, my curiosity about animal migration took me down one of the most fantastic Internet rabbit holes I’ve encountered. Migration turns out to be no easy task.

Birds are probably the most talked about migrators and many migrate really long distances, often traveling across hemispheres or large bodies of water to complete their journeys. I’ve always pictured migratory species as powerful sumo-wrestler type birds—kind of like the Canada Geese actually, who can withstand the demands of a several thousand-mile journey.

However, some species of hummingbirds, tiny little hovering creatures, migrate every year between Canada and Mexico or Central America. For many hummingbirds, this means that they have to cross the Gulf of Mexico, an over 500-mile trip that they usually complete non-stop! But tiny birds are not the only bite-sized creatures that go the long haul.

For instance, one species of dragonfly, appropriately called “Globe Skimmer,” migrates between the southern tip of India, stops over in the Maldives and Seychelles, before ending up along the east coast of Africa, thus moving from one continent to another over an entire ocean. The globe skimmer is the current record holder for the longest migration route by insects, ultimately covering a roundtrip distance of at least 8,700 miles. Check out a cool TedTalk about the discovery of this dragonfly migration below:

But perhaps the most famous of the insect migrators is the monarch butterfly. The monarchs that live near the Great Lakes, for example, may travel distances of over 2,000 miles to reach their southern winter home destination in Mexico! An interesting feature about these butterflies is that not all monarchs migrate.

This fact was key to a study published in the journal Nature this past year that set out to determine the genetic basis behind monarch migration. The study revealed that what separates migratory from non-migratory monarchs is essentially a single gene, called Collagen IV α-1, which is involved in muscle development (morphogenesis) and function. Even more strikingly, a single amino acid distinction in the Collagen IV α-1 protein gives migrating monarchs an edge, ultimately allowing them to be more efficient during flight, as compared to the non-migrating monarchs.

What is particularly insane about the monarchs and dragonflies, unlike most bird migrators, is that the guys who migrate in the winter to warmer destinations will lay their eggs, essentially “retire” and ultimately never return to where they came from. Rather, subsequent generations of these insects will migrate back to the destination from where their parents, grandparents or even great-grandparents originated. Thus, for these insects, the full migratory loop occurs over several generations. What is striking is that migration really seems to be “encoded” in these little beasts.

Answers are starting to emerge as to how certain species are able to migrate and perhaps even some clues as to why. Both the monarchs and dragonflies rely to some extent on tail winds to essentially glide for some parts of their journeys. Exactly why these guys migrate remains a puzzling but fascinating phenomenon of nature. What signals that it is time for migration, and how might this translate into an evolutionary advantage for these creatures? The answer might lie in the changing seasons, the angle of the sun’s rays and food availability, but this is an active and ongoing area of research and one that I’ll be journeying through for a very long time. 

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