Monarch butterflies possess highly-accurate internal compasses that guide them during their long-distance migrations. Now, researchers believe they have determined how the directional systems within the flying insects work.
Every year, as summer turns to autumn, monarch butterflies from across the United States begin a 2,000-mile journey to the warm climate of central Mexico.
University of Washington investigators studied how the insects are able to sense which direction to fly — southwest — during their yearly journey. Researchers believe the internal compass of the insects is able to determine the position of the sun as well as the time of day. Together, this data allows the butterflies to head in the right direction.
Biologists have understood for several years that monarch butterflies utilize these two pieces of information to orientate themselves. However, the process by which their brains receive and process this data was unknown — until now.
Like humans, monarchs possess an internal clock, mediated by the natural rhythms of clock genes. In the body plan of the colorful insects, the workings of this timekeeping system takes place within the antennae. This information is then fed to the brain for processing and analysis. When combined with information from the large eyes of the insect, the tiny animals are able to determine direction.
“We created a model that incorporated this information — how the antennae and eyes send this information to the brain. Our goal was to model what type of control mechanism would be at work within the brain, and then asked whether our model could guarantee sustained navigation in the southwest direction,” said Eli Shlizerman of the University of Washington.
Populations of monarch butterflies have plummeted in recent years, due to the loss of milkweed — the sole source of food for monarch larvae.
Investigators found that, when these insects are thrown off-course during their journey, they do not simply turn the fastest direction toward their desired path. Instead, the animals rely on a specific separation point to determine whether they should turn left or right. The tiny creatures will not cross this point in their field of vision when altering their course.
When the time comes to return back north in the spring, these mechanisms simply switch direction, guiding the brightly-colored animals toward the northeast.
Analysis of the internal compass of monarch butterflies was published in the journal Cell Reports.