Researchers Understand Monarch Butterfly’s Internal Compass And Crack Its Migration Mystery

Researchers Understand Monarch Butterfly's Internal Compass And Crack Its Migration Mystery

Each year, the migratory monarch butterfly embarks on an extraordinary journey from eastern North America to central Mexico. A multidisciplinary team of scientists has now created a model circuit that finally explains how these insects are able to navigate across such vast distances.

In a study published in the journal Cell Reports on Friday, scientists from the University of Washington, Massachusetts and Michigan announced that they have modeled the neural control mechanisms in the butterfly’s brain, solving the mystery of how monarch butterflies are able to navigate through vast distance during their annual migration.

Leading researcher Professor Eli Shlizerman said that as a mathematician, he wanted to understand how the creature processes different types of information during their long-distance migration, and what people can learn from such systems.

Monarch butterflies watch the sun, but that’s not enough to lead them where they need to go. They also need the time of day, the study said. They have a kind of internal clock that keeps track of the daily go-round.

Model shows that both time of day, position of the sun are key

As part of their research, Shlizerman’s team developed a model of how the monarch butterflies’ brains are able to use information sent by the eyes and antennae to make it to their intended destination. The creatures use their large, complex eyes to track the position of the sun and the internal clock located in their antennae to know the correct time of day.

This information is sent to the brain via neurons, and their models used two neural mechanisms, one of which was inhibitory and another that was excitatory, to control signals sent by the antennae’s clock genes. A similar system was used to determine the position of the sun from signals sent by the eyes, and the combination of these systems helped the brains of the butterflies determine which direction was southwest.

Taking the best route, not the shortest

Furthermore, the model suggests that the monarchs do not necessarily take the shortest path to get back on the right path when course corrections are needed. Rather, the model demonstrated that they have a separation point that determines if the insects needed to take a right or left turn in order to head in a southwesterly direction. If the butterfly gets off course, it will innately turn to the direction which does not require it to cross the separation point.

“The location of this point in the monarch butterfly’s visual field changes throughout the day, and our model predicts that the monarch will not cross this point when it makes a course correction to head back southwest,” said Shlizerman. “In experiments with monarchs at different times of the day, you do see occasions where their turns in course corrections are unusually long, slow or meandering. These could be cases where they can’t do a shorter turn because it would require crossing the separation point.”

The model also indicated that the same mechanisms are reversed when the insects need to make their way back to the northeast in the spring. To make the internal compass point in the opposite direction, the neural connections that transmit information about the time and the position of the sun are flip-flopped, making it easy for the creatures to complete the migration in reverse.