Researchers have discovered the secrets of the monarch butterfly’s inner, genetically encoded compass that they use to determine the direction .
When the leaves fall to the ground in August, monarch butterflies all over Canada and the United States face the Rio Grande and make a beeline for Mexico. They travel some 2000 odd miles and reach their destination in the end.
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This trail is followed every year by the new generation of monarch butterflies as if it is a built-in instinct. Even though the numbers of these beautiful butterflies have diminished with time, they continue to make the annual journey.
The reason behind the slashing of the population of monarch butterflies is a reduction in the larval food source – milkweed. Recently, a group of experts claim to have cracked the internal code of the monarch butterfly’s compass.
This is a genetically determined biological GPS device of sorts. It enables the monarch butterflies to determine the direction in which they have to fly every time the fall season arrives. Two data units are encoded in this internal compass. One is the time of day and the other is the sun’s position in the sky.
"Their compass integrates two pieces of information -- the time of day and the sun's position on the horizon -- to find the southerly direction," said Eli Shlizerman, a University of Washington assistant professor.
How the monarch butterfly’s brain perceives and conceives this info remained a mystery until now.
The compass is a part and parcel of the monarch butterfly’s brain. The crux of the matter lies in how its brain processes the information and then decides how to migrate in a southwestern direction. The behavioral repertoire seems to be a constant in the nature of the monarch butterfly.
"We wanted to understand how the monarch is processing these different types of information to yield this constant behavior -- flying southwest each fall," said Shlizerman, who is lead author of the study that was published in the journal Cell Reports.
The large complex eyes of these butterflies determine the position of the sun in the sky. However, this is not enough to indicate the direction to fly towards.
The time of day is the missing link here. Monarch butterflies have an internal clock that allows the expression of certain genes related to navigational abilities.
Thus their patterns of structure and function are fixed and lead many of these gorgeous insects to fly southwest each fall. The antennae of the butterflies collect all the necessary information and then relay it to the brain.
Light is interpreted via the eyes. A simulation model of this situation was created by the scientists. The control centers in the brain were studied in depth.
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There were two neural pathways, one of them being inhibitory and the other being excitatory. The balance between these two mechanisms determined the navigational strategies of the butterflies. These brain networks keep the monarch butterflies from swerving off course in the journeys they make each year.