Butterflies use internal compass to find winter home
Each fall millions of monarch butterflies travel 4,000 kilometres to Mexico, to an area just a few hectares in size. Now a team of researchers, including Queen’s University’s Barrie Frost (Psychology) has determined how they find their way.
“We found butterflies have an internal compass, a knowledge inside them, that ensures they are always flying southwest (towards Mexico) when they are migrating,” says Dr. Frost. “We also found butterflies appear to be programmed not to fly over large bodies of water or over mountains. Therefore, the Gulf of Mexico and the Rockies essentially funnel them towards their winter home.”
To determine the flight path of the butterflies, Dr. Frost and former Queen’s post-doctoral fellow Henrick Mouritsen ( now a professor at University of Oldenburg, Germany) developed a flight simulator. The butterfly is placed in a large cylinder which is open to the sky and gently blows air to keep the butterfly aloft. Using fine wires attached to the butterfly and to a computer, Drs. Mouritsen and Frost determined the butterfly, using its internal compass, always headed in a southwest direction.
To investigate this, the team moved butterflies to Calgary, a starting point much further west, and subjected them to the same test they performed in Ontario. What they found was the butterflies flew in the same southwest direction in both places, indicating they had only a compass and no map. Had they had a map and known where they were, they would have flown just east of south in Calgary which is the direction required to reach their over-wintering site from there.
In a recent study published in the Proceedings of the National Academy of Sciences Dr. Frost, and Dr. Henrik Mouritsen and Julia Stalleicken from Oldenburg, together with Ryan Norris and Rachael Derbyshire from University of Guelph, and Ole Larsen from Aalborg University, Denmark carried out studies to see if the monarchs had both a map and a compass. If creatures have a map they know where they are relative to their goal.
“I was really surprised how accurate their sense of direction is,” says Dr. Frost. “We are talking millions of butterflies successfully landing in a very small area with little deviation from their flight path.”
Dr. Frost started his butterfly research 10 years ago when he found butterflies use the sun to help them determine they are heading in the right direction. His next research project will be to determine if butterflies also use scent to ensure they find the same place they traditionally cluster in the millions in Mexico.