Monarch butterflies (Danaus plexippus) are like the grandparents of the butterfly community, traveling south to warmer weather during winter months, and heading north again when it starts to warm up in the summer. Monarch butterflies are easy to identify, with bright orange and black coloration on their wings. Though the underside of the butterflies’ wings are less brightly colored to allow more camouflage while the animal is at rest, the fluorescent orange serves as warning coloration. The color screams to predators, “I’m poisonous, don’t eat me!”. Monarch caterpillars feed exclusively on milkweed plants, which produce a toxin in their bodies that remains in their system after metamorphosis into a butterfly.
Though most of these recognizable butterflies live east of the Rocky Mountains, there is a population that resides to the west. Probably more familiar to most, the eastern populations of monarchs spend the summer in the northern states of America, as well as Canada. When it starts to cool, around August for the northernmost butterflies, they migrate an incredible distance to Mexico.
The monarch butterflies that live west of the Rocky Mountains do not travel quite so far. Most travel to the coast of southern California, including the Channel Islands and Catalina Island, while some make it to Baja or Mexico. Some monarchs stay in southern California year round, while others migrate back north to northern California or British Colombia, Canada.
Regardless of their origin or destination, the migratory abilities of monarch butterflies are impressive. Monarchs can travel between 50 and 100 miles a day, with the longest recorded distance at 265 miles in one day! Some monarchs fly as far as 3,000 miles to reach their winter site. For most monarchs, the trip is only one-way. They have never migrated before, and won’t again. So, how can they know how to get south, or north for their one lifetime trip? This phenomenon is still being researched, but several hypotheses exist to explain their directional abilities. One hypothesis suggests that monarchs compare the position of the sun in the sky to their biological clock. That is, they know where the sun should be based on what time their biological clock tells them it is, and then they use the angle of the sun to navigate to their destination. Another recently proposed hypotheses contemplated what butterflies do when it’s cloudy if they use the sun for navigation. As it turns out, monarchs have a backup navigational system in the form of an internal magnetic compass. This means that on cloudy days when they can’t use the sun for directional information, they can utilize the Earth’s magnetic field to stay on course. However, their primary navigational tool is thought to be the sun. Google Maps has nothing on monarch navigation!
