Butterfly migration is very common for Lepidoptera species around the world. These journeys' ensure genetic survival of the species given any disadvantaged climate conditions. Butterflies that migrate include several Danaidae butterfly species. These Danaidae are often referred to as milkweed butterflies:
Other butterfly species around
the world that migrate include:
|Photo: Rinus Baak|
All these butterflies migrate for different reasons including dry or winter climates, heavy rains or monsoon season.
This page covers the Monarch Butterfly migration, which the Monarch migration is unique. Even greater strides are taken by the Monarch species to ensure survival when compared to other butterflies. Much of what has been learned of this butterfly migration is through aerial and land observation, as well by placing wing identification tags on an individual butterfly. Monarchs are also part of the Danaidae species and probably the most famous Milkweed butterfly.
Keep in mind these points while discovering this amazing journey:
The Monarch butterfly migration begins in late summer. Winter is coming and the Monarch must leave the United States and Canada for two reasons:
Both the male and female Monarch butterfly will stop any reproductive activity. The male will no longer produce sperm, the female will no longer produce eggs. Although still active, the butterfly's focus now is to prepare for the 2500 - 3000 mile journey that lies ahead. Before traveling lipids, or sugars from their nectar sources, are built up and stored as fat in the abdomen to provide them energy for this long trip.
The autumn sun begins to change angles and drop in the sky cuing the butterfly of shorter days. It's time to start migrating south. The Monarch follows the sun's position and detects day lengths through organs on their antennae and through visual senses. Using these, and the biological clock in their brain, the butterfly can calculate their flight by following the sun from east to west in the sky.
Needing the suns orientation, on cloudy days the Monarch butterfly is able to navigate using polarized light with their sensitive compound eyes. Polarized light very simply stated is light waves that vibrate repeatedly one direction.
This generation of Monarchs is exceptional to other generations. Monarch butterflies born in spring and summer live 2 - 4 weeks. Any butterfly making this migrating trip is genetically programmed live 9 months. They are called the Methuselah Butterfly or Methuselah generation.
Approximately three-hundred million butterflies will make this butterfly migration. It takes about eight months one way. Most butterflies average 50 miles a day, some fly up to 80 miles. With their wings having aerodynamic capabilities, a butterfly is a precision flying machine. They take advantage of gliding on currents of warm thermal air to help save energy.
Monarch Butterflies west of the Rocky Mountains will fly toward
the coast to California and then directly south.
Butterflies east of the Rockies
take a different route for the butterfly migration
|Photo: Michael Schmeling|
By October those butterflies east of the Rockies are at two prominent areas along the Texas border. Those Monarch's coming from the mid-western plain states come together in the Guadalupe Mountains in south-western Texas. Those Monarch's coming from the eastern states will gather at the lowest southern tip of Texas. At both the Guadalupe Mountains and the far southern tip locations butterflies merge creating a fly-away, each about 50 miles wide.
Butterflies migrating down the east coast also take the more direct route of crossing over the Gulf of Mexico. For those butterflies opting this route, it is the longest leg of their journey. Wing identification tags have noted that some butterflies do fly the entire body of water without stopping. Other butterflies have been observed stopping and resting for the night along oil rigs and on cue, when the sun comes up they resume flying.
Butterflies then follow the path of the Sierra-Madre Oriental Mountains that follow down through central and the eastern Mexican coast. Oddly, the butterflies change to a blunt south-westerly direction. This new direction takes the Monarch's to the Sierra Gorda Natural Reserve.
Monarch Butterflies have magnetite in their thorax and abdomen areas along with the base of their wings. The Sierra Gorda is rich with deposits of heavy metals such as gold, iron, manganese and more. Scientists think the key for this abrupt direction change is that the butterflies are 'magnetized' to this trans-volcanic area seeking out the magnetite from these forest reserves.
From the forests the butterflies ultimate destination is about 70 miles west of Mexico City to the Oyamel Fir Forest. Within the Oyamel Fir Forest there are 12 remote areas that will support these massive butterfly colonies. These areas provide a critically balanced micro-climate for survival which include:
The Monarch butterflies begin to arrive in the Oyamel Fir Forest early November. With temperatures just above freezing (35 - 60 degrees Fahrenheit), butterflies cluster on tree branches for warmth for four months. This strategy also helps the colony endure most bad weather. These temperatures are warm enough that butterflies won't freeze and cool enough where little energy is spent while in their semi-hibernation state.
There still is the possibility that a colony can be wiped out completely during their semi-hibernation period. For example, should temperatures drop below freezing for an extended period of time, or excessive moisture combined with dropping temperatures, a colony will die. Any butterfly or butterflies that do survive fly to other colonies.
|Photo: Rinus Baak|
Because of the massive weight tree branches often times bend.
The Males begin to produce sperm and the females produce eggs. The Monarch's biological clock cues them that the days are getting longer and all begin mating. The female's also get needed protein from the sperm pack to assist with additional energy for the butterfly migration back north.
Males that have mated will begin to die. About late March the female makes her way into southern Texas where the Milkweed has begun to grow for the new season. The female Monarch will lay her eggs on these butterfly host plants and die after doing so. The new spring generation of Monarch butterflies live 2 - 4 months, continue mating creating the summer generation that will also live 2 - 4 months.
As the path of Milkweed continues to grow north, this butterfly migration creates about four generations of Monarch's. Throughout this 8 month period these great, great grandchildren of the previous year's Methuselah generation will be the parents to the new Methuselah generation.
Once again, these Methuselah butterflies that live 9 months will be called to duty to ensure the survival of the Monarch butterfly species.
|Photo: Natures Paparazzi|
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