The annual migration of North America’s monarch butterfly is
a unique and amazing phenomenon. The monarch is the only butterfly known to
make a two-way migration as birds do. Unlike other butterflies that can
overwinter as larvae, pupae, or even as adults in some species, monarchs cannot
survive the cold winters of northern climates. Using environmental cues, the
monarchs know when it is time to travel south for the winter. Monarchs use a
combination of air currents and thermals to travel long distances. Some fly as
far as 3,000 miles to reach their winter home!
Where Do Monarchs Go?
Monarchs in Eastern North America have a second home in the
Sierra Madre Mountains of Mexico. Monarchs in Western North America overwinter
in California.
Eastern North American Population
Overwintering in Mexico
The eastern population of North America’s monarchs
overwinters in the same 11 to 12 mountain areas in the States of Mexico and
Michoacan from October to late March.
Monarchs roost for the winter in oyamel fir forests at an
elevation of 2,400 to 3,600 meters (nearly 2 miles above sea level). The mountain
hillsides of oyamel forest provide an ideal microclimate for the butterflies.
Here temperatures range from 0 to 15 degrees Celsius. If the temperature is
lower, the monarchs will be forced to use their fat reserves. The humidity in
the oyamel forest assures the monarchs won’t dry out allowing them to conserve
their energy.
Directional Aids
Researchers are still investigating what directional aids
monarchs use to find their overwintering location. It appears to be a
combination of directional aids such as the magnetic pull of the earth and the
position of the sun among others, not one in particular.
Clustering in Colonies
Monarchs cluster together to stay warm. Tens of thousands of
monarchs can cluster on a single tree. Although monarchs alone weigh less than
a gram, tens of thousands of them weigh a lot. Oyamel trees are generally able
to support the clustering butterflies, but sometimes branches break.
Protection of Oyamel Forest
Conservation of overwintering habitat is very important to
the survival of monarchs. The Mexican Government recognized the importance of
oyamel forests to monarch butterflies and created the Monarch Butterfly
Biosphere Reserve in 1986.
Monarchs can travel between 50-100 miles a day; it can take
up to two months to complete their journey. The farthest ranging monarch
butterfly recorded traveled 265 miles in one day.
Western North American Population
Monarchs living west of the Rocky Mountain range in North
America overwinter in California along the Pacific coast near Santa Cruz and
San Diego. Here microclimatic conditions are very similar to that in central
Mexico. Monarchs roost in eucalyptus, Monterey pines, and Monterey cypresses in
California.
Western North American Population
Monarchs living west of the Rocky Mountain range in North
America overwinter in California along the Pacific coast near Santa Cruz and
San Diego. Here microclimatic conditions are very similar to that in central
Mexico. Monarchs roost in eucalyptus, Monterey pines, and Monterey cypresses in
California.
Stories of Biodiversity on the Move, Monarch Butterflies
(Danaus plexippus)
A Google Earth Tour is posted on YouTube describing the
migration of monarch butterflies, and the people that help them out along the
way. It was produced by Atlantic Public Media in cooperation with the
Encyclopedia of Life. Producers: Eduardo Garcia-Milagros and Ari Daniel
Shapiro.
See the Monarch Butterflies Migration Google Earth Tour…
Article Posted: 03/27/2020 11:57:59 AM