Migratory Behavior
Of The
Monarch Butterfly
The awesome sight of hundreds of monarch butterflies flying by inspires a feeling of wonder in all who are lucky enough to see such a beautiful sight. Many do not know the ordeal that these creatures must undergo during their life span. The migration cycle of the monarch presents numerous obstacles in
which many lose their lives. No one truly understands why these creatures make such a dangerous
journey, but there are many hypotheses as to the reason why.
Life/Reproduction Cycle
A monarch butterfly goes through a complete metamorphosis involving four sages: egg, larva (or
caterpillar), pupa and adult. In addition, each individual monarch contributes to a larger population life cycle, involving many generations. The fall migrants are usually 3 or more generations removed from
the monarchs that overwintered in Mexico during the previous winter. In other words, each fall the last generation of the monarchs must navigate to a location up to 2000 miles away, which they’ve never
visited.
As they migrate north in the spring, monarchs lay eggs on milkweed along the way. These larvae appear in the southern return path in March and early April. This generation will also migrate North following their parents. The reproductive cycle continues and by August to early September, three to four generations will have evolved.
It would be nearly impossible for an individual monarch butterfly to complete this entire migratory cycle. Because of this, their rapid system of reproduction is of great importance to the survival of the species and the completion of the migratory cycle from year to year.
Migrational Pattern/Behavior:
The migration of the monarch butterfly begins in Canada and the northernmost parts of the United States. the fall migration begins in late August ending in the months of November and December. The destination of the butterflies lies in Central Mexico, in the Oyamel forests. Traveling in a southwesterly direction, the monarchs fly east of the Great Lakes and south-southwest in areas west of the Great Lakes. Those that reach the Gulf of Mexico follow the coastline in a continuous stream. They continue in a southwest direction eventually reaching the overwintering site in the Transvolcanic Plateau of Mexico. As many as 300 million spend the winter there.
During the migration, monarchs encounter many dangers. These dangers include storms, predators, humans, cars and simple fatigue. This migration takes up to three generations to complete! The exact migratory path is still being plotted today by scientists.
The monarchs travel approximately 50 miles per day and feed on flowers to gain carbohydrates
from nectars. Monarch speed flights have been measured at 12 miles per hour. They roost in large clusters in the branches and trunks of the oyamel trees. In mid-February, the monarch’s mating behavior begins. By the end of February, some of the monarchs begin moving northward, by mid-March the roosts are empty. 40-60 percent of the monarchs die during their stay in Mexico. During the spring migration, the monarch butterflies return to their homes in Canada and the northern most parts of the United States.
Conservation
“No other animal is more typical of a healthy environment, nor more susceptible to change, than a butterfly” (Feltwell 1986). Monarchs have no control over what happens to their environment, they can only respond to what changes occur, which usually means either surviving or dying. Humans are the ones who have the most control over what will happen to the monarch butterfly population and the biggest problem that the monarchs face is the loss of habitat.
There are only about a dozen known wintering sites in Mexico. Each site is approximately 7.5 acres and contains millions of butterflies. Damage to even one site would be catastrophic to the monarch population. Only two of these sights are well protected from logging. If the roost sites are destroyed, monarch populations are likely to decline. Protection of the roost sites will be difficult since
preservation of these sites and the monarch will conflict with the increasing needs and changing priorities of a growing Mexican population.
Milkweed, the host plant of the monarch, is also a concern. In Canada, milkweed has been declared a noxious weed. This means that the plant is considered illegal and cannot be allowed to grow on private or public lands in Canada. Although not labeled noxious in the states, farmers consider the plant a nuisance to crops and often use herbicides to control it along with other weeds. More and more roadsides are being planted in grass instead of being allowed to overgrow with wildflowers and weeds. The result is that the butterflies have fewer places in the wild to find nectar and lay eggs.
Conclusion
So what can be done to help preserve the monarch population? The most important issue is to stop the destruction of the monarch’s habitat. One thing that we can do on our own properties is to plant Milkweed and Butterfly Weed. Make your backyard a monarch preserve and cater to these amazing creatures before it’s too late.
Monarch butterflies are incredibly fascinating creatures. Only recently have their life and migratory cycles been studied and recorded. We hope that this glimpse into the life of the monarch butterfly has helped you to appreciate more than just their breathtaking appearance.
(check out http://butterflywebsite.com/Articles/uminn/monarchs.html for more information)
