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Creature Feature - Monarchs
The MONARCH BUTTERFLY (Danaus plexippus) is native to North and South America. Monarchs belong to the Family Nymphalidae and Subfamily Danainae which includes milkweed butterflies. Their Genus is Danaus and Species is plexippus.
Monarch caterpillars (larvae) are specialist herbivores, meaning they feed on specialized plants. Can you think of other animals that are herbivores?
Monarch caterpillars eat only plants in the milkweed family (Asclepiadacea). They gain an important toxin from milkweed that protects them from many predators (caterpillars eating Asclepias curassavica - right). Most birds know that eating monarchs will make them sick so they steer clear. However, there are a few types (species) of birds that can tolerate the toxin in monarch butterflies and their caterpillars. Though monarchs are not safe from all predators. Their larvae and chrysalides (pupae) can be parasitized by parasitoides, most commonly the tachinid fly or parasitic wasp. Monarchs can also be infected with Ophryocystis elektroscirrha or OE which is a protozoan spread by infected adult monarchs through contact. Although we might prefer that all monarch caterpillars become healthy butterflies, parasites are a natural part of maintaining balance in the ecosystem.
AN AMAZING MIGRATION ~ Monarchs have three to four generations of offspring each year. In the fall, the fourth generation flies (migrates) to warmer climates to spend the winter (November to March) as an adult butterfly. Can you think of other animals that migrate? The life span for adults depends on if they migrate. For example, the fourth generation can live up to 9 months but the earlier generations live only two to five weeks.
There are primarily three populations of monarch butterflies worldwide. They include the EASTERN MONARCHS (breeding east of the Rocky Mountains), the WESTERN MONARCHS (breeding west of the Rocky Mountains), and a non-migratory population breeding in southern Florida, Hawaii, the Caribbean Islands, and Central and South America. Monarchs have also been introduced in Australia.
The eastern monarch population is famous for its long distance migration. Monarchs may travel up to 2500 km from as far north as Canada to wintering sites in the mountains of central Mexico. They spend their winter in the oyamel fir forests on branches that help them stay not too cold and not too warm.
The western monarch population migrates shorter distances to winter homes along the central and northern coast of California (a cluster of migrants - left). They may travel from as far south as Arizona or from as far north as Canada or Washington. They primarily utilize eucalyptus trees along the coast.
Once spring arrives, the winter butterflies begin to mate and leave their winter homes. These 4th generation winter survivors are the reason we have healthy first generation caterpillars in our gardens in spring and early summer. Without these amazing migrants, we wouldn't have new generations of monarchs to complete the yearly cycle.
That is why it is really important that we encourage everyone to plant milkweed in the garden and in nature areas. Monarchs are declining in numbers and they need our help. Don't use chemicals in the garden and remember, "If you plant it, they will come!"
One of the other ways we can help to protect monarchs is through research and conservation of their migration corridors and winter homes. Tracking the movements of monarchs through tagging (a sticker on the wing - left) helps us to learn about their migration behaviors. If you recover a dead monarch with a sticker and call the phone number, researchers can learn where it started, where it died, how far it traveled, and how long it lived. This data will help us protect all monarchs.
Monarch Overwintering Sites in California