Monarch Butterfly - Danaus plexippus - facts and video

The monarch butterfly may be the most widely recognized of all American butterflies with its distinct orange, black, and white wings. While beautiful, this coloring actually sends a warning to predators that the monarch is foul tasting and poisonous.

Found throughout the United States, as well as Mexico and Canada, one of the most notable characteristics about the monarch is the astonishing 3000 mile journey some will make in the fall to their wintering grounds in the Sierra Nevada Mountains of Mexico or to southern California, depending on which part of the United States or Canada they migrate.

Diet

In their larval stage monarch caterpillars feed almost exclusively on milkweed and as adults get their nutrients from the nectar of flowers. The monarch will always return to areas rich in milkweed to lay their eggs upon the plant. The milkweed they feed on as a caterpillar is actually a poisonous toxin and is stored in their bodies. This is what makes the monarch butterfly taste so terrible to predators.

Population and Behavior

Millions of monarch butterflies make the trip down to Mexico to roost for the winter. During the migration tens of thousands will land on a single tree in certain areas along their migratory path. Monarchs can produce four generations during one summer. The first three generations will have life spans from 2-6 weeks and will continue moving north. During this time they will mate and have the next generation that will continue the northward migration. The fourth generation is different and can live up to nine months. These are the butterflies that will migrate south for winter to either Mexico or southern California.

Range

Wherever there is milkweed there will be Monarch butterflies. The monarch is widely distributed across North America, from Central America northwards to southern Canada, and from the Atlantic to the Pacific coasts. Three geographically distinct populations make up the total North American range of the species, one each both east and west of the Rocky Mountains, and one Central American. Each of these populations has a distinct migratory pattern. Monarchs that live west of the Rocky Mountains will migrate to southern California for winter while monarchs that live east of the Rockies will migrate to Mexico. See a monarch butterfly range map >>

Global Warming and Other Threats

It is predicted that one of the many effects of global warming will be wetter and colder winters. If they are dry, monarchs can survive below freezing temperatures, but if they get wet and the temperature drops they will freeze to death. Because hundreds of millions of monarchs are located in such a small area in the Sierra Nevada of Mexico during the winter, a cold snap there could be devastating.

As the world warms, suitable habitat will begin to move northward resulting in a longer migration. This means the monarchs may be forced to adapt and produce another generation to reach further north. It is uncertain whether they will be able to do so. Therefore, few monarchs may be able to make the longer trip back to Mexico for winter.

Other threats to the monarch include habitat loss and loss of milkweed which they depend upon as larva to survive. Illegal logging remains a problem today in Mexico in protected areas and is devastating monarch winter habitat.

Reasons For Hope

IUCN has designated the monarch migration a threatened phenomenon. In 1986, the Mexican government created the Monarch Butterfly Biosphere Reserve which protects 62-square miles of forests in the Sierra Madres where hundreds of million of monarchs spend each winter. The Biosphere Reserve was expanded to include 217 square miles in 2000. Local organizations are also working to stop the illegal harvesting of trees on the reserve to protect wintering habitat.

Legal Status/Protection

• IUCN has designated the monarch migration a threatened phenomenon.

How You Can Help

• Help butterflies and other wildlife by adopting an imperiled animal from our Wildlife Adoption Center.
• Take Action for habitat and Wildlife at our Wildlife Action Center.

For additional information

• Learn more about Defenders of Wildlife's work on Global Warming.