The monarch butterfly is on the verge of extinction, as scientists put it on the list because of its rapid decline.
Stuart Pimm, an ecologist at Duke University, was not involved in the new listing. One of the most well-known butterflies in the world is this one.
The monarch butterfly has been added to the "red list" of threatened species by the International Union for the Preservation of Nature.
The group estimates that the population of monarch butterflies in North America has declined between 22% and 72% over the last decade.
The rate of decline is what we're worried about. It's easy to see how quickly this butterfly could be in danger.
The population of monarch butterflies in the eastern United States has fallen between 85% and 85% since the 1990s, according to Haddad, who was not directly involved in the listing.
Millions of monarch butterflies migrate the longest in the world.
The butterflies migrate to the north after wintering in the mountains of central Mexico. At the end of the summer, the offspring go back to Mexico.
Anna Walker was involved in determining the new listing and said it was a true spectacle.
A small group of people spend winters in California and then move to other states in the spring and summer. The decline of this population has been more pronounced than that of the eastern monarchs.
The Xerces Society, which monitors the western butterflies, said that the butterflies are in danger due to loss of habitat and increased use of pesticides.
She said that people can help by planting milkweed, a plant that the caterpillar depends upon.
Monarch butterflies in Central and South America are not considered to be in danger.
Several environmental groups believe that the monarch butterfly should be listed in the US.
New estimates for the global population of tigers are 40% higher than the most recent ones.
According to the new figures, there are between 3,726 and 5,578 tigers in the world.
According to Miquelle, tiger populations have increased in Nepal, northern China and perhaps in India in the past 10 years. They are still considered to be an "endangered" group.