The monarch is a large orange butterfly whose wings have prominent dark veins and two rows of white spots at the edges, and the body is dark. The wingspread ranges from 89 to 105 millimeters (about 3.5 to 4 inches). Males are bigger than females and have a visible dark spot over a vein on their hind wings.
Where they Live:
In North America the eastern population (east of the Rocky Mountains) migrate north to the United States and Canada in March from the mature oyamel fir forests in the mountains of central Mexico. The fall migration back to overwintering sites in Mexico is from August to November. The western population (west of the Rocky Mountains) travels inland to breeding areas throughout the west from February to March. They migrate to overwintering sites within 2.4 km of the California coast between Mendocino County and Baja, from September to November. They overwinter on eucalyptus trees (Eucalyptus globulus), Monterey pines (Pinus radiata), and/or Monterey cypress (Cupressus macrocarpa) at sites that are cool (but above freezing), sheltered from wind, with a moisture source and exposure to filtered sunlight. The lower slopes of valleys, bays and inlets support the largest numbers. Monarchs are typically found in open grass areas during the breeding season.
According to the USFWS, monarch populations across North America have declined by 80 percent over the past 20 years. Among the many potential reasons for population decline are loss of habitat at breeding and overwintering sites, pesticides, disease, timber harvesting at overwintering sites and climate change.
The low monarch wintering numbers in 2013 and 2014 resulted in an April 2014 statement of shared concern by leaders of the United States, Mexico and Canada. The monarch butterfly was specifically included in the 2014 Presidential Memorandum on pollinator conservation. Additionally, the FWS is conducting a status review to determine if protection under the Endangered Species Act (ESA) is warranted for monarchs. A decision is expected to be announce in December, 2020. Updates for monarch ESA listing status can be found here.