HORTICULTURE

Detailed explanation-1: -The eastern population of North America’s monarchs overwinters in the same 11 to 12 mountain areas in the States of Mexico and Michoacan from October to late March. Monarchs roost for the winter in oyamel fir forests at an elevation of 2, 400 to 3, 600 meters (nearly 2 miles above sea level).

Detailed explanation-2: -Scientists measure the size of each colony or overwintering site by measuring the area of the trees/land that is occupied by monarchs. With these measurements, they use an estimate of between 10-50 million monarchs per hectare of land occupied.

Detailed explanation-3: -They migrate each winter from the northern United States and southern Canada to oyamel fir forests on high-elevation mountaintops in central Mexico. Scientists estimate the population size by measuring the area of trees turned orange by the clustering butterflies.

Detailed explanation-4: -Climate change, pesticide use, and habitat loss in both Mexico and the U.S. threaten the eastern monarch population (which overwinters in Mexico) and the western population (which primarily overwinters in California).

Detailed explanation-5: -Monarch butterflies must migrate because they cannot survive long cold northern winters. When they arrive in Mexico, they huddle together in on Oyamel fir trees. Each tree may be blanketed in tens of thousands of ‘roosting’ butterflies.