Monarch Populations on the Mend? After years of declining populations, there is evidence that North
Monarch Populations on the Mend?After years of declining populations, there is evidence that North American monarch butterfly populations may be growing. The annual survey of their wintering grounds in the Sierra Madre Mountains of Mexico shows that the area they are occupying has grown from 1.13 hectares (2.8 acres) in 2014 to about 4 hectares (10 acres) in 2015. This increase is even more important since they were at a record low in 2013, covering only 0.67 hectares (1.66 acres). While this is an improvement, 20 years ago they would cover 18 hectares (44 acres). Monarchs clump together so densely on trees that they are counted by the area they cover rather than by counting individuals.Monarchs are the only butterfly species known to migrate long distances annually. The North American populations spend their winters in either Mexico or California, and their summers spread throughout the US and into Canada.Populations have been harmed by activity in both their summer and winter homes. In the US, development and herbicides have greatly reduced the number of milkweeds; the plants monarchs lay their eggs on. When the caterpillars hatch about 4 days later, they spend 2 weeks feeding on the plant before undergoing metamorphosis. If there is no milkweed, there is no place for the monarchs to lay their eggs. In Mexico, illegal logging has destroyed part of their habitat. Additionally, there have been a few years of heavy rains and hail in February that have killed 50% or more of the population.In recent years there have been efforts to restore milkweed and stop illegal logging. While the efforts seem to be paying off, researchers note that monarch populations have rebounded a few times before, but never to the same levels as what they were 20 years ago. Even so, the monarch species is not in immediate danger of going extinct, because monarchs exist on other continents and islands, and they are genetically identical to their North American counterparts despite their long-term reproductive isolation.REPhoto Credit: AP – Rebecca BlackwellReferences:bit.ly/1PonXJQbit.ly/1g5gu6J1.usa.gov/24tqdrUyhoo.it/24tqdYS -- source link
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