March 14, 2013 10:10 ET

Monarch Butterfly Survey Points to Lowest Numbers in 20 Years

ZITACUARO, MEXICO--(Marketwire - March 14, 2013) -

Editors Note: There is a photo associated with this press release.

The percentage of forest occupied by monarch butterflies in Mexico, used as an indicator of the number of butterflies that arrive to that country each winter, reached its lowest level in two decades. According to a survey carried out during the 2012-2013 winter season by the WWF-Telcel Alliance, and Mexico's National Commission of Protected Areas (CONAP), the nine hibernating colonies occupy a total area of 2.94 acres (1.19 ha) of forest - representing a 59% decrease from the 2011-2012 survey of 7.14 acres (2.89 ha).

The survey was conducted in five hibernation colonies inside the Monarch Butterfly Biosphere Reserve (two in the State of Mexico, and three in Michoacán), and four colonies outside the reserve (three in the State of Mexico, and one in Michoacán). To carry out the monitoring, bi-weekly tours are conducted in the premises of the colonies which have been surveyed historically, by calculating the perimeter and systematizing the data with spatial analysis software.

"Colonies located inside the reserve occupied 78.2% of the total area (0.93 has), while colonies outside of the reserve occupied the 21.8% (0.26 has). The largest colony was found in El Rosario, Michoacán, occupying 0.63 has (52.9% of the total area). For the first time the survey registered a colony in the indigenous community of San Pablo Malacatepec, State of Mexico, with a total of 17 properties with colonies of hibernating monarch butterflies in Mexico," said Luis Fueyo, Commissioner of CONANP.

The latest decrease in monarch butterflies is likely due to a decrease in the milkweed plant (Asclepias) - a primary food for monarchs - from herbicide use in the butterfly's reproductive and feeding grounds in the US, as well as extreme climate variations during the fall and summer affecting butterfly reproduction.

"Extreme climate fluctuations in the US and Canada affect the survival and reproduction of butterflies. The monarch's lifecycle depends on the climatic conditions in the places where they develop. Eggs, larvae and pupae develop more quickly in milder conditions. Temperatures above 95ºF can be lethal for larvae, and eggs dry out in hot, arid conditions, causing a drastic decrease in hatch rate," said Omar Vidal, Director General of WWF-Mexico.

The butterflies that migrate to Mexico feed on milkweed in the soy and corn fields of the US. The use of herbicides to eradicate this plant, considered a toxic weed for cattle, has reduced the amount of available milkweed by up to 58%. "The conservation of monarch butterflies is a responsibility shared by Mexico, the US and Canada. By protecting its sanctuaries and practically eliminating large-scale deforestation, Mexico is doing its part. It is necessary that the US and Canada also do their part and protect the habitat of the monarch in their countries," Vidal added.

"The WWF-Telcel Alliance celebrates 10 years of supporting the conservation and sustainable management of the natural resources of Mexico and the well-being of the people that depend on those resources. The Alliance has worked with local communities, the government and civil society to conserve the monarch forests in a way that benefits nature, local populations, and those that visit the Reserve. Among these projects is the development of sustainable business such as tree nurseries, mushroom production modules, and handicraft production, as well as the improvement of tourist infrastructure at El Rosario, and Cerro Prieto in Michoacán," said Marcela Velasco, Director of Marketing at Telcel.

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