Monarch butterfly numbers down for second year in Mexico

Monarch butterflies spend the winter clustering in pine and fir trees in central Mexico

The population of monarch butterflies in Mexico has gone down for the second consecutive year, government officials say.

In the autumn, the orange and black butterflies migrate from Canada and the US to central Mexico, where they hibernate in pine and fir trees.

Every year, scientists measure the area in which the monarchs cluster.

Mexico's Commissioner for Protected Areas Alejandro del Mazo said numbers had diminished by 14.8% this winter.

Fewer colonies

Speaking at a news conference in Mexico City, officials said nine colonies of monarch butterflies had been recorded in Mexico in the 2017/2018 winter months, down from 13 last year.

Mr del Mazo said that "extreme meteorological events" could be a leading cause in the decline of the numbers of Monarch butterflies overwintering in Mexico.

World Wildlife Fund's Mexico Director Jorge Rickards said a particularly busy hurricane season across the insects' migration route, which stretches almost 5,000km (3,100 miles) from Canada to Mexico, could be a factor.

"These climate phenomena without a doubt have an impact on the migration," he said.

Monarchs are one of the few insects to migrate such a vast distance and scientists recently found that they use a kind of internal solar compass to guide them.

While the area in which the monarch butterflies hibernate in central Mexico went up in the winter of 2015/16, the overall trend for the past two decades has been a downward one.

In 1996/97 the butterflies could be found in about 18 hectares of forest in the states of Mexico and Michoacán. This past winter, only 2.48 hectares had monarch colonies.