Flying Northward
Letter from Dr. Ellen Sharp

Journey North

Monarch Butterflies at Cerro Pelon winter sanctuary in Mexico

While driving to Toluca, Ellen Sharp encountered a could of monarchs crossing the highway north of Piedra Herrada Sanctuary.


Equinox on Cerro Pelón by Ellen Sharp
March 21, 2017

Dear Friends,

The equinox on Monday, March 20, was a bittersweet day for us; our last B&B guests of the season trickled out over the course of the day. They were a Guatemalan-Colombian couple, two British travelers, and some half Mexican half gringo families escaping the bustle of Mexico City. They slept in and sunned on the lawn before reluctantly packing up their cars. By midday our ten-bedroom home felt quiet and super-spacious for the first time since late October.

That same day was a federal holiday in Mexico, and the Cerro Pelón sanctuary continued to receive visitors, who were treated to the sight of numerous monarchs still flying about near the water source above the El Aserradero meadow. By the following day (March 21) there were noticeably fewer monarchs in residence, rangers reported, and no tourists in sight at all. They suspect that there will still be some monarchs in evidence until the end of the week.

Meanwhile, on March 21 Joel and I ran an errand to our state capital, Toluca. When we accelerated onto the 15 toll road, right there on the stretch just before the turn off to Valle de Bravo, we ran smack dab into a cloud of migrating monarchs. We sloweddown, put on our blinkers, and started counting: we spotted at least 100 butterflies between 10:11 and 10:16 am. While some were flying high, others darted dangerously low across the road way. Others were already dead on the road. They were most likely headed out from Piedra Herrada, and they were flying straight north.

It amazes me that in all of these 42 years that the wider world has
known about the existence of the monarchs’ winter colonies in Mexico, no one, as far as I know, has ever recorded their spring departure date. When you don’t write things down, memories get fuzzy. Yet in my efforts to pinpoint their departure this year, that date still seems fuzzy. Ranger Patricio Moreno thinks that some monarchs started leaving Cerro Pelón in late February. He also noted that March 11 was a noticeable departure day, as were March 16 and 17.

But these observations lead to more questions, such as: do the Cerro Pelon monarchs fly to other sanctuaries and rest before heading out? Do the El Rosario or Sierra Chincua populations swell in size before the monarchs head north en masse? Do Piedra Herrada residents, like the ones we saw flying today, stop over on Cerro Pelón? We suspect that they do, but have no way really of knowing. For such a beloved and highly-studied insect, there is still a lot that we don’t know about monarch behavior, especially when it comes to what they do here in Mexico.

Best regards,
Dr. Ellen Sharp

Co-owner of JM Butterfly B&B
Co-founder the environmental non-profit Butterflies & Their People
with Joel and Patricio Moreno Rojas.

Both located at the entry of the Cerro Pelón Monarch Butterfly Sanctuary in the village of Macheros in the State of Mexico.


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