Monarch Butterfly Migration | Journey North Citizen Science Project: Tracking Spring and Fall Monarch Butterfly Migration

Monarch Butterflies

Monarch Migration News: November 24, 2015
By Elizabeth Howard

Please Report
Your Sightings!

The overwintering season in Mexico is now underway. The population will be measured in December and predictions are promising — monarch numbers may have doubled since last year.

Felipe Martinez Espero of RBMM (Reserva Biosfera de la Mariposa Monarca) documented the monarch's arrival during official field trips November 6 - 8, 2015.

News: They're Home

Mexican officials have confirmed the monarch's massive arrival to the winter sanctuaries. During field trips November 6-8, clusters were found in the Piedra Herrada, El Rosario, and Sierra Chincua sanctuaries. Notably, 10 trees in the Sierra Chincua were almost completely covered with butterflies. Monarchs had been flying overhead continuously since November 7th and, with sunny skies and gentle winds predicted, conditions for migration into the region were ideal according to the November 15th press release.

"Let's raise our glasses to toast the arrival of this healthy, strong generation of monarchs of the 2015-2016 winter season!" exclaimed Estela Romero, our local reporter in Angangueo.

An Increase Predicted
This year's population will be measured in December, when the monarchs are densely concentrated in their clusters.

Based on Journey North's fall migration data, we predict the population will be twice as large as last year.

Based on tagging data, Dr. Chip Taylor of Monarch Watch also predicts the population will have doubled. He also notes that since conditions this breeding season were similar to those of 2011 he wouldn't be surprised to see the population reach the level of 2011 — 2.89 hectares.

Increase Predicted
	Increase over last year	Area in Hectares	Area in Acres	Number in Millions*
Last Year	—	1.1	2.7	57
This Year	2 times	2.2	5.5	114

*Based on estimate of 50 million monarchs per hectare.

Monarch butterfly overwintering region in Mexico

Winter in Mexico: Month-by-month Highlights

November		December

Arriving Throughout the month, monarchs continue to arrive from the north and settle in at the 12 traditional wintering sites.		Being Counted Scientists visit the 12 wintering sites and measure the surface area the colonies cover. Results will be released by March, 2016.

January		February

Surviving Cold Watch the weather! At this coldest time of year, monarchs are at the greatest risk of mortality from deadly winter storms.		Preparing to Migrate Monarchs that survive four winter months will mate and begin the journey north in March. Join us for weekly updates on Feb. 4, 2016.

Maps: Report Your Sightings


What to Report	Adult Butterflies map \| list \| animation	Eggs and Larvae map \| list

Fall Roosts map \| list \| archives \| animation	Peak Migration map \| list \| animation

Journal and Activities

What conditions make the monarch's overwintering habitat in Mexico ideal for survival?

Slideshow and Journal

Next Update February 4, 2016