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Predicting the number of monarch tags recovered in Mexico each winter is a bit of a guessing game. If we hear of a winter storm causing a lot of mortality at the colonies, we can anticipate that many tags will be available. Following mild winters the number of tags recovered might be as low as 150 from the tens of thousands of monarch butterflies tagged the previous fall. This winter was quite mild, perhaps even a bit on the warm side, and there was only one report hinting at higher than normal rates of mortality. So, we headed for Mexico expecting to acquire roughly 300 tags but were prepared to pay for up to 600 should this many be available. To our surprise, there were over 600 tags available. In fact, if we had had the funds, we could have purchased 200 more. Adding those purchased to those donated to Monarch Watch by various visitors to the Monarch Butterfly Biosphere Reserve (MBBR) brings the total number of tags recovered in Mexico this season to about 670.
Why were there so many tags this year? Two factors were involved: increased mortality at Cerro Pelon and encounters with residents with many tags collected during previous seasons. The colony in the El Capulin edijo formed in a degraded forest and moved into an area with an open canopy later in the winter. This combination led to the death of millions of monarchs due to exposure and consequently the recovery of over 90 tags at Pelon – more than four times the normal rate of recovery for this location. Because we are only able to visit each of the monarch sites once each winter, we don’t meet with everyone who has tags. This year we encountered many residents who had older tags along with some from the 2007 tagging season:
Series Quantity Year Issued J 329 2007 H 139 2006 G 75 2005 E 13 2004 C 19 2003 B 8 2002 A 22 2001 multiple 25 pre-2001
Most of you have sent us your datasheets and these have been sorted into eleven large binders. If you haven’t sent in your data, please do so. If we buy tags for which there is no data (and this happens about 20% of the time) it is money wasted – please send in your data!
We are beginning to process the recovered tags and will be reporting on these recoveries in the coming months.