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Field Notes: State of Mexico, Mexico, January 28-February 1, 2019

Feb 25, 2019


  • Conservation Stories
  • Migration
  • Population Trends
By Monarch Joint Venture Science Coordinator, Alison Cariveau

I want to share my recent visit to Mexico, where I had the great fortune to participate in the Trinational Monarch Science Meeting hosted by the Commission for Environmental Cooperation (CEC). The meeting brought together scientists from Canada, Mexico, and the U.S. to share research findings and advance monarch conservation across North America. This meeting is part of a project sponsored by CEC for the past several years dedicated to tri-national monarch butterfly conservation.

Science sharing
We met in Mexico City, where we heard 30 technical talks from scientists from all three countries. Abstracts from these talks will be published by the CEC for reference. While topics ranged broadly, we heard a number of talks that were refining models of the life cycle of the butterfly and when it is vulnerable – trying to understand more deeply the various threatening factors contributing to population declines. We heard about disease, traffic collision mortality, and anticipated effects of climate change. We learned about a variety of monitoring techniques and programs in all three countries, including a new data collection app developed and applied throughout northern Mexico and a LIDAR technique that estimates numbers of butterflies gathered in winter roosts. We heard about the Trinational Monarch Knowledge Network, a developing effort to bring together data from all three countries into a well-documented, comprehensive, and accessible data source.
A new issue that emerged is the need to develop a body condition index for adult monarchs, using weight and morphological (body structure) measurements to estimate the lipids (stored energy); the technique could be applied when tagging monarchs and on fresh tagging recoveries in an effort to learn about when and where monarchs may be limited energetically. Also using lipids, an emerging technique examines their isotopic signature, indicating the location where the lipids were formed, or the location where the butterfly last gained weight from drinking nectar. Knowing where they gained lipids may provide insights into conditions they encounter during different phases of their life cycle, and complements ongoing studies of isotopic information encoded in the wing tissue that indicates their natal origins.
Overwintering Population Information Release
We were fortunate to attend the annual press conference in which the National Commission of Natural Protected Areas (CONANP) and World Wildlife Fund (WWF) announced the 2018-2019 overwintering population estimate for eastern monarchs. The population is up this year 144% above last year’s numbers, to just over 6 hectares, the size targeted for population recovery. Everyone is very happy with the news.
Excellent questions were put forth by a well-informed press corps. “Why did they do so well this year?” Scientists indicated that this was likely due to favorable weather conditions throughout the year. In response to questions of “Have we met our goals?” and “Is our work done?”, leaders emphasized that this population regularly fluctuates and that this ‘peak’ in the population numbers will likely be followed by a ‘valley.’
We cannot know yet whether this signifies true recovery for the population (a halt to the decline) or not. In the meantime, we know there are so many stressors to these populations – across the continent – that if we value monarchs we will not abandon now our most earnest conservation efforts.
Visiting an Overwintering Colony
We took a bus several hours through and out of Mexico City to Piedra Herrada, an overwintering colony site in the Valle de Bravo situated high in the mountains of the state of Mexico. The forest is beautiful, with long needled pines, and upright Oyamel firs, Abies religiosa, the tree preferred by overwintering monarchs.
The day was idyllic, with crisp dry air, and a fresh blue sky with wispy clouds. We rode small, fuzzy-coated horses to climb most of the steep mountainside, after which we ascended the final stretch at our own pace. Strong men and women accompanied their horses up and down the mountain, never giving away that they were walking straight up at 11,000 ft elevation. This colony is part of an ejido – communal land owned by ejidatarios, 67 in this case, who oversee forest management decisions and the business of running a biological reserve. The monarchs occupy 24 or so colony locations each winter in a variety of jurisdictions, including protected federal lands, ejidos in and out of protected zones (which are protected for a variety of reasons such as for clean water). This variety creates a need for great coordination.
We met a team of forest managers, wildlife biologists, and foresters who care for the butterflies and the sustainability of healthy forest. Because this forest type is naturally short-lived, it is necessary to maintain a dynamic system including tree falls and regeneration. The managers talked about balancing the need to protect the forest from erosion, fragmentation, invasive species, interrupted fire regime, and other anthropogenic stressors with the importance of providing visitor experiences that heighten peoples’ awareness and dedication to monarch conservation.
Seeing the monarchs clustered together in their overwintering colony is always magical. Delicate but hardy, they cling to the trees in dark bunches, in some cases covering the tree trunks like a net. Others are flying around in the warm, dry air. These butterflies originated from Canada and the US and are waiting for spring to cross the border again to reproduce where there is milkweed and nectar available; their children will try to move again northward.
Travelling all this way, I am in wonder of how far they fly and how successive generations find their way year after year to this particular location. Meeting the people from three countries who work to understand and protect these beautiful insects reminds me of our responsibilities as continental citizens, and I am reminded of the profound significance of nature in our lives.
Pictured above: International researchers (left to right) Sonia Altizer (Project Monarch Health), Elizabeth Howard (Journey North), Elise Zipkin (Michigan State University), Isabel Ramirez (Universidad Nacional Autónoma de México), Alison Cariveau (Monarch Joint Venture) visiting Piedra Herrada monarch sanctuary.
The Monarch Joint Venture is a national partnership of federal and state agencies, non-governmental organizations, businesses and academic programs working together to conserve the monarch butterfly migration. The content in this article does not necessarily reflect the positions of all Monarch Joint Venture partners. Header photo taken by Alison Cariveau, February 2019, at Piedra Herrada monarch sanctuary.