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(and habitat restoration)
Chip Taylor and Jim Lovett
Our interstates are populated with gas stations, restaurants, rest stops and other resources needed by travelers. These fueling stations for both vehicles and people are waystations for those of us that migrate across the country. We rely on these resources, but what would happen if these fueling sites weren’t reliable? Let’s suppose your task is to drive/migrate on I-35 from the Texas/Mexico border to Duluth, MN – a distance of 1300 miles. Now suppose that there is a breakdown in fuel delivery in some places, massive and widespread blackouts in others that keep the gas from being pumped and the restaurants closed and that, as a traveler, you have no idea where the gaps in service are located. What would you do? Would you leave the interstate or trust that you would find resources somewhere ahead? If you gambled that there was gas ahead, that might work, but it might not, and you might find yourself stranded on the roadside, along with thousands of other cars and trucks whose drivers also gambled that there was fuel ahead. Millions of cars and trucks use I-35 each day and, if this scenario developed suddenly, tens of thousands of vehicles could become stranded.
Now suppose you are a monarch butterfly and you are driven to migrate north in the spring across a landscape parallel to I-35 in which there are abundant resources in the form of milkweeds and nectar sources in some areas but big, really big, gaps with no milkweeds or nectar plants in other areas. How would these gaps (ecologists call them fragments) affect monarchs? Would some starve? Would females simply lay fewer eggs? The answer to both questions is probably yes. That said, we have no quantitative data on this point, only anecdotes, assumptions, models* and more questions. How is the pace of the migration, mortality, and egg laying rate compromised by the lack of resources? Are the effects large or small? The fact is that we know very little about the physiological capacity of monarchs, but surely they have limitations. I get 52 miles per gallon with my Prius. How many sips of nectar are needed for a monarch to cover the same distance or lay an average number of eggs in a day? Stated another way, monarchs have daily resource needs. In short, they need fuel and they need patches of milkweeds for oviposition. Ultimately, what we need to know is how total reproductive output (also known as realized fecundity) is affected by large gaps in the landscape that lack resources.
My bottom line is this – it’s not only the abundance of resources in some areas but how resources are distributed across the entire landscape used by monarchs. The vast prairies and grasslands that were once the home for monarchs (and many other migratory species as well) have been replaced by farms and rangeland, cities large and small, and their attendant sprawl. And while there are abundant resources remaining for monarchs in some areas, there are also large – very large – gaps and these gaps with no waystations are the very reason for Monarch Watch’s Monarch Waystation Program. Our intention has always been to encourage people to create resources that fill these gaps. In the West, the earliest trains required waystations to take on coal and water to keep going and the Pony Express had waystations so riders could change horses every twenty miles or so. Monarchs also need waystations, just as we need them along our interstate highways.
*The models developed by Myron “Meron” Zalucki and colleagues suggest that increased fragmentation results in a significant loss in egg laying (realized fecundity). See references.
NOTES AND MAPS
The Monarch Waystation program began in the spring of 2005. The program began slowly with only 395 habitats (sites) added to the registry in 2005. The number of habitats added through 2012 remained modest and averaged only 823 per year. However, beginning in 2013, as the extent of the monarch decline became more widely known, the number registered per year jumped rapidly. In 2016, 2869 habitats were added to the Monarch Waystation Registry.
An interactive map and complete listing of habitats that have been registered as Monarch Waystations can be found via the Monarch Waystation Registry (monarchwatch.org/waystations/registry/). The map allows you to zoom in to specific cities or regions and view approximate locations of Waystations in your area. Since Monarch Waystations are mapped only by zip code (for privacy), the number of sites in specific areas are likely to be under-represented (i.e., a single map point may represent several nearby habitats).
Here is a current screenshot of the map:
Brenda Dziedzic kindly sorted and assembled the numbers of Monarch Waystations for each state:
For texts and references dealing with habitat loss, please visit the following Monarch Watch Blog posts.
Is the monarch decline due to an increase in mortality during the fall migration?
Monarch Butterfly Recovery Plan: Part two
Monarch Butterfly Recovery Plan
Monarch Population Status
Monarchs and the spatial distribution of resources
Zalucki, M. P. and Rochester, W.A. (2004). Spatial and temporal population dynamics of monarchs down under: Lessons for North America. In K.S. Oberhauser and M.J. Solensky (Ed.), The Monarch Butterfly 1 ed. (pp. 219-228) Cornell University Press, UK: Comstock Publishing Associates.
Zalucki, M. P., Parry, H. R. and Zalucki, J. M. (2015) Movement and egg laying in Monarchs: to move or not to move, that is the equation. Austral Ecology, 1-14. doi:10.1111/aec.12285
Zalucki, Myron P. and Lammers, Jan H. (2010) Dispersal and egg shortfall in Monarch butterflies: what happens when the matrix is cleaned up?. Ecological Entomology, 35 1: 84-91. doi:10.1111/j.1365-2311.2009.01160.x