Why are fewer monarch butterflies overwintering in Mexico?
Fewer and fewer monarch butterflies are reaching their overwintering grounds in Mexico every year, and new research might shed light on why.A 2016 study found that the monarch population in Mexican overwintering colonies has declined by approximately 80 percent over the past two decades. Pinpointing the causes of this decline has proven difficult, however.A study published in the journal Animal Migration last month suggests a possible cause: The monarchs are simply finding places other than Mexico to spend the winter months, and possibly even giving up their migratory ways altogether, in order to survive. Fewer and fewer monarch butterflies are reaching their overwintering grounds in Mexico every year, and new research might shed light on why.The mountains of central Mexico represent such critical overwintering habitat for monarch butterflies (Danaus plexippus) that a number of reserves have been created specifically to preserve the famous winged insects. Though they still face threats from mining, deforestation, and other human activities once they arrive, ecotourism centered entirely around visiting the monarchs in their winter retreat is so prevalent that it’s a significant factor in the local economy.A 2016 study found that the monarch population in Mexican overwintering colonies has declined by approximately 80 percent over the past two decades. Given its implications for the welfare of the North American monarch butterfly population as well as human livelihoods, the fact that the number of monarchs reaching their Mexican overwintering grounds is declining is a cause for substantial concern.Pinpointing the causes of this decline has proven difficult, however. Some scientists argue that it’s due to an overall drop in the eastern North American monarch population driven by the destruction of their breeding habitat in the Midwestern United States — monarch adults deposit their eggs on milkweed, which has been greatly reduced thanks to the use of herbicides and genetically modified crops in agricultural fields. (There are two populations of monarchs in North America, one east of the Rocky Mountains and another to the west; the western population overwinters primarily in southern California, though they have been discovered in Mexico as well). Another theory is that the fault lies with the increasingly perilous migration the butterflies must make every year to reach Mexico.A study published in the journal Animal Migration last month suggests another possible cause: The monarchs are simply finding places other than Mexico to spend the winter months, and possibly even giving up their migratory ways altogether, in order to survive.Dr. Hannah Vander Zanden of the University of Florida in the United States led a team of researchers that captured monarchs wintering in southern Florida and used a technique called stable isotope analysis to determine the geographic origins of the butterflies based on a tissue sample from their wings or body. The researchers found that nearly half (48 percent) of the specimens they caught had come from the American Midwest, which is believed to be the core breeding grounds of the eastern North American monarch population.Scientists have typically assumed that monarchs from that region travel exclusively towards the mountains of central Mexico in the fall, but Vander Zanden and team have shown that at least some monarchs from the Midwest U.S. are choosing to fly to southern Florida instead.“Previous research had suggested that some migrating monarchs may wind up in southern Florida if they become waylaid by strong westerly winds, but this evidence makes it seem like they purposely traveled to this location,” Andy Davis, a monarch migration expert at the University of Georgia and editor of Animal Migration, said in a statement. If more of these kinds of alternative overwintering locations are found, the discovery made by Vander Zanden and colleagues could help explain the shrinking overwintering population in Mexico.In the Animal Migration paper detailing their findings, the researchers theorize that monarchs may be employing an “alternative life history strategy” in choosing to overwinter in south Florida instead of central Mexico. “Alternative life history strategies are mechanisms by which organisms are able to maximize fitness across a range of environmental conditions. Fitness is maximized by different strategies depending on context, resulting in trade-offs between life history strategies,” the researchers write.Monarchs are known to use two different life history strategies: migratory monarchs pause breeding during their time in their winter grounds, while resident monarchs live year-round in one region and breed throughout the year. Vander Zanden and team discovered that the migrant butterflies in south Florida had larger wingspans than the residents, meaning that “switching to a resident strategy could alter their probability of reproductive success.”In order to develop conservation measures for the butterflies, the researchers note that more research is needed to figure out exactly what factors determine the life history strategy monarchs choose, which in turn could influence migratory trends and geographic distribution in monarch populations. “Further work is needed to investigate the mechanism underlying this pattern, but these findings show that alternate life history strategies and sex-specific behaviors are underexplored factors influencing monarch migration and evolution,” the researchers write.A female monarch butterfly. Photo by Kenneth Dwain Harrelson, licensed under CC BY-SA 3.0.CITATIONS• Semmens, B. X., Semmens, D. J., Thogmartin, W. E., Wiederholt, R., López-Hoffman, L., Diffendorfer, J. E., … & Taylor, O. R. (2016). Quasi-extinction risk and population targets for the Eastern, migratory population of monarch butterflies (Danaus plexippus). Scientific Reports, 6, 23265. doi: 10.1038/srep23265• Vander Zanden, H. B., Chaffee, C. L., González-Rodríguez, A., Flockhart, D. T., Norris, D. R., & Wayne, M. L. (2018). Alternate migration strategies of eastern monarch butterflies revealed by stable isotopes. Animal Migration, 5(1), 74-83. doi:10.1515/ami-2018-0006 Article published by Mike Gaworecki Animal Behavior, Animals, Butterflies, Conservation, Environment, Insects, Migration, Research, Wildlife, Wildlife Conservation Popular in the CommunitySponsoredSponsoredOrangutan found tortured and decapitated prompts Indonesia probeEMGIES17 Jan, 2018We will never know the full extent of what this poor Orangutan went through before he died, the same must be done to this evil perpetrator(s) they don’t deserve the air that they breathe this has truly upset me and I wonder for the future for these wonderful creatures. So called ‘Mankind’ has a lot to answer for we are the only ones ruining this world I prefer animals to humans any day of the week.What makes community ecotourism succeed? In Madagascar, location, location, locationScissors1dOther countries should also learn and try to incorporateWhy you should care about the current wave of mass extinctions (commentary)Processor1 DecAfter all, there is no infinite anything in the whole galaxy!Infinite stupidity, right here on earth.The wildlife trade threatens people and animals alike (commentary)Anchor3dUnfortunately I feel The Chinese have no compassion for any living animal. They are a cruel country that as we knowneatbeverything that moves and do not humanily kill these poor animals and insects. They have no health and safety on their markets and they then contract these diseases. Maybe its karma maybe they should look at the way they live and stop using animals for all there so called remedies. DisgustingConservationists welcome China’s wildlife trade banThobolo27 JanChina has consistently been the worlds worst, “ Face of Evil “ in regards our planets flora and fauna survival. In some ways, this is nature trying to fight back. This ban is great, but the rest of the world just cannot allow it to be temporary, because history has demonstrated that once this coronavirus passes, they will in all likelihood, simply revert to been the planets worst Ecco Terrorists. Let’s simply not allow this to happen! How and why they have been able to degrade this planets iconic species, rape the planets rivers, oceans and forests, with apparent impunity, is just mind boggling! Please no more.Probing rural poachers in Africa: Why do they poach?Carrot3dOne day I feel like animals will be more scarce, and I agree with one of my friends, they said that poaching will take over the world, but I also hope notUpset about Amazon fires last year? Focus on deforestation this year (commentary)Bullhorn4dLies and more leisSponsoredSponsoredCoke is again the biggest culprit behind plastic waste in the PhilippinesGrapes7 NovOnce again the article blames companies for the actions of individuals. It is individuals that buy these products, it is individuals that dispose of them improperly. If we want to change it, we have to change, not just create bad guys to blame.Brazilian response to Bolsonaro policies and Amazon fires growsCar4 SepThank you for this excellent report. I feel overwhelmed by the ecocidal intent of the Bolsonaro government in the name of ‘developing’ their ‘God-given’ resources.U.S. allocates first of $30M in grants for forest conservation in SumatraPlanet4dcarrot hella thick ;)Melting Arctic sea ice may be altering winds, weather at equator: studyleftylarry30 JanThe Arctic sea ice seems to be recovering this winter as per the last 10-12 years, good news.Malaysia has the world’s highest deforestation rate, reveals Google forest mapBone27 Sep, 2018Who you’re trying to fool with selective data revelation?You can’t hide the truth if you show historical deforestation for all countries, especially in Europe from 1800s to this day. WorldBank has a good wholesome data on this.Mass tree planting along India’s Cauvery River has scientists worriedSurendra Nekkanti23 JanHi Mongabay. Good effort trying to be objective in this article. I would like to give a constructive feedback which could help in clearing things up.1. It is mentioned that planting trees in village common lands will have negative affects socially and ecologically. There is no need to even have to agree or disagree with it, because, you also mentioned the fact that Cauvery Calling aims to plant trees only in the private lands of the farmers. So, plantation in the common lands doesn’t come into the picture.2.I don’t see that the ecologists are totally against this project, but just they they have some concerns, mainly in terms of what species of trees will be planted. And because there was no direct communication between the ecologists and Isha Foundation, it was not possible for them to address the concerns. As you seem to have spoken with an Isha spokesperson, if you could connect the concerned parties, it would be great, because I see that the ecologists are genuinely interested in making sure things are done the right way.May we all come together and make things happen.Rare Amazon bush dogs caught on camera in BoliviaCarrot1 Feba very good iniciative to be fallowed by the ranchers all overSponsored