Forests
Wildlife
The patches of red in these false-color Landsat images are the forests where monarch butterflies spend the winter. Starting in late summer and fall, monarchs in the United States and Canada migrate south to Mexico. Some travel up to 3,000 miles. The delicate insects are capable of flying 50–100 miles a day.
Cold weather drives the monarchs to head south to hibernate for the winter. They head for the only habitat suitable for their hibernation, oyamel fir (Abies religiosa) forests. These forests grow in only small areas of mountain tops in central Mexico, about 3,000 m above sea level. The monarchs usually cover whole trees as they keep each other warm. The short needles of the oyamel fir allow the butterflies to cluster together better than they could on flat-needled cedars or long-needled pines.
The oyamel forests provide a microclimate for the butterflies. Temperatures stay above freezing. If the temperatures were lower, the monarchs would have to use their fat reserves. The humidity provided by the forest also keeps them from drying out.
The monarchs stay in Mexico from about November to March. In the spring, they fly back north. On the way, they lay eggs on milkweed. These eggs hatch into caterpillars, who devour the milkweed leaves, then metamorphose into monarchs. These monarchs live about 5 weeks or so.
What’s especially amazing about the monarch migration is that not all monarchs take part in the journey. And unlike birds and whales, the monarchs that do complete the migration only make one round trip.
The great-grandchildren of the overwintering monarchs migrate south the next fall, somehow landing at the same trees as their ancestors. Without the use of maps or satellite imagery!
Location
Mar. 17, 1993, Landsat 5 (path/row 27/46) — Monarch Butterfly Biosphere Reserve, Mexico
Apr. 21, 2000, Landsat 5 (path/row 27/46) — Monarch Butterfly Biosphere Reserve, Mexico
Apr. 1, 2016, Landsat 8 (path/row 27/46) — Monarch Butterfly Biosphere Reserve, Mexico
Apr. 1, 2016, Landsat 8 (path/row 27/46) — Monarch Butterfly Biosphere Reserve, Mexico
Monarch Butterflies, Mexico Additional Imagery & Stories
Degraded Habitats
The monarch migration is an endangered phenomenon. Logging in the overwintering sites in Mexico reduces the area available for the monarchs. The Monar...
Global Forest Maps
Researchers from the University of Maryland and USGS have mapped changes in forests globally from 2000 to 2013. The maps displayed here are from that ...
Lomas de Aparicio
These close-up images show a portion of the reserve. The red spots in the global forest map indicate forest loss. The area in the center of the image ...
Monarch Value
The good news about the monarchs is that they are a beloved bug. Kids in classrooms nationwide capture the caterpillars and watch them transform into ...
NDVI
Subtle changes in vegetation are sometimes difficult for us to see when just looking at the imagery. The Normalized Difference Vegetation Index (NDVI)...
Pelon
These close-ups show another core zone area of the reserve called Pelon. Forest disturbance is most visible in the 2000 image. Later Landsat images re...
References
Brower, L.P., Williams, E.H., Fink, L.S., Zubieta-Hernández, R.R., and Ramírez, M. I., 2008, Monarch Butterfly Clusters Provide Microclimatic Advantages during the Overwintering Season in Mexico: Journal of the Lepidopterists’ Society, v. 62, no. 4, p. 177–188.
Brower, L.P., Taylor, O.R., Williams, E.H., Slayback, D.A., Zubieta, R.R., and Ramírez, M.I., 2012, Decline of Monarch Butterflies Overwintering in Mexico—Is the Migratory Phenomenon at Risk? Insect Conservation and Diversity, v. 5, no. 2, p. 95–100.
Diffendorfer, J.E., Loomis, J.B., Ries, L., Oberhauser, K., Lopez-Hoffman, L., Semmens, D., Semmens, B., Butterfield, B., Bagstad, K., Goldstein, J., Wiederholt, R., Mattsson, B., and Thogmartin, W.E., 2014, National Valuation of Monarch Butterflies Indicates an Untapped Potential for Incentive-Based Conservation: Conservation Letters, v. 7, no. 3, p. 253–262. (Also available online at http://onlinelibrary.wiley.com/doi/10.1111/conl.12065/full.)
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Monarch Lab, 2015, Annual Life Cycle: Monarch Lab, University of Minnesota Web page at http://monarchlab.org/biology-and-research/biology-and-natural-history/breeding-life-cycle/annual-life-cycle. (Accessed June 12, 2015.)
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Slayback, D.A., Brower, L.P., Ramírez, M.I., and Fink, L.S., 2007, Establishing the Presence and Absence of Overwintering Colonies of the Monarch Butterfly in Mexico by the Use of Small Aircraft: American Entomologist, v. 53, no. 1, p. 28–40.
Taylor, C., 2014, Monarch Population Status: MonarchWatch.org Web page at http://monarchwatch.org/blog/2014/01/monarch-population-status-20/. (Accessed June 12, 2015.)
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Taylor, C., 2016, Monarch Population Status: MonarchWatch.org Web page at http://monarchwatch.org/blog/2016/02/26/monarch-population-status-26/. (Accessed March 24, 2016.)
USDA Forest Service, [n.d.], Migration and Overwintering: USDA Forest Service Web page at