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Articles : Tracking Monarch Migration with Hydrogen Isotopes

Monarch Watch

Local and long distance movements of organisms have been tracked by biologists with a wide variety of marking systems. All of these methods require an initial capture and usually some form of recapture. The amount of data recovered per unit effort is often very limited. It would be ideal to be able to obtain information on the origin and movement of every individual. This may now be possible. Recently, a new and promising means of tracking migratory species using stable hydrogen isotopes as a chemical signature has been developed by researchers at Environment Canada. However, to apply this technique to Monarchs, we need volunteers to raise Monarchs in 35 eastern states and provinces.

Deuterium, a stable isotope of hydrogen occurs naturally in rainwater across North America. The deuterium content of rain varies predictably from region to region, depending on climate and the prevailing source of moisture that makes up the rainfall. A strong deuterium concentration gradient in rainwater occurs across the North American continent as a result of climatic and hydrologic patterns. Previous studies have shown that the deuterium content of rain is reflected in tissues of shallow rooted plants. In turn, insects that feed on these plants incorporate that deuterium signal in their body parts. This is pretty nifty, and means that plants and insects raised in Minnesota will have different deuterium contents in their body tissues from those raised in Kansas, Georgia, or Quebec. These differences in deuterium contents should be very useful in helping to establish the geographic origins of Monarchs, as has already been demonstrated by Environment Canada researchers for migratory songbirds.

To use deuterium for tracing Monarch origins we need information from both controlled experiments and field studies. We are currently completing controlled experiments to define the hydrogen isotope dynamics between water, milkweed and Monarch body parts. But, we need your help in obtaining the field data or "ground truth".

Full use of hydrogen isotopes to answer biological questions requires that we determine deuterium contents of Monarchs raised under natural conditions across the eastern U.S. and Canada. This information will be used to calibrate "home signals" for Monarchs. This field study requires that Monarchs be reared on naturally occurring milkweeds over a wide latitudinal gradient, from the Canadian Maritimes to Texas. It is essential that these Monarchs are reared under natural conditions which are isolated from external influences that can affect the natural water cycle (e.g.. inside cities, watered gardens, irrigation districts, etc.). The best locations would be in rural or relatively undisturbed countryside. To successfully complete this experiment we need volunteers to rear Monarchs and to send us the emerged butterflies together with a sample of the milkweed (3 or 4 leaves) on which they were raised. This project integrates information from a number of subject areas and should be very interesting for students. It is also one in which students, teachers and parents can work together to contribute to a unique scientific study. Adult volunteers are welcome to apply as well. We prefer to work with volunteers who have experience rearing Monarchs, but we will be pleased to work with others as well.

Once the "home signals" for Monarchs throughout eastern North America are established, the deuterium content of Monarchs will be used to answer questions about the geographic origins of the Monarchs that reach the discrete roosting sites in Mexico and perhaps, whether Monarchs attempt to return to their region of origin. Results of the project will be provided in the Monarch Watch Season Summary and will also be available here on the Web.


This project is being funded by Environment Canada and Monarch Watch. The scientists collaborating on this study are Drs. Leonard Wassenaar and Keith Hobson (Environment Canada) and Dr. Orley Taylor (Monarch Watch). The Mexican component of the project is sponsored in part by the Monarch Butterfly Model Forest Project (Michoacan, Mexico).


To support this project, we will provide Monarch rearing kits to selected volunteers. The kit will contain 20-30 Monarch eggs, envelopes in which to return the adult butterflies, paper towels in which to dry the milkweed leaves, ziplock bags, labels, data sheets, an addressed return mailing box, and relatively simple rearing and handling instructions. The kits will be sent in July and August by Federal Express to arrive on a prearranged date. The volunteers must agree to rear the Monarchs on naturally occurring milkweeds that are watered only by rainfall and to return at least 3 male and 3 female Monarchs to the Monarch Watch together with a sample of the dried milkweed leaves (identified to species) on which the larvae were reared. The samples must be labeled with the name of the volunteer, location and date.

Each kit will cost us at least $15 dollars (U.S.) to prepare and send by Fed Ex. The only costs to volunteers will be their time and return postage, about $2. We will provide phone, (toll free 888-TAGGING), fax (913-864-5321), and e-mail ( support for volunteers who have questions about the project.


If you wish to raise Monarchs for this project, please fill out the application form and return it to us by 20 June 1996. We will select three qualified applicants in each state and province on the 1st of July. Successful applicants will be notified shortly thereafter and arrangements will be made to send the Monarch rearing kit to arrive on a specific date.

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