Why tag Monarchs?
The Monarch is the long-distance champion of butterfly migration, performing the longest migration of any insect in the world that we know. Each Autumn many millions of Monarchs, sometimes 250 million or more, empty out of the United States and southern Canada, east of the Rocky Mountains, and journey south to overwintering roosts in the mountain fir forests west of Mexico City.
However, scientists in North America want to know more about their migration – and here in NZ there is much speculation but little knowledge as to what takes place in the Autumn.
In the late 1960s Auckland Museum entomologist Keith Wise undertook tagging and his findings were reported in 1980 (Rec Auckland Inst Mus 17: 157-173, 17 December 1980). It was an opportunity to learn about their longevity and dispersal in NZ, overwintering habits etc.
At that time, he stated “…the project did not produce the information sought on dispersal of Monarch butterflies…” and that “…no large scale migrations or movements were detected by tagging.”
“The project, had in the main, established that large numbers of Monarch butterflies in the North Island stayed in their home areas both in summer and winter periods, although a small number did make long flights. At the same time the presence of known overwintering colonies was confirmed, particularly one at Tauranga Bay in the far north, but no movements into or out of these were recorded.”
While thousands of Monarchs were found to be overwintering at Tauranga Bay in the 1980s, by winter 2005 when entomologist Peter Maddison surveyed the area, a maximum of twenty were found. What has happened to this population?
In America, most of the tagged Monarchs recovered are found dead by people who know nothing about Monarch Watch or the tagging program. These people may return the dead specimen with the tag, the tag itself, or just the tag code. Most of the recoveries arrive with information on the location, date and circumstance of the recovery. If this information does not arrive with the tag, the personnel at Monarch Watch do their best to collect it.
Once they have the tag code for a recovery they search the tag database for that particular tag. If a record has not been returned, they must contact the person who received the tag. When they locate the datasheet for the recovered Monarch, they record the participant’s name, along with the tagging location, date, Monarch gender, etc., in the recovery database. They calculate distance according to latitude and longitude to obtain information for the straight-line course (a minimal estimate for the distance the Monarch traveled). The recovery is available as soon as it is entered and both the tagger and the person who recovered the tag can view the records online.
In America the majority of the tags recovered are obtained in Mexico. Early each year Monarch Watch personnel visit the overwintering sites, particularly El Rosario and Sierra Chincua, where they purchase tags from the guides and Mexican people. The ratio of untagged to tagged Monarchs is quite high and it takes most residents several hours to find each tag among the butterflies visiting sites along streams or dead butterflies on the trails and under the Monarch-covered trees. They pay 50 pesos (about NZ$7-8) for each tag – reasonable compensation for the time and energy spent locating each tag.
What do they do with the data?
The recovery data is posted on Monarch Watch’s website and is analysed to test hypotheses concerning Monarch orientation and navigation. The data are also used to determine mortality during the migration and estimate the number of Monarchs in the overwintering population. These analyses will be summarised on their website subsequent to the publication of the articles in scientific journals.
This provides useful information in a way that avoids hurting or harming the butterflies.
When Does Monarch Tagging Begin?
In America, as the length of daylight shortens in mid-August, Monarchs in northern latitudes (i.e., near the Canadian border) begin to migrate southwards. Monarchs further south will begin their journey a few weeks later. Tagging and monitoring begins as early as August, but at various times, depending upon the latitude.
In NZ we tag Monarchs from 1 March onwards as we wish to tag the overwintering generation.
Recording Tagging Data
To record your data use the form on the website. If you wish to enter the data onto the website at a later stage, please print off a sample page, or rule up a notebook beforehand to ensure you capture all of the relevant information.
DO NOT USE the page number tags; these are only on the sheet as a printing reference. Page numbers are repeated each year and are meaningless.
If you keep a notebook as you tag your Monarchs, please log your data into the website as soon as possible after tagging. This will make it easier and ensure that the data is complete should someone pick up your tagged Monarch soon after release.
Believe it or not, in North America many people receive tags, tag Monarchs, record data but never log in their data. Every year Monarch Watch staff spends countless hours (and a lot of money) contacting people who have recoveries but did not return their data. The data for a recovery is useless if they are unable to verify when, where, and by whom the butterfly was tagged.
How to tag
It is very important NOT to touch the glue side of the tags when you place them on the wing. The sticky surface will be affected from oil on the fingers. You can use a clean wooden toothpick to remove the tag from the backing sheet, and place it on the butterfly’s wing.
The tag is placed on the underside of the hindwing. With the head facing to your right, you will see the large, mitten-shaped cell (discal cell) on the underside of the wing. The discal cell position is close to the centre of lift and gravity for the butterfly and will not impede flight.
If you have difficulties please email email@example.com.
If you recover a Monarch while tagging, please enter that data at www.mb.org.nz as soon as possible.
Capturing a Monarch
When in flight, Monarchs are wary, elusive and difficult to catch. To maximise the number of Monarchs collected for tagging, it’s best to locate Monarchs feeding on flowers or in roosts late in the day or early in the morning. With a butterfly net in hand, approach each butterfly slowly (from behind if possible), as sudden movement will startle it into flight. Sweep the net forward quickly and flip the end of the net bag over the net handle. You want the butterfly in the deep end of the net.
With one hand holding the handle, use the other hand to collapse the end of the net bag. Flatten the net bag so the wings of the butterfly are closed over its back (thorax) and place thumb and forefinger over the leading edge of the wings (from outside the net).
Next, with the thumb and forefinger of your other hand, reach into the net and firmly grasp the thorax. Remove the butterfly for tagging.
You can make a good butterfly net – choose see-through materials that won’t rip easily as the net is swept over vegetation. The mesh should also be small enough that the Monarchs aren’t able to wiggle free. Landing nets used by fisherman (available at most discount stores) can usually be converted to butterfly nets. The opening should be 30cm diameter, and depth about 60cm.
Once you become familiar with Monarch adults, sexing is relatively easy. Males have an enlarged pouch midway along a vein that is directly below the discal cell on the hindwing (see below). In species closely related to the Monarch, this is a source of pheromones used in courtship. The pouches do not appear to be functional in the Monarch. Females lack these pouches and appear to have thicker veins than males – this is actually only a difference in pigmentation. Upon close examination, you will also notice that males and females differ significantly in the anatomy at the tip of their abdomen.
Size and mass
Measuring and weighing Monarchs is an optional activity, but will produce useful data for the scientific community. As an example, in America the generation of Monarchs that emerge from the pupae to migrate (in Fall) tend to be heavier, with plump abdomens, full of fat stored ready for the migratory process. If the Monarchs do migrate in NZ, an increase in weight of your tagged Monarchs will indicate this.
Forewing length is measured – from the white spot on the thorax closest to the base of the forewing, then measure from the centre of that spot out to the apex or end of the forewing.
If you have a scale that is accurate to 0.01 grams, place the butterfly in the envelope onto the scale to obtain the gross weight. After you have released the butterfly, weigh the envelope alone. You can calculate the butterfly’s weight by subtracting the envelope’s weight from the gross weight.
We are grateful to Monarch Watch for this information and assistance with our program.
Monarch Watch is a cooperative network of students, teachers, volunteers and researchers dedicated to the study of the Monarch butterfly, especially in North America. Their goals are to further science education, particularly in primary and secondary school systems; to promote the conservation of Monarchs and their habitat; and to involve thousands of students and adults in a cooperative study of the Monarchs’ fall migration.