---

DO Farm-Raised
MONARCHS MIGRATE?

~ NOVEMBER 10, 2000 ~

The purpose of this experiment is to broaden our general understanding of the ability of a laboratory-reared monarch butterfly (Danaus plexippus) to navigate during the fall migration. This information is important because of the recent increase in activity of transfers and releases of commercially-reared monarch butterflies. With this activity came the claims from some butterfly conservation groups, such as The North American Butterfly Association (NABA), that the mixing of lab-reared monarchs and the wild population could cause the failure of the butterfly to migrate. NABA writes:

"Now imagine tens of thousands of mixed-up Monarchs unable to find the way to their overwintering grounds. This depressing image may become a reality if the rapidly-growing fad of releasing butterflies, including Monarch butterflies, at weddings, state fairs, and other public events continues to spread. Because the released Monarchs may have come from California, for instance, where they do not migrate to Mexico, their offspring may not be able to orient properly. Because the Monarchs were raised inside under unnatural conditions, it is possible that their delicate migratory physiology may not have been turned on."

But, this data only provides information for up to 2nd generation monarchs. Many commercial breeders rear anywhere from 2 generations all the way to 9 generations without any exposure to the wild population gene pool. So, we concluded that the Monarch Watch information alone would not be sufficient to confidently answer the question. We decided to design this study around the most extreme case of inbreeding and lab rearing in order to see if these factors had any affect on the migration. So, we chose to use 8th to 9th generation lab-reared monarchs in order to provide data for the "worst case scenario."

METHODS AND MATERIALS

The concept here is to release tagged monarch butterflies in large quantities (approx. 200 each release) timed with the fall migration in hopes of recovering enough tags to produce significant data. We picked locations as far away as possible (within the western breeding population) and one location close by. The majority of the butterflies were released at the distant locations because it was assumed that the recovery rate would be much lower and thus more releases would be necessary in order to provide significant data.

The scheduled releases and locations are as follows:

Release date		Release location
September 16, 1999		Evanston, WY
September 16, 1999		Paonia, CO
September 23, 1999		Paonia, CO
September 30, 1999		Albuquerque, NM
October 7, 1999		Silver City, NM
October 19, 1999		Placerville, CA

The location and timing was determined based upon our current understanding of the western monarch migration. We planned the majority of our releases to be on the eastern most side of the western breeding population, which placed the release locations very close to the Continental Divide. Each of the release dates were timed to coincide with the historic timing of the monarch migration for that particular location. Note that as the date progresses, the planned release location moves further south. Our local release would be done in Placerville, CA in mid-October. This town is located in the Sierra Nevada foothills and is only several hundred miles away from the closest overwintering sight.

· On September 15, 1999, we shipped the following under USDA permit numbers 35485 & 35486:

Quantity	Serial Numbers	Location	FedEx tracking number
200	Y000 - Y199	Evanston, WY	790297326894
200	Y200 - Y399	Evanston, WY	790297326909
200	Y400 - Y599	Evanston, WY	790297326883
200	V000 - V199	Paonia, CO	790297326850
200	V200 - V399	Paonia, CO	790297326861
143	V400 - V542	Paonia, CO	790297326872

· On September 22, 1999, we shipped the following under USDA permit number 35486:

Quantity	Serial Numbers	Location	FedEx tracking number
200	P000 - P199	Paonia, CO	792501266205
200	P200 - P399	Paonia, CO	791792809676
200	P400 - P599	Paonia, CO	791792809893
200	R000 - R199	Paonia, CO	791792809974
200	R200 - R399	Paonia, CO	791792810084
200	R400 - R599	Paonia, CO	791792810257

· On September 29, 1999, we shipped the following under USDA permit number 35462:

Quantity	Serial Numbers	Location	FedEx tracking number
200	A000 - A199	Albuquerque, NM	792388399654
200	A200 - A399	Albuquerque, NM	792388399723
200	A400 - A599	Albuquerque, NM	792388399954
200	M000 - M199	Albuquerque, NM	792388400022
200	M200 - M399	Albuquerque, NM	790424642455
200	M400 - M599	Albuquerque, NM	790424641784

Quantity Serial Numbers Location FedEx tracking number

· On October 6, 1999, we shipped the following under USDA permit number 35462:

Quantity	Serial Numbers	Location	FedEx tracking number
200	X000 - X199	Silver City, NM	790306394418
200	X200 - X399	Silver City, NM	790306394451
200	X400 - X599	Silver City, NM	790306394473
200	H000 - H199	Silver City, NM	790306394624
200	H200 - H399	Silver City, NM	790776720631
200	H400 - H599	Silver City, NM	790776720664

· On October 19, 1999, we released the following (no USDA permit necessary):

Quantity	Serial Numbers	Location	FedEx tracking number
600	S000 - S599	Placerville, CA	Personal delivery

RESULTS

Please see the Master Tagging Report for the actual data and the North American map for a visual of the estimated flight paths. A total of 36 monarchs were recaptured and validated. There are, supposedly, another 2 dozen tags in Mexico that have yet to be identified. Since we are unable to locate them and validate the serial numbers, we can only use our current confirmed data. Nevertheless, the 36 recaptures that we did get will provide a significant amount of data to come to some reasonable conclusions.

1. Local release.

Our first significant finding from the local release is that lab-reared monarchs certainly do migrate after being transferred to a short distance away from their natal origin. Our local release in Placerville, CA greatly exceeded the historic standard recovery rate of ½ % (average recovery rate for the last decade of tag and release published statistics). Out of the 600 monarchs released, we needed at least 3 to be recovered at an overwintering site to be consistent with known averages. We had 20 recoveries which is more than a 3% recovery rate (6 times greater than the average). It was no surprise that we had a high recovery rate due to the short travel distance. But, this data does show clearly that the lab-reared monarchs were able to navigate properly after being released a short distance away from their natal origin.

2. Ability to navigate after a long distance transfer.

With the data starting to come in from the local release, we had hope that we would soon start getting recaptures from the distant releases. Sure enough, this came to pass. From the releases in Evanston, WY on September 16, 1999, monarch #Y137 was found near Chrome, CO, which was clearly on it's way to Mexico (see map). Monarch #Y114 was found in Manifee, CA, which is very close to some of the Southern California overwintering sights. From the releases in Paonia, CO on September 16, 1999 and September 23, 1999, monarch #R259 was found in Amistad, NM, clearly on it's way to the Mexican overwintering sights. From the releases in Albuquerque, NM on September 30, 1999, a total of 8 monarchs were recaptured, both at and on the way to overwintering sights in California and Mexico. Finally, from the releases in Silver City, NM on October 7, 1999, 2 were recaptured in Mexico (#X556 and #X549), one on the way to California (#X238), and the other at a California overwintering sight in San Diego (#X184).

3. Migration direction does not necessarily depend on natal origin.

The next significant finding so far is that we have recoveries at both the Mexican overwintering sites and the California overwintering sites from one single release. For example, monarchs #M267 and #M274 were recovered in Ventura, CA and Goleta, CA, respectively, at the local overwintering sites. Monarch #A314 was recovered at the Cerro Pelon overwintering site in Michoacan, Mexico. All three of these butterflies were released in Albuquerque, NM on September 30, 1999. This data could also indicate that the Mexican overwintering sites are not strictly composed of monarchs from east of the divide and vice versa. Please see the map for a visual of how the monarchs clearly travel in both directions.

4. Wide dispersion.

From these releases, we have a dispersion range from the California coast to Lenora, KS (#R170). This range is over 1,200 miles from a general release location along the Continental Divide. From one release alone, in Albuquerque, NM, we have a dispersion range close to the same distance of 1,200 miles. Monarchs #M267 and #M274 were recovered along the California coast and monarch #A314 was recovered in Mexico. With dispersion that is this widespread, it is inconsistent to believe that isolated genetic populations evolved to form an eastern specific and western specific subspecies.

Map of North America

Master Tagging Report

Release Date	Location	Serial Numbers	Quantity	Recapture Quantity
9/16	Evanston, WY	Y000 - Y599	600	2
9/16	Paonia, CO	V000 - V542	543	-
9/23	Paonia, CO	P000 - P599	600	-
9/23	Paonia, CO	R000 - R599	600	2
9/30	Albuquerque, NM	A000 - A599	600	3
9/30	Albuquerque, NM	M000 - M599	600	5
10/7	Silver City, NM	X000 - X599	600	4
10/7	Silver City, NM	H000 - H599	600	-
10/19	Placerville, CA	S000 - S599	600	20
		Total	5343	36

Recapture Details Report

Date	Location	Serial Number	Notes / Conditions
10/2	Tijeras, NM	M016	found alive and well
10/5	Amistad, NM	R259	found dead in yard
10/12	Lenora, KS	R170	found alive and well
10/16	near Chrome, CO	Y137	found frozen to a stick
10/24	Manifee, CA	Y114	found alive and well
11/1	San Luis Obispo, CA	S230	found alive and well
11/1	Summerland, CA	S592	found clustering
11/5	Santa Fe Springs, CA	S456	barely alive
11/9	Tucson, AZ	X238	alive and nectaring
11/15	Ventura, CA	M267	found clustering
11/15	Ventura, CA	S426	found clustering
11/15	Ventura, CA	S399	found clustering
11/15	Santa Barbara, CA	S350	found clustering
11/16	Summerland, CA	S175	found clustering
11/16	Santa Barbara, CA	S440	found clustering
11/16	Santa Barbara, CA	S048	found clustering
11/17	Santa Barbara, CA	S444	found clustering
11/17	Carpinteria, CA	S340	found clustering
11/20	San Diego, CA	X184	barely alive
11/20	Isla Vista, CA	S412	alive and mating
12/8	San Simeon, CA	S168	found dead
12/10	Goleta, CA (UCSB)	M274	found dead on campus
12/14	Santa Barbara, CA	S255	found clustering
12/14	Santa Barbara, CA	S444	found clustering (2nd sighting)
12/14	Ventura, CA	S025	found clustering
12/15	Santa Barbara, CA	S313	found clustering
12/19	Pismo, CA	S405	found clustering
1/2	Cerro Pelon, Michoacan	A314	found dead at overwintering site
1/18	Santa Barbara, CA	S412	found dead
2/19	Pismo, CA	S195	found dispersing from cluster
2/25	El Rosario, Michoacan	M458	found clustering
3/13	El Rosario, Michoacan	M458	found (2nd time) by guide
3/21	Angangueo, Michoacan	X556	found by guide
3/21	Angangueo, Michoacan	A466	found by guide
3/21	Angangueo, Michoacan	X549	found by guide
3/21	Angangueo, Michoacan	A462	found by guide

CONCLUSION

We have learned that lab-reared monarchs behave similar to wild monarchs in terms of migration behavior. Therefore, we believe that we can confidently answer "yes" to the question of whether or not lab-reared monarchs can navigate during the fall migration. But, we also answered another question about gene flow between the western and eastern breeding populations. Seeing how some of the monarchs ended up at both the Mexican overwintering sites and Californian overwintering sites from the same release, we can conclude that the monarch disperses and mixes enough during the migration to completely homogenize the two breeding populations. With this concept, we can conclude that it would be impossible for any genetic isolation to occur within the entire population. If any isolation did occur during the breeding months, it would then be wiped out from mixing during the fall migration and breeding at the overwintering sites.