The autumn sun in the middle of November gives a warm glow to Keelung. It's an excellent day for catching and marking butterflies. Early in the morning volunteers from the Butterfly Conservation Society of Taiwan set off from Taipei. They climb the slopes of Kangtzuliao, to more than 100 meters above sea level. Three volunteers have only just picked up their nets, charts, measuring sticks and whatnot when a butterfly floats right in front of their eyes. "That's a striped blue crow!" One of the volunteers, Cheng Wan-ching, softly waves a net in the air and catches the butterfly. She kneels down to extract it and then softly spreads its wings against her leg. On them she writes with a waterproof black marker: "CC1117.'

"CC is a code for me and 1117 is today's date," Cheng explains, before measuring the butterfly's wingspan. She then gives a quick glance to judge the amount of wear on its wings and announces: "47 millimeters, M [meaning medium wear], flower-visiting." After another volunteer has noted down her words, Cheng opens her hand, and the butterfly flies off, its body sparkling purple under the sun, like some fantastical fairy of the mountain forests.

The second butterfly they catch is a chocolate tiger (Parantica swinhoei), and the volunteers all remark upon how young it is. Its velvet wings have hardly any visible wear, a sign that it hasn't been long since it emerged from its chrysalis. As a true baby butterfly, it is recorded with an "N" for "new." After being released, it plays dead on the volunteer's hands for a minute or two before ascertaining that it is out of danger and flying off.

"The going was good today, with over 70 butterflies marked in three hours." Cheng, who has volunteered as an association guide for many years, explains that they record the age of the butterflies so as to answer questions about whether the northern groups migrate south to overwinter, and if so, how. Although researchers have already mapped the northward migration paths of the milkweed butterflies, to which the crows and tigers belong, it is not known which routes they take when they move south. There are all manner of unresolved questions about them. Consequently, volunteers observe and mark butterflies in three or four spots in northern, central, southern and eastern Taiwan, hoping to gain understanding about their breeding and about where they go afterwards.

From the beginning of November most of the milkweed butterflies found here are "N"s, which shows that Kangtzuliao is where many of them emerge from their chrysalises. In the spring of the coming year, the volunteers will return to check whether there are large numbers of milkweed caterpillars here to confirm that the young butterflies seen today have become mothers. Not finding any caterpillars here would suggest that butterflies moved to another locale to pass the winter and lay their eggs.

For the past six years Chan Chia-lung, a researcher with the Butterfly Conservation Society of Taiwan, has been researching the migration routes and breeding of crow butterflies. Thanks to the efforts of trained volunteers around Taiwan, he has pieced together their northward migration routes. But many questions about them remain.

Overwintering butterflies

The crow butterflies are members of the subfamily Danainae (milkweed butterflies) of the family Nymphalidae (brush-footed butterflies). The milkweed butterflies are split into the tribes of Euploeini, of which there are five species in Taiwan, and Danaini, of which Taiwan has eight species (see chart, p. 37). Some milkweed butterfly species are among the longest-lived butterflies and among the few that can survive cold winters as caterpillars. Most butterflies start quickly dying off as winter nears, so that they disappear until the following spring, when their eggs hatch to produce the next generation.

Among this oddball family of butterflies, the most famous are the monarchs. At the end of fall every year, a staggering number of them--over 100 million--migrate 4000 kilometers from eastern Canada to Mexico, where they overwinter in valleys, creating a world-class scenic wonder with over 10 million butterflies in a single valley.

Like that ecological marvel in Mexico, in Taiwan, on the other side of the Pacific Ocean, in such locations as Kaohsiung's Maolin, Pingtung's Wutai, and Taitung's Mt. Tawu, great numbers of crow butterflies also come south in November before winter, settling in valleys where they can shelter from the wind and feed on nectar plants. By spring (early March) they once again fly north. Although their total numbers are not as great as the monarchs in Mexico, there are more than ten individual species of milkweed butterflies represented here, as opposed to the single species of Monarch butterfly in Mexico.

Based on the research of Chan Chia-lung and others connected to the Butterfly Conservation Society of Taiwan, and on Internet views of the purple milkweed butterflies in Maolin's valleys, in his 2003 book Butterflies British lepidopterist Dick Vane-Wright listed Taiwan's purple butterfly valleys as one of the world's two great groups of wintering butterfly valleys, alongside the monarch butterfly valleys of Mexico.

Although there has been a lot of media attention about these butterfly valleys in recent years, butterflies have many centuries of history in southern Taiwan's low-elevation valleys. Rukai Aborigines in the Maolin area used images of butterflies in their traditional clothing and headdress.

"Only the tribesmen who ran the fastest or tribeswomen who were best at weaving, and were so acknowledged by the chief, could wear butterfly clothing or ornaments," says Ubakker, a Maolin sculptor, who recalls that a "scary" number of butterflies would appear in the wild guava grove behind his house at the beginning of winter. All you had to do was touch the guava trees to hear the sound of beating butterfly wings. The old folk would say: "Be careful not to scare the butterflies. That's their home."

In the 1970s, Chen Wei-shou, a biology teacher at Taipei's Chenggong High School stumbled upon this ecological marvel of the crow butterflies, and it caused quite a sensation. Yet for more than 20 years afterwards, there was only scattered research in Taiwan about it. Furthermore, there were different views on how the crow butterflies came to the butterfly valleys: one school believed that the butterflies flew en masse along fixed long-distance "butterfly routes" (the migration route hypothesis). Another school believed that the butterflies lived in scattered locations close to the overwintering valleys, and merely gathered in the valleys in winter to shelter from the wind (the scattered population hypothesis). Over the years, although there were many observations of butterfly routes, without "direct evidence" from the recapture of marked butterflies, the controversy was not resolved.

A turning point came in 2000, when Chao Chia-lung, a researcher with the Butterfly Conservation Society, came to Maolin.

Kangtzuliao, Keelung: So as to unravel the mysteries of crow butterfly migrations, volunteers in northern, central, southern and eastern Taiwan mark butterflies and take notes in mountain areas every month.

Gradually seeing the light

In early 2000, Chan brought a friend to Maolin to photograph the magnificent sight of tens of thousands of butterflies gathering in one particular valley. He was shocked to find that the magnificent sight of butterflies that he had seen there in high school had disappeared, because the site had been leveled for a parking lot! Although they found other butterfly valleys to photograph on that trip, the disappearance of some 2-300,000 butterflies from that valley hit him hard, and he resolved to take some active measures. He would proceed to successfully lobby the Council of Agriculture to adopt a research plan, which included research into conserving the butterfly valleys, as well as education and promotion.

Over the next three-plus years Chan Chia-lung compiled some basic information about the Maolin butterfly valleys and discovered that there were eight of them altogether, including three with overwintering populations of 60-80,000 butterflies.

Among them, the dwarf crow was most numerous, accounting for 49% of the total. Striped blue crow and double-branded crow each comprised about 20%. The blue-branded king crow accounted for only 2%, with another six species together totaling less than 2%. Each of the species would select locations for which they were particularly well suited.

As for the mystery of the crow butterflies' migratory routes, which was the source of much speculation, in March of 2001 Chan and several others were able to record three routes in Maolin, with over 120,000 butterflies migrating over the course of six days. These findings supported Chen Wen-lung's early conjectures: that every year the butterflies leave along fixed routes. Later researchers in other areas, such as Chiayi's Tanaiku, Yunlin's Linnei, Changhua's Mt. Pakua, and Taichung's Mt. Tatu, noted butterflies migrating north at rates of about 200 to 350 a minute.

Overwintering crow butterflies often go to the edge of expanses of water or dew-covered roads to drink water. When the sun is high, they retreat to their forested valleys to rest. (photo by Tsai Chih-chi)

A butterfly in a haystack

"But all we could know for sure was that these butterflies had passed through those places. Our findings didn't prove they were flying from the valleys where they spend the winters," explains Chan. To provide proof positive that they were flying from those valleys, it would be necessary to catch butterflies that had been marked at those valleys. The problem was that the times of the large-scale migrations were hard to predict, and a whole group would pass by a location in a short hour or two, so to be successful it was necessary to mobilize a lot of workers and station them at various locations.

By lobbying government agencies and citizen groups, Chan Chia-lung obtained the support of the Council of Agriculture for a national training program for milkweed butterfly conservation volunteers. Since 2004 this program has each year trained more than 100 "research volunteers," which are rare birds indeed. They have to train all winter--or even all year. They can only obtain accreditation by putting in the requisite number of hours. These volunteers are then seeded in various organizations to help promote the research project and train other volunteer butterfly markers.

In 2004 and 2005, over 100,000 butterflies were marked; these ultimately provided friends of butterflies with some earthshaking news: Butterfly YB7, which had been marked in Maolin, was the first of the butterflies marked in a wintering valley to be caught at Changhua's Mt. Pakua and Miaoli's Chunnan en route to Yunlin's Linnei: This provided the link between the west-coast migratory paths and the breeding valleys of Miaoli's Chunan. Another butterfly, FY1030, had lived for more than half a year and traveled a verified recorded distance of 254 kilometers.

In 2005 there were also several records made of "mass migrations," which encouraged researchers. The one recorded in Yunlin's Linnei on April 3 was particularly heartening. The scene that day, as Chan Chia-lung describes it, was "like that of a whole army in motion. To the right, to the left, up and down, butterflies were everywhere, like a swarm of locusts. Without a doubt more than 10,000 were passing per minute." On that day alone 1 million milkweed butterflies passed through Yunlin.

A captured male butterfly extends its yellow "hair pencil," which emits pheromones when it courts females. 

Gold and silver fill the forests

The surveys taken of the breeding areas were also very successful. In the beginning of June 2004, Chan Chia-lung was told that in horsetail-tree windbreak plantations in Long Life Forest Park on the Miaoli coast at Chunan there were large numbers of empty chrysalises and dead butterflies that hadn't completely emerged. Afterwards, the association's local conservation group estimated that there were at least 30,000 empty chrysalises whose butterfly occupants had already left.

"The horsetail trees thereabouts are well spaced, like those of a high mountain forest. The Taiwan cow-plant vines that climb up them are vigorous and lush; they are the only food the double-branded crow caterpillars there eat." Chan Chia-lung explains that this discovery, placed alongside the massive migration in April and May, proves that Chunan is a major breeding place of double-branded crows, and, as opposed to the overwintering valleys, provides a habitat where they can live out al stages of their life cycle."

In May of 2005, a similar scene occurred in Chunan. Many butterfly volunteers had heard about the situation the year before and came to have a look for themselves.

Among them was volunteer Cheng Wan-ching, who visited Chunan several times during that period and witnessed the entire breeding season. At the beginning of May the forest was full of crawling larvae. Because many of the cow-plant vines had been cut down by the park gardeners, the volunteers anxiously picked up the poor caterpillars into buckets and deposited them under trees with living vines. The volunteers returned several days when the larva entered the chrysalis stage to witness a marvelous gold and silver world. "The whole grove of horsetail trees was covered with what appeared to be gold and silver bells, which shimmered in the sunlight," says Cheng, who can't hide her excitement when recalling it. "The feeling was like one had said 'Open, Sesame!' and entered some secret treasure-filled cave." After the butterflies emerged from their chrysalises, she watched them fly off in three directions: north, northeast and east.

A volunteer takes the following steps when marking a butterfly: First, they write their individual number on the back of the wings; next they measure the wingspan; then they note the sex and the level of wear on the wings; and finally they record this information as well as the circumstances of the butterfly's capture.

Three migrations

In 2006, after six years, 90 sightings of butterflies migrating in spring, and 27 instances of recapturing marked butterflies, Chan Chai-lung was finally able to string together the butterflies' spring migration routes.

As described in his thesis of September 2006, the crow butterflies' spring migration routes follow the eastern and western sides of the Central Mountain Range. The western path goes straight north, from Kaohsiung's Maolin all the way to Miaoli's Chunan. Along this route double-branded crows are most numerous and blue-branded king crows are next. Likewise, the eastern migration path goes straight north from the overwintering valleys of the Mt. Tawu area to Lungtung on the Northeast Coast (see map). The blue-branded king crows are the most populous species along this migration path.

Apart from the spring migration that takes place in early April around Tomb Sweeping Day, Chan Chia-lung was also the first to discover a second migration of crow butterfly species in early summer. A survey of butterflies in the evergreen forests in Miaoli's Chunan carried out in May of 2005 revealed that the mass migration to higher altitudes was entirely of double-branded crow butterflies. And 97% of these were "new" butterflies that had just emerged from their chrysalises. The number of butterflies passing in one minute ranged from 300-400 to more than 1900.

The mysteries of the butterflies' northward migration are gradually being resolved, but the starting points and route of the late fall migration south have yet to be pieced together. Currently all that is certain is the time of arrival at certain wintering valleys, and the numbers of various migrating groups. Only one butterfly in the southward migration has been marked and recaptured. In January of 2006 a double-branded crow butterfly was caught in a wintering valley on Taitung's Mt. Tawu that had been marked in Taitung's Chinshan in August. There is a lot of work to be done before the migration routes can be pieced together.

A volunteer takes the following steps when marking a butterfly: First, they write their individual number on the back of the wings; next they measure the wingspan; then they note the sex and the level of wear on the wings; and finally they record this information as well as the circumstances of the butterfly's capture.

Many questions

In contrast to Chan Chia-lung's research of recent years, which has focused on the migration of crow butterflies, another research group is investigating the ecology of wintering valleys in the Mt. Tawu area on the eastern side of the Central Mountain Range.

Chao Jen-fang, a professor of leisure management at Minghsin University of Science and Technology, who lives in Taitung, is the main researcher in this group. He explains that currently there are some 30 known wintering valleys. Although they don't face any immediate threats, there are concerns about human encroachment in valleys that are located at elevations under 500 meters, that are close to settlements, or that are easily accessible.

"Take the overwintering valleys of Taitung, which are hosts to more than ten species of milkweed butterflies: Do all of those species overwinter?" Chao explains that to qualify as "overwintering," a butterfly must satisfy two conditions: "accumulating fat" and "suspending growth." But research has determined that only four species of crow butterflies and two species of tiger butterflies that spend the winter in those Tawu valleys have clearly elevated fat levels. This shows that the other seven species of milkweed butterflies must use some unknown method to pass the winter. The next step is to research the milkweed butterflies' breeding functions. Perhaps some other species will be disqualified on that count.

"Every March the crow butterflies migrate northward from these beautiful butterfly valleys," notes Chao. "But do all of the species have the ability to travel long distances?" By studying the extent to which the wings of each species are damaged when they arrive in the winter valleys, he has found that most of the dwarf crow and striped blue crows have new wings. The double-branded crows and blue-branded king crows, on the other hand, mostly have damaged wings, showing that they have experienced the hardships of flight. It is thus more likely that they have come south flying longer distances. It bears witness to their traveling abilities.

When they overwinter, do the six species of butterflies compete for territory? What factors affect their ability to safely overwinter? If the large populations of migrating butterflies like to feed on invasive foreign species such as Siam weed and bittervine, then what native species can be substituted?

"You've got to have ample knowledge about the ecological phenomena involved in overwintering if you are to find previously undiscovered overwintering valleys and prevent their accidental destruction," says Chao.

The research project that Chao and 200 volunteers have been conducting into Mt. Tawu's overwintering valleys is now in its fourth year. The early data show "differences every year, and mutually contradictory results. Our observations are far from sufficient; we've got a lot more work to do!" he says.

When volunteers mark butterflies they must bring their Butterfly Marker Certificate, which proves that they have received the proper training.

Everyone follow butterflies

"The monarch butterfly valleys of Mexico have only one species of milkweed butterfly, and Americans have been carrying out research on them for 70 years, whereas we have more than ten species and have only been researching them for six years," says Chan Chia-lung. In the United States there are more than ten universities and numerous citizen groups that have been studying every aspect of the phenomenon, separately looking into the biology, ecology, migration photoperiod and so forth of the monarch butterfly (Danaus plexippus). Research into Taiwan's crow butterflies has focused on the overwintering valleys, migration routes and breeding sites. These are just the first steps. What about the mechanisms guiding the migration? What pushes the butterflies to migrate? Answers to these questions are mid- and long-term goals.

Citing the example of Mexican president Vicente Fox, who in 2001 issued a special order to protect the monarch butterflies, Chan Chia-lung calls for society to put more stress on follow-up research into Taiwan's crow butterflies. Thus far these butterflies have not received presidential-level attention, but thousands of volunteers have signed up to help survey and mark them.

"If you are out in the wilds and you see a butterfly with marked wings, what should you do?" asks Chan rhetorically. He requests that citizens take a photograph of it and record the time and location, and then get in touch with the Butterfly Association. Getting butterfly volunteers spread throughout every corner of Taiwan would be more effective than any presidential order!

Crow caterpillars are very colorful, and crow butterflies' wings shimmer in the sunlight. The razzle-dazzle warns predators: "I'm very poisonous!" The leftmost photo shows a double-branded crow caterpillar. The three center photos show the bright gold, silver and light green chrysalises of crow butterflies. Hanging from tree branches, they're strikingly beautiful (photos by Cheng Wan-ching). The photo at right shows an adult double-branded crow butterfly (photo by Chan Chia-lung).

Butterfly Conservation Society of Taiwan
Tel.: (02) 2881 4006
Address: 3F-10, No. 27, Lane 2, Hualing St., Shihlin, Taipei City
Website: www.butterfly.org.tw

Crow caterpillars are very colorful, and crow butterflies' wings shimmer in the sunlight. The razzle-dazzle warns predators: "I'm very poisonous!" The leftmost photo shows a double-branded crow caterpillar. The three center photos show the bright gold, silver and light green chrysalises of crow butterflies. Hanging from tree branches, they're strikingly beautiful (photos by Cheng Wan-ching). The photo at right shows an adult double-branded crow butterfly (photo by Chan Chia-lung).

Crow caterpillars are very colorful, and crow butterflies' wings shimmer in the sunlight. The razzle-dazzle warns predators: "I'm very poisonous!" The leftmost photo shows a double-branded crow caterpillar. The three center photos show the bright gold, silver and light green chrysalises of crow butterflies. Hanging from tree branches, they're strikingly beautiful (photos by Cheng Wan-ching). The photo at right shows an adult double-branded crow butterfly (photo by Chan Chia-lung).

Crow caterpillars are very colorful, and crow butterflies' wings shimmer in the sunlight. The razzle-dazzle warns predators: "I'm very poisonous!" The leftmost photo shows a double-branded crow caterpillar. The three center photos show the bright gold, silver and light green chrysalises of crow butterflies. Hanging from tree branches, they're strikingly beautiful (photos by Cheng Wan-ching). The photo at right shows an adult double-branded crow butterfly (photo by Chan Chia-lung).

Crow caterpillars are very colorful, and crow butterflies' wings shimmer in the sunlight. The razzle-dazzle warns predators: "I'm very poisonous!" The leftmost photo shows a double-branded crow caterpillar. The three center photos show the bright gold, silver and light green chrysalises of crow butterflies. Hanging from tree branches, they're strikingly beautiful (photos by Cheng Wan-ching). The photo at right shows an adult double-branded crow butterfly (photo by Chan Chia-lung).

In recent years tens of thousands of double-branded crow caterpillars have been found in Long Life Forest Park at Chunan on the Miaoli coast. The Taiwan cow-plant vines that grow on the massive horsetail trees there are the only food they eat in that area. (photo by Cheng Wan-ching)

Unraveling the mysteries surrounding the migration routes of Taiwan's crow butterflies will require more volunteers to help track butterfly migrations. The photo shows volunteers getting trained in the Maolin Ecological Park. Academics are giving them field training in marking butterflies and distinguishing between more than ten different species.

Covering leaves and branches, crow butterflies overwinter in certain sheltered valleys in southern Taiwan every year. Along with the great gatherings of monarch butterflies in certain Mexican valleys, these are regarded as the largest aggregations of overwintering butterflies in the world. Pictured here are butterflies overwintering in a valley near Taitung's Mt. Tawu. (photo by Hsu Ming-cheng)