Hugh Dingle

Dingle, who served as a professor in the UC Davis Department of Entomology from 1982 to 2002, achieving emeritus status in 2003, recently published the second edition of Migration: The Biology of Life on the Move (Oxford University Press), a sequel to the first edition published in 1996.

A worldwide authority on animal migration, Dingle says the full understanding of migration, or “life on the move,” involves genetics, physiology, and morphology, as well as behavior and ecology. Among the animals that migrate: whales, monarch butterflies, armyworm moths, pelicans, locusts, winged aphids and ballooning spiders.

Dingle has researched in seven countries: UK, Kenya, Thailand, Panama, Germany and  Australia, as well as the United States. National Geographic featured him in its cover story on “Great Migrations”  in November 2010.  LiveScience interviewed him for its November 2010 piece on“Why Do Animals Migrate."

Now Dingle will be heading to the Pacific islands to study monarchs. He just received the UC Davis Edward A. Dickson Professorship Award to research “Monarchs in the Pacific: Is Contemporary Evolution Occurring on Isolated Islands?”

Monarch butterflies established just 200 years ago in remote Pacific islands are undergoing contemporary evolution through differences in their wing span and other changes, Dingle believes. He will be working with community ecologist Louie Yang and molecular geneticist Joanna Chiu, assistant professors in the UC Davis Department of Entomology and Nematology, to examine the ecology and physiology of monarch butterflies (Danaus plexippus) in three islands where contemporary evolution might be expected. The islands are Oahu (Hawaii), Guam (Marianas) and Weno (Chuuk or Truk).

“This is the necessary first step in a long-term analysis of the evolutionary ecology and physiology of monarch butterflies on remote Pacific islands,” said Dingle, a fellow of the American Association for the Advancement of Science and the Animal Behavior Society.

The monarch, widely distributed “for eons” in the New World, is fairly new to the Pacific islands and to Australia. He speculates that the monarchs arrived in the Pacific islands with their host plant, milkweed, which was valued at the time for its medicinal properties.

An analysis of a monarch population in Hawaii shows that resident monarchs have shorter, broader wings than the long-distance migrants. The Hawaii butterfly wings were shorter than the eastern U.S. long-distance migrants, but “not so short-winged as the residents in the Caribbean or Costa Rica, which have been present in those locations for eons, rather than the 200 years for Hawaii.”

“If there are indeed wing shape changes associated with evolution in isolation, are there other changes that may have occurred under selection and local adaptation for residency?” Dingle wonders. “Are there other changes that may have occurred under selection and local adaptation for residency? Examples of such traits might be changes in flight muscle physiology, changes in photoperiodic diapause response, changes in the characteristics of orientation ability and its relation to antennal circadian rhythms, or changes in the reproductive capacity or tactics (re-colonization of ‘empty' habitats is no longer part of the life cycle)."

“Diapause and fat storage, necessary to support migration, are triggered by short photoperiods,” Dingle said, “and the butterflies orient using a sun compass synchronized to a circadian rhythm in the antennae." Overwintering sites in North America include the Transvolcanics Mountains of central Mexico, and the California Coast, particularly Santa Cruz, Pismo Beach, and Pacific Grove.

The UC Davis team will study the monarchs on the three islands and compare them with California mainland monarchs. Using an image analyzer and camera equipment available in Yang lab, the team will photograph “chilled” butterflies in a fixed position with wings spread and then release them back into the wild. The image analyzer will measure different variables, including length, width and angles from the photographs and compute multivariate-shape parameters.

The Chiu lab will assess genetic differences using a transcriptomic approach with monarch caterpillars. “This assessment will be greatly facilitated by the fact that the monarch genome has now been sequenced,” Dingle noted. “A major focus of Dr. Chiu's research is circadian rhythm genes, and these will be especially relevant here because of the association of these genes with monarch capabilities. Because the monarch cell line is cycling and has a functional circadian clock, effects of mutations in specific clock genes can be examined with regard to clock function.”

Dingle expects the one-year research program not only to form the basis for “long-term research on the evolutionary genetics of behavior, ecology and physiology on Pacific island monarch butterflies” but on “the general aspects of island biogeography, a subject of great practical theoretical interest in evolutionary biology.”

That's exciting research. We look forward to the results!

Hugh Dingle (Photo by Kathy Keatley Garvey)

For years we've marveled at the migrating whales passing Point Reyes as we stood glued to our binoculars.

And we've expressed awe that a bird--a plover--makes nonstop flights over the central Pacific Ocean from Alaska to Australia and New Zealand.

Amazing. Nothing short of incredible, especially when you consider that many homo sapiens can't find their way out of a parking lot.

They're all on the move. But how many of us have seen the lesser known migrants, such as winged aphids, ballooning spiders, mites, locusts, pelicans, grasshoppers, and armyworm moths, on the move?

Enter Hugh Dingle, an emeritus professor of entomology at the University of California, Davis, and a worldwide authority on animal migration.

Dingle, who was featured in National Geographic's cover story on "Great Migrations in November 2010 and interviewed by LiveScience for its November 2010 piece on “Why Do Animals Migrate?", has just published the second edition of his book, Migration: The Biology of Life on the Move (Oxford University Press), a sequel to the first edition published in 1996.

The full understanding of migration, or “life on the move,” involves genetics, physiology, and morphology, as well as behavior and ecology, Dingle says.

"The program or syndrome includes specific modifications of metabolic physiology like enhanced fat storage to fuel migration and of sensory systems to detect inputs from the sun, stars, and magnetic field lines to determine compass direction. Intimately involved in the latter are daily and yearly biological clocks. The pathway followed is an outcome of the syndrome of migratory behavior and is part of the ecology that provides the natural selection acting to determine the evolution of migration.”

Not all migration is a round trip; sometimes it's one-way, Dingle says.  “Important defining behavioral characteristics are specific departure and arrival tactics and the refusal to stop even in favorable habitats until the migration program is complete,” Dingle says. “In the words of National Geographic reporter David Quammen migrants ‘are flat-out just gonna get there.'"

Why is it important to understand the biological basis of migration and its evolution? “Because migration is so widespread and because migrants have such impact on both natural and man-altered ecosystems,” says Dingle, who achieved emeritus status in 2003 after serving on the faculty of the UC Davis Department of Entomology (now the UC Davis Department of Entomology and Nematology) from 1982 to 2002.

In his book, Dingle covers the interaction between behavior and outcome. Another important focus: he covers the relation between migration and life histories, including the evolutionary genetics of the relationship. Long-distance round-trips, for example, require long lifespans, hence most insects, although not all, migrate only one-way.  

“Natural selection acts differently on long versus short lives," Dingle says. "With long lives there are usually many opportunities to produce offspring; with short lives there may be only one. Thus reproductive opportunities may determine when and where to migrate. Migrating aphids postpone reproduction until they colonize new host plants; birds reproduce following migration in the spring, but not in the fall. Some birds and insects use migration to exploit ‘rich patches' and breed in different places in different years or even in the same year."

Dingle, former secretary of the International Society for Behavioral Ecology and past president of the Animal Behavior Society, says he wrote the book for "students of migration and for those biologists who are generally interested in the functioning and adaptations of whole organisms."

Dingle is a fellow of the American Association for the Advancement of Science and the Animal Behavior Society. His research has taken him throughout the world, including the UK, Kenya, Thailand, Panama, Germany and  Australia.

In some respects, he, too, migrated.

This Pacific Northwest-reared Monarch butterfly was found in San Mateo on Oct. 10. It had flown 330 miles in 10 days. (Photo by Albert Wong)

It may have flown hundreds of miles from the Pacific Northwest, and Washington State University entomologist David James is eager to know where you found it.

James, an associate professor at Washington State University,  studies the migration routes and overwintering sites of the Pacific Northwest Monarch population, which are thought to overwinter primarily in coastal California but also in  central Mexico. He spearheads a Monarch-tagging project in which volunteers--primarily inmates at the Washington State Penitentiary, Walla Walla--rear and release the butterflies.

“There are currently more than 2000 monarchs (Danaus plexippus) in the Northwest that are carrying tags and many of these I have good reason to believe are in the general Sacramento to San Francisco area," James said this week.

“Last Friday, Oct. 10, one of our tagged Monarchs was seen near San Mateo--this one was tagged 10 days earlier in Applegate, southern Oregon. It had flown 330 miles! Then a few weeks ago (Sept. 27) another was seen at Glen Ellen, Calif. This one had flown a whopping 600-plus miles from Yakima in central Washington."

James explained that “we have very little data to support the notion that they all fly to coastal California for overwintering. Before our project there was just a single tagged Monarch from Washington recovered in California. Recent observational evidence suggests that some PNW Monarchs fly in a more southerly-south-easterly direction, away from California and we speculate these may end up in Mexico! We have had one tag to date that supports this idea...a monarch released at Walla Walla turned up at Brigham City in Utah.”

Because the summer Monarch population in Washington, Oregon, British Columbia and Idaho is so small, James and his team have had to resort to mass breeding of Monarchs for tagging.

“We obtain wild females in Washington and rear their progeny,” the entomologist said. “Much of the rearing is done by inmates at Walla Walla Penitentiary.” He described it as “a very successful program for the butterflies and the prisoners! “

James is also increasingly using citizen scientists to rear and tag as well. See more details of recent recoveries and information about the program at the program's Facebook page.

You don't need a professional camera to capture an image. James said that "the two California recoveries we have had so far were both confirmed by cell phones or regular cameras! This technology definitely aids recoveries. It's so easy to take a high quality 'snap' that can be used to determine the tag details."

“I am confident there are a number of tagged Monarchs currently in your area," James told us. "We are actually still releasing them here in Washington, so the opportunity to see one will persist for a few weeks yet. “

He figures they are "likely heading to the overwintering sites at Bolinas, Santa Cruz and Pacific Grove--maybe further south as well.”

So, if you see a WSU-tagged monarch, take a photo and let WSU know. Contact: david_james@wsu.edu or the Facebook page.

For more information about the project, see WSU's Monarch Butterfly news story.

The Xerces Society for Invertebrate Conservation issued news today that is both disturbing and hopeful.

Disturbing in that the monarch butterfly population (Danaus plexippus) has declined by more than 90 percent in under 20 years.

Hopeful in that the monarch may receive federal protection through the Endangered Species Act.

The Xerces Society, the Center for Biological Diversity,  the Center for Food Safety, and monarch scientist Lincoln Brower, have filed a legal petition with the U.S. Fish and Wildlife Service to protect the monarch through the Endangered Species Act. The agency must respond within 30 days as to whether the petition warrants further review.

“Monarchs are in a deadly free fall and the threats they face are now so large in scale that Endangered Species Act protection is needed sooner rather than later, while there is still time to reverse the severe decline in the heart of their range,” related Lincoln Brower, preeminent monarch researcher and conservationist, who has been studying the species since 1954.

Tragicallly, the monarchs have lost more than 165 million acres of habitat, including nearly a third of their summer breeding grounds that contain their host plant,  milkweed. The female monarchs lay their eggs on milkweed and this is the only food their larvae eat.

As Lynn Kimsey, director of the Bohart Museum of Entomology and professor of entomology at UC Davis, told us today: "Might be too little too late but they have to preserve/conserve milkweeds (Asclepias spp.) That's more important than the butterfly itself."

Xerces earlier sounded the alarm on the critical role that milkweeds play in the monarch's life cycle.

Senior scientist Tierra Curry of the Center for Biological Diversity, hammered home this point in the news release: “The 90 percent drop in the monarch's population is a loss so staggering that in human-population terms it would be like losing every living person in the United States except those in Florida and Ohio.”

And the loss of habitat is equal in size to the state of Texas.

The news release said that the butterfly's dramatic decline is "being driven by the widespread planting of genetically engineered crops in the Midwest, where most monarchs are born. The vast majority of genetically engineered crops are made to be resistant to Monsanto's Roundup herbicide, a uniquely potent killer of milkweed, the monarch caterpillar's only food. The dramatic surge in Roundup use with Roundup Ready crops has virtually wiped out milkweed plants in midwestern corn and soybean fields."

Science policy analyst Bill Freese of the Center for Food Safety was quoted as saying: "The widespread decline of monarchs is driven by the massive spraying of herbicides on genetically engineered crops, which has virtually eliminated monarch habitat in cropland that dominates the Midwest landscape. Doing what is needed to protect monarchs will also benefit pollinators and other valuable insects, and thus safeguard our food supply.”

Monarch butterflies are known for their spectacular multigenerational migration each year from Mexico to Canada and back, the news release said.

"The population has declined from a recorded high of approximately 1 billion butterflies in the mid-1990s to only 35 million butterflies last winter, the lowest number ever recorded," according to the release. "The overall population shows a steep and statistically significant decline of 90 percent over 20 years. In addition to herbicide use with genetically engineered crops, monarchs are also threatened by global climate change, drought and heat waves, other pesticides, urban sprawl, and logging on their Mexican wintering grounds. Scientists have predicted that the monarch's entire winter range in Mexico and large parts of its summer range in the states could become unsuitable due to changing temperatures and increased risk of drought, heat waves and severe storms."

Endangered species director Sarina Jepson of the Xerces Society worries--and rightfully so--that the monarch may become extinct, just like the passenger pigeon.

We are, too. We've seen only two--two--of these majestic butterflies fluttering in our family bee garden this year.