Posts Tagged: Monarch butterflies
Reporter Lizzie Wade, Science's Latin America correspondent based in Mexico City, led with: "It started with the best of intentions. When evidence emerged that monarch butterflies were losing the milkweed they depend on due to the spread of herbicide-resistant crops in the United States, people across the country took action, planting milkweed in their own gardens. But a new paper shows that well-meaning gardeners might actually be endangering the butterflies' iconic migration to Mexico. That's because people have been planting the wrong species of milkweed, thereby increasing the odds of monarchs becoming infected with a crippling parasite."
Wade pointed out that "tropical milkweed—at least when planted in warm environments like southern Texas and the U.S. Gulf Coast—doesn't die back in the winter like native milkweed does. When presented with a place to lay their eggs year-round, many monarchs don't bother making the trip to Mexico at all." Some think the year-round tropical milkweed is "an even more direct threat to the butterflies. Milkweed hosts a protozoan parasite called Ophryocystis elektroscirrha (OE). As caterpillars, monarchs ingest the parasite along with their normal milkweed meals, and when they hatch from their chrysalises they are covered in spores."
She quoted a butterfly scientist as saying that infected monarchs are much weaker than their healthy counterparts and don't live nearly as long. And if an OE-infected monarch tries to migrate, it will probably die long before it arrives in central Mexico, she wrote.
Shapiro has been monitoring and studying populations of butterflies in central California for more than four decades and posts the information on his website. In an email response to inquiries from a UC Master Gardener and Farm Advisor (initially sent my way), wrote: “The story is basically correct, but there has to be more to it. Monarchs are normally in 'reproductive diapause' in winter, which means their sex organs and sex drive are inactive; this condition (as in migratory birds) is believed to be induced by seasonal day-length changes. We never used to get attempted winter breeding. Tropical milkweed has been in gardens in California for decades, but only very recently are we seeing attempted winter breeding, first in Southern California and now in the Bay Area. Many of us would like to understand why these animals are NOT in diapause! There have been unexplained changes in the seasonal geography of monarch breeding: for example, here in the Sacramento Valley, there is now virtually no spring breeding (as before) but tons of fall breeding (which didn't use to happen; the animals migrating coastwise were generally in reproductive diapause)."
The reference to OE is correct, Shapiro said. "However, there is an easy 'fix' that nobody talks about for some reason: just cut the plants to the ground a few times a year. This will encourage new growth, which will be cleaner, prettier, more nutritious, and uncontaminated with OE. There is nothing inherently 'bad' about winter breeding if it's clean. Infected winter breeding is a population sink. The animals are often too feeble to fly, and may be unable to expand their wings. But perfectly healthy ones are being produced right now in the East Bay on clean plants."
Many of the public comments that people posted about the research, Shapiro said, show a large amount of ignorance. “Observation: the commonest eastern (Asclepias syriaca complex) and Californian (A. fascicularis) milkweeds are usually almost if not quite non-toxic, which means the monarchs that feed on them will be edible to birds. If you want to breed monarchs as bird food, by all means plant those! But if you want to breed nasty monarchs that will make birds vomit and never try one again, plant one of the more toxic species! There is no good evidence that the females discriminate between high-and low-cardenolide milkweeds, or that larvae do better on one than on the other. There is no garden equivalent of "one size fits all." You want to use species that make sense where you are located! That's what gardening 'zones' are there for...The genus Asclepias extends south to Argentina (the s-most species, A. mellodora, is the major host of the South American Monarch, Danaus erippus) so yes, there are milkweeds in Mexico…. There are so many resources readily available, but people are lazy, don't know how to search properly, or prefer to create their own 'facts' a la Fox News...it gets discouraging. God bless Master Gardeners and Farm Advisers!”
A male monarch nectaring Mexican sunflower (Tithonia). (Photo by Kathy Keatley Garvey)
From 75 to 80 feet below, they bore no resemblance to monarch butterflies (Danaus plexippus), the most familiar butterfly in all of North America.
"Wait 'til the sun shines on them," a docent whispers. "That will be about 10 to 15 minutes." State park rangers and docents do not yell; they whisper.
At around 11 a.m. on Saturday, Dec. 27, the sun's rays struck the cluster. Soon after, a bluejay scattered them.
The crowd below broke into applause. It's not often that a crowd applauds a miracle of nature, but that's exactly what it is. A miracle of nature as roosting monarchs winter in a Eucalyptus grove.
The Natural Bridges State Park is the only monarch butterfly preserve in the United States, according to a park publication. More than 100 permanent overwintering colony sites dot the California coast. They include Pismo Beach and Pacific Grove.
At the Natural Bridges State Park Visitors' Center, guests can see the four stages of the monarch: egg, larva, chrysalis and adult. Milkweed, the host plant, grows in a demonstration garden outside. Last Saturday the milkweeds were blooming as if were spring.
The winter-generation monarchs are usually born in late August or September "as the sun's rays and the days begin to shorten," according to a park publication. "This shortening of the light seems to trigger several important changes in these monarchs:
(2) They have the ability to store fat, which summer generations do not have, and they feed earnestly to build up stored body fats for the migration and the overwintering periods.
(3) They begin a serious migration to safe wintering roosts. They arrive at sites in California during October and in Mexico in November.
(4) At the wintering sites, they reduce their activity, extend their life span and wait until spring, usually February, to begin mating activities and producing the next generation of monarchs."
The roosting monarchs cluster like shingles on the limbs, needles and leaves of a number of trees, including the Eucalyptus, native to Australia. Among the other trees they favor: native Monterey pine, Monterey cypress and sycamore.
How are the monarchs able to hold on? With their tarsi, or backfacing claws. They roost in areas where winter temperatures don't dip to freezing. "The monarchs are looking for the refrigerator, not the freezer" in order to slow their metabolism, a park publication pointed out.
Other predators include the chestnut-backed chickadees, mockingbirds, phoebes, shrews and mice. In addition, several flies and wasps lay their eggs on the caterpillar.
School children touring the preserve soon learn how they differ from monarchs. Humans have two legs; butterflies have six legs; humans travel with their feet; butterflies with their wings; human smell with their noses; butterflies smell with their antennae. Humans taste with their tongues; butterflies have taste sensors on their feet, which are reportedly 2000 times more sensitive than the human taste buds.
Unfortunately, North America's monarch butterfly population is declining. Wintering groves are disappearing due to coastal development in California and logging in Mexico. And inland, loss of milkweed resources means a loss of their host plant. The Xerces Society for Invertebrate Conservation recently related that the North America population of Monarchs has decreased by 90 percent in the past 20 years.
The good news, however, is that we humans are focused on the plight of the Monarch.
On Dec. 29, a Xerces press release proclaimed: "Monarch Butterfly Moves Toward Endangered Species Act Protection."
"In response to a petition by the Center for Biological Diversity, Center for Food Safety, Xerces Society and renowned monarch scientist Dr. Lincoln Brower, the U.S. Fish and Wildlife Service said today that Endangered Species Act protection may be warranted for monarch butterflies," the press release began. "The agency will now conduct a one-year status review on monarchs, which have declined by 90 percent in the past 20 years."
Sarina Jepsen, the Xerces Society's endangered species director, was quoted as saying: “We are extremely pleased that the federal agency in charge of protecting our nation's wildlife has recognized the dire situation of the monarch. Protection as a threatened species will enable extensive monarch habitat recovery on both public and private lands.”
Monarchs roosting on the leaves of a Eucalyptus tree. (Photo by Kathy Keatley Garvey)
Sun rays light up the cluster. (Photo by Kathy Keatley Garvey)
Close-up of monarchs in flight. (Photo by Kathy Keatley Garvey)
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!
A monarch and a honey bee sharing a Mexican sunflower, Tithonia. (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.
A mighty male Monarch on the move. On its way to one of coastal California's overwintering sites, it stops to sip from flight fuel (nectar) from a Mexican sunflower, Tithonia. (Photo by Kathy Keatley Garvey)
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.”
For more information about the project, see WSU's Monarch Butterfly news story.
Close-up of a tagged Monarch butterfly. (Photo by David James, entomologist at Washington State University, Pullman, Wash.)
Entomologist David James demonstrates how to tag a Monarch. This image was taken at a meeting of the Washington Butterfly Association at a Monarch breeding site near Vantage in central Washington on Aug. 23 2014.
Inmates at the Washington State Penitentiary, Walla Walla, rear most of the Monarchs. The photo, taken during a WSU Media Day, shows the release of the butterflies. (Photo by David James)
This Monarch butterfly, reared by inmates at the Washington State Penitentiary, heads for freedom. (Photo by David James)