Bluebird

March 23, 2012, 11:03 AM

Ancient Hawaiians Caught More By Fishing Less

By DOUGLAS M. MAIN

Getty ImagesA school of manini fish pass over a coral reef in Hanauma Bay in Honolulu.

Centuries ago, Hawaiians caught three times more fish annually than scientists generally consider to be sustainable in modern times — and maintained this level of harvest for more than 400 years, researchers report in a new study in the journal Fish and Fisheries.

The findings could be instructive for agencies that enforce fishing limits in overfished waters around the globe.

Native Hawaiians caught about 50 percent more fish than modern fleets catch today in both Hawaii and the Florida Keys, the two largest reef ecosystems in the United States, said a co-author of the study, Loren McClenachan, a fisheries researcher at Colby College in Waterville, Me.

Hawaiians harvested about 15 metric tons of fish per square kilometer of reef annually from 1400 to 1800, the study found. That’s five times the median harvest in island nations worldwide today.

Dr. McClenachan and her co-author, John Kittinger, a researcher at theCenter for Ocean Solutions in Monterey, Calif., drew on a variety of historical records and a method called catch reconstruction to estimate historical harvests in the Hawaiian Islands and the Florida Keys.

The Hawaiians used many techniques similar to those employed today, like temporary or permanent bans from fishing in certain areas, restrictions on certain species and gear, and catch limits. But they enforced the rules strictly; breaking them could mean corporal punishment or even death.

While the authors obviously don’t advocate such extremes, penalties in some areas could be stricter, the authors suggested, and enforcement could improve. In Hawaii today, “you get penalized much more harshly if you shoplift sunglasses from a store than if you take a bunch of fish that are the wrong size or kind,” Dr. Kittinger said in an interview.

Dirk Zeller, a fisheries scientist at the University of British Columbia who was not involved in the study, said that the conclusion makes sense: Hawaiians were able to maintain such high levels because their fishing activities were so well managed and focused on a wide variety of different species, he said. They also left well enough alone, regularly outlawing fishing in spawning grounds and other areas to allow populations to regenerate, Dr. Zeller said.

The two places studied tell very different stories. As historians have documented, native Hawaiians employed a carefully controlled community-based system of regulations on fishing. Rules were passed down by oral tradition and recorded when missionaries introduced printing presses to the islands in the early 1800’s, Dr. Kittinger said.

In the Florida Keys, however, where intensive fishing didn’t take off until the mid-19th century, there have been fewer regulations and a repeating pattern of overfishing of one species for sale on global markets followed by a crash in that fish population and a switch to a new species. This cycle has severely depleted green turtles, sponges, sawfish and other creatures.

Now reefs in both places are overfished — “and there are less fish coming off the reef then back in the day,” Dr. Kittinger said.

Given that enforcement agencies are often underfinanced, he said, they might do better to devise a bottom-up approach. That is already happening in some areas, where officials have adopted co-management schemes with community groups that help draft rules and regulations.

Most productive reefs in long-ago Hawaii had community managers who knew a reef well and made rules unique to their own neck of the ocean, Dr. Kittinger noted.

The researchers reconstructed historical harvest levels by calculating the amount of fish consumption per capita necessary to maintain estimated population levels in Hawaii over the last 700 years. Dr. Kittinger said the results are conservative because he and his colleague used the low end of anthropologists’ population estimates in their calculations.

While some may question the use of such historical data, Daniel Pauly a researcher at the University of British Columbia, said that such information is probably just as accurate as current harvest estimates. One can estimate the catch of an isolated society like Hawaii by using population rates, which can be inferred quite reliably by anthropologists, said Dr. Pauly, who was not involved in the study.

Dr. Zeller suggested that the study shows “that we must learn from the past to save the future.”

If more marine reserves were established and limits were firmly imposed on fishing, he said, the fishing industry could actually catch more fish while making less of an effort.

But the blame should not be assigned solely to regulatory agencies, Dr. Pauly said. “We moderns cannot stomach restrictions on fishing that are necessary to maintain the stocks,” he said.

 

March 19, 2012, 7:45 AM

A Spring Sprung Too Soon Is a Death Blow to Butterfly

By JOSIE GARTHWAITE

Carol L. BoggsAn early snow melt can cause a cascade of negative effects on the Mormon fritillary butterfly.

Early snow melts caused by climate change could deliver a mighty one-two punch to the delicate Mormon fritillary butterfly, shrinking the insect’s favored nectar supply, killing caterpillars and causing a steep population decline, a new studyin the journal Ecology Letters finds.

In all, the researchers report, the combined effects of two consecutive years of early snow melt explained as much as 84 percent of the variation seen in the fritillary’s population growth rate between 1980 and 2005.

“It is very unusual for research to uncover such a simple mechanism that can explain almost all of the variation in growth rate of an insect population,” one of the study’s co-authors, David W. Inouye, a biology professor at the University of Maryland, said in a statement.

The deadly power of an early snow melt has to do with the particulars of the butterfly’s life cycle. During the first summer of a female fritillary butterfly’s life, she lays eggs and dies. Caterpillars from these eggs spend the winter without food and become adult butterflies the following summer.

The adult butterflies eat nectar, mostly from the aspen fleabane, which blooms from mid-late July to mid-late August — the peak of the fritillary flight season. The number of eggs laid has been found to depend upon how much nectar the fritillary consumes, according to laboratory experiments cited in the journal paper.

By analyzing decades of data on fritillary populations, aspen fleabane blooms and snow melt dates in the Colorado Rocky Mountains, scientists discovered that one early snow melt can throw these phases out of whack. Working out of the Rocky Mountain Biological Laboratory, Dr. Inouye and the the study’s other author, Carol L. Boggs, found that two consecutive years of early snow melt and frosts at the beginning of the growing season make matters worse for the fritillary.

That is because early season frosts can kill both young caterpillars and aspen fleabane buds. As snow begins to melt, signaling winter’s end, the caterpillars and fleabanes enter a development stage in which they are poorly equipped to survive frost. If flower buds are killed off early in the season, that means less nectar will be on tap for each butterfly come summer, which in turn leads to fewer eggs. So the adults are eating less and laying fewer eggs, while the next generation is being struck down by frost.

Dr. Boggs and Dr. Inouye considered more than 30 years of records on the first day of bare ground, and the number of aspen fleabane flowers blooming in seven wildflower plots in the Elk Mountains of Colorado. They analyzed the annual population density of male fritillaries during nine pairs of sequential years between 1980 and 2005.

Estimated population densities during that time spanned two orders of magnitude, ranging from just 28 males per hectare (2.47 acres) in 1985, apparently due to a severe snowstorm in late June, to nearly 4,500 males per hectare in 1980. More often, the researchers found fewer than 2,000 fritillary males per hectare.

The road is not getting any easier for the Mormon fritillary, said Dr. Boggs, a professor of biology at Stanford.

“We already can predict that this coming summer will be a difficult one for the butterflies,” she said in a statement, “because the very low snowpack in the mountains this winter makes it likely that there will be significant frost damage.”

 

Snow Fleas in the UP

March 12, 2012, 7:38 PM

When Snow Fleas Surface, Winter Study Comes to a Close

By JOHN VUCETICH

John VucetichWolves in the Chippewa Harbor Pack.

John Vucetich, a wildlife ecologist from Michigan Technological University, leads the wolf-moose Winter Study at Isle Royale National Park.

Saturday, March 3

Snow fleas by the hundreds have congregated on the surface of the snow. They belong to a group of creatures collectively known as collembola. They look like insects, but recent research suggests they may be as closely related to insects as mammals are to reptiles. They live in the soil, sustaining themselves on decomposing vegetation. Of the earth’s animals large enough to see with the unaided eye — and collembola barely qualify — these are reputed to be the most abundant. Usually they escape our attention almost entirely.

Then on certain warm days in late winter, some adventurous snow fleas crawl to the surface of the snow, where you can’t help but notice them. I wonder what the life of a snow flea is like. Is it itchy to molt your exoskeleton? Do their “springtails” feel stiffer on cold days, when their bodies are soaked in glycine-rich proteins that work like antifreeze? Why do they come to the surface of the snow?

What we do know is that when the snow fleas congregate, the end of winter is not far off. Soon the snow will begin receding and exposing stumps, and south-facing exposures will see the sun again as the snow recedes. The chickadees will switch to their spring song. And the ice will begin to break up.

Our plan, should the weather cooperate, is to fly home three days from now. If today’s snow and wind continue as forecast, then the last research flight of Winter Study 2012 was yesterday. It’s as sad as the last day of summer.

 

John VucetichThe skull of a wolf-killed moose.  The inset shows a tooth impacted with rotting vegetation.

JOHN VUCETICH

Posts From Isle Royale

• Preparing to Live With Wolves
• In Winter Weather, Flying to Find Wolves
• Wolves, Snow and the Red Dragon
• A Wolf-Moose Standoff at Isle Royale
• One Moose, Two Moose
• Following the Wolf Pack
• Much to Learn From What Remains
• A Luscious Meal for Moose
• An Eruption of Ravens
• A Pack of Hungry Wolves
• As Wolf Diminish, Moose Flourish
• Keeping an Eye on Two Intimate Wolves
• For Moose, an Easy Winter Turns Hard
• A Band of Boy Wolves

Sunday, March 5

In preparation for our departure, I decommission the bone boiling pot. The bones are cleaned, tagged, inventoried. Later we’ll move them to a permanent storage facility, where they’ll join the ranks of skeletal remains of some 4,500 other moose, souvenirs of 54 years of effort and the subject of many scientific papers on topics ranging from the causes of arthritis to long-term trends in atmospheric deposition of mercury and lead.

For now, the bones we collected this winter will wait here in the bone shed. Two of the specimens catch my attention. One is what remained of a skull that belonged to an old cow moose. Wolves consumed most of the skull, leaving only the palate — the roof of a mammal’s mouth — and two rows of teeth. It is rare for wolves to consume so much of an adult moose’s skull. It’s an indication of how tough a time they had capturing food this winter.

The skull of another old cow moose shows severe periodontal disease. Rotting, fermenting twigs and needles are packed in a space between the roots of her teeth. I don’t imagine that a human could endure such a severe infection. Of all the moose we’ve ever collected, more than half have significant debilitation, like severe periodontal disease or arthritis.

The next two days will be a blur, and tonight is the last time until next year for the three of us to relax together. We stay up late to watch the “Mollie B Polka Party.”

Monday, March 5

Tomorrow’s forecast is dicey. If we can fly off the island, there will only be a small window of opportunity in the morning. We’ll break down base camp today – all manner of gear and equipment; boxes of canned goods to the root cellar; dry goods, dishes, pots and pans to the shed; seven weeks’ worth of long underwear and winter socks in boxes; decommission the sauna, the water hole and the red dragon.

The Winter Study generates quite a few statistics about the wolves and moose. One of the most important is the kill rate — how frequently wolves kill moose. Right now the Chippewa Harbor Pack’s kill rate stands at five moose killed, divided by the six wolves in that pack, divided by the 42 days that we’ve been able observing them. If we fly today, we might find another kill, but at least we can add a couple more days to the denominator.

No kill in the past few days. As soon as we land, with the sun setting, we strip the Flagship of her telemetry gear and survival equipment and decommission the pump used to refuel her.

George DesortFrom left, Don Glaser, pilot of the Flagship; Rolf Peterson; and John Vucetich, leaders of the wolf-moose project, on Isle Royale National Park’s Washington Harbor.

Tuesday, March 6

At 10:30 a.m., we take off from the ice on Isle Royale’s Washington Harbor for the last time this winter. A warm, moist south wind blurs the boundary between Lake Superior and the sky. Before long, the island has faded into the haze.

This winter we observed the wolves of Isle Royale National Park experience one of their toughest years ever — high mortality rates and low recruiting left relatively few wolves. The Middle Pack is gone. The Chippewa Harbor Pack may not have any females. The future of this population may well rest with the West-End Duo. They mated last week. If all goes well, within a day or two of April 26, the female will be nursing half a dozen pups, each a little larger than your fist.

Despite recent snowstorms, the moose haven’t experienced times this good in more than a decade. That is partly a result of declining wolf predation. Climate warming is adversely affecting many populations of moose living at the southern limit of their range. Isle Royale moose are one of the few moose populations that have been doing well in recent years. It’s important to observe the moose respond positively to reduced wolf predation. With climate warming, that response cannot be taken for granted.

Over the next few weeks, we’ll prepare an annual report summarizing and contextualizing what we learned this past year. Throughout the year, Rolf and I will write papers and visit universities, high schools, local communities and government agencies to share what the wolves and moose have taught us and what our observations mean.

John VucetichThe Chippewa Harbor Pack heads into the forest.

The first lesson draws our attention away from “What does it all mean?” The more important question is, “From where does the meaning come?” The meaning comes from caring, and caring can be ignited by the simple act of paying attention. Pay attention to another creature from one day to the next, but understanding those observations may well require the context of observing from one year to the next, one generation to the next. Scientists can do this in a special way — enlivened with theories and equations.

But the essential lesson of Isle Royale wolves and moose is for all of us. Meaning comes from paying attention to the life that surrounds us, life in all its varied forms.

We land in Duluth at noon, and drive for the rest of the afternoon around the western end of Lake Superior to Houghton, Mich. There we reunite with our sweeties. Every year it ends just the same. We leave in a hurry, and our lives change tremendously. Indoor plumbing and complete disregard for the weather are two of the biggest changes. But we’ll return to Isle Royale in just a couple of months to begin the summer field season, and then again next January for the 55th annual Winter Study. Don, our pilot, captures the spirit entirely with an old English proverb: “It’s a long road that has no turning.”

“Fortunate Wilderness” is a documentary illustrating wolf and moose behavior in Isle Royale National Park over a four-year span. It was filmed by George Desort and had its premiere in the summer of 2008.

 

Unprecedented number of sea otter deaths along California coast

After being brought back from the brink of extinction, the mammal is again in peril. The U.S. Geological Survey reported that 335 dead, sick or injured otters were found in 2011, a record high.

A sea otter basks in the sun in Moss Landing Harbor in Monterey Bay. The U.S. Geological Survey reported that 335 dead, sick or injured otters were found along the California coast in 2011, a record high. (Vern Fisher, Monterey County Herald / February 3, 2009)

By Dalina Castellanos, Los Angeles Times

February 26, 2012, 9:28 p.m.

After being brought back from the brink of extinction, sea otters are again in peril, with an unprecedented number of deaths along the California coast in the last year.

The U.S. Geological Survey reported that 335 dead, sick or injured otters were found in 2011, a record high.

"We're starting to see a perplexing trend suggesting increased shark attacks on sea otters," said Tim Tinker of the USGS' Western Ecological Research Center.

Shark bites accounted for 15% of otter deaths in the late 1990s, but that percentage nearly doubled in 2010 and 2011, Tinker said.

Sharks have long received some of the blame for the otter's mortality rate, but the population has also been thinned by infectious diseases, boat strikes and gunshot wounds, among other factors.

"If these stressors remain high and shark mortality remains high, then there is no chance" for the population to regenerate, Tinker said.

Sharks seem to favor breeding-age female otters, he said, which could deliver more of a blow to the sea mammals' numbers.

The last official population reported for the sea otter was 2,711, only 379 short of the threshold that would begin consideration for it being removed from the federal endangered species list.

 

February 23, 2012, 7:59 AM

A Luscious Meal for Moose

By JOHN VUCETICH

John VucetichLush growth of a balsam fir tree, untouched by moose teeth.

John Vucetich, a wildlife ecologist from Michigan Technological University, leads the wolf-moose Winter Study at Isle Royale National Park.

Thursday, Feb. 9

We check the wind hourly: 31 miles per hour at 8 a.m., 36 m.p.h. at 9 a.m., 33 m.p.h. at 10 a.m., 32, 33, 34, 37, 38 m.p.h. throughout the afternoon. As we wait, we manufacture meteorological explanations for why we should expect the wind to let up. It seems like it is shifting directions, we say; the barometer seems to be stabilizing, we say. We stare at the treetops and lie to ourselves about how the wind seems to be letting up. The wind continues at 31 m.p.h. as the sun sets. No flying today.

Friday, Feb. 10

Wind gusts exceed 30 m.p.h. each daylight hour.

Saturday, Feb. 11

The wind whips at 30 m.p.h. at 8 a.m. and builds throughout the day. At 10:24 p.m., the anemometer on Ojibway Tower records a 59-mile-an-hour gust. We fall asleep with the wind pounding in a fury against the cabin walls.

Sunday, Feb. 12

On Day 5 five of the windstorm, we have been given a task on the ground. We find the tracks of two wolves on the harbor near the cabin — the same pair of wolves we’d first seen scent-marking on the beach of Siskiwit Bay. They made the tracks while leaving the moose they killed a week ago at a site about a mile north of the harbor. We can hike in, perform a necropsy on the moose carcass and collect scats for the first time from these wolves.

 

John VucetichWolves making tracks through the winter landscape.

JOHN VUCETICH

Posts From Isle Royale

• Preparing to Live With Wolves
• In Winter Weather, Flying to Find Wolves
• Wolves, Snow and the Red Dragon
• A Wolf-Moose Standoff at Isle Royale
• One Moose, Two Moose
• Following the Wolf Pack
• Much to Learn From What Remains

On our hike in, Rolf Peterson and I marvel at the balsam fir trees. Many have grown 12 to 18 inches in the past few years. The apical meristems (the root and shoot tips where vertical growth occurs) of some now reach four feet or so above the forest floor.

Moose arrived on Isle Royale about 100 years ago. And fir trees that were just seedlings at that time here on the west end of Isle Royale (the story on the east side is completely different) were the last to grow tall into the canopy. Since that time, not a single fir tree has escaped the teeth of moose. Moose are paragons of patience, when you think of the thousands of bites they take each day of their lives, and the hundreds of hours a week they spend chewing their food.

But then you think of a fir tree. Every year of their lives, they spend all summer mustering all the energy and material they can from the air and soil to produce a little twig reaching a few inches higher toward the sky. And each winter, in a moment that is absolutely insignificant to a moose, that entire summer’s effort is ripped, chewed and digested, along with thousands of other twigs. Fir trees endure, year after year. They witness the entire lifetime of a moose, and her son and his daughter. A fir tree can endure the browsing of three or four generations of moose and never grow more than a yard. But they don’t die, either. They just keep producing those twigs, waiting and hoping — hoping not in the way that you and I understand, but hoping in the only way that a fir tree can — that it can escape being browsed not for a single year, but for the 10 to 15 years it might take to come out of its stupor and grow into the forest canopy, out of reach of the teeth of moose.

John VucetichTo check for arthritis, Rolf extracts the pelvis from frozen carcass of a moose.

And that is what we saw today on our hike in to perform a necropsy: something that hasn’t happened in a century. The fir trees are rising from their moose-induced stupor. And wolves get most of the credit — they have played a dominant role in bringing moose to levels low enough for long enough.

The carcass is an old cow moose. The bone marrow was full of white, flaky fat, a little like vegetable shortening. She had been well nourished. But her worn teeth betrayed her old age, and her hips showed signs of arthritis.

We search for wolf scats with the enthusiasm of children on an Easter egg hunt. We find 11. I pick one up and wonder if its DNA has a Y chromosome, which only males carry, or the two X chromosomes that all females carry.

I think the wind storm will end tonight.

 

February 10, 2012, 5:26 PM

Darwin’s Papers Show the Evolution of His Ideas

By JENNIFER SCHUESSLER

Cambridge University LibraryA drawing by Darwin’s son on a page of a manuscript of  “Origin of Species.”

Just in time for Charles Darwin’s 203rd birthday on Sunday, the American Museum of Natural History is unveiling the first phase of its online Darwin Manuscripts Project, a collection of more than 15,000 digitized manuscript pages and thousands of other documents drawn from Cambridge University Library, the Biodiversity Heritage Library and other institutions around the world. Among the documents available on the Web site are notes from Darwin’s time aboard the HMS Beagle, pocket diaries, early drafts of works like “The Origin of Species” (viewable with and without Darwin’s revisions), and previously unpublished manuscripts like an “experiment book” describing Darwin’s original research on plant breeding strategies, begun in 1856. In addition to revealing Darwin’s intellectual evolution, the project also reveals Darwin’s sometimes less-than-careful treatment of some of his own papers. Today, a first-edition of the “Origin” is a highly sought after rare book, but pages of the original manuscript are even rarer, thanks to Darwin’s habit of passing them out as scrap paper. Among the 42 full pages known to survive today, a few feature fanciful drawings on the reverse by his son Francis showing birds undreamed of in the Galápagos Islands as well as a soldier on a carrot battling a cavalier on an eggplant.

 

February 7, 2012, 8:07 AM

Crossed Fingers for a Threatened Butterfly

By JIM WITKIN

Stuart WeissThe Bay checkerspot butterfly, which conservationists are trying to reintroduce in Edgewood Park in Northern California. The insect is viewed as a poster child for the harmful effects of nitrogen on biodiversity, which could be even more profound than the impacts of global warming.

If you stand with your back to the sun and inspect the place on the ground where your shadow is cast, you might spot the tiny larvae of the threatened Bay checkerspot butterfly.

“It takes some practice,” said Stuart Weiss, a conservation biologist from the Creekside Center for Earth Observation. “But when you see a little black object that stays black, that’s usually a checkerspot.”

Dr. Weiss explained the technique as we hiked through the grasslands ofEdgewood Park, a 500-acre nature preserve on the San Francisco peninsula where I have been volunteering.

To reintroduce the checkerspot to the park, Dr. Weiss and his team placed 4,000 larvae, or caterpillars, here last winter. Over the next several weeks, he and several volunteers whom he refers to as “checker spotters” will be searching their shadows for signs of success: a new batch of larvae, descendants from last year’s transplants, that will be transformed into thousands of bright orange and black spotted butterflies in late March.

While the work may seem tedious, especially for an insect whose adult life as a winged butterfly spans a mere 10 days, the study of this tiny creature has far broader implications. The checkerspot, Dr. Weiss explains, “has become the poster child for the effect of nitrogen on the environment.” The impact on California’s biodiversity could be even more profound than that of global warming, many scientists say.

Vehicle exhaust from nearby Interstate 280 deposits up to 15 pounds of nitrogen per acre each year in the park. The interstate runs along the park’s western border, carrying more than 100,000 cars between San Francisco and San Jose on a busy day.

Nitrogen from car exhaust fertilizes the soil just as common lawn fertilizer does and favors faster-growing nonnative plants. “It’s a matter of competitive ability — the nitrogen-rich soil produces a very strong growth response in annual grasses, like Italian ryegrass,” Dr. Weiss said. “They thatch over and smother native plants.”

As native plants disappear, so do the native species like the Bay checkerspot that depend on them. “When you continue to dump nitrogen into the atmosphere, it has all sorts of negative impacts on the ecosystem, on human health, on the air you breathe and the water you drink,” Dr. Weiss said.

The Bay checkerspot once thrived at Edgewood but has not been seen here since 2002. Since then, an aggressive program of mowing and weeding has helped keep invasive plants in check and restore the native grasslands.

Using grant money from the San Mateo Parks Foundation to finance the work, Dr. Weiss and his team collected 4,000 Bay checkerspot larvae last winter from Coyote Ridge park in San Jose, the only remaining habitat for the species. They carried the larvae to Edgewood and placed them over 20 acres on the west side of the park, where its favorite meal, the native California plantain, is plentiful.

During this year’s hunt, which runs throughout February and March, the team hopes to find 4,000 new larvae. A lot depends on the weather conditions, Dr. Weiss said. A wet winter and a cool spring are ideal, as sufficient moisture in the soil helps extend the lifespan of the plants that support the larvae and adults.

Ultimately, the project will be counted a success if 2,000 adults are observed flitting among the wildflowers in late March. Once the adults appear, over the course of about 10 days, they will feed on nectar from the wildflowers, mate, lay their eggs on the native plantain and then die. The annual cycle begins again.

Based on early counts of larvae, Dr. Weiss is optimistic about this year’s outcome, although he expects it will take additional cycles to re-establish the butterfly at Edgewood.

The checkerspot is not the only threatened species that occupies his time. In a remote corner of the park, he points to a few square meters of ground that hold the only known remaining patch of the San Mateo thornmint, an endangered annual wildflower. The plant has also fallen victim to invasive Italian ryegrass, its population dwindling to a few hundred plants by 2008.

Thinning the nonnative grasses and carefully replanting thornmint seeds has brought the population back to nearly 3,500 plants. He is hopeful that the plant has reached critical mass and may now come back on its own without his continuing intervention.

Although the tiny thornmint has not attained the celebrity status of the Bay checkerspot, Dr. Weiss says that nurturing the species is important work. “It’s an utterly unique form of life and we shouldn’t let it go extinct on our watch,” he said.

Jim WitkinStuart Weiss, a conservation biologist,  demonstrating the technique of “shadow hunting” to find Bay checkerspot caterpillars in the grass. Interstate 280 is in the background.  

 

pulling focus

OBSERVATORY

Jumping Spiders Focus Like a Camera to Hunt

By SINDYA N. BHANOO

Published: January 30, 2012

Jumping spiders do not weave webs. Instead, they jump about and then pounce on their prey. For this reason, depth perception is very important to their survival.

E

Science/AAAS

A jumping spider's eyes show how far to pounce by sharpening the prey and blurring the background.

Now Japanese researchers have discovered that the spiders use an unusual technique to estimate how close or far away an object is.

The technique, called image defocus, involves blurring out objects in the distance while keeping closer ones sharp. Jumping spiders are the only animals known to use it, but a camera with a good lens demonstrates the same principle — keeping a person’s face sharp in the foreground while blurring out the trees in the background.

Takashi Nagata and Mitsumasa Koyanagi of Osaka City University and their colleagues write about the jumping spiders in the current issue of Science.

The researchers studied each of the four layers of the retina in one of the spider’s eyes. They found that green light is never in focus in one of the layers, and that in another layer it is always in focus.

“So the spider seems to capture a sharp image and a blurry image and compare the information to estimate the distance of an object,” Dr. Koyanagi said. Depending on whether a fly, for instance, looks blurry or sharp, the spider can decide how far to jump.

“It’s done in real time, so studying this may help develop better computer vision,” Dr. Koyanagi added.

 

Life writ large in the vastness

January 24, 2012, 6:11 PM

In Winter Weather, Flying to Find Wolves

By JOHN VUCETICH

John VucetichApproaching Isle Royale in winter snow and fog.

John Vucetich, a wildlife ecologist from Michigan Technological University, leads the wolf-moose Winter Study at Isle Royale National Park.

Friday, Jan. 20

“Dispatch, Beaver 1, departing Shagawa Lake, eastbound for Washington Harbor, Isle Royale, two aboard, four hours fuel,” said Pat Lowe, a United States Forest Service pilot. We were supposed to fly to Isle Royale on Jan. 17, but for three days, low clouds, snow and then high winds kept us waiting impatiently on the shore in Ely, Minn. It was clear, calm and cold (minus 18 degrees Fahrenheit) this morning as Pat and I lifted off from Shagawa. Rolf Peterson, a co-researcher, and Don Glazer, our Winter Study pilot, were 30 minutes ahead in the Flagship, our tiny research plane. In an hour we landed on Lake Superior ice.

The island was loosely veiled by low gray clouds — a collaboration of the west wind and moist lake air. Waves lapped on ice-covered rocks that separate Lake Superior from the forest. That forest has insights to share, if we pay attention.

 

JOHN VUCETICH

Posts From Isle Royale

• Preparing to Live With Wolves

The Forest Service plane dropped our gear on the ice and took off. It’s been six months since I was last here, and it is good to be back. It is comfortable and familiar — the feeling of being alive that only minus 5 degrees Fahrenheit can bring, the feeling of openness that comes from standing on several square miles of frozen ice, and the feeling of content from being among so many spruce and cedar trees. Wilderness is not just part of the world in which we live — it is a part of us.

There is a great deal to do. Knock holes in the ice for water. Secure the Flagship to the ice. Bring a snowmobile and several generators to life. Fire up the communications systems. Make sure the refueling system is working. Start a fire in the cabin. Haul gear from the harbor up to the cabin. The chores will keep us busy all night and into the morning. We can’t begin to make observations until we’ve prepared at least some of the essential gear.

John VucetichUnloading supplies on the ice of Washington Harbor at Isle Royale.

Saturday, Jan. 21

We worked diligently because the weather was deteriorating, and we wanted to get a flight in before the snow clouds we could see building began to unload their contents. By noon we were ready to fly.

Where do you begin when you don’t know what you may find, when you know you won’t have much time and when you need to keep an eye on the weather? We began with the south shore, where wolves spend a great deal of time looking for moose. In the flat light filtering through thick clouds, we strained to spot wolf tracks. Finally we saw the tracks of a lone wolf at Long Point. Several miles to the northeast, they hooked up with tracks of what seemed to be three wolves that had spent the night on a rocky crag near Atwood beach. They didn’t look particularly fresh, so we left seeking better prospects. At Senter point we found more tracks, most likely from the same group of wolves.

We flew northeast, listening through headsets for telemetry signals from the radio-collared wolves and staring out the cockpit window for wolf tracks that might cut across any creek, drainage or inland lake. An hour passed without another clue. Plenty of time to wonder: Are three wolves all that remain here in what had been Middle Pack (MP) territory? If they are MP wolves, none of them is collared. It could take days to find them.

Then comes a beep, and another and another. Within a few minutes we were circling over the alpha male of Chippewa Harbor Pack (CHP). He is traveling southwest through a swamp near Lane Cove with four other wolves.

John VucetichWolves of Chippewa Harbor Pack following their alpha male.

Last year CHP had nine wolves. One of them, Romeo, was not among them today. He’d tried to disperse from his natal pack during the winter of 2010, but returned home without success and spend the winter of 2011 with CHP. Had he now taken control of territory that once belonged to Middle Pack? Or was he just temporarily away from CHP? Even though Romeo wears a radio collar, we were unable to find him before having to land as falling snow began to blanket the forests.

Sunday, Jan. 23

Big, wet, heavy snowflakes let us sleep in. We won’t be able to fly again until the snow clears.

 

Mummies in Antartica

December 19, 2011, 12:12 pm Awakening Streams and Mummified Seals

By ALIA KHAN

Alia KhanA mummified seal on a hike between Lake Bonney and Lake Hoare in the Taylor Valley.

Alia Khan, a graduate student at the University of Colorado, Boulder, writes from the McMurdo Dry Valleys in Antarctica, where she is studying ephemeral glacier fed streams.

Thursday, Dec. 15

Early in the season, the streams are fickle. We arrived in the field on Oct. 22 and were greeted by cold temperatures and no flow the first five weeks we were in the field. While there was still plenty of prep work, like retrofitting stream controls and switching out data-logging systems from the end of last season, we eagerly awaited the arrival of flowing water.

Chris DeanThree Stream Team members, Chris Jaros, Tyler Kohler, and Alia Khan, in a stream gauge box at the lower Onyx River. The boxes also double as an emergency shelter in severe weather.

The hydrological cycle in the McMurdo Dry Valleys is a unique system. The streambeds are covered with a layer of permafrost, there is less than 4 inches of water equivalent precipitation per year, and there are no groundwater contributions. Like most hydrological cycles, climate is a large driver; however, unlike many other locations, surface energy budgets play a larger role than precipitation. The source waters for the streams in this polar desert almost entirely come from glacial melt. Runoff from the glaciers is largely based on glacial elevation, solar radiation exposure, air temperature and winds. High winds, like katabatic events, can blow increased sediment loads onto the glaciers, which absorb more radiation because of their dark color, decreasing surface albedo and increasing rates of meltwater generation.

As the midnight sun came out, the 24 hours of daylight increased radiation on the glacier surfaces and raised average daily temperatures above freezing, two important factors in meltwater generation and the start of seasonal streamflow. The first sight of sparkling flowing water on Canada Stream, glistening under the sun on Nov. 29, filled me with excitement as I knew the flow season had begun. Canada is the first stream to flow each season because of the aspect of the glacier which enables it to receive more solar radiation compared with others in the valley. It is also at a lower elevation and has a short stream length. Since then, we had one week of warmer temperatures in which about 10 other streams started flowing. However, on any given day, just a few hours of below-freezing temperatures or cloudy skies can be enough to cause the streams freeze up and cease flowing.

Alia KhanThe F6 Hut, named after the stream gauge next to it. It is the 6th of 10 stream gauges in the Fryxell basin.

Alia Khan

Posts From Antarctica

• Extreme Ecology in a Polar Desert
• Camp Life in the Dry Valleys

A typical field day consists of visiting three to five streams. After having breakfast and morning coffee, we prepare our gear for the day. This includes items like a pygmy meter for measuring stream discharge, waders, water sample bottles, snacks and a field note kit. We split the heavy gear among team members as we often hike up to 5 miles to stream sites. After hiking, driving by all-terrain vehicle or flying to the sites, we measure the discharge and take water samples for chemical analysis. The water samples are filtered at the hut after returning to camp that day, stored in a refrigerator and then sent to McMurdo for analysis.

Alia KhanEmily Bernzott takes water chemistry samples on Bowles stream, a stream with abundant algal mats.

Lee StanishA light microscope image of live Antarctic algae. Despite the harsh conditions, stream microbial mats harbor a diversity of organisms.

Biological analyses of algal mats are also a focus of the streams. Diatoms, cyanobacteria and green algae are the abundant microbes. Diatoms are unicellular algae that can be found all over the world in a variety of environments. Existence of microbial life in the Dry Valleys is especially interesting because of the oligotrophic (low nutrient) and harsh environment. Despite extreme conditions, diverse communities exist in this polar desert.

The peak flow time for the streams here is late December to early January. There is still no telling if it will be a high or low flow season, but both can have significant impacts on the connectivity of the ecological systems in the Dry Valleys. High flows can scour algal mats, decreasing microbial activity, whereas under low-flow conditions, some streams may not flow at all, prohibiting nutrient transport to algal mats along the streambed. Since the streams are also the primary transport mechanisms of nutrients to the lakes, high- and low-flow seasons can also have significant impacts on their biogeochemistry.

One of my favorite gauge sites is on the Onyx River, the longest river in Antarctica. It is in the Wright Valley, one valley north of Taylor Valley, where we spend a majority of our season. Since we can’t see this river from our home base, our eyes and ears are often the helicopter pilots who frequently fly over the streams and inform us if they have begun flowing. A task this year is also to implement telemetric systems that will allow us to monitor flow remotely.

Alia KhanA helicopter sling carrying empty barrels for urine and graywater.

Alia KhanMummified seal on Lake Fryxell.

There are no polar bears in Antarctica, but penguins and seals are plentiful on and near the sea ice. In the Dry Valleys, it is extremely rare to encounter a live animal, but there are a surprising large number of mummified penguins and seals. Miles away from the ocean, it is hard to think what could inspire a marine mammal to journey into the Dry Valleys. The jagged rocks, rough sediments and lack of running water and prey are an unfortunate and sure death for the animals. My adviser, Diane McKnight, has an interesting story about a live seal she came across in the Dry Valleys. This was the first documented live encounter with a seal here; it was relocated to the sea ice and a stream in the Fryxell basin is now called “Lost Seal.”