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Navigating by the Earth’s Magnetic Field

Migrating geese, sea turtles, wolves—and worms—find their way.  And for the first time scientists think they know how.

c_elegans

c_elegans
Photo from www.genome.gov

A team of scientists and engineers at the University of Texas at Austin has identified the first sensor of the Earth’s magnetic field in an animal, in the brain of a tiny worm. The sensor, found in worms called C. elegans, is a microscopic structure at the end of a neuron, and looks like a nano-scale TV antenna. The worms use it to figure out which way is down, as they scavenge for food.

This AFD neuron was already known to sense carbon dioxide levels, humidity, and temperature, all very handy things to know if you’re a worm.

The discovery came about as the researchers noted that C. elegans in gelatin-filled tubes moved in the direction that the worms believed was down. When they tested this phenomenon in their lab with C. elegans from various places on the globe, they observed that all of the worms didn’t move down—in fact, Australian worms moved up. Each of the worms moved at a precise angle to the magnetic field that would have corresponded to down if they had been in their local environments. Each worm’s magnetic field sensor system is apparently finely tuned to where it lives.

When the researchers altered the magnetic field around the worms, they noted that the worms changed direction to their new “down.” Worms that were genetically engineered without the AFD neuron weren’t able to orient themselves up or down.

The researchers believe that other animals probably have similar sensors, given similarities in brain structure across species. (One of the scientists has suggested that it might be possible to manage agricultural pests by manipulating magnetic fields. I find myself wondering what the unintended consequences of that will be.)

The research was published in the journal eLife in June.

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Bad eggs

Reed warbler feeding cuckoo chick

A reed warbler feeding a “brood parasite” common cuckoo chick. Photo by Harald Olsen, via Wikimedia

For decades, researchers have been trying to figure out how birds identify and reject the eggs that other birds, known as “brood parasites,” sometimes sneak into their nests. These rogue birds don’t build their own nests, they “dump and drive”—they lay their eggs in the nests of other birds, which then may incubate and raise the imposter chicks, often at the expense of their own.

The brood parasite species include cuckoos, cowbirds, black-headed ducks, indigobirds, whydahs, and honeyguides.

This evolutionary battle between host species and brood parasites goes beyond just dropping eggs off in a random nest to hatch and mature. The imposter eggs that most closely mimic the host eggs are more likely to endure, so brood parasites learn which species’ nests to impose on. And, over time, as it turns out, host species learn to identify imposter eggs, which they then reject. So the brood parasites start producing eggs that look even more like the host species’ eggs. And so on.  Read more…

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The fox came back. But not quite the very next day…

Sierra Nevada Red Fox

Sierra Nevada red fox caught on remote camera in Yosemite National Park

The Sierra Nevada red fox is one of the rarest mammals in North America: until recently they hadn’t been spotted in Yosemite National Park for nearly 100 years. They used to be plentiful in the region, but hunting and habitat destruction from logging, livestock grazing, and off-road vehicles have cut their population to fewer than 50 individuals. Climate change is also affecting the foxes’ habitat, forcing them farther up into the mountains. Fewer Sierra Nevada foxes mean that their genetic diversity is limited, which may have grave implications for the species’ survival.

The Yosemite Conservancy is funding a study to determine the occurrence and distribution of rare carnivores in the park. Good news: Biologists have announced that in the past two months there have been two sightings of one (or two) Sierra Nevada foxes in the northern part of Yosemite, caught on remote cameras in the back country. (It’s unclear if the cameras have caught two images of the same Sierra Nevada fox or one image each of different foxes.)

Near the remote cameras, the park’s biologists have set up hair snare stations in an effort to collect hair samples for genetic analysis. A few Sierra Nevada foxes have been seen north of the park, in the Sonora Pass area, over the past few years, and the biologists want to determine if the fox(es) spotted in Yosemite are related genetically to the Sonora Pass foxes. The more the merrier: more foxes = a more diverse gene pool, which may help the Sierra Nevada red fox stage a real comeback.

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Early Warbler System

Supercell storm

A windmill standing alone against a supercell thunderstorm. Photo by Stephen Corfidi

Apparently birds—in this case, golden-winged warblers—know big storms are headed their way several days before the storms actually arrive. According to a story in the UC Berkeley News Center, a research team led by a UC Berkeley ecologist discovered that warblers in the mountains of eastern Tennessee fled their breeding grounds one to two days ahead of the arrival of devastating supercell storms in April 2014. The storms spawned dozens of tornados, killing more than 30 people.

The discovery was accidental: the golden-winged warblers were part of a migration study, and were being tracked by miniature GPS devices attached to their backs. The scientists knew that birds can change their route to avoid weather disruptions during regular migration, but had no idea they’d leave their established breeding territory to avoid severe weather.

The birds fled the scene when the storm was about 300 miles away—even before the air pressure dropped and the winds picked up. And they went some distance: according to the study, the warblers flew over 900 miles as they avoided the weather system. They returned to their breeding grounds just after the storm passed. Read more…

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The Lowdown on Getting Downstream (if you’re a fish)

Rocky Reach Dam Fish Ladder Dam: Garrett Fitzgerald [GFDL, CC-BY-SA-3.0 or CC-BY-SA-2.5-2.0-1.0], via Wikimedia Commons

Rocky Reach Dam Fish Ladder
Photograph by Garrett Fitzgerald via Wikimedia Commons

Salmon have a rough commute. When they go upstream to spawn in the fall, they face a lot of obstacles along the way, including dams. Lots of dams. In the spring, the juvenile salmon make their way back downstream to the ocean, and they, too, have to navigate the dams.

Many dams have fish ladders that help the fish safely make their journey upstream. But getting downstream is a whole different story. Hydroelectric dams, in particular, present a huge challenge. Between strong currents, rapidly changing water pressure, and huge turbines, the young fish can get stunned, injured, or killed.  Although there are various methods in place to keep the fish away from the turbines, many still end up going through the the engines.

As many hydroelectric dams built during and before the 1970s are currently due for relicensing, their environmental impact is being assessed. And one of the key indicators of a dam’s environmental impact is how well fish fare when they encounter one. Collecting precise data was nearly impossible until the invention of a nifty device. Read more…

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Using TV Whitespaces to Monitor Endangered Species

The Zoological Society of London mines the gap.

European Otter

European Otter at the London Zoo
Photo by Drew Avery (European Otter {Lutra lutra}) [CC-BY-2.0], via Wikimedia Commons

I am always impressed with the imaginative ways the Zoological Society of London uses technology to try to protect and conserve endangered species. Here’s their latest brainstorm, as described on the ZSL website:

“ZSL and Google are working together to pilot the use of TV whitespaces (TVWS) – unused channels in the broadcast TV spectrum – at ZSL London Zoo. The trial aims to show how TVWS can be used to provide wireless connectivity over a large area and in non-line-of-sight scenarios. This exciting technology has huge potential to deliver fast internet to ZSL’s remote conservation sites and help monitor wildlife globally.

The pilot consists of cameras and TVWS radios installed at the otter, meerkat and Galapagos tortoise enclosures within the Zoo. Live footage from each enclosure is transmitted using TVWS technology to a base station and then streamed live onto ZSL’s YouTube channel. Members of the public can tune in to the live feeds and watch the animals anytime, anywhere.

To ensure there is no interference with licensed spectrum holders, Google’s spectrum database is being used to identify available whitespace.

This trial is the first step in understanding how ZSL can effectively use TVWS to support its field conservation projects. A particular area of interest is integrating TVWS into ZSL’s Instant Wild remote surveillance system to enhance data transmission range. ”

The YouTube streams started on October 9th, and will be live for two months.

 

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“Save the Whales”

Whalers

Whalers and their catch, ca. 1913.

Back in the 1970s, a lot of cars sported “Save the Whales” bumper stickers. More than 2 million whales were caught by commercial whalers in the 20th century, and by the middle of the century, many populations were severely depleted. The “Save the Whales” campaign brought millions of people together, resulting in a near-worldwide ban on commercial whaling in 1986. Today, many fewer whales are being taken, but there are still many threats to their survival, including commercial marine traffic.

Big ships run into whales. Inadvertently, of course, but because today’s shipping lanes overlap with whale feeding and migration areas, whales (many of them endangered species) are at great risk of being injured or killed. Obviously, the best way to save the whales is to avoid running into them—and commercial ships now have some free tools that make that possible.

There’s an app for that.

For the past two years, mariners along the U.S. East Coast have been able to download a free iPad and iPhone app that warns them when they enter areas with a high risk of collision with critically endangered North Atlantic right whales. Whale Alert  provides a central source for information about how to navigate around right whales in specific areas, along with the latest data about their whereabouts, all overlaid on NOAA digital charts. Read more…