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Minggu, 26 Juni 2011
Pictures: Biggest Whale Shark "Swarm" Found
Photograph by Mauricio Handler, National Geographic
A photographer snaps a whale shark feeding near Isla Mujeres, Mexico, in an undated picture taken during a separate whale shark aggregation.
Whale sharks predictably congregate along Mexico's eastern coast each summer, but where they roam the rest of the year remains a puzzle, Maslanka noted.
"How populations are linked, if they're linked, what mixing takes place in terms of genes, whether there's any passage between the Atlantic and Pacific populations—it all still remains to be seen."
(See "NASA Tool Helps Track Whale Sharks, Polar Bears.")
Published June 13, 2011
Among Giants
Photograph by Mauricio Handler, National Geographic
Snorkelers swim with whale sharks off Isla Mujeres in an undated file picture.
Whale shark ecotourism is blooming in this region of Mexico, which is close to the major tourism hub of Cancún, Maslanka said.
Overall, tour companies have done well in establishing rules to keep the whale sharks safe—for example by not allowing people to touch the sharks and limiting the number of swimmers in the water at one time.
"It's a very easy and accessible wildlife experience for people in North America," he said. (Related video: "Swimming With Giant Whale Sharks.")
Published June 13, 2011
Filter Feeder
Photograph by Mauricio Handler, National Geographic
The whale shark (like this one pictured off Mexico's Isla Mujeres in an undated photo) is a filter feeder.
To gather its food, the beast juts out its formidable jaws to take in plankton-filled water. It then closes its mouth and opens its gill flaps, using the tooth-like dermal denticles lining its gills as a sieve to catch any organisms bigger than two to three millimeters wide.
Published June 13, 2011
Whale of a Time
Photograph courtesy Mauricio Handler
In a file picture, snorkelers and whale sharks surround a boat in Isla Mujeres.
Due to fishing, the whale shark is listed as "vulnerable" by the International Union for Conservation of Nature. The animals continue to be hunted in parts of Asia, primarily for their meat, liver oil, and fins.
Published June 13, 2011
Plenty of Fish
Photograph courtesy Smithsonian Institution
You could call it a whale of a "swarm"—the biggest observed gathering ofwhale sharks was spotted off the coast of Mexico's Yucatán Peninsula (see map) in 2009, according to a recent study. Snapped from a small plane, the above picture shows a white boat (bottom right) amid the fishy gathering.
Usually the oceans' biggest fish—which reach lengths of up to 40 feet (12 meters)—stick to themselves as they cruise the world's tropical waters looking for plankton and other small prey. (See picture: "Smallest Whale Shark Discovered—On a Leash.")
But aerial and surface surveys spotted at least 420 of the sharks rubbing fins as they gorged on eggs freshly spawned by little tunny fish, a relative of the mackerel.
"To see a group of that many all in one place was phenomenal—to the point where you couldn't navigate a boat through that without having concern for the fish. That's impressive," said study co-author Mike Maslanka, head of the Nutrition Science Department at the Smithsonian Conservation Biology Institute in Virginia.
Other organizations that contributed to the study include the Comisión Nacional de Áreas Naturales Protegidas in Cancún, Mexico; the Center for Shark Research in Sarasota, Florida; the Mexico-based conservation group Project Domino; and Atlanta's Georgia Aquarium.
"It doesn't go understated that they're not small animals," added Maslanka, whose study was published in April in the journal PLoS ONE. "You don't realize how big they are until you're swimming beside them or you pull a boat up next to them."
—Christine Dell'Amore
Published June 13, 2011
Iceberg Penguins
Photograph by Ralph Lee Hopkins
A group of chinstrap penguins lines the edge of an iceberg adrift in Antarctic waters. Chinstraps are among the most abundant penguins, and some colonies live on floating icebergs.
Barracuda School
Barracuda School
Photograph by Tim Laman
A thick, swirling school of blackfin barracuda plies the blue waters off Sipadan Island, Malaysia. The fish are formidable predators, but they sometimes gather in groups for protection against sharks higher up on the food chain.
Whale Shark
Whale Shark
Photograph by Brian Skerry
The sweeping color of sea and sky, blue is a common thread in nature, seen in the cerulean of a whale shark (pictured here), the indigo of a stormy night, and the cobalt of a peacock's feathers. Over the centuries, the hue has come to represent calm, cold, mysticism, and sadness.
Jumat, 24 Juni 2011
Neumeyer Channel
Neumeyer Channel
Photograph by Gordon Wiltsie
Icebergs drift across Antarctica's Neumeyer Channel. The Larsen Ice Shelf Expedition team predicts melting Antarctic shelves and bergs will raise sea levels around the world, flooding hundreds of thousands of square miles and displacing tens of millions of people. The team will collect evidence from their expedition to better understand how global warming is changing the continent and how we can prepare ourselves for its effects.
Leopard Seal
Leopard Seal
Photograph by Paul Nicklen
A leopard seal plunges through Antarctic waters. Swift and stealthy, adult leopard seals tend to be solitary creatures, hunting alone at the fringes of pack ice. Finding a mate can be challenging given their isolation, but seals attract one another by singing—females to announce their readiness to a mate, males to serenade potential mates.
Penguin and Chick
Penguin and Chick
Photograph by Maria Stenzel
An Antarctic gentoo chick stays near its parent for warmth. Gentoos are the fastest underwater swimming birds and can reach speeds of 22 miles an hour (36 kilometers an hour). Scientists worry that warming temperatures will encroach on penguin habitats, threatening their populations across Antarctica.
Large Iceberg
Large Iceberg
Photograph by Bill Curtsinger
Global warming is forcing ice shelves to calve, producing icebergs like this monolith jutting into the waters of the Antarctic Peninsula. National Geographic's Larsen Ice Shelf Expedition team will examine calving shelves and the bergs they spawn, determining how shelves fragment and how diminishing ice mass affects the world's oceans and climate.
Penguins on Shore
Photograph by Gordon Wiltsie
A group of gentoo penguins nests on an icy shore of Cierva Cove, Antarctica. The continent is home to a number of penguin species, including Adélie, chinstrap, emperor, gentoo, and rockhopper.
Glacier Advance
Glacier Advance
Photograph by George Mobley
A stark white lobe of a glacier advances across Antarctica's dry valleys region, so called because of its scarcity of snow. Earth's fifth-largest continent contains more than two-thirds of the world's freshwater in the form of ice, yet some areas receive less than two inches (five centimeters) of precipitation a year.
Inform For Us
Larsen B Ice Shelf Breakup
Photograph courtesy NASA
Over a 35-day period in early 2002, Antarctica's Larsen B ice shelf lost a total of about 1,255 square miles, one of the largest shelf retreats ever recorded. This image, captured by NASA's MODIS satellite sensor on February 23, shows the shelf mid-disintegration, spewing a cloud of icebergs adrift in the Weddell Sea. In December 2007, a team of National Geographic explorers will begin a five-week expedition across the continent's Larsen ice shelf to study how global warming is changing the topography of Antarctica.
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