Great White Sharks Feast on Fat After Road Trips

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Footage of great white sharks often shows them ravenously feeding on marine mammals, and now a new study reveals that such feasts often occur after the sharks go on long journeys.

The study, published in the latest issue of Proceedings of the Royal Society B, reveals how important protection of established shark feeding grounds are, since so much concentrated feasting takes place at these sites.

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“We know from researchers observing white sharks feeding on whale carcasses that one shark can eat more than 30 kg (66 pounds) of blubber in a single feeding,” lead author Gen Del Raye told Discovery News. “This has been estimated to be sufficient energy to allow a shark to survive for 1.5 months.”

“We also know that the sharks feed fairly frequently on juvenile northern elephant seals at certain seasons,” added Del Raye, who is a researcher at Stanford University’s Hopkins Marine Station and the University of Hawaii. “One of my co-authors, Salvador Jorgensen, for example, has identified the same shark feeding on 3 juvenile elephant seals in the course of one week.”

Del Raye, Jorgensen and their colleagues assessed great white shark fat stores over long periods by examining depth records from pop-up satellite tags affixed to sharks in the Eastern Pacific Ocean. Changes in shark buoyancy served as a proxy for how much weight the toothy predators were packing.

As a shark’s single largest organ, the liver, can account for 28 percent of an adult’s body weight. Other fat is stored in the shark’s muscles. While sharks fill up on fatty food after long journeys, no shark has ever been classified as obese. Their lifestyle is probably inherently too active for them to keep the pounds on.

The Loneliest Whale in the World?

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Next fall, a team of documentary filmmakers and scientists will head out into the North Pacific in search of a whale.

They know which whale they’ll be looking for, although nobody is completely sure what species it is. It may be a blue whale, is more likely a fin, but could be a hybrid of the two. No human has knowingly set eyes on it, although quite a few have been listening to it for over 20 years. And there are many more around the world who may not have heard recordings of its vocalizations, but have heard of them, and who have been inspired to write music, poetry and books about the whale that makes them -- a whale they have dubbed the 'loneliest whale in the world.'

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The story begins in the late 1980s, when the U.S. Navy began providing whale researchers with recordings from hydrophone arrays it deployed to listen for submarines in the North Pacific, and which also happened to pick up the haunting moans of baleen whales as they cried out across hundreds of miles of ocean in search of mates.

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In 1989, William Watkins of the Woods Hole Oceanographic Institution began sifting through those recordings and soon noticed something unusual. Whereas most male fin and blue whales vocalize at a range of about 17-18 Hertz, well below the limits of human hearing and ideal for traveling across vast distances underwater, one whale was consistently vocalizing at a much higher range of 52 Hz.

From 1992, when the Navy made more recordings available, Watkins and his team studied the so-called 52 Hz whale in more detail, triangulating the recordings to track his movements across the North Pacific during mating season. (Outside of mating season, the whales do not generally vocalize.) In 2004, they published a paper in the journal Deep Sea Research, which noted how the whale’s unique vocal properties made it easier to chart its movements.

“It’s very difficult to track a signal consistently in the ocean, without seeing the animal,” explained Mary-Ann Daher, who was part of the team that wrote the paper. “Because if other animals are making sounds at the same frequency, you don’t know if it’s the same guy. But this one, it was the 52 Hz signal that we were able to pick up frequently.”

But that wasn’t the aspect of the research that resonated. What might reasonably have been expected to be a relatively obscure paper in a relatively obscure journal was picked up by media and public alike, who responded to the notion of a whale that was swimming through the ocean, calling out on a frequency no other whale was using, never hearing a response.

The "loneliest whale in the world" was born.

Great Tits Built to Survive Climate Change?

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Early birds get worms in the evolutionary race against climate change.

The great tit (Parus major), a small bird, depends on a boom in caterpillar numbers in the spring to feed their young. However, spring and the caterpillar buffet now arrive earlier due to a warming global climate. If the birds were hard-wired to lay their eggs at the same time every year, they would miss the spring insect surge. That caterpillar catastrophe would leave many young birds starving.

However, great tits in England now lay their eggs earlier in the year which allows the early birds to catch the caterpillar boom, according to a study published in PLOS Biology.

Great tits now lay their eggs an average of two weeks earlier than they did 50 years ago. The birds’ rate of change could allow them to adapt to global warming of 0.5 degrees Celsius per year, suggested the study’s authors from the University of Oxford.

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The key to the great tits’ survival comes from a biological ability known as phenotypic plasticity. Phenotype refers to the physical expression of a living thing’s genetic code along with the influence of environmental factors on the creature. The ability of species to adapt behaviors and physical characteristics to meet environmental needs is phenotypic plasticity.

Smaller birds with faster life cycles, such as the great tit, may have the phenotypic plasticity needed to keep up with climate change. However, other creatures that take longer to reproduce may face challenges.

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“Our results show us under what conditions we can expect species to be able to cope with a changing environment, and under what conditions we should be more pessimistic,” lead author Ben Sheldon said in a press release. “We should be particularly concerned about slow-reproducing species, for which the need to show just the right response to the environment is particularly crucial. A key area for future work is to understand why some species respond by the right amount, and others show the wrong response.”

Why Turtles Love Golf

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Is that a turtle crossing the fairway? Quite possibly: According to new research, golf courses can provide ideal homes for turtles, reports National Geographic News as part of a series on global water issues.

University of Kentucky herpetologist Steven Price and colleagues examined turtles in Charlotte, N.C., netting turtles in ponds on golf courses, cow pastures and local parks.

The ponds on the golf courses seem to be “providing something that other ponds are not,” he told National Geographic. It’s not clear exactly what, although the vast open spaces of golf courses are good for turtle nests.

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The researchers found painted turtles and sliders in similar rates at the golf courses and farm ponds, and golf courses boast a greater variety of species.

Turtles seemed to prefer golf courses with the least amount of development, however: “If golf courses are to be seen as reserves for wetland-dependent animals, golf courses with low housing density should be considered as a more preferable option than courses associated with extensive residential development,” the researchers wrote in the Journal of Herpetology.

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“There’s potential for (courses) to be really good habitat if they’re managed properly,” said Davidson College herpetologist Jacquelyn Guzy, one of the researchers.

And not all courses are, researchers are quick to point out. Courses with lots of space left wild in addition to the groomed fairways offer habitat for many types of animals. But courses without trees that are completely manicured do not.

Photo: A group of turtles sun themselves by the 16th green at the 2013 Masters golf tournament in Augusta, Ga., on April 8, 2013. Credit: Phil Noble/Corbis