New York Times News Service

A new detailed map of Antarctica

You may never make it to the South Pole, but you can now see Antarctica and its glaciers in unprecedented detail.

Researchers recently announced the release of a new high-resolution terrain map of the southernmost continent, called the Reference Elevation Model of Antarctica, or REMA, which they say makes Antarctica the best-mapped continent on Earth.

Antarctica is the most desolate and inhospitable place on Earth, and its remoteness makes monitoring changes in ice and water levels difficult. Because of the warming climate, seasonal changes at Antarctica are becoming more severe, making the need to understand the loss of ice even more important.

Ian Howat, the project’s principal investigator and a professor of earth sciences at Ohio State University, and Paul Morin, of the University of Minnesota, used data from a constellation of polar orbiting satellites to image the frozen wastes. The satellites are owned by the National Geospatial-Intelligence Agency, which is part of the Department of Defense.

Previous maps of the continent had a resolution similar to seeing the whole of Central Park from a satellite. With this new data, it is possible to see down to the size of a car, and even smaller in some areas. The data is so complete that scientists now know the height of every feature on the continent down to a few feet.

“If you’re someone that needs glasses to see, it’s a bit like being almost blind and putting on glasses for the first time and seeing 20/20,” said Howat.

The team used 187,585 images collected over six years to create the map. The pictures are so detailed that researchers had to use one of the most powerful supercomputers on Earth to ingest the data.

Observing snowfall, ice growth and the rate of melt and fissures will allow scientists to monitor sea-level rise and glacial melt with more accuracy.

Explorers and scientists stationed at Antarctica will also find the map useful. By having such a detailed topographical map, new routes to science stations can be planned around the continent’s dangerous terrain.

The omnivorous sharks that eat grass

Sharks are not known for their taste for greenery. But at least one species of shark enjoys a salad of sea grass as well as the prey it hunts.

The bonnethead shark, a diminutive species that reaches up to 3 feet in length, lives in the shallow sea grass meadows off both coasts of the Americas. It eats small squid and crustaceans ferreted from the swaying underwater fronds. But researchers say in a study published in Proceedings of the Royal Society B that they also eat large quantities of sea grass. The grass isn’t just passing inertly through the sharks’ guts. They extract nutrition from it just as they do from the meaty portion of their diet. These sharks must, therefore, be reclassified as omnivores — the first omnivorous sharks known to science.

In 2007, researchers first reported that the digestive tracts of bonnethead sharks caught in the Gulf of Mexico were full of sea grass, up to 62 percent of the contents by weight.

At the time, some reasoned that the grass might have been ingested incidentally, as the sharks dove for scurrying prey in the meadows. But Samantha Leigh, a graduate student at the University of California, Irvine, and lead author of the paper, and her colleagues wondered whether there was more to it.

They caught bonnethead sharks just off the Florida Keys and transported them to an outdoor lab facility. There, the sharks lived in a large tank and received a meal every day consisting of a wad of sea grass wrapped in a piece of squid, resembling a large inside-out sushi roll. The sea grass, which made up 90 percent of the roll, had been loaded with a tracker isotope that could be detected later in their blood if the grass was truly being digested, not just passing through. The researchers also filtered the sharks’ feces from the water using a fine mesh, allowing them to test how much of what went in came out.

The sharks thrived on this diet, all of them gaining weight during the experiment. When the researchers checked their blood, they found very high levels of the tracker, indicating the grass was being digested and used for nutrients.

Hundreds of seals are dying off of New England

Harbor and gray seals are dying by the hundreds from southern Maine to northern Massachusetts, apparently from a combination of a measleslike illness and the flu.

Late last month, the federal government declared the summer’s toll on seals an “unusual mortality event,” meaning federal resources would be provided to help understand and cope with the deaths.

Teams have responded to more than 600 reports of dead or dying harbor and gray seals, but there are probably more that have gone unreported or washed up on private property, said Mike Asaro, chief of the marine mammal and sea turtle branch of the National Oceanic and Atmospheric Administration. “The total could be up to 1,000 at this point. We just don’t know,” he said.

Marine mammal stranding agencies always expect to find some sick and deceased animals this time of year, as a percentage of newborn pups fail to thrive after weaning. But the carcasses washing up on New England beaches reveal an epidemic that’s touching all ages, said Katie Pugliares-Bonner, a senior biologist and necropsy coordinator for the New England Aquarium in Boston.

“That’s one thing that was largely concerning — not only the volume, but the variety of age classes,” she said.

Although research is still underway, the disease outbreak appears to be centered on the Isles of Shoals, a small group of islands off the coasts of southern Maine and northern New Hampshire, Pugliares-Bonner said.

Animals are suffering from phocine distemper virus, which is closely related to canine distemper in dogs, and a cousin of the measles, said Tracey Goldstein, a professor at the University of California, Davis, and a member of NOAA’s unusual mortality working group.

Phocine distemper causes lung infections and seizures as it attacks the seal’s brain tissue. Some animals have washed up on beaches still alive, but lethargic and coughing, she said.

Some of the seals have also been found to have the flu, though it’s not clear whether the compound infections are killing them, or whether the distemper is reducing the animals’ immunity and making them vulnerable to the flu, Goldstein said.

Infections are more likely to spread at this time of year, when the seals are living in close quarters as they nurture their babies on the beaches, she said.

The best way to hand-feed a hummingbird

It’s fun to feed hummingbirds and see them up close — almost like encountering fairies. But how? Start by picking out a spot and staying very still. And you may try wearing lots of colors.

“A really gaudy Hawaiian print shirt is an excellent hummingbird attractor,” said Sheri Williamson, a naturalist, ornithologist and author of “A Field Guide to Hummingbirds of North America.”

Your best chance to hand-feed hummingbirds is when they’re under stress, like this time of year, when some birds are preparing to migrate and unsure where they’ll find their next meal. Birds have already started to fly from the North. But in the South, the time is near perfect for creating a safe place for young birds.

Should people feed hummingbirds like this?

“It’s sort of a meditative exercise we could all use to slow down a bit,” said Williamson. “Sitting still you start to notice things in your garden you may not have noticed before. It makes for a nice excuse to get out and just commune with nature.”

To discourage the birds from thinking of any human as a possible food source, she said, try blending in with the environment as much as possible. That’s important because not every human has good intentions, she notes.

Getting hummingbirds too accustomed to people can make them vulnerable to those who may swat at them out of fear or attract them for reasons other than just observation. “There are reports of people attracting hummingbirds and doing terrible things to them,” she said, like selling them as love charms.

Does feeding nectar to hummingbirds undermine their foraging? No, but it may distract them from flowers.

In the tropics, Williamson said, nonmigratory hummingbirds seem to be doing a poorer job at pollination of some flowers near year-round feeding stations.

“This doesn’t seem to be as much of a problem here in the temperate zone — as long as we practice good feeding habits,” she said.

Regularly clean feeders — the ones you wear or the ones hanging in your garden — every few days or more often in hot weather with hydrogen peroxide to keep the nectar from fermenting and to fend off microbes that may make hummingbirds sick.

Also, use low-sugar nectar that won’t distract them too much from natural nectar sources they need to pollinate. The rule of thumb for all the species of hummingbirds in North America is four parts water to one part cane sugar.

— New York Times News Service