On the horizon

Jupiter's junior spot

The Hubble Space Telescope is giving astronomers close-up views as Jupiter builds a red-spot munchkin. The feature is emerging farther south than the larger rust-hued storm that has captivated astronomers for some 340 years. It may signal that the solar system's largest planet is in the throes of global climate change, researchers say.

The older red spot is large enough to swallow three Earths and represents a storm system whose clouds tower nearly five miles above the surrounding cloud layers. The new system formed between 1998 and 2000 from the merger of three smaller storms, astronomers say. Currently, it's about half the size of its older sibling, which may be slowly bidding astronomers adieu. Over the past century, the larger red spot has shrunk by half.

The latest images, released earlier this month, were taken in April by two groups - one led by Amy Simon-Miller at NASA's Goddard Space Flight Institute, the other by Imke de Pater and Philip Marcus at the University of California at Berkeley.

Mammoth extinction: blame plants

What closed the book on mammoths, Pleistocene horses, and other large animals that roamed North America at the end of the last ice age?

Some scientists blame the migration of humans across the Bering Strait land bridge and their blitzkrieg form of hunting. But the picture may be far more complex, suggests University of Alaska biologist R. Dale Guthrie - at least in his part of the world. An examination of plant and pollen remains show that the region's plant population changed dramatically between 13,500 and 11,500 years ago, affecting the kinds of food available for grazers.

Dr. Guthrie says that a "unique tide of resource abundance" was created by a shift in climate from the icy Pleistocene to the warmer Holocene. This shift in plant life, which preceded human settlement, favored some large mammals at the expense of others.

Using new radiocarbon dates for signature species such as mammoths, horses, elk, moose, and bison, as well as for human settlement in Alaska and the Yukon, Guthrie found that mammoths and horses already had declined sharply by the time humans put down roots. Meanwhile, bison, elk, and moose were thriving before humans settled in the region. The results appear in Thursday's issue of the journal Nature.

Dolphin calls get personal

The next time Flipper goes "eeee-eeh, eeee-eeh," be careful: He may be calling you names.

Scientists at the University of St. Andrews in Britain say they have found that dolphins may have the equivalent of names - sound patterns embedded in the dolphin's calls that are unique to each animal and can help identify it to its sea mates. Each baby dolphin develops a unique set of whistlelike calls that they use for the rest of their lives. Some scientists have speculated that these carry identification information, much as names do for humans.

To test the idea, biologist Vincent Janik and colleagues traveled to Florida and recorded "signature" calls from bottlenose dolphins. Then they synthesized them and removed all of the subtleties peculiar to the original dolphin "squeaker" except the shape of the sound waves themselves. The researchers played back the synthesized sounds through underwater speakers. In nine out of 14 dolphins tested, a dolphin would turn toward the speakers if it heard a sound resembling that of a known close relative - even if the relative was off somewhere else.

The study, the team concludes, shows that dolphins are the only animals other than humans known to communicate information about identity when the "subject" of that information doesn't originate the exchange and is nowhere around at the time. The results appear in the current issue of the Proceedings of the National Academies of Science.

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