SCIENCE
Notebook

Monday, March 20, 2006

Chinese Torrent Frogs Share Bats' Ultrasonic Capabilities

Not only can a rare Chinese frog sing like a bird, it can also apparently hear like a bat, according to new research.

Albert S. Feng of the University of Illinois at Urbana-Champaign and colleagues previously reported that male torrent frogs that live in an area west of Shanghai produced calls that were remarkably similar to bird songs.

In a new study, published in Thursday's issue of Nature, Feng and his colleagues determined that the creatures also communicate with one another through high-frequency ultrasonic calls, which previously only bats, marine mammals and some rodents were known to use.

Feng and his colleagues recorded the frogs' audible and ultrasonic calls and then studied how eight other males responded to them, finding that most of them responded to calls in both the audible and ultrasonic ranges.

Feng and his colleagues speculated the frogs evolved the ability so they could hear each other above the sound of waterfalls and other noise in their mountainous habitat.

"Nature has a way of evolving mechanisms to facilitate communication in very adverse situations," Feng said. "One of the ways is to shift the frequencies beyond the spectrum of the background noise. Mammals such as bats, whales and dolphins do this and use ultrasound for their sonar system and communication. Frogs were never taken into consideration for being able to do this."

-- Rob Stein

Fishing Fleets Overexploiting Seas at High Rate, Study Warns

Highly mobile fishing fleets are exploiting the sea's resources at an unsustainable rate, according to a new paper published Friday by more than a dozen international researchers in the journal Science.

The paper, which looks at how "roving bandits" swoop in and plunder fisheries at a rapid rate, looks at how some fish populations have collapsed within a matter of years. In Maine, the sea urchin became a popular commodity in Japanese sushi markets in the mid-1980s: After peaking in 1993, the catches declined precipitously.

The paper, authored by 15 Canadian, Australian, U.S., Swedish and Dutch ecologists, social scientists and resource economists, concludes that even marine protected areas such as the Great Barrier Reef Marine Park, the largest marine protected area in the world, "is too small to fully maintain stocks of marine mammals, turtles and sharks that migrate across its boundaries."

Dalhousie University professor Boris Worm, one of the paper's co-authors, said that "existing marine protected areas are too small, too few and too far apart to prevent the tragedy of the oceans, which is arising due to the unbridled demand for seafood."

A number of factors have contributed to this trend of overexploitation, according to the study, including new export demands from the restaurant and aquarium trades, more sophisticated fishing technology, and rapid air transport of fish.

"What makes roving banditry different from most commons dilemmas is that a new dynamic has arisen in the globalized world: New markets can develop so rapidly that the speed of resource overexploitation often overwhelms the ability of local institutions to respond," said the paper's lead author, professor Fikret Berkes of Canada's University of Manitoba.

-- Juliet Eilperin

Rising Ocean Temperatures Linked to Stronger Hurricanes

The primary reason why hurricanes worldwide have become increasingly strong over the past 35 years is that ocean temperatures have been rising, creating conditions favorable to Category 4 and 5 storms.

Using statistical analysis and information theory to tease out the causes of hurricane strength in six ocean basins, researchers at the Georgia Institute of Technology concluded that only the surface water warming had a significant long-term effect. The results support two other studies published last year that found a similar correlation.

The rise in water temperatures in oceans worldwide is widely seen as a consequence of the buildup in greenhouse gases in the atmosphere -- the same phenomenon that is believed to be causing general global warming.

The new hurricane study, published in the journal Science, looked at a number of other factors that could cause hurricanes to become more intense -- including vertical wind shear (winds at ocean levels blowing in different directions or speeds than winds at higher altitudes), decreased humidity levels in the lower atmosphere, and large-scale air circulation patterns.

While all the factors were associated with some short-term variation in hurricane intensity and some lasting changes in North Atlantic wind-shear patterns were noted, only the increased surface temperatures had a long-term effect.

"With this new paper, we firm up the link between the increase in sea surface temperatures and hurricane intensity, which has been a key issue in the debate about whether global warming is causing an increase in hurricane intensity," author Judith Curry said.

-- Marc Kaufman