News of the Wild

Animal News

03-01-1997 // NWF Staff

A Little Butterfly Told Them

if the earth heats up, will animals seek cooler habitat? and plants growing seasons lengthen?those are two of the questions scientists ask to help gauge potential biological effects of climate change. now a butterfly and a trend in carbon dioxide levels have yielded some answers.Biologist Camille Parmesan of the University of California, Santa Barbara, studied 151 populations of the Edith checkerspot butterfly found that in past 100 years, sensitive insects slowly have been moving northward or to higher altitudes, from warmer climes. orange-and-black can be much of western north america; it is dying out at its southernmost limit mexico expanding canada. parmesan calls finding exactly what has been predicted will happen with global warming; it indicates that the changing climate is already influencing species' distributions.

In separate work, at Scripps Institution of Oceanograpy in La Jolla, California, scientists have deduced that the Northern Hemisphere's average annual growing season begins one week earlier than in previous decades. Researcher Charles Keeling and colleagues came to that conclusion by studying atmospheric carbon dioxide levels, which rise in autumn and decline in spring and summer with new plant growth. At the same time, overall carbon dioxide levels have been increasing due to the burning of fossil fuels. Keeling has kept track of that trend too, charting it for the past 40 years on what is known as the "Keeling curve." In this latest study, he looked at annual carbon dioxide cycles to determine the timing of plant growth. "The plants are being influenced by climate in a way that might be unprecedented," says Keeling.

Scientists generally agree the planet has warmed by at least one degree Fahrenheit in the past century. Any biological response to that change and to future changes may have broad implications for conservation, agriculture and health.

The Oldest Scuba Gear

Like many of humankind's inventions, the scuba tank apparently was created first by nature. The first scuba diver was likely the chambered nautilus, which has existed for millions of years and is often called a living fossil. Scientists have long known that its shell has about 30 gas-filled chambers, to which the animal adds or subtracts ballast water in order to regulate its ocean depth. Recently, zoologist Robert Boutilier of the University of Cambridge in England and colleagues reported they have found strong evidence the nautilus also makes use of oxygen from the stores in its chambers.

The tipoff was a discovery that at times, oxygen in the animal's veins is at higher levels than in its arteries--a finding that stands basic physiology on its head. A resulting calculation, wrote the researchers in the journal Nature, "obviously gives the embarrassing result that blood is flowing in reverse." They added dryly, "We are reasonably certain this is not the case." Instead, they conclude, when the creature is especially oxygen-deprived during lengthy trips to the ocean floor, it slowly draws extra oxygen into a large vein located adjacent to the gas-filled chambers.

Not All Ducky Just Yet

Although bird lovers have been celebrating a dazzling recovery of migrant waterfowl across North America in the past three years, not all the news about the birds is good. The U.S. Fish and Wildlife Service (FWS) reports that some species are not doing as well as others: There have been decreases in breeding females of migrant Canada geese along the Eastern Seaboard and of pintails, wigeon, scaup and mallards in the Midwest.

Still, for the most part, waterfowl conservation in North America is a great success story. In the late 1980s, only an estimated 56 million ducks and geese headed south in the fall through the four major flyways out of Canada and Alaska. But after heavy rains ended a decade-long dry spell, filling in the prairie potholes of the Midwest and Canada known as North America's duck factory, the birds responded in force. Last fall, their numbers rose to an estimated 90 million, one of the highest counts on record.

Rain was only part of the reason for the good news, however. "Also key has been conservation of pothole-related habitat in farm country, due to efforts such as the federal Conservation Reserve Program, which rewards farmers for setting aside nesting habitat," says NWF Regional Executive Dan Limmer. "The key is to continue to preserve the potholes and nesting cover so that when weather conditions improve, there are places for waterfowl to nest." But future habitat protection is not assured. Says acting FWS Director John Rogers, "The excellent nesting conditions we have will not last indefinitely. We must strive to ensure a healthy habitat base every year, regardless of how much snow and rain fall."

Adds Limmer, "We can't say waterfowl is in full recovery until we know we can continue to safeguard the birds' habitat in the future. Not only that, we must work to learn why some species are still having difficulty."

High-Fat Diets Are For The Birds

When birds pick seeds for winter meals, fatty foods are favorites, according to research recently completed at the Cornell Laboratory of Ornithology in Ithaca, New York. Scientists enlisted the help of more than 5,000 U.S. birders who, in 1994 and 1995, monitored birds at feeders.

The Seed Preference Test, designed to reveal avian food preferences, showed that six of eight bird species tested in some Canadian provinces and northern states preferred fatty sunflower seeds over less oil-rich seeds more often than did individuals of the same species farther south. Black-capped chickadees, for instance, chose sunflower seeds in almost 100 percent of observations in eastern Canada but in only 80 percent of observations at the southern extreme of their range. Mourning doves in northern areas were twice as likely to pick sunflowers compared to mourning doves in Florida.

Researchers believe that the birds choose the higher calorie fatty seeds to get extra energy during cold winters. However, not all species in the study showed a taste for fat. Dark-eyed juncos, rather than pack in the calories when the going gets cold, simply pack up and then leave for warmer climes.

Perfect Pitch

If you want a cricket to approach you, make noises like a cricket, not like a bat. That might seem a logical assumption, but proof of the insect's ability to differentiate between such sounds was an exciting recent discovery for a team of researchers led by Cornell University biologist Ron Hoy.

The scientists placed crickets in a chamber and then observed their reactions to a range of tones. The insects turned away from ultrasounds that are incidentally inaudible to humans, such as those made by bats, but were drawn toward the source of cricket songs. The creatures apparently share with humans an ability called "categorical perception," which allows them to distinguish among types of sound--a surprisingly sophisticated knack in a cricket.

That doesn't mean crickets have the same auditory system as humans, but they are coping with "the same kinds of perceptual problems we are," says biologist Robert A. Wyttenbach of Cornell University, one of the members of the research team.

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