December 8, 2006, 5:01 AM CT

Built In Compass Helps Bats Find Their Way Home

Bats have a novel device for guiding them home on starless nights. In addition to their well-known sensory talents, it seems that big brown bats can tune into the Earth's magnetic field, using it as a compass to guide them to roost.

This ability comes in handy on long-distance flights, where their usual mode of navigation - bouncing sounds waves off objects using ultrasound - doesn't do much good.

Richard Holland from Princeton University, New Jersey, and his colleagues looked at 15 North American big brown bats (Eptesicus fuscus), which travel up to 100 kilometres to find hibernation sites for the winter.

To first test the animals' natural navigational abilities, they attached small radio transmitters to the bats and transported them 20 kilometres from their roost. One by one they let them go, and tracked them from a small aircraft. All of them headed directly back to their roost.

How did they do this? Scientists have previously suggested that bats might use the direction of the sunset to set their compass. Others have found traces of magnetic materials within bats, suggesting that they might use the planet's magnetic fields to find north.

To tease these effects apart in a single experiment, the scientists put the bats inside a helmet that generates a strong magnetic field offset from the planet's true north. They let the bats watch sunset while sitting in this artificial magnetic field for about an hour and a half. "We then took them to the same release site," says Holland. And they all took off in the wrong direction. "It was a neat trick".........

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December 5, 2006, 8:44 PM CT

What Does Giraffe Eat?

The giraffe browses on the twigs of trees, preferring plants of the Mimosa genus; but it appears that it can live without inconvenience on other vegetable food. A giraffe can eat 63 kg (140 lb) of leaves and twigs daily.

The pace of the giraffe is an amble, though when pursued it can run extremely fast. It can not sustain a lengthened chase. Its leg length compels an unusual gait with the left legs moving together followed by right (similar to pacing) at low speed, and the back legs crossing outside the front at high speed.

The giraffe defends itself against threats by kicking with great force. A single well-placed kick of an adult giraffe can shatter a lion's skull or break its spine.

The giraffe has one of the shortest sleep requirements of any mammal, which is between 10 minutes and two hours in a 24-hour period. This has led to the myth that giraffes cannot lie down and that if they do so, they will die.

A giraffe will clean off any bugs that appear on its face with its extremely long tongue (about 18 inches/45 centimeter). The tongue is tough on account of the giraffe's diet, which includes thorns from the tree it is making a meal of. In Southern Africa, giraffes are partial to all acacias - particularly Acacia erioloba - and possess a specially-adapted tongue and lips that appear to be immune to the vicious thorns.........

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December 4, 2006, 10:03 PM CT

Clues to Pregnancy in Male Pipefish

Genetic archaeology is providing a new clue to one of the greatest gender mysteries in the fish world: how did male pregnancy evolve in a family of fish?

A gene discovered in the gulf pipefish hints that a gene already busy with kidney and liver function may have learned new tricks in the male womb, said April Harlin-Cognato, a biologist at Michigan State University, and her colleagues. Their research results, funded by the National Science Foundation (NSF), are published in this week's online edition of the journal Proceedings of the National Academy of Sciences (PNAS).

"We're interested in the evolution of novelty and how novel traits evolve," Harlin-Cognato said. "Why is this the only fish that exhibits male pregnancy? It's one of the more difficult phenomena to explain in evolutionary biology, and we're wondering if it's a matter of old genes learning new tricks".

Gulf pipefish are a member of the same family as seahorses. They look like seahorses without the curved tails. As in seahorses, male pipefish accept eggs from the females, fertilize them and carry them in pouches. These brood pouches have evolved into complex organs able to nurture and protect the eggs.

Harlin-Cognato, who conducted the research along with Eric Hoffman of the University of Central Florida, and Adam Jones of Texas A&M University, found a new type of gene that codes for a protein called astacin, which performs a variety of functions in bony fish.........

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November 30, 2006, 9:27 PM CT

Zebra stripes

Zebra stripes are typically black stripes on white background.These stripes are typically vertical on the head, neck, forequarters, and main body, with horizontal stripes at the rear and on the legs of the animal. The zebra crossing is named after the zebra's white on black stripes.

Zoologists think that the stripes act as a camouflage mechanism. This is accomplished in several ways. First, the vertical striping helps the zebra hide in grass. At first glance, this may seem absurd considering that grass is neither white nor black, but it makes sense because the zebra's main predator, the lion, is color blind. A zebra standing still in tall grass may not be noticed at all by a lion. However, zebras are herd animals and do not commonly travel alone, so the second way the stripes help in camouflage is by confusing the lion - many zebras standing or moving close together may appear as one large animal, making it more difficult for the lion to pick out any single zebra to attack.

Stripes are also believed to play a role in social interactions, with slight variations of the pattern allowing the animals to distinguish between individuals.

A more recent theory, supported by experiment, posits that the disruptive coloration is also an effective means of confusing the visual system of the blood-sucking tsetse fly.[citation needed] Alternative theories include that the stripes coincide with fat patterning beneath the skin, serving as a thermoregulatory mechanism for the zebra, and that wounds sustained disrupt the striping pattern to clearly indicate the fitness of the animal to potential mates.........

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November 29, 2006, 9:39 PM CT

Save the whales? Sure, but how many?

How a number of wildebeest should live in the Serengeti" How a number of grizzly bears should call Yellowstone home" Are there too few tigers in the world" Conservationist biologists grapple with the task of setting population targets for the species they are trying to protect a decision steeped in politics, emotion, and sometimes, science.

In a new paper appearing in the journal Bioscience, the New York-based Wildlife Conservation Society (WCS) examines the current hodgepodge of population target levels (PTLs) being used by wildlife managers, and proposes a simpler, four-tiered system to measure conservation success. The paper cataloged 18 different approaches currently used to set PTLs, and showed the diverse ways in which they apply to national laws and international treaties.

As per the paper's author, WCS ecologist Dr. Eric Sanderson, 'minimum viable populations' the goal usually used by wildlife managers that aims to have self-sustaining populations should be seen as the beginning, not the end, of conservation.

'People want much more from wild animals than to see them just persist: we want animals to interact with their environment, evolve over time, be beautiful and useful to us, and to satisfy ethical teachings regarding respect for nature,' said Dr. Sanderson.........

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November 28, 2006, 8:47 PM CT

Old Engravings Of Animals Are Charmingly Strange

Mark Frauenfelder:

Bibliodyssey has an excellent gallery of 18th century engravings from 'Die Saugthiere in Abbildungen' at Ecole Nationale Veterinaire de Lyon (named as 'Histoire naturelle des quadrupedes'.

The absurd rendering of a number of of the animals comes about because the engravers/artists working on the project did not actually see the animals. They had to rely on descriptions and their imagination and, as was the fashion of the time, the animals were placed in contrived settings and often given human facial qualities, which only serves to heighten the sense of bizarre. And thankful we are too.........

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November 27, 2006, 4:47 AM CT

Humpback Whale Brain Cells

Cetaceans, the group of marine mammals that includes whales and dolphins, have demonstrated remarkable auditory and communicative abilities, as well as complex social behaviors. A new study published online November 27, 2006 in The Anatomical Record, the official journal of the American Association of Anatomists,compared a humpback whale brain with brains from several other cetacean species and found the presence of a certain type of neuron cell that is also found in humans. This suggests that certain cetaceans and hominids may have evolved side by side. The study is available online via Wiley InterScience at http://www.interscience.wiley.com/journal/ar

Eventhough the biology of the humpback whale is well understood, there have been virtually no studies published on its brain composition, leaving an open question as to how brain structure may relate to the extensive behavioral and social abilities of this mammal. Eventhough brain to body mass ratio, a rough measure of intelligence, is lower for baleen whales such as the humpback in comparison to toothed whales such as dolphins, the structure and large brain size of baleen whales suggests that they too have a complex and elaborate evolutionary history.

Patrick R. Hof and Estel Van der Gucht of the Department of Neuroscience at Mount Sinai School of Medicine in New York, NY, examined the brain of an adult humpback whale and compared it with the brain of a fin whale (another baleen species) and brains from several toothed whales, including three bottlenose dolphins, an Amazon river dolphin, a sperm whale, two beluga whales, a killer whale and several other whale and dolphin species. They observed that the humpback cerebral cortex, the part of the brain where thought processes take place, was similar in complexity to smaller sized cetaceans such as dolphins. The large area of cortex found in these mammals is believed to be correlation to acoustic capabilities and the current study shows that it is organized into a system of core and belt regions. However, substantial variability was found between the cell structure of the cortex in humpbacks in comparison to toothed whales. The authors suggest that these differences may indicate differences in brain function and behavior in aquatic species that are still not understood.........

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November 26, 2006, 7:56 AM CT

Dramatic Shift In Marine Ecosystems Occurred 250m Years Ago

The earth experienced its biggest mass extinction about 250 million years ago, an event that wiped out an estimated 95% of marine species and 70% of land species. New research shows that this mass extinction did more than eliminate species: it fundamentally changed the basic ecology of the world's oceans.

Ecologically simple marine communities were largely displaced by complex communities. Furthermore, this apparently abrupt shift set a new pattern that has continued ever since. It reflects the current dominance of higher-metabolism, mobile organisms (such as snails, clams and crabs) that actually go out and find their own food and the decreased diversity of older groups of low-metabolism, stationary organisms (such as lamp shells and sea lilies) that filter nutrients from the water.

So says embargoed research would be published in Science on November 24, 2006. An accompanying article suggests that this striking change escaped detection until now because prior research relied on single numbers--such as the number of species alive at one particular time or the distribution of species in a local community--to track the diversity of marine life. In the new research, however, researchers examined the relative abundance of marine life forms in communities over the past 540 million years.........

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November 26, 2006, 7:41 AM CT

Serengeti Patrols Cut Poaching Of Buffalo, Elephants, Rhinos

A technique used since the 1930s to estimate the abundance of fish has demonstrated for the first time that enforcement patrols are effective at reducing poaching of elephants, African buffaloes and black rhinos in the Serengeti National Park in Tanzania.

"Wildlife within protected areas is under increasing threat from the bushmeat and illegal trophy trades, and a number of argue that enforcement within protected areas is not sufficient to protect wildlife. Some say the $2 million spent annually in the Serengeti on patrols would be better spent on other preventive activities," says Ray Hilborn, University of Washington professor of aquatic and fishery sciences and lead author of a paper in the Nov. 24 issue of Science.

The 5,700-square-mile Serengeti is one of Africa's most pristine preserves.

"The animals are 'telling' us poaching is down now that there are 10 to 20 patrols a day in comparison to the mid-1980s when there might be 60 or fewer patrols a year," Hilborn says. They tell us, he says, by increasing in abundance, something that can measured using aerial surveys.

It's been impossible to actually count the number of animals that are poached because poaching is illegal and most animals apart from elephants and rhinos which are traditionally not eaten are caught in snares set by local villagers for their own use or sale. A recent article in National Geographic, for example, said estimates of the poaching toll range as high as 200,000 in the Serengeti. Hilborn says that poaching cannot be nearly that great or the populations still would be declining.........

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November 22, 2006, 5:11 AM CT

The Power Behind Insect Flight

Scientists from Rensselaer and the University of Vermont have discovered a key molecular mechanism that allows tiny flies and other "no-see-ums" to whirl their wings at a dizzying rate of up to 1,000 times per second. The findings were reported in last week's online early edition of the Proceedings of the National Academy of Sciences (PNAS).

"We have determined important details of the biochemical reaction by which the fastest known muscle type - insect flight muscle - powers flight," said Douglas Swank, assistant professor of biology at Rensselaer and lead author of the PNAS paper.

The findings will help researchers gain a better understanding of how chemical energy is converted into muscle movements, such as human heart muscle pumping blood. The research also could lead to novel insights into heart disease, and might ultimately serve in the development of gene therapies targeted toward correcting mutations in proteins that detrimentally alter the speed at which heart muscle fibers contract.

Since insects have been remarkably successful in adapting to a great range of physical and biological environments, in large part due to their ability to fly, the research also will interest researchers studying the evolution of flight, Swank noted. The project is supported by a three-year $240,000 grant from the National Institutes of Health and a four-year $260,000 grant from the American Heart Association.........

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