Swamp Sparrows Change Their Tune for Competitors
Tuesday January 13, 2009
Ornithologist Adrienne DuBois, a graduate student from the University of Miami, has discovered that male swamp sparrows modify their song when competing males are nearby. The song of a male swamp sparrow is a slow trill of two or more pitches (listen to the swamp sparrow's song).
Previously, scientists thought that once the swamp sparrow learned its song, it did not modify it—the swamp sparrow simply sang the same tune repeatedly. But DuBois' research shows that swamp sparrows do not sing the same song over and over again. Instead, when competitors are in range, they modify their song—increasing the frequency range and the speed at which they sing.
The results from DuBois' research have implications outside of the field of ornithology. Birdsong provides scientists with insight into the evolution of communication. Steve Nowicki of Duke University, a co-author of DuBois' study, explains what birdsong reveals about communication in aniamls:
"By understanding what animals do in their natural environment, we get a glimpse of what their brains can do. In a broader sense, we can make assumptions about the way the animal brain develops to support a complex communication system."
Swamp sparrows (Melospiza georgiana) are small songbirds that inhabit wetlands throughout eastern and central North America. During the summer months, swamp sparrows inhabit a range that extends from Canada's Yukon Territory eastward to Labrador and southward to Nebraska, the upper midwest, and coastal New England. Their winter range extends from Southern New England to Florida, the midwest, and down into Texas and Mexico. Swam sparrows inhabit a variety of freshwater and tidal wetlands including marshes, meadows, swamps, and bogs.
Find out more:
DuBois A, Nowicki S,
Searcy W. 2008. Swamp Sparrows Modulate Vocal Performance in an Aggressive Context. Biology Letters.
Photo © Robert Lachlan.
Wildlife News Roundup - December 2008
Wednesday December 31, 2008
In this issue of Wildlife News Roundup, we find out about the effects rising carbon dioxide levels have on large marine animals, the northward expansion of the range of European butterflies, and the Old World origins of the world's large cats. There is also news of a surprising tendency for snowy owls to spend their winter on Arctic sea ice and the disturbing news of poaching and habitat destruction in Zimbabwe.
- To Find Way Home, Some Crabs Find It’s All in the Stride (New York Times) — December 29, 2008. Scientists investigating fiddler crabs reveal that these creatures use their own strides to measure the distance they wander and use their measurements to find their way home.
- Ancient Cheetah Fossil Points to Old World Roots? (National Geographic) — December 29, 2008. A new study provides evidence that large cats first evolved in the Old World, not North America, as competing opinions suggest.
- Bigger Sea Creatures, Like Squid, May Feel Effects of Higher CO2 (New York Times) — December 22, 2008. As atmospheric carbon dioxide rises, more of the gas is absorbed into the world's oceans. The dissolved carbon dioxide causes a rise in the acidity of the sea water and this could affect many marine species, including larger organisms such as squid.
- Microscopic Plankton Get the Big Picture (Times Online) — December 22, 2008. Richard Kirby of the University of Plymouth shares close-up images of a variety of plankton in an exhibition that will tour aquariums around Great Britain.
- Snowy Owl - A Marine Species? (Science Daily) — December 24, 2008. Satellite tracking has revealed that six adult female snowy owls spent much of their time last winter out on the Arctic sea ice.
- Whistling Orangutan May Hint at Language Evolution (National Geographic) — December 22, 2008. The whistles of an orangutan from the National Zoo in Washington DC has captured the attention of scientists studying the origins of human language.
- New York City Beaver Returns (Science Daily) — December 20, 2008. Jose the beaver returned to the Bronx Zoo for the second time and is in the process of constructing a lodge on the Bronx River.
- 'Sexy' Tusks Led to New Whale Species? (National Geographic) — December 19, 2008. Scientists revealed that the unique tusk-like teeth of male beaked whales evolved to attract females as well as for use in battling other rival males.
- Zimbabwe: Extinction Looms in a Paradise Lost to Guns, Greed and Hunger (Times Online) — December 18, 2008. Poaching and habitat destruction are rampant in Zimbabwe, threatening the regions rare wildlife with extinction.
- Exotic Butterflies Seek Sanctuary in Britain (Times Online) — December 11, 2008. More than 60 species of butterflies have moved into Britain from regions to the south, as they follow a changing climate.
About Wildlife News Roundup
Wildlife News Roundup is a monthly digest featuring animals and wildlife headlines from around the web. It includes headlines from well-established sources such as the World Wildlife Fund, BBC News, New York Times, National Public Radio, National Geographic, and Birdlife International. The sources are selected with care and include only those that archive articles for many years, offer top-notch science writing, and follow stories as they develop over time.
← November 2008 | 2008 Archive
Photo © Graeme Purdy / iStockphoto. Snowy owl.
'Soft Spoken' Bison Bulls Win More Mates
Tuesday December 30, 2008
During the bison mating season, male bison produce loud, low-frequency bellows. These bellows are most often used when one male challenges another and may enable rival bulls to determine which bison is the more dominant. A team of scientists has now revealed that the way bellows convey information between bison is counterintuitive and perhaps far more complex than they had expected. Their findings indicate that males whose bellows are quieter win more mates and produce more offspring than their louder-bellowing rivals. They had expected to find the opposite—that more dominant males produced the louder bellows.
The research team, led by Megan Wyman, included experts from the University of California, Davis and the Point Loma Nazarene University. They studied bison in the Fort Niobrara National Wildlife Refuge in north-central Nebraska. For two consecutive rutting seasons, which occur during the months of July and August, the scientists kept a daily, 14-hour watch on the bison heard.
From the safety of a pickup trucks (the bison were habituated to these trucks and were not scared off by them), Wyman and her colleagues measured vocalizations, making note of challenges among bulls as well as which bulls successfully mated with females. They used hand-held sound-level meters to record the amplitude (loudness) of the bison bellows and were careful to note any factors that might influence the sound measurements such as wind direction, orientation of the bison's head relative to the sound-level meter, and the distance of the bellowing bull from the meter. The team also noted each observed mating between bulls and cows and rival challenges among bulls to produce a clear understanding of the social structure of the herd and the relative mating successes of the various bulls.
At the end of the study, Wyman sifted through the sound-level readings to include only those of the highest quality and was left with 408 readings from 44 bulls. When she analyzed those sound readings, she found that the bulls with the lowest number of matings and offspring bellowed at least 50 percent louder than their rivals who were more successful at mating and producing offspring.
"We were expecting to find that the bigger, stronger guys—the higher-quality maltes—would have the loudest bellows, because they can handle the costs of it, but instead we found the opposite. It could be that bulls provide information about their high quality through other signals—for example, the frequency or duration of their bellows. So they don't have to be louder, they just have to be heard." ~ Megan Wyman, UC Davis.
Find out more:
Quiet Bison Sire More Calves Than Louder Rivals (Eurekalert)
Photo (top) © Paul Haverkamp / UC Davis Photography / UC Regents. UC Davis geography graduate student Megan Wyman measures the amplitude of a bison's bellow in Nebraska's Fort Niobrara National Wildlife Refuge.
Photo (bottom) Photo © Megan Wyman / UC Davis Photography / UC Regents. A bull bison (right) bellows as he guards a female from other males.
New Adhesive Mimics Geckos' Toe Pads
Monday December 29, 2008
Geckos (Family Gekkonidae) belong to a group of small lizards that possess a remarkable ability to climb smooth, vertical surfaces with speed and ease. This impressive talent hinges on the geckos' specially adapted toe pads.
Each of the gecko's toe pads is covered with microscopic hair-like stalks known as setae. These tiny bristle-like structures are stiff and frayed at the ends. The setea have unique adhesive properties—they are not sticky or moist like more familiar adhesives (such as tape or glue) yet they attach strongly to a wide range of surfaces. Unlike tape or glue, gecko toe pads stick without marring the surface with adhesive, they are easy to remove, do not stick to one another, and do not collect dirt from the surfaces to which they stick. Setae are formed from stiff hydrophobic keratin that act as a bed of angled springs and adhere to surfaces via molecular forces known as van der Waals forces.
Scientists have now developed a 'next generation' of adhesives that are modeled after geckos' remarkable toes. These new adhesives attach with great strength and release with ease and for that reason are far better than conventional pressure-sensitive adhesives such as tapes and glues (which are either strong and difficult to remove or weak and easily removed).
The development of the new adhesive was possible thanks to a unique team of scientists that included biologists (Professor Keller Autumn from Lewis and Clark College and Robert Full from University of California, Berkely) and engineers (Ron Fearing and his colleages, also from University of California, Berkely).
Find out more:
Photo (top) © K. Autumn / Lewis and Clark College. A gecko sits atop a glass surface in this image from the NIRT laboratory.
Photo (bottom) © J. Lee and R.S. Fearing / UC Berkeley. A close-up of the new adhesive material developed to mimic the way gecko toe pads stick to surfaces.
