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Date: Fri, 2 Apr 1999 02:50:42 EST
From: C
Subject: In Animal Groups, Scientists See Patterns That Could Predict The Future
1 APRIL 1999
Contact: Vince Stricherz
vinces@u.washington.edu
206-543-2580
University of Washington
In Animal Groups, Scientists See Patterns That Could Predict The
Future
Like teenage boys hanging out on a street corner or fans cheering
at a football game, animals behave differently when they're in a
large group than they do when they're by themselves.
The mechanics and patterns of nature's aggregations - schooling
fish, flocking birds or swarming insects - provide valuable
understanding for how such groups behave in, and survive, trying
conditions, says a University of Washington zoologist.
What looks like a complex dance - an entire group suddenly changing
directions or exploding and reforming - is actually a series of
interactions between members of the group reacting to outside
influences, says UW research assistant zoology professor Julia
Parrish.
"There's a beautiful, aesthetic, very artistic side of it, but
there's also a very mathematical and a very evolutionary aspect of
animal aggregation," says Parrish, who writes about the complexity
and patterns of animal aggregations in the April 2 issue of the
journal Science. The paper, co-authored by Leah Edelstein-Keshet,
an associate mathematics professor at the University of British
Columbia, is part of a package of Science articles that explore the
uses of complexity theory in natural and social science.
Pattern that emerges from aggregation is not limited to living
systems, Parrish says. Snowflakes are a classic example. A single
flake falls and is beautiful to look at. A stormful of flakes stick
together and are carved by the wind into elaborate ridges and
cornices. A winter's worth of flakes slip and slide and adjust to
gravity, eventually producing an avalanche.
But animal aggregations have an evolutionary side.
How individuals react to outside influences can determine their own
survival, as well as the survival of other group members. A herring
that turns right when the school turns left faces certain death,
Parrish says. But a herring that always cooperates with the group
and never competes might die of starvation. Finding the threshold
between cooperation and conflict eventually could provide
scientists with the proverbial "canary in the coal mine" that
allows humans to grasp the effects that their actions today will
have on the world a century from now.
For example, a slight increase in water temperature because of
global warming or a change in the ocean's chemical balance because
of coastal pollution could alter the point at which schooling
breaks down. Given the added stress of overfishing - humans consume
40 million to 50 million metric tons of schooling organisms each
year - fish might end up in groups too small or too unfamiliar to
survive. People wonder how massive flocks of passenger pigeons
could ever have become extinct, Parrish says. As flocks got
smaller, social interactions between the birds broke down. Hundreds
or even thousands of birds were simply too few to form the flock
sizes needed for the species to survive, she says.
Documenting how animal groups behave allows computer models to
predict what will happen under various conditions in the future.
A school of fish, for instance, can sense the approach of a
predator and take evasive action. The group might scatter to avoid
being consumed, though stragglers or individuals at the outer edges
of the group might be devoured. But once the danger has passed, the
group reforms. With a computer model, scientists can change the
intensity of predation to see at what level the school is slow to
reform or doesn't get back together at all.
Likewise, the models can assume conditions that don't yet exist -
higher water temperature, for instance, or lower fish populations,
possibly because of overfishing. The scientists study the models
to see how fish react to those conditions.
"As resources are strained, it creates greater competition within
the group. That has implications for all things human," Parrish
says.
Humans are among the most social species and display all sorts of
crowd behavior, no matter whether the individual knows the person
in the next seat.
"With models, we may be able to predict the switch from standing
ovation to rampage and adjust the outside influences accordingly,"
Parrish says. "Fish and humans are not so different. Fish have just
had a lot longer to practice."
###
For more information, contact Parrish at 206-616-2958 or
jparrish@u.washington.edu , or Edelstein-Keshet at 604-822-5889 or
keshet@math.ubc.ca
URL: http://www.eurekalert.org/releases/uwash-iag033199.htmleleases/pr788m.htmlspp
=========================================================
MINDLESS CREATURES ACTING 'MINDFULLY'
from The New York Times
Oblivious to its fellows, the single-celled creature called
the cellular slime mold slithers amoeba-like along the ground,
lapping up the nutrients in its path. But when the food supply runs
out, it has a biochemical panic attack, frantically sending out
molecular signals to other nearby slime molds, which in turn are
sending out signals of their own. Guided by these primitive
conversations, the individual cells come together to form a
multicelled organism, sprouting a stalk and a head of spores that
become the seeds of the next generation. When these fall to the
ground, the cycle begins anew. Exotic as it seems, this behavior
is just a stark example of one of the most familiar phenomena in
the living world: the way individuals, whether cells in a body,
plants and animals in an ecosystem, or members of a corporation or
society, congregate into complex wholes that take on autonomous
existences of their own. There is no need for a central controller
orchestrating their movement.
http://www.nytimes.com/library/national/science/032399sci-cellular-automata.html
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Date: Fri, 2 Apr 1999 03:54:53 EST
From: C
Subject: GL: Birds may sing a song of climate change
Birds may sing a song of climate change
Saturday, March 27, 1999
Laurent examined the abundance patterns of 14 songbird species,
including the black-capped chickadee, and compared populations
with temperature changes.
Winter songbird populations may serve as a short-term ecological
indicator of climate change, according to a University of
Michigan study showing a link between temperatures in the Great
Plains over the last 30 years and the abundance of several common
species of winter songbirds.
Chad Laurent, a sophomore at the U-M School of Natural Resources
and Environment, has studied the relationship between winter
temperatures from 1960 to 1990 and the populations of 14 species
of winter songbirds using statistics from the National Audubon
Society's annual Christmas Bird Count. His research shows that
particular bird populations are directly affected by winter
temperatures.
"One year's winter temperatures alone don't seem to affect the
abundance of certain species," said Laurent. "But when you look
at average temperatures for three years, you can begin to see the
correlation. Birds who track temperature move very quickly in
response to temperature variations."
Laurent examined the abundance patterns of 14 songbird species,
including the black-capped chickadee, the horned lark, the
white-breasted nuthatch, the American goldfinch, the American
tree sparrow, and the dark-eyed junco, in four Great Plains
states: North Dakota, South Dakota, Nebraska and Kansas.
His research correlated low, medium and high abundance of
temperature-linked species with average winter temperatures over
several different periods of time, from one to five, 10, and 30
years. The study refines previous research by Prof. Terry J.
Root, of the School of Natural Resource and Environment, which
has shown that some species of wintering birds are associated
primarily with vegetation while others are associated mainly
with temperatures.
"Since watching and feeding winter songbirds
is such a popular pastime in this country," says Laurent,
"elucidating the effects that global warming has on bird
abundance has tremendous potential to increase public awareness
of the problem."
Laurent will present his research, part of the university's
Undergraduate Research Opportunity Program, April 14 on Capitol
Hill in Washington, D.C. For more information, contact Diane
Swanbrow, University of Michigan, (734)647-4416, email:
swanbrow@umich.edu .
Copyright 1999, Environmental News Network
http://www.enn.com/news/enn-stories/1999/03/032999/songbird_2375.asputomata.html