Date: June 8, 2016
Source: Lehigh University
Class is in session for a group
of chickadees at their temporary quarters inside an aviary in Lehigh's
department of biological sciences.
Today, the students are beginning
a 10-day lesson on spatial memory. A wooden board hanging on one of the
aviary's walls contains 60 small holes, each covered with a ball of cotton. One
of those cotton balls conceals a worm. One at a time, each bird must find the
hole hiding the worm.
Over the next nine days, the test
will be repeated daily, with a new worm hidden each day inside the same hole.
The experiment, says Michael
McQuillan, is designed to measure each bird's ability to remember where it has
stored food -- a trait vital for chickadees and other animals that scatter and
hoard their food to survive in the wild.
It is also designed to shed light
on speciation, the process by which new species arise over time.
McQuillan, a Ph.D. candidate in
biological sciences, is particularly interested in hybridization, which occurs
when parents from two different species mate. Their offspring, called a hybrid,
may or may not become a new species.
McQuillan's chickadees include
the black-capped chickadee, whose range covers Alaska, Canada and the northern
United States, and the Carolina chickadee, which lives in the southeastern U.S.
The two species of songbirds do not migrate and are similar, but
distinguishable, in appearance. The black-capped variety is darker and larger,
its tail is longer, and its black bib has sharper edges.
The ranges of the two purebred
species overlap in the Lehigh Valley. The intermingling has led to
interbreeding and produced hybrid chickadees, which McQuillan is also testing.
Hybridization occurs in about 10
percent of animals and 25 percent of plants, says McQuillan. Some hybrids
thrive, but most do not. The mule, a cross between a horse and donkey, is
valued for its strength and endurance but is unable to reproduce and thus to
speciate. And roughly 60,000 years ago, says McQuillan, scientists believe
human beings interbred with Neanderthal men.
No comments:
Post a Comment