such as "Introduction", "Conclusion"..etc
The giraffe's elongated neck has long been used in textbooks as an
illustration of evolution by natural selection, but this common example
has received very little experimental attention. In the January issue
of the American Naturalist, researchers at the Mammal Research
Institute in the Department of Zoology and Entomology at the University
of Pretoria tested whether foraging competition with shorter herbivores
could explain why giraffes feed mostly on leaves high in trees, despite
being able to feed at lower levels as well.
[study] provides the first real experimental evidence that the long
neck of the giraffe might have evolved as a consequence of competition,
which provides support for a previously untested textbook example of
natural selection," says Elissa Cameron (University of Pretoria), who
coauthored the study with Johan du Toit (University of Pretoria and
Utah State University).
Giraffes are well known for their unusual height, and they generally
feed high in the tree canopy, above the height other herbivores can
reach. Giraffes receive more leaves per bite by foraging high in the
tree, but it's unclear whether this is caused by competition - smaller
browsers eating some of the leaves at lower heights - or if more leaves
grow at higher levels.
The researchers built low fences around
trees in greater Kruger National Park to stop smaller browsers from
eating leaves. After a complete growing season they found that the
number of leaves on the fenced trees was roughly the same, revealing
that small browsers are responsible for most of the foraging.
Therefore, the researchers argue, it is competition from other
herbivores, such as kudu, that appears to drive giraffes to eat leaves
high in the trees. University of Chicago Press Journals. December 2006.
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