Biology Reference
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are found in “all” species but tend not to become fixed unless selected for by
humans, or appearing on isolated islands.
Many household dogs are the approximate size, color, and shape of their
working ancestors. Many of these are registered by national or international
kennel clubs under the breed name of their phylogenetic working ancestors.
They tend to be historical representations of an ancestral breed without the
breed-specific behaviors. Working breed-specific behaviors often turn out to
be obnoxious to pet owners.
Phenotypically this is a difficult group to generalize. Choice is often for
novel shapes and sizes for their own sake. Morphological exaggerations exist
for gargantuanism or miniaturization of an ancestral breed. Tendencies
toward brachycephaly (short heads) or dolicephaly (long heads) are
enhanced, producing deformations such as occluded jaws, dental anomalies,
and nasal restrictions. These often have adverse behavioral and physiological
consequences, i.e. lowered oxygen tensions, improper thermoregulation,
atypical ocular overlap ( Evans and Christensen, 1979 ), or inability to feed
properly. Some household breeds cannot walk without pain or damage
to themselves, or reproduce without assistance or caesarian section
( Wolfensohn, 1981 ). The English bulldog, no longer an historical representa-
tion of its infamous ancestor (the “catch” dog), is perhaps an extreme case of
these selective processes ( Thomson, 1996 ).
There has been growing awareness regarding the health and welfare of
pedigree dogs, particularly in the U.K. Darwin mentioned the connection
of extreme breed size and breed-typical health problems as early as 1858
( Darwin, 1858 ). But concern for the welfare of pedigree dogs has come to
the forefront with the 2008 BBC documentary, “Pedigree Dogs Exposed”,
which spurred several independent reports on dog breeding ( APGAW,
2009; Bateson, 2010; Gallant and Gallant, 2008; Rooney and Sargan,
2009 ) and the formation of the Advisory Council on the Welfare Issues of
Dog Breeding. The reports by the Associate Parliamentary Group for
Animal Welfare (2009) , Rooney and Sargan (2009) ,and Bateson (2010)
all determined that the breeding for extreme morphological characteristics
and the practice of inbreeding to reach breed standards, were a cause for
concern in regards to the welfare of the dogs created through these
practices.
Character selection is frequently capricious. There is no real functional
purpose for the morphology. For those of us who think of behavior as the
selective agent for morphological diversification, the term “unnatural
selection” should apply to household dogs ( Coppinger, 1996 ). As we have
seen, sled dogs are not chosen for their legs, but for their running abili-
ties. In household dogs, a morphology (e.g., double dew-claws; long,
pointed nose; short, flat nose; achondroplasia) which is in some way
pleasing to humans, is chosen regardless of the animal's ability to cope
with the form.
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