Differences in the Behavior of Landraces and Breeds of Dogs - Genetics and the Behavior of Domestic Animals - page 225

head shape starts with the palate. Rostral changes start later and end later
than palate allometries, followed by a period of isometric growth. At about
16 weeks, all members of the genus have essentially adult-shaped skulls,
including the borzois, in their palate length proportions, but not the adult ros-
tral proportions. Sub-adult wolves have short faces and overlapping dentition
once thought to be diagnostic of dogs.
Growth, both isometric and allometric, continues through the acquisition of
the permanent teeth, and accommodation of the various parts to one another
modify the resulting shape. Animals neutered early in ontogeny end up without
the secondary sexual characteristics of adults. Environmental over- or under-
stimulation can affect the formation of the brain which in a sense builds its own
brain case, and affects the final outcome of both size and shape. The point is
that the resulting head shape in any of the species is not strictly genetic, but
rather epigenetic. Brachycephalic dogs have adult palates but neonatal rostrums
only in the sense that they do not grow very much. Examination of that growth
indicates that it is the nasal bones that don't grow and the rest of the face is an
accommodation of the maxillary and pre-maxillaries to the genus-specfic palate
proportions, adult teeth, and the short adult nasals. Describing such skulls as
paedomorphic is incorrect ( Drake, 2011 ).
Coppinger and Schneider (1995) described mesaticephalic dogs as having
normally shaped canid skulls but tending to be small proportionately to body
size (more pronounced in large breeds). The claim was that dogs have reduced
brain sizes. Brains of big dogs are equivalent to 4-month-old wolves (approx.
100 cc in big dogs). Arresting brain development early in ontogeny would
support the behavioral observations that these animals lack adult foraging and
hazard avoidance behaviors and are more puppy-like in behavior. But what is
true of big dogs is not true of dogs in the 12- to 16-kg size range, which have
genus-typical head sizes, brain sizes and tooth sizes. Brain sizes grow with a
negative allometry, so indeed big dogs have small proportions compared to
small dogs. The same is true of big wolves which have proportionately smaller
heads and brains than smaller wolves. Certainly one could not make the argu-
ment that big wolves were ontogenetic snapshots of smaller wolves. Goodwin
et al. (1997) take the nonsensical argument one step further, arguing that
breeds of dogs that least look like wolves are the most paedomorphic
What is true of morphology is also true of behavior. Just as the elongated
rostrum of the borzoi is a result of changing juvenile allometries, so is the
eye-stalk behavior of the border collie. These herding dog behaviors may be
homologous to the ancestors' predatory behaviors just as dogs' nasal bones
are homologous to wolves' nasal bones. They are not juvenile characters
carried into the adult stage of the dog. During play, border collies display
many of the component parts of the ancestral hunting behavior significantly
earlier than wolves ( Lord, 2010 ).
Because so many different systems are developing simultaneously early
in life, any heterochronic changes occurring during the juvenile stage can