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(Science Daily, 17, Jan 2013) - Dogs and wolves are
genetically so similar; it's been difficult for biologists to understand why
wolves remain fiercely wild, while dogs can gladly become "man's best
friend." Now, doctoral research by evolutionary biologist Kathryn Lord at the
University of Massachusetts Amherst suggests the different behaviours are
related to the animals' earliest sensory experiences and the critical period of
socialization. Details appear in the current issue of Ethology.
Journal article: A Comparison of the Sensory Development of Wolves (Canis lupus lupus) and Dogs (Canis lupus familiaris)
Until now, little was known about sensory development in
wolf pups, and assumptions were usually extrapolated from what is known for
dogs, Lord explains. This would be reasonable, except scientists already know
there are significant differences in early development between wolf and dog
pups, chief among them timing of the ability to walk, she adds.
To address this knowledge gap, she studied responses of
seven wolf pups and 43 dogs to both familiar and new smells, sounds and visual
stimuli, tested them weekly, and found they did develop their senses at the
same time. But her study also revealed new information about how the two
subspecies of Canis lupus experience their environment during a four-week
developmental window called the critical period of socialization, and the new
facts may significantly change understanding of wolf and dog development.
When the socialization window is open, wolf and dog pups
begin walking and exploring without fear and will retain familiarity throughout
their lives with those things they contact. Domestic dogs can be introduced to
humans, horses and even cats at this stage and be comfortable with them
forever. But as the period progresses, fear increases and after the window
closes, new sights, sounds and smells will elicit a fear response.
Through observations, Lord confirmed that both wolf pups and
dogs develop the sense of smell at age two weeks, hearing at four weeks and
vision by age six weeks on average. However, these two subspecies enter the
critical period of socialization at different ages. Dogs begin the period at four
weeks, while wolves begin at two weeks. Therefore, how each subspecies
experiences the world during that all-important month is extremely different,
and likely leads to different developmental paths, she says.
Lord reports for the first time that wolf pups are still
blind and deaf when they begin to walk and explore their environment at age two
weeks. "No one knew this about wolves, that when they begin exploring
they're blind and deaf and rely primarily on smell at this stage, so this is
very exciting," she notes. She adds, "When wolf pups first start to hear, they are
frightened of the new sounds initially, and when they first start to see they
are also initially afraid of new visual stimuli. As each sense engages, wolf
pups experience a new round of sensory shocks that dog puppies do not."
Meanwhile, dog pups only begin to explore and walk after all
three senses, smell, hearing and sight, are functioning. Overall, "It's
quite startling how different dogs and wolves are from each other at that early
age, given how close they are genetically. A litter of dog puppies at two weeks
are just basically little puddles, unable to get up or walk around. But wolf
pups are exploring actively, walking strongly with good coordination and
starting to be able to climb up little steps and hills."
These significant, development-related differences in dog
and wolf pups' experiences put them on distinctly different trajectories in
relation to the ability to form inter-species social attachments, notably with
humans, Lord says. This new information has implications for managing wild and
captive wolf populations, she says.
Her experiments analysed the behaviour of three groups of young animals: 11 wolves from three litters and 43 dogs total. Of the dogs, 33 border collies and German shepherds were raised by their mothers and a control group of 10 German shepherd pups were hand-raised, meaning a human was introduced soon after birth.
At the gene level, she adds, "the difference may not be
in the gene itself, but in when the gene is turned on. The data help to explain
why, if you want to socialize a dog with a human or a horse, all you need is 90
minutes to introduce them between the ages of four and eight weeks. After that,
a dog will not be afraid of humans or whatever else you introduced. Of course,
to build a real relationship takes more time. But with a wolf pup, achieving
even close to the same fear reduction requires 24-hour contact starting before
age three weeks, and even then you won't get the same attachment or lack of fear."
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