Peter Donck schreef op maandag 30 november 2009, 21:20:
>> ElkeW schreef op maandag 30 november 2009, 20:44:
>>> Ben je zeker dat het zo zat met die vossen Peter? Ik weet het
>>> niet meer zeker, maar ik dacht onthouden te hebben: hoe meer
>>> het jong een product was van op lieve aanhankelijke karakters
>>> geselecteerde oudervosjes, hoe meer witte tekening er begon op
>>> te duiken?
>>>
en ja hoor, omgekeerd lukt ook, dus we hebben allebei gelijk
kan ook anders als die dingen gerelateerd zijn
voor alle lezertjes met flapoorhonden en rondkopkatten :
"Belyaev's silver foxes: The most famous example of a connection between depigmentation and docility is Belyaev's foxes (Belyaev and Trut 1975, Belyaev 1978, Trut 1999). Belyaev brought wild silver foxes into captivity and bred them specifically for tame behavior. Experimenters tested the animals' temperaments by reaching into the cages of young foxes and trying to touch them, stroke them, and give them food. Foxes were also placed in a large enclosure with a human. The most docile foxes were retained for breeding, foxes that reacted with more fear and aggression were not bred.
The experiment lasted for over forty years and tested more than ten thousand foxes. The results were striking. Through this process of breeding exclusively for tameness, Belyaev obtained foxes that eagerly approached humans and licked their hands and faces. These foxes even tried to attract human attention by whining and wagging their tails.
But these behavioral differences weren't the only changes that Belyaev obtained in his tame foxes. These foxes also differed morphologically and physiologically from their wild counterparts. The tame foxes had floppy ears, curly tails, and domed skulls. The females went into heat twice a year (like domestic dogs) instead of once a year (like wild foxes). And instead of having a solid silvery black coat, many had patches of depigmented, white fur. The percentage of foxes with white patches went up from 0.71% to 12.4% of the population, an increase of 1646% over forty years (Trut 1999).
What happened? By selecting for tamability, Belyaev selected for physiological changes in the systems that govern the body's hormones and neurochemicals. Those changes had far-reaching effects on the animals' behavior and development, and ultimately on their morphology and physiology.
Trut's rats: Belyaev's fox breeding experiments were repeated in wild Norway rats (Trut 1997), with same result. After 15 years of selection for tameness (over 30 generations of rats) in a captive colony, the percentage of piebald rats (berkshire and hooded) increased rapidly until about 73% had white bellies. The white belly-patches of these rats were large, sometimes spreading to the sides. About half of the piebald rats had white socks too. Over time, solid-colored rats disappeared almost entirely from the population.
In a control population of wild rats bred for 15 years and not selected for tameness, a few piebald rats appeared but they never comprised more than 10% of the population. The white patches of these unselected piebald rats remained very small (a small white spot on the belly or chest) and none of the rats had white socks.
Therefore, in this experiment, selection of Norway rats for tameness correlated with their depigmentation. The population selected for tameness had a much higher percentage of depigmented animals than a similar group that was not selected for tameness.
* For more detail and experimental evidence on Trut's rats, see coat color and temperament in Norway rats and deermice
Note that while moderate depigmentation tends to correlate with calmness, extreme depigmentation can correlate with neurological problems (Grandin 1998), as well as vision and hearing impairments. Here's more information on mutations in pigment cell migration. "
Warboel
