Domestication effects on foraging strategies in fowl.
Birds of two different breeds differing in degree of domestication were studied to reveal any differences in foraging strategies between them. The breeds were wild-type birds (crossing between red jungle fowl (Gallus gallus) and Swedish bantam (Gallus gallus domesticus) and domestic birds (Swedish bantam), breeds representing an increasing level of domestication. Bantam birds have not been selected for any specific characteristics. The birds were allowed to forage in an experimental pen containing two separate food patches, which depleted as a function of being exploited, to see how well the different breeds were able to assess costs and benefits as the distance between patches were changed (short distance between patches compared to long distance between patches). Both breeds behaved in accordance with some general predictions of optimal foraging theory, i.e. moved between patches, left patches before these were empty and stayed for a shorter time in more depleted patches. Wild-type birds responded more than domestic birds to an increase of distance between patches, by spending longer average time in patch when there was a long distance between them compared to when there was a short distance. The wild-type birds adopted what seemed to be a more costly foraging strategy, moving more between patches than the domestic birds without ingesting more feed. During domestication, in the protected environment provided by man, individuals using less costly behavioural strategies may have gained increased fitness over those spending more energy on foraging. Although domestic birds still possessed the ability to respond adaptively to environmental conditions, the differences between the wild-type and the domestic breed might be a result of the reduction of the natural selection pressure which accompanies domestication.
Andersson
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Department of Animal Environment and Health, Section of Ethology, Faculty of Veterinary Medicine, Swedish University of Agricultural Sciences, P.O. Box 234, S-532 23, Skara, Sweden
Nordin
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Jensen
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