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Cattle Colors in Pastoral Herds: Natural Selection or Social Preference?
Author(s) -
Finch Virginia A.,
Western David
Publication year - 1977
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1935090
Subject(s) - coat , pastoralism , herd , livestock , geography , altitude (triangle) , range (aeronautics) , ecology , biology , natural selection , zoology , selection (genetic algorithm) , mathematics , artificial intelligence , computer science , materials science , geometry , composite material
Indigenous cattle in East Africa show a wide range of coat colors. A study was undertaken to establish whether the observed variations resulted from social preference of herdsmen or natural selection. Cattle of different coat colors were compared under experimental conditions at 1,400—m altitude. Dark cattle absorbed more solar radiation than light cattle, drank more H 2 O, lost less weight during a drought, and gained weight faster after it. In the same drought, significantly more light than dark cattle died in an adjacent pastoral area, whereas in a lowland area more dark than light apparently do so in droughts. From a geographic analysis cattle colors were found to vary, with an increased proportion of dark animals at higher altitudes. However, cattle herds in northern Kenya were found to have a higher proportion of light cattle than at comparable altitudes in southern Kenya. When prevailing heat stress values were calculated, the proportion of light cattle was found to increase linearly with heat stress with no significant difference between northern and southern localities. The selective effect of heat stress on coat color is discussed. The trend line of lighter coat color with higher heat stress was found to operate within and between tribal boundaries. Social preferences apparently do not strongly influence the prevailing natural selective formce but may reinforce it as the ecological significance of coat color is widely recognized by pastoralists.