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On the Selective Advantage of Fratricide in Raptors
Christopher H. Stinson
Vol. 33, No. 4 (Dec., 1979), pp. 1219-1225
Published by: Society for the Study of Evolution
Stable URL: http://www.jstor.org/stable/2407480
Page Count: 7
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Cainism is a form of fratricide common to many large raptors where the older chick attacks and can cause the death of its sibling(s), often regardless of immediate food abundance. In raptors, cainism apparently occurs only in species which usually lay two eggs; the second egg is probably insurance against infertility in the first egg or against early death of the elder nestling. Cainism is probably a method of brood size reduction which permits the parents to rear the maximum number of healthy young which can be fed adequately However, cainism can be selected for when it reduces parental fitness, and, under certain conditions, may be selected for even when no survival advantage is conferred on the cainistic nestling. When cainism reduces parental fitness, parental behaviors which inhibit cainism are expected, and it is suggested that raptors are able to suppress fratricidal behavior when it would lower parental fitness.
Evolution © 1979 Society for the Study of Evolution