Pregnancy block male advantages

Thus, rather than providing a reproductive benefit to males as traditionally assumed, the Bruce effect may have evolved solely to female advantage. Notably, this response also increases selective pressure on stud males to increase their investment in the territorial defence of nest sites that are preferred by females (Ims 1987). Females may improve their own reproductive success through threat of pregnancy block, compelling stud males to invest more heavily in nest defence. 

Dawkins (1976) suggested that pregnancy block may be advantageous for a female that has been deserted by her mate, for although she forfeits her initial investment, the female benefits from remating quickly with a male that will provide parental care. However, since parental care is not the... 

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