Behavioral Ecology - dominant and having his own...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
Behavioral Ecology Battle of the Sexes A 1:1 sex ratio of males to females is an evolutionarily stable strategy. If there were more females than males, males would have the reproductive advantage, and their genes would be passed down at a higher rate. All offspring should receive equal parental investment since they share the same relatedness to their parents. In humans, 20% more males are conceived than females, but only 6% more males are born than females. By age 15, the ratio is 1:1. In other words, males have a higher mortality rate, and this has been evolutionarily compensated for by increasing the conception rate of males. In some social species, there is a correlation between the mother's dominance rank and the sex of her offspring. High-ranking females are more likely to birth males while low ranking females are more likely to birth females. High-ranking females will likely attract high quality males, and so her male offspring will have a good chance of being
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: dominant and having his own reproductive advantage. Low ranking males have a much higher mortality rate than low ranking females, and so if the mother is low-ranking in the dominance hierarchy, her female offspring have a better chance at survival than her lower quality male offspring. Direct Benefits In mating with a particular male, some females may receive direct benefits, such as good territories. This is known as resource defense polygyny, where males fight for territory early in the breeding season, and females are attracted to males based on their territory. Another direct benefit comes in the form of nuptial gifts. The male katydid, for example, produces a spermatophore, which is basically a ball of sperm with highly proteinaceous material. The protein boost is very valuable to females when food is scarce, and they will even compete for matings to win this nuptial gift....
View Full Document

Ask a homework question - tutors are online