lecture_6 - Lecture 5: Mating Systems Four basic categories...

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Lecture 5: Mating Systems Four basic categories of mating systems Monogamy (92% of birds) Polygymy (2% of birds) Polyandry (<1% of birds) Promiscuity (6% of birds) *The fact that monogamy is so prevalent is surprising, because: - Eggs are larger than sperm (cost more to produce) - Females can only produce limited # of eggs while males can produce many sperm - Males should mate with many females (polygyny) SO WHY DON’T THEY? Discussion of recipe (equation) for mating systems RE = ME + PE (Reproductive effort = Mating effort + parental effort) Trade-off determines the final amount of parental care given by males and how long they stay with their females. Why do male birds invest more parental effort than mammals? - Mammary glands – not as much need for male parental care in mammals - Oviparous vs. viviparous development of offspring – male birds can aid in incubation Other Factors That Determine Mating Systems : 1. Quantity of resources available – where food is abundant, females may be able to feed their young adequately on their own. Rich environments tend to favor polygyny. 2. Predation – monogamy may yield a higher return because young must be attended at
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lecture_6 - Lecture 5: Mating Systems Four basic categories...

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