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5 - Mating Systems Parental Care Monogamy male female form...

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Mating Systems & Parental Care Monogamy - male & female form pair bond - long (lifetime) or short (breeding season) term - both care for eggs & young - rare except in birds (90% of birds) Polygyny - male mates with several females - simultaneous polygyny or successive polygyny - females provide parental care Polyandry - reverse of polygyny - males provide parental care Promiscuity - both male & female mate several times with multiple partners - no parental or either sex may provide parental care
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Ecological conditions favouring monogamy 1) important & scarce resource require 2 individuals to defend 2) difficult conditions require presence both parents - incubation & high energy demand in birds 3) short breeding season requires rapid pair formation short breeding season advantage goes to early breeders eg. seabirds such as kittiwake gull - permanent pair cooperate better - egg laying begins earlier - 'divorces' 3x more common among pairs that were unsuccessful the previous season - strong selection to find efficient partner
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Ecological conditions favouring polygyny 1) heterogeneous environment & scarce resource - males defend territories & resource - great variation in quality of breeding site (Polygyny threshold model) 2) biased operational sex ratio a) all females ready at same time operational sex ratio = real sex ratio = 1:1 no time for male to mate with >1 female monogamy eg. toad Bufo bufo all females lay eggs within 1 week each male only has time to mate with 1 female b) females become receptive in sequence - males successive polygynous eg. bullfrog Rana catesbeiana females arrive at pond over several weeks males mate with all arriving females polygyny
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