Mating Systems Causes Types and distribution Ecological factors

Mating Systems • Causes • Types and distribution • Ecological factors – Polygyny threshold – Polyandry

Causes of spacing patterns Males disperse in space to maximize mating opportunities with females

Parental care and female dispersion influence mating system

Monogamy Lar gibbon Silver-backed jackal

Social monogamy • > 90% of all birds, most biparental care • < 10% of all mammals – males help provision young • canids, marmosets, carnivorous bats – males defend single female • dik-dik, some rodents • Rare in – insects (carrion beetles) – Fishes, reptiles, amphibians

Mate assistance in Peromyscus californicus

Mate assistance monogamy in snow buntings

Social monogamy ≠ genetic monogamy

Polygyny (> 90% of mammals)

Ecological correlates of polygyny • Females solitary, but ranges defensible by male – prosimian primates • Females solitary, range not defensible – Moose, orangutan • Females social, range defensible – Seasonal harems - elephant seals, red deer – Permanent harems - baboons, zebra, spear-nosed bats • Females social, range not defensible – Female movements unpredictable • males follow females, e. g. elephants – Female movements predictable - males display on leks

Polygyny (< 10% of birds) • Males defend food or nesting sites – Blackbirds – Grouse – Cotingas

Ecological factors affecting polygyny • Female sociality • Female movement predictability • Habitat heterogeneity

Habitat heterogeneity • If there is spatial habitat heterogeneity • And fixed territory size • Then females will have to choose between unmated males on poor territories or mated males on rich territories or • If territory size is related to size or age • Then females should choose largest territory

Resource defense polygyny

Polygyny threshold model

Polygyny threshold predictions • Polygyny should be most common in patchy habitats • Male territory quality influences # of females • Females mating to already mated males should have RS comparable to females pairing with unmated males

Polygyny in pied flycatchers

Polygyny in anolis lizards depends on size

Polyandry • Rare in birds – Sequential - sanderling, stint – Simultaneous - phalarope, jacana – Cooperative - pukeko • Very rare in mammals – Tamarins • Common in fish

Ecological reasons for polyandry • Rich resource, eggs are cheap • Short breeding season • Male biased sex ratio

Why should females multiple mate?

Pseudoscorpions gain fertility benefit

Human mating systems