Mating Systems

• Causes

• Types and distribution

• Ecological factors– Polygyny threshold– Polyandry

Causes of spacing patterns

Males disperse in space to maximizemating 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