Chapter 10: Sexual selection. Males and females often are strikingly different in size and appearance (sexual dimorphism). E.g long-tailed widowbirds male is black with long tail, female is dull brown. Sexual dimorphism. Less extreme sexual dimorphism occurs in humans.
are common in mammals e.g. deer,
lions, antelope, elephant seals.
secure harems of females and obtain
exclusive mating access to them.
Bull elk and harem
and reproductive success.
Southern Elephant Seals
extreme sexual dimorphism when males
can potentially control large harems.
between harem size and relative sizes
of males and females.
In harbor seals, harems are small and
sexes similar in size.
In elephant seals, harems are large and
males much larger than females.
maintain successfully in each of two study years.
Damselfly penis (note spines for extracting sperm).