Mating Strategies Monogamy Polygamy Polygyny: one male, 2+ females Polyandry: one female, 2+ males Promiscuity: no pair bond

Sexual Selection Females assess males b) Males battle for access to females

Life History Patterns Cost of reproduction Senescence age-related Reproductive effort Cost of reproduction Senescence age-related experience-related Previous breeding experience

N. Elephant Seals Iteroparous, one offspring per year, Polygynous, K-selected and long-lived Iteroparous, one offspring per year, 8-month gestation Males breed at age 7-8, females at 2-3 Sexual selection by male battles, only female raises pup

Western Gulls Iteroparous, multiple offspring, lay 2-3 eggs per year Monogamous, K-selected and long-lived Iteroparous, multiple offspring, lay 2-3 eggs per year Third Chick Disadvantage Males breed at age 3-5, females at 4-6, both sexes raise young

New study by Dr. Tim Clutton-Brock (Cambridge Univ.) (2007, Proceedings of the Royal Society) Renowned expert on life history studies in long-lived mammals Review of polygynous vs monogamous species: males live longer in monogomous in 16 of 19 polygynous species, males have significantly shorter lifespan cost of reproduction—defending a harem