COSTS OF REPRODUCTION

COSTS FOR FEMALES A. Gestational Costs – greatest costs in last trimester – caloric cost 44% of RMR (ungulates) – protein cost 45% of maintenance (ungulates)

COSTS FOR FEMALES B. Lactational Costs – Compared with pregnancy costs 80% 200+%

COSTS FOR FEMALES B. Lactational Costs – Effect of litter size 2x

COSTS FOR FEMALES C. Variation Due to Sex of Offspring – Polygyny and sexual dimorphism bigger males = more energy invested by mom?

COSTS FOR FEMALES C. Variation Due to Sex of Offspring – Example: Deer male success = number of females inseminated female success = successful rearing of offspring, and quality

COSTS FOR FEMALES C. Variation Due to Sex of Offspring – Red deer: males are more costly to raise 2 days longer gestation more milk demand Faster growth rates Only 64% females breed following season, compared to 72% that nurse daughters

COSTS FOR FEMALES C. Variation Due to Sex of Offspring – Bighorn sheep: lambs born in 2 nd year = 25% less likely to survive a 2 nd year if mom had a son in 1 st year

COSTS FOR FEMALES C. Variation Due to Sex of Offspring – Bighorn sheep: males are more costly

COSTS FOR MALES A. Behavioral – Increased movements during breeding season

COSTS FOR MALES A. Behavioral – Increased scent marking during breeding season

COSTS FOR MALES A. Behavioral – Costs of fighting red deer – 13-29% of mortality mule deer – 19% injury

COSTS FOR MALES B. Morphological – antler growth

COSTS FOR MALES B. Morphological – antler growth

COSTS FOR MALES C. Physiological – Example: Brown antechinus Males stop eating for 3-week breeding season Congregate in tree cavities Lek system All males die at end of breeding season

COSTS FOR MALES C. Physiological – Brown antechinus males don’t eat lose hair lose teeth lose 1/3 of body weight develop stress responses exhibit high glucocorticoid levels

COSTS FOR MALES C. Physiological – Example: Brown antechinus – Iteroparity versus Semelparity

COSTS COMMON TO BOTH SEXES The cost of poor mate choice l inbreeding l immunodeficiencies l lowered reproductive success

CUTTING REPRODUCTIVE COSTS: SEX RATIO VARIATION A. Theories for Adjusting Sex Ratios at Birth – Variation in reproductive success of males and females (Trivers-Willard hypothesis)

CUTTING REPRODUCTIVE COSTS: SEX RATIO VARIATION A. Theories for Adjusting Sex Ratios at Birth Predictions of Trivers-Willard for polygynous species: – females in good condition produce sons – females in poor condition produce daughters – evidence? » red deer: high-ranking vs. low-ranking females

CUTTING REPRODUCTIVE COSTS: SEX RATIO VARIATION A. Theories for Adjusting Sex Ratios at Birth – Local resource competition In primates: – inheritance of female dominance, so …

…male reproductive success is not closely tied to maternal investment Mandrill Japanese macaques Proboscis monkeys

CUTTING REPRODUCTIVE COSTS: SEX RATIO VARIATION A. Theories for Adjusting Sex Ratios at Birth – Local resource competition Predictions: – produce philopatric sex if resources plentiful – only dominant females produce philopatric sex if food scarce – Evidence? » Spider monkeys: only high- ranking females produce sons (philopatric)

CUTTING REPRODUCTIVE COSTS: SEX RATIO VARIATION B. Potential Causes – Timing of insemination

CUTTING REPRODUCTIVE COSTS: SEX RATIO VARIATION B. Potential Causes – Sperm selection in females Production of leukocytes

CUTTING REPRODUCTIVE COSTS: SEX RATIO VARIATION B. Potential Causes – Sperm selection in males Semen composition (differential motility of X and Y sperm) sensitive to steroid hormone levels

CUTTING COSTS: COOPERATIVE BREEDING A. Carnivores biparental or communal care higher milk production increased postnatal growth rates

CUTTING COSTS: COOPERATIVE BREEDING B. Primates (marmosets) elevated growth rates reduced intervals between births

CUTTING COSTS: COOPERATIVE BREEDING C. Rodents (prairie voles) older juvenile helpers increased weight at weaning shorter time to eye opening

CUTTING COSTS: INFANTICIDE AS A REPRODUCTIVE STRATEGY A. An Evolutionary Perspective – Males safeguard paternity – Males increase offspring sired – Females reduce losses Hanuman langurs

CUTTING COSTS: INFANTICIDE AS A REPRODUCTIVE STRATEGY B. Removing the Log from Our Own Eye

CUTTING COSTS: INFANTICIDE AS A REPRODUCTIVE STRATEGY B. Removing the Log from Our Own Eye – Darwin on infanticide in humans – Infanticide in societies hunter-gatherers ancient Greece 18th century Europe and bed deaths girls in colonial America girls in India, China

CUTTING COSTS: INFANTICIDE AS A REPRODUCTIVE STRATEGY Sarah Blaffer-Hrdy “…the behavior of animals is determined mostly by evolution, while humans have options for self- improvement in line with their civilized ideals.”