BREEDING SYSTEMS AND REPRODUCTIVE STRATEGIES OF MAMMALS

BREEDING SYSTEMS: COMPETING INTERESTS OF MALES AND FEMALES Description of mating behavior and parental care by both sexes Parental care & potential rate of reproduction of each sex If males contribute no parental care (many mammals), they have high potential rate of reproduction; fitness limited by access to females; males most competitive sex

Reynolds Animal Breeding Systems. TREE OSR = operational sex ratio = ratio of available adult females to males *Time budget for males = competition for mates and/or advertisement – not choosy *Females invest in gametes & care (lower rate & resource limits) – choosy females ****What if males contributed to parental care?

BREEDING SYSTEMS: COMPETING INTERESTS OF MALES AND FEMALES Are the result of a “battle” of competing interests between the sexes –opportunities & constraints set by environment

COMMON TYPES OF BREEDING SYSTEMS IN MAMMALS Monogamy (<10% of mammals) Some canids, primates, prairie voles, beavers – facultative low density low density – obligate delayed maturity delayed maturity assisted rearing assisted rearingMonogamy (<10% of mammals) Some canids, primates, prairie voles, beavers – facultative low density low density – obligate delayed maturity delayed maturity assisted rearing assisted rearing

COMMON TYPES OF BREEDING SYSTEMS IN MAMMALS Polygamy Mating 1 sex with >1 individual of opposite sex

COMMON TYPES OF BREEDING SYSTEMS IN MAMMALS Polygamy Polyandry = 1 female and several males unknown except possibly in pine voles (but mainly facultative monogamy) ???

COMMON TYPES OF BREEDING SYSTEMS IN MAMMALS Polygamy Polygyny = 1 male with several females Not promiscuity >80% of mammals 2 types Female (harem) defense polygyny Male dominance polygyny

COMMON TYPES OF BREEDING SYSTEMS IN MAMMALS Polygamy – Polygyny Female (harem) defense – males control access to females directly (gregarious females)

COMMON TYPES OF BREEDING SYSTEMS IN MAMMALS Polygamy – Polygyny Male dominance – males sort out dominance hierarchy among themselves – some ungulates with lek mating systems

BREEDING SYSTEM AND DEVELOPMENT AT BIRTH Lactation believed to precede evolution of parental care –females benefit from monogamy –predict larger litters, shorter gestation Review of 500 placental species indicates: –Monogamy 1) large litters 2) altricial young 3) short gestation

BREEDING SYSTEM AND DEVELOPMENT AT BIRTH Polygyny 1) small litters (<2) 2) precocial young 3) longer gestation 4) greater maternal investment before parturition

BREEDING SYSTEM AND SIZE OF MALES AND FEMALES Monogamous –monomorphy Polygynous –sexual dimorphism

F Mom F M M BREEDING SYSTEM AND JUVENILE DISPERSAL Natal Dispersal in Mammals is Male-Biased – frequency & distance – Females philopatric – Why? F

BREEDING SYSTEM AND JUVENILE DISPERSAL The Inbreeding-Avoidance Model What’s the critical assumption?

BREEDING SYSTEM AND JUVENILE DISPERSAL Effects of Inbreeding on Mammals – inbreeding depression decrease in fitness of offspring – Homozygosity deleterious, recessive alleles

BREEDING SYSTEM AND JUVENILE DISPERSAL Effects of Inbreeding on Mammals – field studies white-footed mice island releases of matings from siblings lower survival

Effects of Inbreeding on Mammals golden lion tamarin No offspring survive Father-daughter mating Sibling mating 80% outbred survive

BREEDING SYSTEM AND JUVENILE DISPERSAL Fit of the Inbreeding- Avoidance Model? – Father present: do females disperse?

BREEDING SYSTEM AND JUVENILE DISPERSAL Fit of the Inbreeding-Avoidance Model? –Monogamy: sex bias in dispersal? 11 of 12 monogamous species studied show similar female vs. male dispersal