BREEDING SYSTEMS AND REPRODUCTIVE STRATEGIES OF MAMMALS

1. BREEDING SYSTEMS AND REPRODUCTIVE STRATEGIES OF MAMMALS

2. 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

3. Reynolds. 1996. 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?

4. 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

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

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

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

8. 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

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

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

11. 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

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

13. BREEDING SYSTEM AND SIZE OF MALES AND FEMALES • Monogamous • monomorphy • Polygynous • sexual dimorphism

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

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

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

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

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

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

20. 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