BREEDING SYSTEMS AND REPRODUCTIVE STRATEGIES OF MAMMALS BREEDING

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. 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?

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 obligate • • delayed maturity 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

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

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