Breeding systems and reproductive strategies of mammals
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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

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Breeding systems competing interests of males and females
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 females1
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
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 mammals1
COMMON TYPES OF BREEDING SYSTEMS IN MAMMALS

Polygamy

  • Mating 1 sex with >1 individual

    of opposite sex


Common types of breeding systems in mammals2
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 mammals3
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 mammals4
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 mammals5
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
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 birth1
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
BREEDING SYSTEM AND SIZE OF MALES AND FEMALES

  • Monogamous

    • monomorphy

  • Polygynous

    • sexual dimorphism


Breeding system and juvenile dispersal

M

F

F

Mom

M

BREEDING SYSTEM AND JUVENILE DISPERSAL

Natal Dispersal in Mammals is Male-Biased

  • frequency & distance

  • Females philopatric

  • Why?

F


Breeding system and juvenile dispersal1
BREEDING SYSTEM AND JUVENILE DISPERSAL

The Inbreeding-Avoidance Model

What’s the critical assumption?


Breeding system and juvenile dispersal2
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 dispersal3
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 dispersal4
BREEDING SYSTEM AND JUVENILE DISPERSAL

Fit of the Inbreeding-Avoidance Model?

  • Father present: do females disperse?


Breeding system and juvenile dispersal5
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


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