BREEDING SYSTEMS AND REPRODUCTIVE STRATEGIES OF MAMMALS.

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


MonogamyMonogamy(<10% of mammals)(<10% of mammals)

Some canids, primates, Some canids, primates, prairie voles, beaversprairie voles, beavers– facultative facultative

• low densitylow density

– obligateobligate• delayed maturitydelayed maturity• assisted rearingassisted rearing

MonogamyMonogamy(<10% of mammals)(<10% of mammals)

Some canids, primates, Some canids, primates, prairie voles, beaversprairie voles, beavers– facultative facultative

• low densitylow density

– obligateobligate• delayed maturitydelayed maturity• assisted rearingassisted rearing


Polygamy • Mating 1 sex with >1 individual

of opposite sex


Polygamy • Polyandry = 1 female and several males

• unknown except possibly in pine voles (but mainly facultative monogamy)

???


Polygamy • Polygyny = 1 male with several females

• Not promiscuity• >80% of mammals• 2 types

• Female (harem) defense polygyny• Male dominance polygyny


Polygamy – Polygyny

• Female (harem) defense

– males control access to females directly (gregarious females)


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

• Polygyny1) 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

MomF

M

M

BREEDING SYSTEM AND JUVENILE DISPERSAL

Natal Dispersal in Mammals is Male-Biased– frequency & distance– Females philopatric– Why?

F

Lactation

Polygynous fathers

Wide-ranging or intense competition

Short residence or tenure of male

Female philopatry

Male inbreeding avoidance

Male-biased dispersal


The Inbreeding-Avoidance Model

What’s the critical assumption?


Effects of Inbreeding on Mammals– inbreeding depression

• decrease in fitness of offspring– Homozygosity

• deleterious, recessive alleles


Effects of Inbreeding on Mammals– field studies

• white-footed mice• island releases of

matings from siblings• lower survival

Effects of Inbreeding on Mammalsgolden lion tamarin

• No offspring survive• Father-daughter mating• Sibling mating• 80% outbred survive


Fit of the Inbreeding-Avoidance Model?– Father present: do

females disperse?


Fit of the Inbreeding-Avoidance Model?– Monogamy: sex bias in dispersal?

• 11 of 12 monogamous species studied show similar female vs. male dispersal

BREEDING SYSTEMS AND REPRODUCTIVE STRATEGIES OF MAMMALS.

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