BREEDING SYSTEMS AND REPRODUCTIVE STRATEGIES OF MAMMALS
Dec 13, 2015
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
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
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
• 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
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 Mammalsgolden 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?