Download 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
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
L actatio n
P o lyg yn o u s fath ers
W id e-ran g in g o r in ten se co m p etitio n
S h o rt resid en ce o r ten u re o f m ale
F em ale p h ilo p atry
M ale in b reed in g avo id an ce
M ale-b iased d isp ersal
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 InbreedingAvoidance 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