Transcript COSTS OF REPRODUCTION - Central Michigan University

COSTS OF REPRODUCTION
COSTS FOR FEMALES
A. Gestational Costs
–
–
–
greatest costs in last trimester
caloric cost 44% of RMR (ungulates)
protein cost 45% of maintenance
(ungulates)
COSTS FOR FEMALES
B. Lactational Costs
Compared with
pregnancy costs
C a lo ric In ta k e o f B a n k V o le s
K c a l/d a y /in d iv id u a l
–
50
40
80%
B re e d in g fe m a le
30
20
N o n -b re e d in g fe m a le
10
S o u rc e : F lo w e rd e w (1 9 8 7 , M a m m a ls : th e ir
re p ro d u c tiv e b io lo g y a n d p o p u la tio n e c o lo g y )
0
0
18
P re g n a n c y
36
L a c ta tio n
200+%
COSTS FOR FEMALES
B. Lactational Costs
M u ltip le s o f M a in te n a n c e
–
Effect of litter size
L a c ta tio n C o s ts fo r C a ts
4
4
5 K it t e n s
3
3
3 K it t e n s
2
2
2x
2 K it t e n s
1
1
M a in t e n a n c e n e e d s
0
0
0
1
2
3
W e e k o f L a c t a t io n
4
5
COSTS FOR FEMALES
C. Variation Due to Sex of Offspring
–
Polygyny and sexual dimorphism
•
bigger males = more energy invested by mom?
COSTS FOR FEMALES
C. Variation Due to Sex of Offspring
–
Example: Deer
• male success = number of females
inseminated
• female success = successful rearing of
offspring, and quality
COSTS FOR FEMALES
C. Variation Due to Sex
of Offspring
–
Red deer: males are
more costly to raise
• 2 days longer
gestation
• more milk demand
• Faster growth rates
• Only 64% females
breed following
season, compared
to 72% that nurse
daughters
COSTS FOR FEMALES
C. Variation Due to Sex of Offspring
–
Bighorn sheep:
•
lambs born in 2nd year = 25% less likely to
survive a 2nd year if mom had a son in 1st year
COSTS FOR FEMALES
C. Variation Due to Sex of Offspring
Bighorn sheep: males are more costly
Survival of Second-year Lam bs (%)
–
70
60
Source: Berube et al. (1996, Behav.
Ecol. 7:60-68)
50
40
30
20
10
0
M ale
Fem ale
Sex of First-year Lam b
COSTS FOR MALES
A. Behavioral
–
Increased
movements during
breeding season
COSTS FOR MALES
A. Behavioral
–
Increased scent
marking during
breeding season
COSTS FOR MALES
A. Behavioral
–
Costs of fighting
• red deer – 13-29% of mortality
• mule deer – 19% injury
COSTS FOR MALES
B. Morphological
–
antler growth
COSTS FOR MALES
B. Morphological
antler growth
% A b o v e M a in t e n a n c e
–
C o s ts o f A n tle r s in D e e r
120
120
R e la tiv e p r o te in
cost
90
90
60
60
R e la tiv e e n e r g y
cost
30
0
0
100
200
300
A d u lt M a s s (k g )
400
30
0
500
COSTS FOR MALES
C. Physiological
–
Example: Brown
antechinus
•
•
•
•
Males stop eating for
3-week breeding
season
Congregate in tree
cavities
Lek system
All males die at end of
breeding season
COSTS FOR MALES
C. Physiological
–
Brown antechinus males
• don’t eat
• lose hair
• lose teeth
• lose 1/3 of body weight
• develop stress responses
• exhibit high glucocorticoid levels
COSTS FOR MALES
C. Physiological
–
–
Example: Brown antechinus
Iteroparity versus Semelparity
COSTS COMMON TO BOTH
SEXES
The cost of poor mate choice



inbreeding
immunodeficiencies
lowered reproductive success
CUTTING REPRODUCTIVE COSTS:
SEX RATIO VARIATION
A. Theories for Adjusting Sex Ratios at
Birth
Variation in reproductive success of
males and females
(Trivers-Willard hypothesis)
–
CUTTING REPRODUCTIVE COSTS:
SEX RATIO VARIATION
A. Theories for Adjusting Sex Ratios at Birth
•
Predictions of Trivers-Willard for
polygynous species:
– females in good condition produce sons
– females in poor condition produce
daughters
– evidence?
» red deer: high-ranking vs. low-ranking
females
CUTTING REPRODUCTIVE COSTS:
SEX RATIO VARIATION
A. Theories for Adjusting Sex Ratios at Birth
–
Local resource competition
• In primates:
– inheritance of female dominance, so …
Japanese macaques
Mandrill
…male reproductive
success is not closely
tied to maternal
investment
Proboscis monkeys
CUTTING REPRODUCTIVE
COSTS: SEX RATIO VARIATION
A. Theories for Adjusting Sex Ratios at
Birth
–
Local resource competition
• Predictions:
– produce philopatric sex if resources
plentiful
– only dominant females produce
philopatric sex if food scarce
– Evidence?
» Spider monkeys: only highranking females produce sons
(philopatric)
CUTTING REPRODUCTIVE COSTS:
SEX RATIO VARIATION
B. Potential Causes
–
Timing of insemination
P e r c e n t o f M a le s
S e x D e t e r m in a t io n in H u m a n s
70
70
60
60
50
50
40
30
-1 0
F e m a le
b ia s
M a le b ia s
40
M a le
b ia s
30
-8
-6
-4
-2
0
2
D a y s B e f o r e o r A f t e r O v u la t io n
4
CUTTING REPRODUCTIVE COSTS:
SEX RATIO VARIATION
B. Potential Causes
–
Sperm selection in females
Production of leukocytes
CUTTING REPRODUCTIVE COSTS:
SEX RATIO VARIATION
B. Potential Causes
–
Sperm selection in males
•
Semen composition (differential motility of
X and Y sperm) sensitive to steroid hormone
levels
CUTTING COSTS: COOPERATIVE
BREEDING
A. Carnivores
•
•
•
biparental or
communal care
higher milk
production
increased
postnatal growth
rates
CUTTING COSTS: COOPERATIVE
BREEDING
B. Primates (marmosets)
•
•
elevated growth rates
reduced intervals
between births
CUTTING COSTS: COOPERATIVE
BREEDING
C. Rodents (prairie voles)
•
•
•
older juvenile
helpers
increased weight at
weaning
shorter time to eye
opening
CUTTING COSTS: INFANTICIDE AS A
REPRODUCTIVE STRATEGY
A. An Evolutionary Perspective
–
–
–
Males safeguard paternity
Males increase offspring sired
Females reduce losses
Hanuman langurs
CUTTING COSTS: INFANTICIDE AS A
REPRODUCTIVE STRATEGY
B. Removing the Log from Our Own Eye
CUTTING COSTS: INFANTICIDE
AS A REPRODUCTIVE STRATEGY
B. Removing the Log from Our Own Eye
–
–
Darwin on infanticide in humans
Infanticide in societies
• hunter-gatherers
• ancient Greece
• 18th century Europe and bed deaths
• girls in colonial America
• girls in India, China
CUTTING COSTS: INFANTICIDE
AS A REPRODUCTIVE STRATEGY
Sarah Blaffer-Hrdy
“…the behavior of animals is
determined mostly by evolution, while
humans have options for selfimprovement in line with their
civilized ideals.”