Chapter 6 Flashcards
Why do primate females always care for their young, while male contributions are more varied?
-Mating System- the way animals find mates and care for offspring.
In all primates , the females cares for the baby.
Some species males will also care for the babies example tamarins and humans.
Variations in parental care in animals ( trade offs)
Frogs:
Lay many eggs, likelihood of survival is quiet high.
No parental care.
Birds:
Parenting from both males and females foe hatchlings to survive.
Mammals:
Female care critical
Male care varies.
Sea horses:
Males provide majority of care.
Males do not care for their offspring when:
1) they can easily use their to acquire many additional matings
2) when caring for their offspring would not appreciably increase the offsprings fitness.
So unequal parenting will be favored when :
1) Acquiring additional mates is relatively easy, so considerable gains are achieved by investing in mating efforts.
2) The fitness of the offspring raised by only one parent is high, so the payoff for investing in parenting is relatively low.
What limits reproductive success in females and in males?
-Understand differences in male and female reproductive strategies (e.g., what behaviors enhance reproductive
success for each sex and when would a different strategy be used)
-Male reproductive strategies:
Contribute a single cell to the offspring.
To maximize his reproductive success he must choose between:
1. Energy towards finding new mates
- if finding new mates is relatively easy
- if offspring can be raised by one parent.
2. Energy towards helping offspring survive
- If benefit of taking care of young outweighs cost of not finding new mates.
Females reproductive strategies:
Female primates invest heavily in offspring
Gestation
Lactation
Resources critical for female reproductive success
- More food equals more offspring?
Young mothers:
Allocating energy towards own growth
- Cannot allocate resources to infant and self
- Consequence 50% higher infant mortality rate
Lack experience
Older mothers:
Senescence ( General decline in all bodily functions]
What are the different types of mating systems in primates and what are the anatomical correlates of these?
-Primates living in different systems have different levels of sexual dimorphism.
Pair bonds -have a little male male competition. Little dimorphism.
One male, multi females- huge body and canine dimorphism
Multi male, multi female- large dimorphism
Why are males and females often different in coloration, size, and behavior?
Sexual dimorphism -Selection that results in males looking quite different from females size coloration or both .
Baboons
Males are considerably larger
Live in multi-male, multi female groups
Males compete to have access to breeding females
Largest males with large canines often win fights and breed with females
They pass on genes of large body and canine size in the males.
Over generations, the sexes become more dimorphism.
Dominance
-the ability of 1 individual to intimidate or defeat another individual in a pair wise ( dyadic) encounter. In some cases , dominance is assessed from the outcome of aggressive encounters; in other cases, dominance is assessed from the outcome of competitive encounters.
Infanticide predictions
-Change in male residence or status:
Only kill infants that result in resumption of female cycling
Kill others’ infants:
-Reproductive benefits to male
Intersexual and intrasexual sélection
-intersexual selection- a form of sexual selection in which female chooses who they mate with. The result is that traits making males more attractive to females are selected for.
Intrasexual selection- a form of sexual selection in which males compete with other males for access to females. The result is that traits making males more successful in such competition., like large body size or large canines, are selected for.
Gestation
Long pregnancies
Birth growth energetically expensive
A lot of primates have long gestation period because it take long to develop the brains
Lactation
Long infant periods
Very few offspring
Female must obtain enough resources to sustain herself and her offspring
Limiting factor for reproductive success is food
What influences female reproductive success?
- longevity – 50 to 70% of variance
- Longer a female lives, more offspring she will have - Group size -primates living in smaller in smaller groups have more offspring
- Primates living in larger groups are competing for relatively fewer resources - Rank -Higher ranking females can monopolize valuable food resources
- Sociality- More social females have more surviving offspring
Higher rank= Best feeding sites= more Offspring
Example Long tailed Macaques
Offspring of high-ranking females are more likely to survive
Through infant years, grow more quickly, and reach reproductive maturity soon.
Variations in primate mating systems
1.Sexual reproduction : Impress members of opposite sex Behaviorally evolved 2.Female gestation: Carries offspring internally. 3.Female lactation: Produce milk through mammary glands.
Language of adaptive explanations
- Strategy- shorthand foe evolved behaviors that are a product of natural selection.
- Costs and benefits- trade offs in reproductive success
Lactational amenorrhea
When a primate mother is lactating, she will often cease to ovulate, and therefore cannot become pregnant.
Dominance relationships
When an interaction between 2 individuals becomes predictable.
One individual is always submissive to the other.
Dominance matrix
Compiled data on all of the outcomes of confrontations between all individuals in a group.
