Exam 3: Reproductive Stages & Strategies

Question 1

Lactation, costs?

Answer 1

• Feeding to produce milk
• More costly to lactate
• The offspring needs to be dependent on the mother
• Lactation is the most costly reproductive stage for the mother
• -Costs increase the longer lactation occur
• –Baby becomes bigger
• -And as number of infants increase
• -Can be managed dependent on what strategies are done

Question 2

Mother should thus have maternal strategies to reduce reproductive costs

Answer 2

• Vary length of gestation, lactation
• Vary the number of babies produced and how fast they grow
• Vary the degree of development of infants at birth

Question 3

Strategies: Degree of development at birth

Answer 3

• Degree of development at birth: the primary factor determines length of gestation
• Altricial
• Precocial

Question 4

Altricial

Answer 4

• infants born with eyes closed, born completely dependant on mother
• -Kittens, puppies
• -If mother dies after birth, the babies will also die

Question 5

Precocial

Answer 5

• infants born with eyes open, high level of independence at birth. Most primates are born precocial
• Well developed brain
• Survive on its own for short times

Question 6

Maternal strategies: non-social mammals

Answer 6

• Possums produce many altricial young who live in the mothers pouch and grow quickly
• Mothers reduce pregnancy costs by having underdeveloped young, have a high cost during lactation for a short time, but lower costs overall
• Producing a lot of babies, growing up fast, not a lot of lactation

Question 7

Maternal strategies: social mammals

Answer 7

• Produce offspring that can move on their own quickly after birth due to predators
• Longer gestation
• Born with a well developed brain
• Produce a few offspring and take advantage of the social group
• Make a central area where the babies can stay
• Zebras produce a baby that’s ready to go produce one, precocial young. So costs here are higher in pregnancy. Zebra babies must be able to move with group

Question 8

Evidence that primates are k selected

Answer 8

• Compared to other mammals of similar size, primates:
• -Produce fewer young at a time
• -Most carry their infants wherever they go, and this limits the number of offspring they can produce
• –Babies participate on holding onto the mother
• –Baby has to be able to hold on or else it dies

Question 9

Other evidence - gestation length of primates versus non-primate mammals

Answer 9

• For non-primate mammals - the bigger they are the longer it will gestate
• Primates - line is above the mammal line, take longer in gestation
• Primates need to work harder to gestate and require more energy
• Primate gestation lengths are longer than non-primates of the same body size, e.g. slower life history