Chapter 17 SUMMARY

Male Care

Patterns of Paternal Care
(occurs in less than 10%
of mammals, 40% of primate genera)

Prevalence of paternal care

1. Probability of future survival
2. Paternal uncertainty
3. Long-term male-female associations
with females increase opportunities for care
with infants.
4. Infants are costly, paternal care increase
value for survival.

Variations of Male-infant interactions

1. Direct care: behaviors that are immediately beneficial for infant welfare. Ex: carrying and provisioning infants, for Cotton-top Tamarins males experience weight loss with few helpers, protection from infanticide.
2. Indirect care: actions that might benefit offspring but would also be performed in the absence of infants. Ex: grooming, playing, and tolerating them.

Paternity Certainty
and Male Care

Monogamous breeders- paternity
certainty is NOT necessary for paternal care.

1. Owl Monkey: monogamous, care is only provided after the infant is born.
2. Titi Monkey: monogamous
3. New World Callitrichines: polyandrous pair units, males will carry, cuddle, play with infants.

Leaders of single male groups show
little investment in young.
Ex: Silverback mountain gorillas,
and Hamadryas Baboons

Costly Infants and
Male Care

Costs of Transport:
Since traveling, can be costly to the mother, as the infant grows, some species provide paternal care to help the mother. Ex: Callitrichines (twins),
-The cost of transport can be solved by "parking" infants as well.

Leaders of single male groups show
little investment in young.
Ex: Silverback mountain gorillas, and Hamadryas Baboons

There is little evidence that males care is beneficial for infants. Yet there are signs that male care may improve infant quality.

Male Care as
Mating Efforts

Male-Male interactions and use of Infants: males may carry infants during male-male interactions to reduce aggression from other males, or temporarily increase their own status yet, these may vary across species and specifc reasons for infant carrying are unclear.

Future Reproduction: Male Care allows
for increased female reproduction rates
which allows for more/future offspring to be born.

How male care --> mating efforts
1. Female choice
2. Promotion of infant survival

Male Protection

Having a male protector reduces a
lactating female's stress response
to the presence of an immigrant male.
Ex: Older males/grandpas

Infanticide:
Generally, a threat within group with large
reproductive skew, or from immigrant males from other groups. Therefore, infanticide and infant protection is connected to mate defense.

Male Mating Effort

Canine Dimorphism

- Canine dimorphism correlates with competition levels and sexual selection between male primates
- Body size may be more important that male-male competition for attracting females

In some species, dentition is monomorphic because females have impressive, male like, canines

Coalitions have positive correlation with aggressive interactions within group

Competition for Mates

Investment in young is
minimal from males.

Agressive Competition:
1. Long term: males can compete
to monopolize permanent access to
females.
2. Short term: males can compete to
mate with estrous females.
-Varies among species

Body Size Dimorphism

Sexual dimorphism in body
size can be explained by sexual
selection acting as an agent of
male-male competition.

Absence of dimorphism
doesn't mean that there
are aggressive male-male
competition exists.

Sperm Competition

Males with more sperm have an advantage in achieving fertilization (obviously) for females who mate with multiple partners

Body size is predictably correlated with testes size, some exceptions (Gorilla = 30g, Chimpanzees = 120g)

Testes size is related to mating systems and competition. Less males (such as one) living together tend to have smaller testes size

Integrating the Effects of
Sexual Selection

Despite living in multimale-multifemale groups, humans have pattern of low canine dimorphism, low body size dimorphism, and smaller than expected testes for body weight that generally characterizes monogamous primates

Alternative Reproductive Tactics

Sneaking copulations with
females instead of fighting for them.