Animal Behavior Exam 4 Part 2

Mating Systems

Monogamy

• one female and one male

• favored when the female’s partner provides high levels of resources to the young such as high-quality territory and a great deal of parental care

Genetic Monogamy

A male and a female exclusively reproduce with each other and each other only.

• occurs when male contribution is essential for offspring survival

• occurs when finding mates is hard or resources are scarce

Social Monogamy

A male and female form a lasting social bond, living together, sharing resources, and cooperating in raising offspring (biparental care). 

• Often involves pair-bonding, reduced aggression towards each other, and shared territory. 

• occurs when females are spread out and it is hard to defend a group

• occurs when there is patchy high-quality food sources. They can’t defend multiple patches so they stick to one patch

Serial Monogamy

When a male and a female mate for a breeding period and form a pair-bond, but “divorce” for the next breeding cycle

• occurs because offspring need both parents to survive (vulnerable offspring)

• divorce occurs because there is potential for the introduction of new genes over time and also both parties have the opportunity to find better mates

Polygyny

• one male with multiple females

• favored when males that mate with multiple partners have higher fitness than those that mate with a single female

• bi-parental care is not required and parental care is female based

Female Defense Polygyny

• occurs when males monopolize aggregations of females directly

• aggregations of females may experience lower predation risks than solitary females and could avoid harassment from males

Resource Defense Polygyny

• if resources required by females are clumped, males can monopolize females by defending territories with large amounts of that resource.

• occurs when males defend terriroties rich in the resources that are used by and attract multiple females.

Male Dominance Polygyny

• if it is too costly for males to successfully defend resources or females, males seek each other out and increase costs

• they reduce these costs by settling in leks and display to females

• within the lek, there is a hierarchy and the most dominant male occupies the most preferred and central locations

• males benefit because they are reduced in predation risks and could appear to be more attractive to females

• females benefit because it reduces the amount of time it takes to find a mate

Polyandry

one female with multiple males

• favored when multiple males all provide care to the female’s offspring

• could occur when there is high predation on offspring

  • when all offspring are harmed, it is beneficial that the female produce more offspring. However, egg production is costly so it is beneficial for the males to take care of the offspring that are left so that the female can replenish her energy stores for reproduction

Polygynandry

• social associations found

• multiple males mate with multiple females

• found in mammals that defend a territory from other groups

Promiscuity

• evolves when social living is low

• multiple males and multiple females

• males and females are solitary

• conditions also favor this system when it is uneconomical to defend mates or resources

Enforced monogamy

Sexual conflict

The differential selection on males and females to maximize their fitness

Leks: Hotspot vs. Hotshot

• Remove the male:

  • if you remove the hotshot, lek attractiveness decreases

  • if you remove the hotshot, another make takes over and the lek attractiveness is maintained

Lek Paradox Solved

• preference of mates depends on: quality-dependent predictors

• heredity

• physiological limitations of the species

• female attraction — mating opportunity

  • males still benefit from being around the “sexy male”

Operational Sex Ratio

The operational sex ratio is the difference in the number of males and females in a population that are sexually receptive and ready to mate at a given time.