Primate Mating Strategies
Primate mating strategies vary between and within species. But all the mating strategies are ways of ensuring essential aspects of reproductive fitness: the ability to mate, and the ability of young to reach adulthood.
Group: Groups of five, determined with help of the instructor.
Goals:
Consider the role of mating strategies and social organization in determining reproductive fitness
Recognize that not all individual primates within a population have the same interests or goals
Help explain the origin of different primate mating strategies
Procedure
Form groups of five as guided by the instructor. Introduce yourselves! Make sure everyone knows how to pronounce each person's name.
Alphabetize yourselves within your group, based on your first name. Divide into roles based on your name, as follows:
Member of group with first name in alphabetical order: recorder The recorder will take notes on the group's discussion. If anything needs to be turned in, the recorder will take care of it.
Member of group with second name in alphabetical order: time-keeper The time-keeper makes sure the group stays focused on the activity and completes the steps on time.
Member of group with third name: presenter The presenter will speak for the group during the whole class discussion.
Member of group with fourth name: leader The leader makes sure every voice is heard, and helps encourage the group to stay on-task
Member of group with fifth name: role director Your job is to make sure every person stays "in character" (this will make more sense as we go along)
Your group members will assess how well you fulfilled your role, so please do your best!
The recorder should write down each person's name, making sure it is spelled correctly, on the top of your activity sheet.
We will be modeling the conditions under which apes and monkeys develop their mating strategies. Each member of the group will be given a role?, and a description of that role. (The role director will have a sheet with all five roles, in addition to his or her own). Take five minutes to read these roles out to each other. The roles are: juvenile, high-ranking male, low-ranking male, high-ranking female, and low-ranking female.
As a group, you must come to a consensus about the type of mating strategy your group uses (fictitiously, only!). During the "negotiations" to reach a consensus, you will represent your role, with the goal of maximizing your reproductive fitness (number of offspring raised to maturity). Keep in mind the following parameters:
Although you are asked to come to a "consensus" about mating strategies, not everyone's vote is equal. More powerful members of the community get more "say".
Maximizing reproductive fitness does not mean the same thing to every individual. For a male, that might mean finding as many mating opportunities as possible (or not). For a female, that may mean preventing harm to her offspring from other individuals. For a juvenile, that may just mean survival.
Having your own offspring is not the only way to get your genes into the next generation. Having more siblings (or lots of cousins) would do the trick, too.
High-ranking males and females have first-rights to mating opportunities and food. But they cannot keep others from mating or eating unless they are willing to fight for exclusive rights, and that takes a great deal of energy, and risks possible injury. Sometimes it is worth it, sometimes it is not.
Low-ranking males and females cannot "take on" high-ranking members of the community directly, unless they are willing to work together. But working together also has costs, and risks reprisal. Sometimes it is worth it, sometimes it is not.
Incest depression will decrease your reproductive fitness.
Apes and monkeys do not have the same conceptions of morality as we do. Some actions are common among non-human primates that we would find abhorrent (such as forced mating, or males killing infants that they are certain are not theirs so the mother will become fertile sooner.)
Scenario One Your group lives in a tropical forest environment. Food is plentiful. There is no need to cooperate in order to obtain food, but a small area of the forest provides enough food for 5-10 individuals, if they can defend it from other groups. Infants are born very dependent on the mother, however the mother does not need any help to raise them from infancy to self-sufficiency. Males are twice the size of females. Take ten minutes to answer the following questions (remember, each of you is trying to maximize your own reproductive fitness):
Which individuals get to mate? Are some individuals kept from mating entirely? Which ones? Are all individuals allowed to mate but some have priority? Which ones?
Are mating relationships long-term or short-term? How long do mates stay together - minutes? the fertile period? years?
What role, if any, do males play in raising offspring? Do males help females with infants? Which females do they help?
What groups do individuals live in on a day to day basis? Do all members of the community live together? Are there family groups? Are individuals solitary most of the year?
How do individuals avoid committing incest? Do certain members of the community leave when they reach sexual maturity? Which ones?
Scenario Two Your group lives in a tropical forest environment. Food is plentiful, and widely scattered. There is no need to cooperate in order to obtain food, or to defend it from other groups. Infants are born very dependent on the mother, however the mother does not need any help to raise them from infancy to self-sufficiency. Males are only slightly larger than females. Take ten minutes to answer the following questions (remember, each of you is trying to maximize your own reproductive fitness):
Which individuals get to mate? Are some individuals kept from mating entirely? Which ones? Are all individuals allowed to mate but some have priority? Which ones?
Are mating relationships long-term or short-term? How long do mates stay together - minutes? the fertile period? years?
What role, if any, do males play in raising offspring? Do males help females with infants? Which females do they help?
What groups do individuals live in on a day to day basis? Do all members of the community live together? Are there family groups? Are individuals solitary most of the year?
How do individuals avoid committing incest? Do certain members of the community leave when they reach sexual maturity? Which ones?Scenario Two - males and females equal size
Scenario Three Your group lives in a tropical forest environment. Food is plentiful, and widely scattered. There is no need to cooperate in order to obtain food, or to defend it from other groups. Infants are born very dependent on the mother, and mothers need a lot of help from others in order to raise their infants to reproductive age. Three of four individuals are needed to raise one infant. Males are the same size as females. Take ten minutes to answer the following questions (remember, each of you is trying to maximize your own reproductive fitness):
Which individuals get to mate? Are some individuals kept from mating entirely? Which ones? Are all individuals allowed to mate but some have priority? Which ones?
Are mating relationships long-term or short-term? How long do mates stay together - minutes? the fertile period? years?
What role, if any, do males play in raising offspring? Do males help females with infants? Which females do they help?
What groups do individuals live in on a day to day basis? Do all members of the community live together? Are there family groups? Are individuals solitary most of the year?
How do individuals avoid committing incest? Do certain members of the community leave when they reach sexual maturity? Which ones?
When you are finished with the scenarios, the presenter will present your consensus to the class and we will discuss the patterns that emerged.
Take-home Messages
Primate mating strategies and social organization can be understood through their relationship to individual reproductive fitness.
Environmental and biological parameters will affect which mating strategies are most effective.
Not everyone benefits equally from some mating strategies. For example, high-risk mating strategies can benefit some males, leave others without any offspring, and cannot benefit females the same way as males.
Reflection
Take five minutes to reflect on the activity. You may reflect on any aspect of the activity, but if you have trouble, consider answering these questions: Did role-playing help you to learn the differences between types of primate social organization? Do you have a better understanding of why these mating strategies exist?