Module 9 Flashcards
Behavior
Anything organisms do that involves action in response to internal or external stimuli.
Behavioral Ecology
The study of the evolution of behavior.
Ecological Factors
Aspects of the environment such as temperature, predators, availability of food and water, types of food available, disease, other species that come into daily contact, etc. (Are selective pressures or agents in natural selection).
Social Structure
What defines a group of animals (a.k.a. population ) in terms of quantity of individuals included within a group, as well as the sex ratio (how many males to females within a group.
Social Structure Determining Factors
Overall: Natural selection encourages behavior that supports the optimum social structure for a particular environment, with a balance between the various selective pressures.
- Distribution of Resources:
a. The availability and distribution of food resources have an impact on group size. (abundant food = increased group size, Sparse or widely dispersed food = decreased group size).
b. Metabolism and body size have an impact on group size as well. (Large body = low metabolism = need less food = reduced competition = increased group size. Small body = high metabolism = need more food = increased competition = decreased croup size). - Predation: The amount of predation pressure has an effect on group size. ( High predation = increased group size pressure).
a. Distribution of resources is going to limit community size, despite predation. A group that’s too big will outstrip food and all group members will be at risk of starvation. A group that’s too small makes a likely target for predators.
b. Natural selection encourages the careful balance between the two selective pressures. - Life Histories:
a. Ecological factors have a significant impact on the development stages of a species, including life expectancy, length of gestation, interbirth interval, period of infant dependency, age at sexual maturity. (marginal/unstable environments = decreased life histories. Stable environments = increased life histories).
b. Shorter life histories are advantageous to species that live in marginal or unpredictable habitats. Longer life histories are better suited to relatively stable environmental conditions. - Activity Patterns:
a. Diurnal primates, being active during the day, are not as susceptible to big predators that hunt at night and their group size is more limited by the availability of food resources. However, nocturnal primates, being active during the night, must be wary of exposing themselves to nocturnal predators and will forage for food either alone or in very small groups to avoid attracting attention. (Group size limited by activity patterns).
Primate Social Behaviors
Primates are very social because social structure and related behaviors help them to deal with various adaptive problems.
Common behaviors that characterize primate societies
- Dominance: Primates have systems of social organization in which individuals have a ranking within the society. This is called a dominance hierarchy.
a. Higher ranking individuals have greater access to preferred food items and mating partners than lower-ranking ones.
b. Dominance hierarchies establish parameters of individual behavior. Although some aggression and physical conflict can be a way of increasing an individual’s status, a dominance hierarchy frequently reduces the amount of ACTUAL physical violence. - Communication: Any act that conveys information in the form of a message to another individual.
a. Displays: Complex combinations of communicative behaviors (tools for conveying important messages such as aggression or mating rituals, for example). Main Purpose of communication is to achieve a desired result in another individual. - Aggressive Behaviors:
a. Although aggression can occur within primate societies, dominance hierarchies provide strict rules that usually reduce frequent intragroup conflict. The most common form of aggressive behavior is used to protect a territory. (The most common cause of intergroup conflict is protection of limited resources within a territory.) - Affiliative Behaviors:
a. A careful balance must be kept between aggression and affiliation. Too much aggression leads to group disruption, losing the benefits of a large group. Too little aggression, dominance hierarchies can’t be maintained and the threat of actually lethal violence rises. Affiliatve behaviors promote group cohesion, balancing aggressive behaviors. (grooming helps with affiliative behavior as well as altruism.)
Example: Gorillas
Their community is composed of 1 or 2 adult males typically related, and several females, males tend to be more dominant.
Example: Gibbons
Only 2 individuals in a monogamous pair bond, males and females are co-dominant.
Example: Chimps and Bonobos
communities where there are many males and females, there will be separate male and female dominance hierarchies.
Territory
An area which has desired resources (typically food or mates), and is heavily defended, especially against members of the same species.
Grooming
A common integral affiliative behavior where individuals groom one another to create and maintain close social bonds. (grooming can be used to elicit particular reactions such as gain favor with an ally or sexual partner, or it can also help in conflict resolution).
Altruism
A behavior that benefits another individuals but at some potential risk or cost to oneself. Altruistic behaviors are most commonly found between closely related individuals, such as mother and child or between siblings. Saving or defending others, sharing food, and adopting orphaned offspring are examples of altruistic acts. From an evolutionary standpoint most altruistic behaviors occur because the success and survival of close genetic relatives means more of your genes passed into succeeding generations. However primates have been known to engage in alturistic acts with non-relatives because every individual’s survival is dependent on the cohesiveness of the group.
Primate Reproductive Behavior
- Estrus: The period of time when a female is receptive to males for mating. (humans don’t have a visible estrus).
- Types of mating bonds:
a. Monogamy: Permanent bonds between 1 male & 1 female.
b. Polyandry: A female mates regularly with 2 or more males. (rare)
c. Polygyny: A male mates regularly with 2 or more females.
d. Serial Monogamy: A male and female will form a temporary monogamous relationship for a period of time.
e. As reproduction is a great investment for females, selecting a mate is a crucial choice relative to her reproductive success. Thus, a female will choose mates who will:
I. Help provide her with food resources for
herself and her offspring.
II. Help protect against predators and other
individuals that could be harmful to her offspring.
III. Be genetically superior so that her own
offspring will have good chances of finding a
mate and producing offspring.
f. As reproduction is a small investment for males, it is most advantageous to his reproductive success to secure as many mates and produce as many offspring as possible.
Consortship
When a female will have a covert affair with a male that is not typically her mate.
Benefits of consortship:
- Having a consort with an up-and-coming male who may shortly become alpha male could prove beneficial to a female and help protect her offspring from being killed by the new alpha.
- Confusing paternity can be helpful as then males would have a vested interest in offspring who are potentially theirs.
- From an evolutionary perspective, the behavior of mating with a consort means fresh genetic material is frequently inserted into a population, creating greater variation, and helps faster adaptation to changing environments.
