View
217
Download
0
Category
Tags:
Preview:
Citation preview
Sociality and the adaptive value of helpful behavior
ZOL 313
June 17, 2008
Sociality and the adaptive value of helpful behavior
ZOL 313
June 17, 2008
Objectives:
1. Become familiar with some of the costs and benefits of social living.
2. Understand the differences between cooperation, reciprocity, and altruism and be able to generate hypotheses and predictions.
3. Understand why altruism usually occurs between kin and be able to use Hamilton’s rule to calculate whether altruistic behaviors are adaptive.
Costs and benefits of social living
Foraging
Costs:
Benefits:
Predation
Costs:
Benefits:
Costs and benefits of social living
Costs and benefits of social living
Disease/parasitism
Costs:
Benefits:
Mating
Costs:
Benefits:
Costs and benefits of social living
Parental Care
Costs:
Benefits:
Costs and benefits of social living
Prediction: Parasitic coot eggs that look less like their host’s eggs will be more likely to be rejected.
Donor Recipient
Selfish behavior
Spiteful behavior
Mutualism/ Cooperation
Reciprocity
Altruism
The adaptive value of helpful behavior
Types of social interactions between animals
The adaptive value of helpful behavior:
Example: Bubble net hunting by humpback whales
Example:
Cooperation: A mutually beneficial interaction between two members of the same species.
http://youtube.com/watch?v=-_IYBJjnw2U&feature=related
The adaptive value of helpful behavior:
Example: Cooperative courtship in the long-tailed manakin
The beta male helps the alpha male display to receptive females but NEVER gets to mate with any of them.
How can this be cooperation?
Cooperation: A mutually beneficial interaction between two members of the same species.
Example: Cooperation among competitors in the lazuli bunting
The adaptive value of helpful behavior
Cooperation: A mutually beneficial interaction between two members of the same species.
Bright, dominant males allow dull competitors to claim high quality territories next to them but drive away intermediate colored males.
Benefit to bright males:
Benefit to dull males:
Problem: Vulnerable to cheating. Why should the recipient repay
the donor?
Reciprocity: The recipient of a helpful action repays the donor later in time.
The adaptive value of helpful behavior
Game theory shows that reciprocity is more likely to occur when
Example:
The adaptive value of helpful behavior
Reciprocity: The recipient of a helpful action repays the donor later in time.
Hypothesis 1: Reciprocity. Meerkat sentinels help others at a personal cost now because
The adaptive value of helpful behavior
Reciprocity: The recipient of a helpful action repays the donor later in time.
Hypothesis 2: Personal Safety. Meerkat sentinels are the animals that are sated, so they obtain
Example: Meerkats forage in groups. Sometimes an individual will stop foraging and act as a “sentinel”, watching for predators and giving an alarm.
The adaptive value of helpful behavior
Reciprocity: The recipient of a helpful action repays the donor later in time.
Sentinels are not more likely to be preyed on than foragers.
Meerkats that are given food supplements spend more time as sentinels.
Prediction:
The adaptive value of helpful behavior
Reciprocity: The recipient of a helpful action repays the donor later in time.
Example: Belding’s ground squirrels alarm calls
1. Squirrels that alarm call are more likely to be killed by predators than non-callers.
2. The probability that an individual will alarm call is not correlated with familiarity/length of association with recipient.
3. Females with kin (sisters, aunts, cousins) nearby
The adaptive value of helpful behavior
Altruism: Helpful behavior that lowers the direct fitness of the donor and raises the fitness of the recipient
Most (non-human) altruistic behaviors that we know of are performed toward relatives.
Is this really altruism?
Altruism: Helpful behavior that lowers the direct fitness of the donor and raises the fitness of the recipient
C=cost to donor B=benefit to receiver
R=relatedness (between donor and recipient)
Hamilton’s Rule: R x B > C
2
Inclusive fitness=
The adaptive value of helpful behavior
Example: A Belding’s ground squirrel who gives alarm calls will have 2 fewer offspring over her lifetime than if she never called. However, by calling when she sees a predator she will save the lives of 5 of her sisters. Is this “altruistic” behavior adaptive?
R= B= C=
Altruism: Helpful behavior that lowers the direct fitness of the donor and raises the fitness of the recipient
C=cost to donor B=benefit to receiver
R=relatedness (between donor and recipient)
Hamilton’s Rule: R x B > C
2
The adaptive value of helpful behavior
Prediction:
The adaptive value of helpful behaviorCooperative breeding: “altruistic” helpers increase their inclusive fitness
In pied kingfishers, some yearling males are not able to find a mate. Options:
Primary helper: Help parents breed Secondary helper: Help non-related birds breed Delay: Wait until next year
The adaptive value of helpful behaviorCooperative breeding: “altruistic” helpers increase their inclusive fitness
Prediction:
Example: Cooperatively breeding paper wasps.
Subordinate females help care for the brood and defend the nest against predators.
One dominant female monopolizes the egg laying.
The adaptive value of helpful behaviorCooperative breeding: “altruistic” helpers increase their inclusive fitness
Based on what you know about altruism, when might it be adaptive for subordinate females to help instead of trying to reproduce on their own?
Transactional Theory Dominants and subordinates “negotiate” their reproductive rights within the group.
A dominant might allow a non-relative subordinate a small amount of reproduction to secure her help.
The adaptive value of helpful behaviorHow can cooperative breeding among non-relatives be adaptive?
Prediction:
Recommended