Transcript Social behavior I

Sociality and the adaptive value
of helpful behavior
ZOL 313
June 17, 2008
Sociality and the adaptive value
of helpful behavior
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.
ZOL 313
June 17, 2008
Costs and benefits of social living
Foraging
Costs:
Benefits:
Costs and benefits of social living
Predation
Costs:
Benefits:
Costs and benefits of social living
Disease/parasitism
Costs:
Benefits:
Costs and benefits of social living
Mating
Costs:
Benefits:
Costs and benefits of social living
Parental Care
Costs:
Prediction: Parasitic coot
eggs that look less like
their host’s eggs will be
more likely to be rejected.
Benefits:
The adaptive value of helpful behavior
Types of social interactions between animals
Donor
Selfish behavior
Spiteful behavior
Mutualism/
Cooperation
Reciprocity
Altruism
Recipient
The adaptive value of helpful behavior:
Cooperation: A mutually beneficial interaction
between two members of the same species.
Example:
Example: Bubble net hunting
by humpback whales
The adaptive value of helpful behavior:
Cooperation: A mutually beneficial interaction
between two members of the same species.
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?
http://youtube.com/watch?v=-_IYBJjnw2U&feature=related
The adaptive value of helpful behavior
Cooperation: A mutually beneficial interaction
between two members of the same species.
Example: Cooperation among competitors in the lazuli bunting
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:
The adaptive value of helpful behavior
Reciprocity: The recipient of a helpful action repays the donor
later in time.
Problem: Vulnerable to cheating.
Why should the recipient repay
the donor?
Game theory shows that reciprocity is
more likely to occur when
The adaptive value of helpful behavior
Reciprocity: The recipient of a helpful action repays the donor
later in time.
Example:
The adaptive value of helpful behavior
Reciprocity: The recipient of a helpful action repays the donor
later in time.
Example: Meerkats forage in groups. Sometimes an individual will stop
foraging and act as a “sentinel”, watching for predators and giving an alarm.
Hypothesis 1: Reciprocity. Meerkat sentinels
help others at a personal cost now because
Hypothesis 2: Personal Safety. Meerkat
sentinels are the animals that are sated, so
they obtain
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.
The adaptive value of helpful behavior
Reciprocity: The recipient of a helpful action repays the donor
later in time.
Prediction:
The adaptive value of helpful behavior
Altruism: Helpful behavior that lowers the direct fitness of the
donor and raises the fitness of the recipient
Example: Belding’s ground squirrels alarm calls
1. Squirrels that alarm call are more likely to be killed by predators than noncallers.
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
Most (non-human) altruistic behaviors that we
know of are performed toward relatives.
Is this really altruism?
The adaptive value of helpful behavior
Altruism: Helpful behavior that lowers the direct fitness of the
donor and raises the fitness of the recipient
2
Inclusive fitness=
Hamilton’s Rule:
RxB>C
C=cost to donor
B=benefit to receiver
R=relatedness
(between donor and recipient)
The adaptive value of helpful behavior
Altruism: Helpful behavior that lowers the direct fitness of the
donor and raises the fitness of the recipient
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?
2
R=
Hamilton’s Rule:
RxB>C
B=
C=
C=cost to donor
B=benefit to receiver
R=relatedness
(between donor and recipient)
The adaptive value of helpful behavior
Cooperative breeding: “altruistic” helpers increase their inclusive fitness
Prediction:
The adaptive value of helpful behavior
Cooperative 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
Prediction:
The adaptive value of helpful behavior
Cooperative breeding: “altruistic” helpers increase their inclusive fitness
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.
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?
The adaptive value of helpful behavior
How can cooperative breeding among non-relatives be adaptive?
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.
Prediction: