FUCKING FINAL Flashcards
(46 cards)
How does sociality evolve?
Sociality only evolves if it results in an individual in a group obtaining higher fitness than it would living alone
AKA Net Benefits > Net Costs
What re the Benefits of Sociality
1) Increased diet breadth for predators
2) Increased ability to find resources
3) Decreased search time to find food or mates
4) Decreased predation
5) Decreased physiological costs of movement in air or water
6) Decreased physiological costs of thermoregulation via huddling
7) Division of labor: individuals can specialize on different tasks (food acquisition, nest defense, etc.)
8) Communal care of young: enhanced feeding and defense of offspring
Costs of Sociality
1) Increased competition for resources
2) Increased opportunity for aggressive behavior
3) Increased likelihood of pathogen transmission
Minnow Foraging Study
As schoal size increases, the average foraging time decreases
This study demonstrates how it is often harder for lone animals to find food, thus sociality provides foraging benefits
Insects/Bees Foraging Study
Bees share up-to-date information about floral resources in the local environment
Demonstrating foraging benefits of sociality
Coyote Experiment
Coyotes living in larger groups have a greater volume of larger prey items in their scat, and a decrease in smaller prey
Foraging benefits of sociality: increased capture
Aerodynamic Benefit: Reduced cost of movement in pelicans
Research Question: Why do large birds fly in a V-formation?
Hypothesis: This formation reduces the cost of flying
Prediction: Birds in formation will have a lower wingbeat frequency and heart rate than solitary birds
Methods:
1) Placed heart rate monitors on trained white pelicans
2) Videotaped flight formations, collected data on wingbeat frequency and location of each bird in formation
Results: Birds in formation behind the leader had a slower wingbeat frequency and lower heart rate; still not as low as gliding though
Conclusion: Birds can thus reduce flight costs by flying in V-formation
The cost of sociality: Competition
Therefore competition for resources can limit group size, in which:
1) Low-resource environments will have smaller group sizes than high-resource environments
2) Positive relationship between resources in a Habitat and Group Size
Group Size and Competition in Primates – red colobus monkeys and red-railed guenons
Research Question: Does competition affect the size of social groups?
Hypothesis: Competition for food limits group size
Prediction: Low-resource environments should have smaller group sizes than high-resource environments
Methods:
Monkeys were fed a variety of fruits and vegetation
Group size ranged from <10 to >36
Each month, recorded the density of food trees on transects and the average group size of each species i four different sites
Results:
Average group size was positively correlated with the density of food trees
Conclusion: Competition for food appears to be associated with group size
The Cost of Sociality: Disease Transmission
Parasites and pathogens can reduce an animal’s fitness;
Transmitted by close contact;
Disease transmission rates should increase with group size;
Positive correlation between group size and proportion of infected individuals
Sociality and disease transmission in guppies
Research Question: How does sociality affect disease transmission?
Hypothesis: Tighter spacing between individuals enhances disease transmission
Prediction: Disease transmission rates will be higher in tighter social groups
- Guppies live in shoals (schools)
- Frequently infected with worms
- Females are more social – provides an opportunity to test how sociality/group spacing affects disease transmission
Methods:
- Removed all external parasites
- Created single-sex groups of sex
- Recorded average nearest neighbor distance in each school
- On 3rd day, infected a single fish in each school with 100 parasitic worms
- Recorded the spread of parasitic worms to other school members after three days
Results:
1) Females spent more time shoaling than males, and nearest neighbor distance was smaller in females than male groups
2) A higher proportion of females became infected than males
Conclusion: Disease transmission is affected by degree of sociality; this is a cost of group living/sociality
Do costs affect all members of a group equally?
NOOOOOOOOOOO
In the case of aggression, the better competitor wins an interaction, with boy parties receiving differing levels of risk of injury
How is aggression reduced in a group?
Dominance Hierarchy: An organized social system with dominant and subordinate members
How aggressive interactions affect stress, and how it is affected by the dominance hierarchy
Adrenal glands secrete glucocorticoids in response to help utilize fat stores to deal with that stress;
chronic glucocorticoids secretion can negatively affect health and reproduction = COST OF AGGRESSION
If dominance hierarchies help reduce aggression, it should also reduce stress;
Conversely, disruption in hierarchy could increase stress
Stable Dominance Hierarchies and Stress in Baboons
Research Question: How do do dominance hierarchies affect stress levels?
Hypothesis: The formation of a dominance hierarchy reduces aggression and stress in individuals
Prediction: Aggression level and stress hormones such as glucocorticoids will be lowest when stable hierarchies exist
Methods:
1) Observed chacma baboons; noted periods when stable dominance hierarchies existed and other periods when changes occurred
2) Collected fecal samples and characterized glucocorticoid levels of individuals
Results:
1) Aggression was lowest during stable periods
2) Fecal glucocorticoid levels were also lowest during stable periods
Conclusion: Aggression and stress levels are lowest during periods when dominance hierarchies are stable
Animal Altruism
A behavior that results in the increased fitness of another individual and involves a cost to the individual performing the behavior;
AKA Helping Behavior
Is often directed towards close kin
Inclusive Fitness
An individual’s genetic success (progeny produced) plus the genetic success of its relatives (which share a portion of the individual’s genes)
Helping a close kin increases inclusive fitness
Kin Selection
Natural selection for behavior by individuals that may decrease their own survival or reproductive success, but increases that of their kin (who share a portion of their genes);
Based off of inclusive fitness
Hamilton’s Rule and Kin Selection
States that altruism only evolves when B x r (relatedness) > C
B x r = the amount of altruist’s genes passed on through helping behavior
Degree of relatedness chart
Parent-offspring: 0.5 Sibling-Sibling: 0.5 Grandparent-grandchild: 0.25 Aunt/Uncle-Nephew/Niece: 0.25 First Cousins: 0.125 Friends: 0
Testing Hamilton’s Rule: Altruistic Turkeys
Male turkeys may form social coalitions (a pair of males) and display together to attract females;
BUT only the dominant male mates
Research Question: Why do subordinates in social coalitions help the dominant male?
Hypothesis: Kin selection explains the helping behvior
Prediction: For a subordinate male: B x r > C
Methods:
1) Captured and marked individual turkeys, collected blood
2) Determined degree of relatedness among coalition males
3) Determined reproductive success of males in coalitions vs. solo males
Results:
1) Coalition males were close relatives (r = 0.42)
2) Solo males sired on average 0.9 offspring per male = C
3) Dominant males sired 7 offspring = B (6.1 more than solo males)
Thus,
(B x r) > C
[(6.1 x 0.42) = 2.56 > 0.9]
Conclusion:
Kin selection and Hamilton’s rule explain helping behavior by subordinate male turkeys
Kin Discrimination Hypotheses: How individuals discriminate kin from non-kin
1) Direct Familiarization – Individuals learn to discriminate kin from non-kin via previous associations
2) Indirect Familiarization – Individuals learn a reference phenotypic cue from themselves or known close relative. They then assess the degree of similarity of the learned cue to the cue in others.
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Research Question: How do stickle-backs discriminate kin from non-kin?
Hypothesis: Sticklebacks discriminate kin from non-kin through association
Methods: Raised individuals with all kin or with both kin and non-kin
Experiment 1) Tested fish raised with all kin for preferences to associate with a group of familiar kin vs. (unfamiliar) non-kin
Experiment 2) Tested fish raised with kin and non-kin for preference to associate with familiar kin vs. unfamiliar non-kin
Results:
1) Individuals reared with only kin preferred to associate with familiar kin over unfamiliar non-kin
2) Individuals reared with both kin and non-kin did not display any preference between familiar kin and familiar non-kin
Conclusions: Stickleback learn kin via prior associations
ASK: Does this not count as direct familiarization?
Cooperative Breeding
A situation in social groups in which adults physiologically capable of reproducing forgo breeding and instead help others to raise offspring
- Helpers do not reproduce; they pay a cost of care and so are exhibiting altruistic behavior
