Animal Behavior ch18

wilson’s characteristics for Eusociality

1. reproductive division of labor

2. cooperative brood care

3. overlapping generations

Cornwallis et al.

study suggested that cooperative breeding is more likely to evolve in populations where females mate with fewer males

Paul Sherman

studied alarm calls in Belding’s ground squirrels and tried to determine if the alarm calls were directed at the predator or at kin.

He found that the answer varied with the circumstances.

nepotistic society

where most interactions occur between females and their offspring and kin

Benefits of group living?

1. improved foraging

2. decreased predation risk

3. conserving heat & water

4. conserving energy

information sharing

improved foraging by observing the behavior of group members.

informational centers

communal roosts or colonies where animals can observe the foraging success of conspecifics and follow the successful ones to food sites.

Costs of group living?

1. increased intraspecific competition

2. increased risk of disease & parasites

3. reproduction interference

kin selection

refers to apparent strategies in evolution that favor the reproductive success of an organism's relatives, even at a cost to the organism's own survival and reproduction.

coefficient of relatedness

r

Hamilton’s rule

developed a theorem for determining how the coefficient of relatedness affected altruism

kin recognition

refers to an animal's potential ability to distinguish between close genetic kin and non-kin.

4 ways that an animals may be ale to tell kin from nonkin:

1. location

2. familiarity

3. phenotype matching

4. recognition alleles (green beard effect)

Location kin recognition

works well in species with established distribution patterns.

familiarity kin recognition

involves animals learning to recognize individuals with whom they were raised.

Phenotype matching

allows animals to identify kin even if they had never previously met. Family members tend to share phenotypes so phenotypic similarities can be used to determine relatedness.

recognition Alleles

involves an inherited allele or group of alleles that the individual can use to recognize others with the same allele.

ex: green beard effect

Cooperative breeding

social system in which individuals contribute care to offspring that are not their own at the expense of their own reproduction.

• was first observed in birds

Benefits of cooperative breeding

1. increase inclusive fitness

2. gain parental experience

3. group augmentation

Costs of cooperative breeding

1. unable to increase own direct fitness

2. expending energy on someone else’s offspring

The benefits of cooperative breeding will only occur…

in a population only if it is better to stay and help other individuals than to move somewhere else and attempt breeding.

Other reasons for cooperative breeding?

1. habitat saturation

2. lack of mates

Eusociality

term used for the highest level of social organization in a hierarchical classification

• usually find a queen and unsterile workers

examples: insects (ants, bees, wasps, and termites)

Narrow definition of eusociality

specifies the requirement for irreversibly distinct behavioral groups or castes

• sterility in lower castes

Broader definition of eusociality

allows for any temporary division of labor or non-random distribution of reproductive success

Isopterans

termites

hymenopterans

bees, wasps, and ants

Haplodiploidy

Sisters are more related to each other than to their offspring

"supersisters" who share 75 percent of their genes on average—> workers will invest more care into their sisters over having their own offspring

Evolution of Eusociality

1. haplodiploidy

2. shared defensible resource

3. extended parental care and lasting sibling associations