Cooperative breeding

Question 1

Diversity of cooperative breeding systems

Answer 1

• Have more data for some species than others so data is biassed
• Some debate as to what cooperative breeding is
• 4-9% of bird species
• 3% of mammals
• Describes in >10 fish species
• Social insects

Question 2

What is the most common type of cooperative breeding?

Answer 2

• Helpers at the nest
• 80%

Question 3

Examples of ‘helpers at the nest’

Answer 3

Florida scrub jay

• pair + 1.8 helpers
• helpers feed and protect young from predators
• helpers usually related
• to breeding pair

Silver-backed jackal

• Pair + 1-3 helpers
• Helpers regurgitate food to pups or lactating female

Naked mole rats

• Similar social structures to eusocial insects e.g. bee queen
• Reproductive division of labour
• Caste system?
• Dispersal morph - longer legs.

Question 4

What are plural breeders?

Answer 4

Several males / females that share a nest and raise a brood together

Question 5

Examples of plural breeders?

Answer 5

Banded mongoose

• 4-40 in a group
• Several females reproduce
• Number of helpers that don’t reproduce

Acorn woodpecker

• 2-14 in a group
• Often brothers and sisters
• 1-4 breeding males
• 1-4 breeding females
• Will breed with unrelated individuals
• Helpers in group that are non breeders

Question 6

What is the Ecological Constraints Hypothesis ?

Answer 6

When Independent breeding is constrained → grown offspring delay dispersal and ‘stay at home’

1. Habitat saturation / ecological constraints
2. Fitness benefits of helping exceed those of not helping

Question 7

What are the assumptions of the Ecological Constraint Hypothesis?

Answer 7

There is a better fitness return from breeding than helping (but breeding is constrained)

Question 8

Ecological constraints theory hypothesis?

Answer 8

Constraints cause offspring to delay dispersal instead of breeding independently

Question 9

Correlational evidence for acorn woodpecker delaying dispersal

Answer 9

• Years where resources are hard to come by or reproductive opportunities are low the young (below 2yrs old) delay dispersal.
• More likely to disperse when resourcces are more abundant
• Bad years = more helpers needed.
• No obvious pattern after 2 years old

Question 10

Experimental evidence: How does manipulating the constraints on breeding effect cooperative breeding in species like superb fairy wrens?

Answer 10

• 60% of pairs have male helpers
• Strong male bias in the population
• 1.8 males : 1 females
• Exp. 1 - male removed from pair - helper males filled vacancy
• Exp. 2 - males and female removed - helpers did not fill vacancy until female returned

Question 11

Conclusions from superb fairy wren experiment?

Answer 11

• Helpers are capable of reproduction
• Habitat is limiting (ecological constraints hypothesis)
• Mates are limiting

Question 12

General theme of cooperative breeding constraints

Answer 12

When the constraints are relaxed helping reduces

Question 13

What are the two types of inclusive fitness?

Answer 13

• Direct fitness
• Indirect fitness

Question 14

What is direct fitness?

Answer 14

Fitness gained from personal reproduction

Question 15

What is indirect fitness?

Answer 15

Fitness gained from increasing porduction of non-decendant kin (via kin selection)

Question 16

What are the direct fitness benefits?

Answer 16

• Increased vigilance
• Can benefit from increased resources
• Increases survival (dilution effect)

Question 17

What is the Group Augmentation Hypothesis ?

Answer 17

• Producing extra offspring benefits helpers by increasing group size
• Groups will kidnap offspring from other groups to increase size of group
• Cichlid fish are more likely to accept immigrants when predation risks are high

Question 18

Costs of living in groups ?

Answer 18

• Costs of living in groups - more competition for resources

Question 19

Examples of kidnapping

Answer 19

• Banded mongoose
• White-winged chough

Question 20

Benefits of helping: Territory inheritance in Florida scrub jays

Answer 20

48% of helpers eventually acquire all or part of parental territory

Question 21

Benefits of helping: Mate aquisition in Pied kingfishers

Answer 21

• Primary helpers - close kin
• 2nd degree helpers - distant kin \ non-kin
• Secondary helpers benefit: 41% inherited female when breeding males died

Question 22

Increased experience (skills hypothesis)

Answer 22

• Seychelles warbler
• Evidence that helping gives birds a higher chance of reproductive success

Question 23

Direct reproduction: Seychelles warbler

Answer 23

• Helpers are usually female
• 44% of helpers lay eggs in helped nest
• 15% of all young in a population were produced by helpers

Question 24

Indirect fitness benefits: Increased reproductive success of relatives

Answer 24

• Long tailed tit & white-fronted bee-eater
• Reproductive success increases with number of helpers
• Different things at play - productivity is high within groups with lots of helpers - could have a lot of resources
• Correlation doesn’t take other factors into account

Question 25

Indirect fitness benefit: Increased survival of related breeders

Answer 25

• Load-lightening
• Helpers have load-lightening effect
• One or both parents reduced their effort when assisted by helpers
• Improved parental survival is hard to demonstrate