11: cooperative breeding

Question 1

what are cooperative breeders?

Answer 1

helpers that assist breeders to raise offspring that are usually no their own

Question 2

how many are cooperative?

a) bird species
b) mammal species
c) fish species
d) and what other group?

Answer 2

a) 4-9%
b) 3%
c) > 10 species
d) primitive social insects

Question 3

what are the 2 main social organisations of cooperative breeders and a brief description of each?

Answer 3

• helpers at the nest: breeding pairs aided by one or more helpers
• plural breeders: several M + F share nest and raise communal brood

Question 4

what % off cooperative breeders are helpers at the nest?

Answer 4

80%

Question 5

list 3 examples of helpers at the nest

Answer 5

• florida scrub jay
• silver backed jackal
• naked mole rat

Question 6

what is the florida scrub jay example of a helper at the nest? (3)

Answer 6

• pair and 1.8 helpers
• helpers feed and protect young
• helpers are usually related to breeding pair

Question 7

what is the silver backed jackal example of a helper at the nest? (2)

Answer 7

• pair and 1.3 helpers

- helpers regurgitate food to pups and the lactating female

Question 8

what is the naked mole rat example of a helper at the nest? (4)

Answer 8

• similar to eusocial insects
• reproductive division of labour and caste system
• some fight and others forage
• colonies of 80-100 with only 1 reproducing female

Question 9

list 2 examples of plural breeders

Answer 9

• banded mongoose

- acorn woodpecker

Question 10

what is the banded mongoose example of plural breeders? (2)

Answer 10

• 4-40 in a group

- several female reproduce

Question 11

what is the acorn woodpecker example of plural breeders? (5)

Answer 11

• 2-14 group
• often brothers and sisters but not related to each other
• 1-4 breeding males
• 1-4 breeding females
• up to 8 non breeding helpers

Question 12

who proposed the ecological constraints hypothesis and when?

Answer 12

Emlen 1982

Question 13

what is the main key assumption of the ecological constraints hypothesis?

Answer 13

there is better fitness return from breeding than helping

- but the breeding is constrained

Question 14

what is the long tailed tit example to support the ECH assumption?

Answer 14

long tailed tit

• raising brood through breeding: 0.5 genetic equivalents
• through helping: 0.14 genetic equivalents

Question 15

what are the 3 stages to the ecological constraints hypothesis?

Answer 15

• independent breeding constrained by habitat saturation or ecological constraints
• causes grown offspring to delay dispersal and stay home
• if the fitness benefits of helping exceeds not then the offspring will help to rear later broods

Question 16

what is the acorn woodpecker example for correlational evidence for if constraints cause offspring to delay dispersal?

Answer 16

• in bad crop years there is more helping

- larger crop means less constraint on independent breeding

Question 17

which species was studied to show experimental evidence for constraints causing offspring to delay dispersal?

Answer 17

superb fairy wren

Question 18

in the superb fairy wren

a) what % pairs have male helpers
b) what is the sex ratio?
c) who helps mothers raise broods

Answer 18

a) 60%
b) 1.8M : 1F
c) males that cant find mates

Question 19

what was experiment 1 on the superb fairy wrens to determine if helpers are constrained from breeding? (2)

Answer 19

• male removed from pair

- 31/33 vacancies were filled by helpers within 5 hours

Question 20

what was experiment 2 on the superb fairy wrens to determine if helpers are constrained from breeding? (4)

Answer 20

• male and female removed
• this left 7 empty territories occupied by no helpers
• females released after 3 days
• 7/7 vacancies filled by helpers as more opportunity to breed

Question 21

what were the conclusions from the experiment on the superb fairy wrens to determine if helpers are constrained from breeding? (3)

Answer 21

• helpers are capable of reproduction
• habitat is limiting (ECH)
• mates are limiting

Question 22

experiments reveal different constraints and there is a diverse range - give 3 examples

Answer 22

• sociable warbler constrained by food
• red cockaded woodpecker constrained by nest cavities
• seychelle warbler constrained by high quality territory and food

Question 23

a) what is direct fitness

b) list the 4 direct fitness benefits

Answer 23

a) fitness gained from personal reproduction
b) - increased survival from group living
- increased probability of future breeding
- increased experience/skills
- direct reproduction

Question 24

what is the direct fitness benefit of increased survival through group augmentation? (4)

Answer 24

• producing extra offspring benefits helpers by increasing group size
• in a large group will help contribute to offspring
• kidnapping in mongoose and white winged chough so is a helper in the new group
• cichlid groups more likely accept immigrants when high predation risk

Question 25

what is the direct fitness benefit of increased probability of future breeding through territory inheritance? (2)

Answer 25

- florida scrub jay | - 48% helpers eventually acquire all or part of parental territory

Question 26

what is the direct fitness benefit of increased probability of future breeding through mate acquisition? (6)

Answer 26

- pied kingfisher - primary helpers are close kin - secondary kin are distant/non kin - 41% secondary males inherit female when breeding male died - 18% secondary males ousted breeding male - opportunity for unrelated male to breed

Question 27

what is the example for the increased experience/skills hypothesis for direct fitness benefits?

Answer 27

seychelle warblers - difference in successful hatchings and no of fledglings between those with no experience and those with help - helping helps to become a better parent

Question 28

what is the direct fitness benefit of direct reproduction? (4)

Answer 28

- seychelle warbler - helpers usually female so they more likely gain the fitness benefits - 44% lay eggs in helped nest - 15% all young produced by helpers

Question 29

list the 2 indirect fitness benefits

Answer 29

- increased reproductive success of relatives | - increased survival of related breeders

Question 30

what is the long tailed tits example for indirect fitness benefits? (2)

Answer 30

- reproductive success increases with number of helpers | - if 3 or more helpers roughly 50% chance of survival and fledging

Question 31

what is the white fronted bee eater example for indirect fitness benefits? (2)

Answer 31

- reproductive success increases with number of helpers | - BUT correlation does not mean causation

Question 32

what is the removal experiment example for indirect fitness benefits?

Answer 32

in 3 bird groups when the group size was reduced there was a reduction in reproductive success

Question 33

what is the load lightening example for indirect fitness benefits? (3)

Answer 33

- increased survival of related breeders if reproductive costs reduced - helper gains indirect and direct fitness from helping - observed acorn woodpecker and dwarf mongoose

Question 34

what can constrain independent breeding

Answer 34

shortage of breeding opportunities/delayed dispersal

Question 35

the nature of what remains uncertain?

Answer 35

constraints and relative importance of indirect/direct fitness benefits in evolution and maintenance of cooperative breeding