Lecture 11: co-operative breeding

Question 1

‘helpers’ assist

Answer 1

breeder to raise offspring that are (usually) not their own

Question 2

Diversity of cooperative systems:

Answer 2

quite diverse

• 4-9% of bird species
• 3% of mammal species
• described in >10 fish spp.
• ‘primitive’ social insects

Question 3

‘Helpers at the nest’ (80%) florida scrub jay

Answer 3

• pair + 1.8 helpers
• helpers feed & protect young form predators
• helpers usually related to breeding pair

Question 4

‘Helpers at the nest’ (80%) silver-backed jackal

Answer 4

• pair + 1-3 helpers

- helpers regurgitate food to pups and lactating female

Question 5

‘Helpers at the nest’ (80%) naked mole-rat

Answer 5

• c.f. eusocial insects

- reproductive division of labour (caste system)

Question 6

plural breeders =

Answer 6

several males and females share a nest and raise a communal brood

Question 7

plural breeder examples

Answer 7

• banded mongoose
• • 4 - 40 in a group
• • several females reproduce
• acorn woodpecker
• • 2 -14 in a group

Question 8

plural breeder typical group

Answer 8

1-4 breeding males
1-4 breeding females
up to 8 non breeding helpers

Question 9

evolution of cooperative breeding: hypothesis

Answer 9

Ecological constraints hypothesis Emlen 1982

Question 10

Ecological constraints hypothesis: ellen 1982

Answer 10

indépendant breeding is constrained –habitat saturation/ecological constraints–> grown offspring delay dispersal and “stay at home” –Fitness benefits of helping exceed those of not helping –> Grown offspring help to rear later broods

Question 11

ecological constraints hypothesis assumption:

Answer 11

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

Question 12

cooperative breeding: hypothesis; constraints cause offspring to delay dispersal instead of breeding independently CORRELATION EVIDENCE

Answer 12

e. g. acorn woodpecker. Correlation evidence

- ‘bad’ years –> more helping

Question 13

cooperative breeding: hypothesis; constraints cause offspring to delay dispersal instead of breeding independently EXPERIMENTAL EVIDENCE

Answer 13

e. g. superb fairy-wren
- - 60% of pairs have male helpers
- - sex ratio is 1.8 M : 1F

Manipulate constraints on breeding –> effect on incidence of cooperation

exp1: male removed from pair, vacancy for helper 31/33 spots filled in 5 hours
exp2: M & F removed. 7 empty territories–> 0/7 occupied by helpers. Female released after 3 days –> all territories filled

Conclusions:

• helpers are capable of reproduction
• habitat is limiting (ecological constraints hyp)
• mates are limiting

Question 14

are helpers constrained from breeding?

Answer 14

experiments reveal different constraints:

e.g. food, nest cavities, territory and mates

Question 15

inclusive fitness:

Answer 15

direct & indirect fitness benefits

Question 16

direct fitness =

Answer 16

fitness gained from personal reproduction

Question 17

indirect fitness =

Answer 17

fitness gained for increasing production of non-descendant kin (via kin selection )

Question 18

direct fitness benefits:

Answer 18

• increased probability of future breeding
• increased survival
• direct reproduction

Question 19

increased survival benefits of group living: Group augmentation hypothesis:

Answer 19

hypothesis: help = payment for being allowed to stay

- producing extra offspring benefits helpers by increasing group size

Question 20

increased survival benefits of group living: Group augmentation hypothesis: circumstantial evidence:

Answer 20

circumstantial evidence: Kidnapping in banded mongoose and white-winged chough

Question 21

increased survival benefits of group living: Group augmentation hypothesis: Experimental evidence:

Answer 21

cichlids groups more likely to accept immigrants when predation risk high

Question 22

increased probability of future breeding: territory inheritance

Answer 22

florida scrub jay

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

Question 23

increased probability of future breeding: mate acquisition

Answer 23

pied kingfisher: the distant kin helpers 41% inherit female when breeding male dies

Question 24

increased probability of future breeding: increased experience (skills hypothesis)

Answer 24

seychelles warbles

– performed better if they’d been helper before

Question 25

Direct reproduction:

Answer 25

seychelles warbler: helpers are usually female

• 44% lay eggs in helped nest
• 15% of all young produced by helpers

Question 26

indirect fitness benefits:

Answer 26

• increased reproductive success of relatives

- increased survival of related breeders

Question 27

indirect fitness benefits: increased reproductive success of relatives

Answer 27

long tailed tit & white-fronted bee-eater

– reproductive success increases with number of helpers

Question 28

indirect fitness benefits: Increased survival of related breeders

Answer 28

= ‘load lightening’

Question 29

helpers gain __ & __ fitness benefits from helping

Answer 29

direct and indirect