11: cooperative breeding Flashcards
what are cooperative breeders?
helpers that assist breeders to raise offspring that are usually no their own
how many are cooperative?
a) bird species
b) mammal species
c) fish species
d) and what other group?
a) 4-9%
b) 3%
c) > 10 species
d) primitive social insects
what are the 2 main social organisations of cooperative breeders and a brief description of each?
- helpers at the nest: breeding pairs aided by one or more helpers
- plural breeders: several M + F share nest and raise communal brood
what % off cooperative breeders are helpers at the nest?
80%
list 3 examples of helpers at the nest
- florida scrub jay
- silver backed jackal
- naked mole rat
what is the florida scrub jay example of a helper at the nest? (3)
- pair and 1.8 helpers
- helpers feed and protect young
- helpers are usually related to breeding pair
what is the silver backed jackal example of a helper at the nest? (2)
- pair and 1.3 helpers
- helpers regurgitate food to pups and the lactating female
what is the naked mole rat example of a helper at the nest? (4)
- 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
list 2 examples of plural breeders
- banded mongoose
- acorn woodpecker
what is the banded mongoose example of plural breeders? (2)
- 4-40 in a group
- several female reproduce
what is the acorn woodpecker example of plural breeders? (5)
- 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
who proposed the ecological constraints hypothesis and when?
Emlen 1982
what is the main key assumption of the ecological constraints hypothesis?
there is better fitness return from breeding than helping
- but the breeding is constrained
what is the long tailed tit example to support the ECH assumption?
long tailed tit
- raising brood through breeding: 0.5 genetic equivalents
- through helping: 0.14 genetic equivalents
what are the 3 stages to the ecological constraints hypothesis?
- 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
what is the acorn woodpecker example for correlational evidence for if constraints cause offspring to delay dispersal?
- in bad crop years there is more helping
- larger crop means less constraint on independent breeding
which species was studied to show experimental evidence for constraints causing offspring to delay dispersal?
superb fairy wren
in the superb fairy wren
a) what % pairs have male helpers
b) what is the sex ratio?
c) who helps mothers raise broods
a) 60%
b) 1.8M : 1F
c) males that cant find mates
what was experiment 1 on the superb fairy wrens to determine if helpers are constrained from breeding? (2)
- male removed from pair
- 31/33 vacancies were filled by helpers within 5 hours
what was experiment 2 on the superb fairy wrens to determine if helpers are constrained from breeding? (4)
- 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
what were the conclusions from the experiment on the superb fairy wrens to determine if helpers are constrained from breeding? (3)
- helpers are capable of reproduction
- habitat is limiting (ECH)
- mates are limiting
experiments reveal different constraints and there is a diverse range - give 3 examples
- sociable warbler constrained by food
- red cockaded woodpecker constrained by nest cavities
- seychelle warbler constrained by high quality territory and food
a) what is direct fitness
b) list the 4 direct fitness benefits
a) fitness gained from personal reproduction
b) - increased survival from group living
- increased probability of future breeding
- increased experience/skills
- direct reproduction
what is the direct fitness benefit of increased survival through group augmentation? (4)
- 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
what is the direct fitness benefit of increased probability of future breeding through territory inheritance? (2)
- florida scrub jay
- 48% helpers eventually acquire all or part of parental territory
what is the direct fitness benefit of increased probability of future breeding through mate acquisition? (6)
- 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
what is the example for the increased experience/skills hypothesis for direct fitness benefits?
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
what is the direct fitness benefit of direct reproduction? (4)
- 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
list the 2 indirect fitness benefits
- increased reproductive success of relatives
- increased survival of related breeders
what is the long tailed tits example for indirect fitness benefits? (2)
- reproductive success increases with number of helpers
- if 3 or more helpers roughly 50% chance of survival and fledging
what is the white fronted bee eater example for indirect fitness benefits? (2)
- reproductive success increases with number of helpers
- BUT correlation does not mean causation
what is the removal experiment example for indirect fitness benefits?
in 3 bird groups when the group size was reduced there was a reduction in reproductive success
what is the load lightening example for indirect fitness benefits? (3)
- increased survival of related breeders if reproductive costs reduced
- helper gains indirect and direct fitness from helping
- observed acorn woodpecker and dwarf mongoose
what can constrain independent breeding
shortage of breeding opportunities/delayed dispersal
the nature of what remains uncertain?
constraints and relative importance of indirect/direct fitness benefits in evolution and maintenance of cooperative breeding
