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Behavioural Ecology > L12 > Flashcards

L12 Flashcards

1
Q

Examples of species that co-operatively breed:

A

-Meerkats

  • Social insects
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2
Q

What is co-operative breeding characterized by?

A
  • The presence of helpers
  • Eg cleaning, mutualistic feeding
  • Individuals who help hamper their own reproductive success
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3
Q

Diversity of cooperative systems

A
  • Cooperative breeding has different interpretations
    • Most widespread in birds 4-9% of bird species
    • 3% of mammal species
    • Described in >10 fish species
    • Social insects that aren’t yet eusocial
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4
Q

In what species is cooperative breeding most widespread?

A

Birds

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5
Q

Helpers at the nest e.g. Florida Scrub Jay

A
  • Florida scrub Jay
    • Pair + 1.8 helpers
    • Helpers feed and protect young from predators
    • Helpers usually related to breeding pair
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6
Q

Helpers at the nest eg Silver backed Jackal

A
  • Pair + 1-3 helpers
  • Helpers regurgitate food to pups and lactating female
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7
Q

Helpers at the nest eg Naked mole rat

A
  • Naked mole rat
    • Larger societies up to 80 individuals
    • Queen breeds
    • Normal moles have different morphology to queen
    • Reproductive division of labour (some fight, some forage, reproductive female breeds in chamber)
    • Dispersal morphs who try and founder new colonies
    • Debated whether it is a caste system or part of species aging
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8
Q

Plural breeders

A

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

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9
Q

Banded mongoose

A

-Plural breeders

- 4-40 individuals in a group

- Several reproductive females and males
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10
Q

Acorn woodpecker

A
  • Plural breeding
    • 2-14 individuals in a group
    • Reproductive individuals are often brothers and sisters
    • These breed with individuals that have moved into the colony
    • Helpers are non-breeding
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11
Q

Ecological constraints hypothesis

A

Independent breeding is constrained - thus leading to grown offspring delay dispersal and stay at home
1. Habitat saturation/ ecological constraints

Grown offspring delay dispersal and stay at home leads to grown offspring helping to rear later broods

  1. Fitness benefits of helping exceed those of not helping
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12
Q

Main assumption of the evolutionary constraints hypothesis

A

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

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13
Q

Species Example eg Long-tailed tit

A

Genetic equivalents = fitness

Breeding productivity = 0.5 GE
Helping = 0.14 GE

Hypothesis: constraints cause offspring to delay dispersal instead of breeding independently

Correlational evidence

- Bad years =  more helping

- Good years = less helping
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14
Q

Acorn woodpecker

A
  • In nearly all bad years (low acorn crop) there is high delayed dispersal
    • In good years (high acorn crop) there is less delayed dispersal

> 2Y acorn woodpeckers

- Less delayed dispersal
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15
Q

Superb fairy wren

A
  • 60% of pairs have male helpers
    • Arise due to male sex ratio
    • Sex ratio at birth is 1:1 but many females die so it is 1.8M: 1F
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16
Q

Are fairy wren helpers constrained from breeding experiment 1?

A

Male removed from pair

Leaving 33 vacancies for 33 helpers

31/33 vacancies filled by helpers (within 5 hours)

17
Q

Are fairy wren helpers constrained from breeding experiment 2?

A
  • Removed male and female
    • Empty territories
    • Initially helpers didn’t take over territory as there was no reason (no one to mate with)
    • Female released (after 3 days) then 7/7 vacancies filled
    • No interest in helping, strictly reproducing
18
Q

Are fairy wren helpers constrained from breeding conclusions

A
  • Helpers are capable of reproduction
    • Habitat is limiting (ECH)
      • mates are limiting
19
Q

Experimental work has revealed different constraints such as…?

A
  • Food
  • Nest cavities
  • Territory and mate
  • High quality territory (food)
20
Q

How do helpers benefit from helping?

A

Direct fitness: fitness gained from personal reproduction

and

Indirect fitness: fitness gained from increasing production of non-descendant kin ( via kin selection)

21
Q

The three direct fitness benefits:

A
  • Increased survival
  • Increased probability of future breeding
  • Direct reproduction
22
Q

Group augmentation hypothesis

A

Benefits may select for helpers to then keep adding to benefits

23
Q

Increased survival

A
  • Group augmentation hypothesis

Producing extra offspring benefits helpers by increasing group size

Kidnapping in banded mongoose and white-winged chough

Gaining benefits associated with larger group living

- Some cons of group living but benefits must outweigh for it to occur
24
Q

Experimental evidence for increased survival

A
  • Cichlid groups more likely to accept immigrants when predation risk is high
25
Q

Increased probability of future breeding

A

Territory inheritance

48% of helpers eventually acquire all or part of parental territory so they can become breeders

Mate acquisition

- Pied kingfishers

Primary helpers

- Relatives

Secondary helpers

- Not relatives
- Don’t benefit indirectly but buy their way into a territory and inherit female when the male dies

Kick out breeding male sometimes

26
Q

Increased experience (skills hypothesis)

A
  • Comparison of success of various breeders eg 1st time, previous breeders
    • 1st time breeders who never helped had no/ low reproductive success
    • 1st time breeders who helped had more reproductive success as did previous breeders
27
Q

Direct reproduction

A
  • 44% lay eggs in helped nest
    • 15% of all young produced by ‘helpers’
    • Helpers are usually female
    • Helpers taking advantage of producing their own offspring
    • Not strictly helpers
28
Q

Indirect fitness benefits

A
  • Increased reproductive success of relatives
  • Increased survival of related breeders
29
Q

Increased reproductive success of relatives

A
  • Long-tailed tit
    • Reproductive success increases with no of helpers
    • Raised by offspring alone reduces survival chance
    • If helpers Is related there is a large indirect payoff

White fronted bee-eater

- Reproductive success increases with no of helpers

- However these correlation studies may be a result of more individuals in group size, more experienced parents etc
30
Q

Does removal of helpers impact reproductive success?

A

Removal experiments

- Socially disruptive

- No sig effect on all species, but some species there is an effect
31
Q

Increased survival of related breeders

A

= load-lightening

- Investing more in reproduction means less in self- maintenance

- Helpers can assist with costs

Hatchwell 1999

- 20/26 species of cooperative breeder

- One or both parents reduce their effort when assisted by helpers

-  improved parental survival hard to demonstrate

Helpers are typically related to breeders

Behavioural Ecology (24 decks)

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