Families and cooperative breeding

Question 1

what are the different types of conflict in a family?

why are families complex?

Answer 1

sibling conflict

sexual conflict

parent-offspring conflict

they are complete entities with shared and differing interests

Question 2

what is cooperative breeding?

Answer 2

when individuals other than genetic parents (helpers/subordinates) help raise young

Question 3

explain cooperative mating in Florida scrub jay

what is the group size?

who are the helpers?

what is their helping behaviour?

Answer 3

group size = breeding pair + 1-2 helpers (young birds that fail to disperse)

defend natal territories
feed young
defend nest when adults are away
protect fledgelings

Question 4

explain cooperative mating in Silver-backed jackal

what is the group size?

who are the helpers?

what is their helping behaviour?

Answer 4

group size = 3-5 adults

helpers
= young from previous breeding season

feed young 
provision nursing females 
guard pups when parents are away feeding 
play with young 
teach hunting skills

Question 5

explain cooperative mating in Daffodil cichlid

what is the group size?

who are the helpers?

what is their helping behaviour?

Answer 5

group size = 1 breeding pair + <16 helpers

helpers = young from previous broods in territory
- largely unrelated to breeding pair

defence
territory maintenance
brood care

Question 6

what are other potential features of cooperative mating?

Answer 6

more complex + larger groups

complex social organisations

extended rather than immediate families

overlapping generations

more than one breeding pair

Question 7

explain cooperative mating in white-fronted bee eater

what is the group size?

who are the helpers?

what is their helping behaviour?

Answer 7

colonies of 50-300 birds
composed of extended family groups (=clans)

helping occurs within clans but helpers attach themselves to 1 nest

helpers = adults from failed nests
(birds switch between helper and breeder roles)

incubate nests 
defend nest + colony 
care for chicks 
excavate the nest 
feed incubating females

Question 8

explain cooperative mating in Callitrichids

Answer 8

female always gives birth to twins that are 25% her body weight

requires multiple males to carry them

males don’t know if they father offspring
- so some are helpers

in established breeding pairs
- the older offspring stay as helpers

Question 9

explain cooperative mating in Acorn woodpeckers

what is the group size?

who are the helpers?

what is their helping behaviour?

why is this example unique?

Answer 9

1-4 breeding males
1-2 breeding females
<8 helpers

helpers
= grown up offspring

incubate eggs
defend nest
feed young

no pair bonds
>1 male mates with a breeding female
in 25% of cases 2 females contribute eggs to communal nest

Question 10

explain cooperative mating in Naked mole rats

what is the group size?

who are the helpers?

what is their helping behaviour?

Answer 10

40-300 group size
1 breeding female + 1-3 breeding males

helpers
= non-breeders

maintain tunnels

• smaller ones build tunnels + bring food
• larger ones defend tunnels against predators

Question 11

what is the evidence that subordinates actually help?

BUT what could be a problem with this correlation?

Answer 11

correlation between group size + offspring survival

= increases success of breeding attempts

helper number could be correlated with territory quality

-> territory quality could be responsible for differences in offspring survival e.g. better resources so offspring stay

Question 12

describe experimental removal of helpers in Grey-crowned babblers

Answer 12

matched territories for quality ad helper number

removed helpers of 9 territories + used 11 controls

territories with helpers had 3x higher nesting success than in controls

Question 13

in addition to increasing survival of offspring, how else may subordinates help?
give examples

Answer 13

increase the no. of breeding attempts
- e.g. Grey-crowned babblers, breeding pairs may re-nest sooner if they have helpers

increase survival of breeding pair
e.g. Acorn woodpeckers

decrease egg investment

Question 14

how could cooperative breeding evolve?

Answer 14

inclusive fitness
- if the fitness benefits that result from helpers exceed the costs

delayed dispersal

• dispersal too costly
• if young males/females cannot acquire mates
• if young cannot find resources to produce offspring
• > helping siblings may be the best option

OR unrelated helpers may inherit territory/mate in future when current breeders leave

non-adaptive reason
- parental care instinct to respond to offspring

Question 15

what are the 2 components of inclusive fitness?

Answer 15

direct fitness
= own offspring

indirect fitness
= through other non-descendent kin

Question 16

what is Hamilton’s rule?

Answer 16

describes whether a gene for altruistic behaviour will spread in a population:
rB > c

B = reproductive benefit to recipient of altruistic behaviour

r = probability that the recipient and the artist share the altruistic gene
(i.e. degree of relatedness)

c = the reproductive cost to the altruist

Question 17

give an example of kinship correlating with help

Answer 17

Long tailed tits

failed breeders assist successful breeders to rear young

the amount of help depends on the degree of relatedness

Question 18

what are the potential routes to cooperative breeding?

Answer 18

individuals aggregate to form groups because of the advantages of living in the family

• inclusive fitness
• learning from breeders

OR

remain in groups due to costs of dispersing e.g. increased risk of predation

Question 19

what is the habitat saturation hypothesis?

Answer 19

helpers don’t breed on their own because they can’t
- not a good enough territory available

best to wait in familiar natal territory at proven quality with familiar relatives

Question 20

describe the typical demography of cooperative breeders

Answer 20

high juvenile and adult survival

permanent residency on all purpose territories

surplus of mature individuals to territorial vacancies
= habitat saturation

Question 21

what other factors may influence dispersal?

Answer 21

probability of finding a mate after dispersal

in more polygynous species:
shortage of potential mates
- skewed sex ratio affecting the probability of finding a mate

probability of reproducing successfully

Question 22

e. g. superb fairy wrens
- what is the wild type situation?
- what happens in the experiment?

Answer 22

male-biased sex ratio induces young males to stay on natal territory

experimental removal of males:
>helpers moved into vacant territories
males >responded to availability of territories and females