Families and cooperative breeding Flashcards
what are the different types of conflict in a family?
why are families complex?
sibling conflict
sexual conflict
parent-offspring conflict
they are complete entities with shared and differing interests
what is cooperative breeding?
when individuals other than genetic parents (helpers/subordinates) help raise young
explain cooperative mating in Florida scrub jay
what is the group size?
who are the helpers?
what is their helping behaviour?
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
explain cooperative mating in Silver-backed jackal
what is the group size?
who are the helpers?
what is their helping behaviour?
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
explain cooperative mating in Daffodil cichlid
what is the group size?
who are the helpers?
what is their helping behaviour?
group size = 1 breeding pair + <16 helpers
helpers = young from previous broods in territory
- largely unrelated to breeding pair
defence
territory maintenance
brood care
what are other potential features of cooperative mating?
more complex + larger groups
complex social organisations
extended rather than immediate families
overlapping generations
more than one breeding pair
explain cooperative mating in white-fronted bee eater
what is the group size?
who are the helpers?
what is their helping behaviour?
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
explain cooperative mating in Callitrichids
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
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?
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
explain cooperative mating in Naked mole rats
what is the group size?
who are the helpers?
what is their helping behaviour?
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
what is the evidence that subordinates actually help?
BUT what could be a problem with this correlation?
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
describe experimental removal of helpers in Grey-crowned babblers
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
in addition to increasing survival of offspring, how else may subordinates help?
give examples
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
how could cooperative breeding evolve?
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
what are the 2 components of inclusive fitness?
direct fitness
= own offspring
indirect fitness
= through other non-descendent kin
what is Hamilton’s rule?
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
give an example of kinship correlating with help
Long tailed tits
failed breeders assist successful breeders to rear young
the amount of help depends on the degree of relatedness
what are the potential routes to cooperative breeding?
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
what is the habitat saturation hypothesis?
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
describe the typical demography of cooperative breeders
high juvenile and adult survival
permanent residency on all purpose territories
surplus of mature individuals to territorial vacancies
= habitat saturation
what other factors may influence dispersal?
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
e. g. superb fairy wrens
- what is the wild type situation?
- what happens in the experiment?
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
