Family life & cooperative breeding
The evolution of family
Families: conflicts and cooperation
Families are complex entities with shared and differing interests. Often there is intra-familial conflict over parental
investment.
SEXUAL CONFLICT between male and female parents: where both parents invest, they are in conflict over the amount
each should contribute to caring for the offspring.
SIBLING CONFLICT: siblings compete over the investment from parents – each individual wants the largest share of
resources and care from the parent
PARENT-OFFSPRING CONFLICT: offspring have different interests from their parent(s) over investment. Parent want
the offspring to do as well as possible but don’t want to give all resources to current offspring because they want to
produce more offspring. However, offspring want the maximum amount of resource from parents.
In EXTENDED FAMILIES, this becomes even more complex with HELPERS – individuals in the group (may be related
or unrelated) which interact with the dominant breeding pair and offspring and aid in raising the offspring.
<= <= Parker et al:
Cooperative breeding
Individuals other than genetic parents (dominant
breeding pair) help raise young. Also called subordinates
or auxiliaries.
CB is relatively widespread in the animal kingdom,
particularly common in birds. >200 species of birds, >100
species of mammals and >20 fish species
Individuals other genetic parents are called helpers (or
auxiliaries or subordinates)
How can cooperative breeding evolve?
, From evolutionary perspective seems maladaptive: natural selection implies that individuals should act selfishly to survive and reproduce, maximising their own
fitness. Why help raise offspring that are not their own?
Two questions:
1. WHY do helpers not breed? / WHY delay dispersal (stay in home territory)?
2. WHY do they help (could simply stay home and not help)?
Example: Florida scrub jay
Aphelocoma coerulescens endemic to Florida
Group sizes: breeding pair and 1 or 2 helpers
Helpers: young birds that fail to disperse
Helping behaviour:
help defend natal territories – many cooperative breeding species have territories with resources to defend against conspecifics (individuals of the same species)
and heterospecifics (members of other species that use similar resources).
help feed young
defend nest when adults are away
protect fledglings
Example: silver-backed jackal
Canis mesomelas – (SW & E Africa)
Group sizes: 3-5 adults
Helpers: young from previous breeding seasons which have not dispersed, remaining with parents in following breeding season non-breeders!
Helping behaviour:
provision nursing females
feed young
guard pups when parents are away feeding
play with young
teach hunting skills
Both Florida scrub jays and silver-backed jackals:
- breed in small groups
- helpers are offspring from previous litter (or clutch) – definitely related individuals, remaining in territory of parents
The evolution of family
Families: conflicts and cooperation
Families are complex entities with shared and differing interests. Often there is intra-familial conflict over parental
investment.
SEXUAL CONFLICT between male and female parents: where both parents invest, they are in conflict over the amount
each should contribute to caring for the offspring.
SIBLING CONFLICT: siblings compete over the investment from parents – each individual wants the largest share of
resources and care from the parent
PARENT-OFFSPRING CONFLICT: offspring have different interests from their parent(s) over investment. Parent want
the offspring to do as well as possible but don’t want to give all resources to current offspring because they want to
produce more offspring. However, offspring want the maximum amount of resource from parents.
In EXTENDED FAMILIES, this becomes even more complex with HELPERS – individuals in the group (may be related
or unrelated) which interact with the dominant breeding pair and offspring and aid in raising the offspring.
<= <= Parker et al:
Cooperative breeding
Individuals other than genetic parents (dominant
breeding pair) help raise young. Also called subordinates
or auxiliaries.
CB is relatively widespread in the animal kingdom,
particularly common in birds. >200 species of birds, >100
species of mammals and >20 fish species
Individuals other genetic parents are called helpers (or
auxiliaries or subordinates)
How can cooperative breeding evolve?
, From evolutionary perspective seems maladaptive: natural selection implies that individuals should act selfishly to survive and reproduce, maximising their own
fitness. Why help raise offspring that are not their own?
Two questions:
1. WHY do helpers not breed? / WHY delay dispersal (stay in home territory)?
2. WHY do they help (could simply stay home and not help)?
Example: Florida scrub jay
Aphelocoma coerulescens endemic to Florida
Group sizes: breeding pair and 1 or 2 helpers
Helpers: young birds that fail to disperse
Helping behaviour:
help defend natal territories – many cooperative breeding species have territories with resources to defend against conspecifics (individuals of the same species)
and heterospecifics (members of other species that use similar resources).
help feed young
defend nest when adults are away
protect fledglings
Example: silver-backed jackal
Canis mesomelas – (SW & E Africa)
Group sizes: 3-5 adults
Helpers: young from previous breeding seasons which have not dispersed, remaining with parents in following breeding season non-breeders!
Helping behaviour:
provision nursing females
feed young
guard pups when parents are away feeding
play with young
teach hunting skills
Both Florida scrub jays and silver-backed jackals:
- breed in small groups
- helpers are offspring from previous litter (or clutch) – definitely related individuals, remaining in territory of parents
