10 - Cooperative breeding in vertebrates

Question 1

What are the two types of cooperative breeding?

Answer 1

Communal breeding: essentially everyone has eggs in one basket

Helping-at-the-nest/den: where you have a main set of parents that produce young, and other individuals help to raise those young

Question 2

What are forms of helping-at-the-nest/den? (5)

Answer 2

• Defend territory
• Excavate burrows or build nests
• Incubate eggs
• Feed young
• Feed nursing female

Question 3

Do helpers actually help to increase breeder’s reproductive success? (in helping-at-the-nest/den type of cooperative breeding) (2)

Answer 3

• Yes, correlational evidence shows that higher group sizes are related to offspring survival.
• They also reduce the workload of breeders (eg. with feeding)

Question 4

True or false? Experimentally removing helpers in a cooperative breeding group reduces reproductive success of the group

Answer 4

True

Question 5

Why should an animal stick around with its parents or at its birthplace? (2)

Why help? (4)

Answer 5

Why stay?

• Lack of breeding/relocation opportunities (often from habitat saturation, particularly in long lived species)
• High pay-off for staying (eg. territory inheritance)

Why help?

• Indirect fitness benefit (eg. helping siblings gives close kinship genetic payoff)
• Direct fitness benefit (eg. mutualism, group members help each other and help to produce a big group)
• Delayed direct fitness benefits (eg. in some species, more likely to inherit territory/fitness benefits if you help and stay)
• Direct fitness enforcement (any females that are coming into reproductive condition, that look like they are trying to have kids, they’ll get stressed out from harassment from others and abort, no choice but to help raise kids of dominant females)

Question 6

What is skew theory?

Answer 6

It says that reproductive success of different individuals in a group will be skewed in different ways. Some groups will have a more uniform skew, some will have more contrasting skews.

Evidence hasn’t really provided any support or evidence for this being a thing…

Question 7

What is the monogamy hypothesis?

Answer 7

If you are screwing around a lot, your offspring won’t be as strongly related to one another. Less helping with species that mess around a lot.

You find that this is actually the case in many bird species. Cooperative breeders are less promiscuous and non-cooperative breeders are more promiscuous.

Question 8

What is the monogamy hypothesis?

Answer 8

A theory in kin selection.

The monogamy hypothesis, formulated by Jacobus Boomsma, is currently the leading hypothesis concerning the evolution of eusociality and uses Hamilton’s kin selection approach in a way that applies to both haploid and diploid organisms. If a queen is lifetime-strictly monogamous - in other words, she mates with only one individual during her entire life - her progeny will be equally related to their siblings and to their own offspring (r=0.5 in both cases - this is an average of sisters [0.75] and brothers [0.25]). Thus, natural selection will favor cooperation in any situation where it’s more efficient to raise siblings than offspring, and this could start paving a path towards eusociality. This higher efficiency becomes especially pronounced after group living evolves