10.5 Cooperative breeding

Cooperative breeding is a social system where non-parent individuals help raise offspring. This behavior occurs in various animals, including birds, mammals, fish, and insects. It's relatively rare but more common in certain groups like birds and carnivores.

The evolution of cooperative breeding is explained by theories like kin selection and ecological constraints. These systems often have a dominant breeding pair and helper individuals. Benefits include increased offspring survival and better territory defense, but costs can involve reproductive suppression for helpers.

Definition of cooperative breeding

• Cooperative breeding is a social system in which individuals other than the parents help raise offspring
• Involves alloparental care, where non-breeding individuals (helpers) assist in rearing young
• Helpers are often, but not always, related to the breeding pair

Prevalence in animal kingdom

• Cooperative breeding occurs in a diverse range of taxa, including birds, mammals, fish, and insects
• Relatively rare overall, but more common in certain groups (birds, carnivores, primates)

Cooperative breeding in birds

Top images from around the web for Cooperative breeding in birds

• 

  1288002 | European bee-eater (Merops apiaster) male displayi… | Flickr - Photo Sharing! View original

  Is this image relevant?

• 

  Superb Fairy-wren (Malurus cyaneus) | The breeding male of o… | Flickr View original

  Is this image relevant?

• 

  The Happy Couple | A beautiful pair of Variegated Fairy-Wren… | Flickr View original

  Is this image relevant?

• 

  1288002 | European bee-eater (Merops apiaster) male displayi… | Flickr - Photo Sharing! View original

  Is this image relevant?

• 

  Superb Fairy-wren (Malurus cyaneus) | The breeding male of o… | Flickr View original

  Is this image relevant?

1 of 3

Top images from around the web for Cooperative breeding in birds

• 

  1288002 | European bee-eater (Merops apiaster) male displayi… | Flickr - Photo Sharing! View original

  Is this image relevant?

• 

  Superb Fairy-wren (Malurus cyaneus) | The breeding male of o… | Flickr View original

  Is this image relevant?

• 

  The Happy Couple | A beautiful pair of Variegated Fairy-Wren… | Flickr View original

  Is this image relevant?

• 

  1288002 | European bee-eater (Merops apiaster) male displayi… | Flickr - Photo Sharing! View original

  Is this image relevant?

• 

  Superb Fairy-wren (Malurus cyaneus) | The breeding male of o… | Flickr View original

  Is this image relevant?

1 of 3

• Approximately 9% of bird species exhibit cooperative breeding
• Examples include fairy-wrens, bee-eaters, and scrubwrens
• Helpers are typically offspring from previous breeding seasons that delay dispersal

Cooperative breeding in mammals

• Less common than in birds, but still observed in various mammalian taxa
• Examples include meerkats, African wild dogs, and marmosets
• Helpers may be siblings, offspring, or unrelated individuals

Evolutionary basis for cooperative breeding

• Multiple hypotheses attempt to explain the evolution of cooperative breeding
• Kin selection and ecological constraints are two primary theories

Kin selection theory

• Helpers gain indirect fitness benefits by assisting related individuals
• By helping to raise relatives' offspring, helpers increase the representation of their genes in future generations
• Degree of relatedness between helpers and offspring is a key factor

Ecological constraints hypothesis

• Cooperative breeding evolves when ecological factors limit independent breeding opportunities
• Habitat saturation, resource scarcity, or high predation risk may prevent individuals from dispersing and reproducing on their own
• Remaining in the natal group as a helper becomes the best alternative strategy

Roles within cooperative breeding groups

• Cooperative breeding groups typically have a distinct social structure and division of labor

Dominant breeding pair

• The dominant pair monopolizes reproduction within the group
• Usually the oldest, largest, or most experienced individuals
• Responsible for the majority of breeding and decision-making

Helper individuals

• Non-breeding individuals that assist in various aspects of offspring care
• May be related or unrelated to the breeding pair
• Engage in activities such as feeding, grooming, and protecting young

Division of labor

• Helpers often specialize in specific tasks based on age, sex, or experience
• Examples include babysitting, territory defense, or foraging for food
• Task specialization can improve overall group efficiency and productivity

Benefits of cooperative breeding

• Cooperative breeding provides various advantages for both breeders and helpers

Increased offspring survival

• Presence of helpers can significantly enhance offspring survival rates
• Additional care, protection, and provisioning from helpers improve chances of reaching adulthood
• Larger groups may also better detect and deter predators

Improved territory defense

• Cooperative breeding groups are more effective at defending high-quality territories
• Multiple individuals can coordinate to patrol borders and repel intruders
• Larger groups are less likely to be challenged by neighboring groups or floaters

Enhanced foraging efficiency

• Helpers can increase overall food acquisition for the group
• Larger groups may be able to exploit a wider range of food sources
• Information sharing about resource locations can improve foraging success

Costs of cooperative breeding

• Despite the benefits, cooperative breeding also involves potential costs for individuals

Reproductive suppression

• Helpers often forfeit their own reproduction to assist the dominant pair
• Physiological or behavioral mechanisms may suppress helper reproduction
• Dominants may actively prevent helpers from breeding through aggression or eviction

Delayed dispersal

• Helpers may postpone dispersal and independent breeding for extended periods
• Missed opportunities for direct fitness gains while waiting for a breeding vacancy
• Tradeoff between indirect fitness benefits and potential direct fitness costs

Increased competition for resources

• Larger groups can lead to increased competition for limited resources (food, shelter)
• Helpers may experience reduced growth, survival, or future reproductive success
• Dispersing to breed independently may be preferable when resources are abundant

Factors influencing cooperative breeding

• Various ecological and social factors can promote or hinder the occurrence of cooperative breeding

Habitat saturation

• Cooperative breeding more likely when suitable breeding territories are limited
• Offspring may delay dispersal when vacant territories are scarce
• Remaining as a helper can provide a "safe haven" until breeding opportunities arise

Resource availability

• Abundant, predictable resources can facilitate cooperative breeding
• Stable food supplies may allow for larger group sizes and helper retention
• Conversely, resource scarcity may favor dispersal and independent breeding attempts

Genetic relatedness

• Higher relatedness between helpers and offspring can promote cooperative breeding
• Kin selection benefits are more significant when helpers are closely related to breeders
• Unrelated helpers may still cooperate if reciprocal or mutualistic benefits exist

Examples of cooperative breeders

• Cooperative breeding has been studied extensively in several iconic species

African wild dogs

• Highly social carnivores living in packs of up to 40 individuals
• Subordinate adults help raise pups by regurgitating food and babysitting
• Cooperative hunting and territory defense are crucial for pack success

Meerkats

• Desert-dwelling mongoose species known for their cooperative behavior
• Helpers assist in pup rearing, sentry duty, and teaching foraging skills
• Complex social hierarchy and division of labor within meerkat mobs

Acorn woodpeckers

• Cooperative breeding bird species found in western North America
• Live in family groups with multiple co-breeding males and females
• Helpers participate in acorn storage, nest excavation, and offspring provisioning

Comparison of cooperative vs non-cooperative breeders

• Studying differences between cooperative and non-cooperative breeders can provide insights into the evolution and maintenance of this social system

Differences in life history traits

• Cooperative breeders often have slower life histories compared to non-cooperative species
• Characterized by delayed maturity, lower reproductive rates, and higher adult survival
• Life history adaptations may be a cause or consequence of cooperative breeding

Variation in social structure

• Cooperative breeders exhibit a range of social structures and mating systems
• Can include singular breeding pairs with helpers, plural breeding groups, or complex hierarchies
• Non-cooperative species typically have simpler social organizations (pairs, solitary)

Future research directions in cooperative breeding

• Many questions remain regarding the evolution, mechanisms, and consequences of cooperative breeding

Impact of climate change

• Changing environmental conditions may alter the costs and benefits of cooperative breeding
• Shifts in resource availability or habitat suitability could affect helper retention and group dynamics
• Long-term studies are needed to assess the resilience of cooperative breeders to climate change

Role of individual personality

• Individual variation in behavior and personality may influence cooperative breeding dynamics
• Bold, aggressive, or exploratory individuals may be more likely to disperse or attain dominance
• Shy, submissive, or risk-averse individuals may be more prone to helping behavior

Interspecific comparisons

• Comparative studies across different cooperative breeding species can reveal common patterns and divergent strategies
• Investigating the ecological and evolutionary drivers of cooperative breeding in diverse taxa
• Identifying key factors that promote or constrain the evolution of cooperative breeding systems