Reverse audience effects on helping in cooperatively breeding marmoset monkeys

Area of Science:

• Primate behavior
• Animal social systems
• Cooperative breeding

Background:

• Cooperative breeding in common marmosets exhibits significant variation in helping behaviors.
• Existing models propose audience effects (pay-to-stay, social prestige) or other factors (kin selection, group augmentation, experience) to explain helping variation.

Purpose of the Study:

• To investigate the influence of audience presence on food-sharing behavior in cooperatively breeding common marmosets.
• To test predictions of pay-to-stay and social prestige models against observed helping behaviors.

Main Methods:

• Quantified food-sharing readiness of adult marmosets towards immatures.
• Compared food sharing in the presence versus absence of other group members (audience effect).

Main Results:

• A reverse audience effect was observed: marmosets shared significantly more food with immatures when no audience was present.
• Helping behavior did not increase with the presence of other group members.

Conclusions:

• Results do not support pay-to-stay or social prestige models, indicating helpers do not manage reputation through food sharing.
• The findings suggest marmoset helping behavior, particularly in family groups, may stem from genuine concern for immature well-being, especially when solely responsible.