Within-group vigilance in red colobus and redtail monkeys

Area of Science:

• Behavioral Ecology
• Primatology
• Animal Behavior

Background:

• Theoretical models predict reduced vigilance in larger animal groups due to increased safety.
• Previous studies on primates have not supported this theory, showing no decrease in vigilance with increasing group size.
• An increase in vigilance related to social interactions, such as surveillance of associates, may mask reduced anti-predator vigilance.

Purpose of the Study:

• To investigate the relationship between group size and within-group surveillance in wild red colobus and redtail monkeys.
• To determine if increased social interactions in larger groups affect vigilance patterns.
• To test the hypothesis that primate vigilance is unresponsive to group size.

Main Methods:

• Analysis of observational data on glances toward associates in wild red colobus and redtail monkeys in Uganda.
• Quantification of within-group surveillance based on frequency of glances.
• Statistical analysis to assess the effect of group size on surveillance, considering factors like mating periods and infant care.

Main Results:

• No significant effect of group size on within-group surveillance was detected in either red colobus or redtail monkeys.
• Vigilance patterns were influenced by reproductive strategies, with males showing increased surveillance during mating and females when infants were young or out of contact.
• These findings align with previous research indicating primate vigilance is largely unresponsive to group size.

Conclusions:

• Primate vigilance patterns are primarily driven by reproductive strategies rather than group size.
• The expected decrease in vigilance with increasing group size is not observed in these monkey species.
• Future research may require more complex models that consider fine-scale association patterns within groups to fully understand primate vigilance.