Is sentinel behaviour safe? An experimental investigation

Amanda R. Ridley*, Martha J. Nelson-Flower, Alex M. Thompson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

32 Citations (Scopus)


Sentinel behaviour, where individuals take turns to watch for danger and give alarm calls to approaching predators, has been observed in a number of animal societies. However, the evolutionary causes of this behaviour remain unclear. There are two main, competing hypotheses regarding the evolution of sentinel behaviour. The first hypothesis is that it is a cooperative behaviour, where group members benefit from the detection of danger but share the workload of acting as a sentinel. The second is that it is a safe, selfish behaviour. Under the second hypothesis, once an individual is satiated, being a sentinel is safer because sentinels can detect threats more readily and can therefore escape from predators faster. We examined whether sentinels are safer than foragers in a wild, free-living cooperative bird (the pied babbler, Turdoides bicolor) with a well-described sentinel system. We found that sentinel behaviour was costly because (1) sentinels were targeted by predators more often, (2) they were further from cover than foragers, and (3) they took longer to reach the safety of cover following a predator alarm. These results suggest that individuals do not become sentinels because it is safer. This is the first study to demonstrate that sentinels are at greater risk of predator attack than foraging group members and suggests sentinel activity may have evolved as a form of cooperative behaviour.

Original languageEnglish
Pages (from-to)137-142
Number of pages6
JournalAnimal Behaviour
Issue number1
Publication statusPublished - Jan 2013


  • Cooperative breeding
  • Kin selection
  • Pied babbler
  • Safe location
  • Selfish sentinel
  • Sentinel behaviour
  • Turdoides bicolor

Fingerprint Dive into the research topics of 'Is sentinel behaviour safe? An experimental investigation'. Together they form a unique fingerprint.

Cite this