Sentinel dwarf mongooses, Helogale parvula, exhibit flexible decision making in relation to predation risk

• Sentinel decisions are influenced by direct and indirect indicators of risk.
• Individuals become a sentinel and do so faster following an alarm call.
• Sentinels adjust guarding height according to factors varying in the medium term.
• Sentinels adjust bout duration according to factors varying in the short term.

To maximize survival, animals should adjust their behaviour flexibly in response to indicators of predation risk. Predation risk is affected by a range of ecological, social and individual variables, which can fluctuate over different timescales. In general, current risk levels are known to influence the behaviour of sentinels, individuals that adopt a raised position to scan for danger while groupmates are engaged in other activities. However, there has been little consideration of whether decisions made at different stages of a sentinel bout are affected in the same way by perceived predation risk and whether the same level of behavioural plasticity is exhibited when making these different decisions. Here we used detailed behavioural observations and a playback experiment to investigate the behavioural choices of dwarf mongoose sentinels at three different stages of a bout (before, start, during). Individuals were more likely to begin a bout, and did so sooner, following alarm calls, which are immediate, direct indicators of elevated risk. Sentinels selected an initial height from which to guard depending on factors that tended to vary in the medium term (hours), choosing higher positions in denser habitat and less windy conditions. In contrast, decisions about bout duration were made in relation to short-term (seconds/minutes) changes in information, with sentinels guarding for longer when an alarm call was given during a bout, and terminating bouts sooner when groupmates moved out of sight. Our results demonstrate that sentinel decisions are influenced by both direct and indirect indicators of likely predation risk and that sentinel behaviour is adjusted flexibly with regard to information presented on various timescales, highlighting the complexity of decision-making processes.