2008 Cooperative sentinel calling? Foragers gain increased biomass intake

checking in this way and thus maximize foraging time. Forthe time [11], and these individuals tend to be the first to detect a predator and give an alarm call [11]. All adult group members act as sentinels on some occasions, with bouts lasting between 0.2 and 6.3 min (mean 6 standard deviation [SD] = 1.6 6 1.3 min, n = 152 bouts by 27 individuals). Because group members generally forage within 20 m of one another, continuous monitoring of their positions is possible communication to be efficient in this regard and allow foragers the greatest flexibility in their behavior, sentinel calls need to be given throughout a bout, as is the case in pied babblers (this study), meerkats [7], and dwarf mongooses [8]. Calls that are only given at the start and end of a bout, as in white-browed sparrow weavers [15], or simply at the end of a bout, as in jungle babblers [16], might aid coordination of sentine