Amid all this frantic chaos, I noticed something strange. There were no drongos.
Chlorophyll (HM004) on sentinel duty.
To find out if the mongooses felt safer when drongos were present, I recorded how often the groups mounted sentinels when a drongo was there, compared with when it wasn't; and a student (from Stellenbosch University) monitored how frequently individual mongooses interrupted their foraging to look around for danger. We found that the mongooses halved both these behaviours when drongos were present. But were the drongos actually causing this change? Perhaps drongos only escorted the mongooses when birds of prey were scarce and the mongooses didn't need caution.
To test this, we artificially simulated the presence of a drongo by playing recordings of its territorial calls. We also played to the mongooses recordings of the white-bellied sunbird (Cinnyris venusta). This beautiful little bird is very common at the study site, but it never accompanies the mongooses.