The African savanna can be a dangerous place – especially if you are only 30 centimeters (12 inches) tall. That is why meerkats (Suricata suricatta) forage in packs, or more specifically, "gangs" or "mobs".
Foraging trips require at least one individual to stand guard for predators while the rest of the group dig their heads in the sand in search of insects and small vertebrates to eat. Having your head stuck in the sand isn't the best way to watch out for predators that might be lurking about, which makes the job of the sentry an extremely, extremely important one.
But what makes a good guardsman? As far as meerkats are concerned, it is their reputation and experience (not their age or social rank) that makes a respected sentry. That's according to a study recently published in Nature.
Ramona Rauber from the Department of Evolutionary Biology and Environmental Studies at the University of Zurich studied nine meerkat gangs living in the Kalahari desert, South Africa. Her team monitored the foraging activity of each group, which ranged from three to 23 individuals, for three months to find out what exactly it takes to earn a meerkat's trust.
This involved recording "all-clear" calls from sentries and playing them to individual meerkats (temporarily) foraging solo to gauge their reaction, specifically how many times they looked up from the task at hand to check for predators. It was important to find these lone meerkats so that their reaction was not tainted by the behavior of their mates. In total, there were 544 playbacks.
The researchers tested dominance status, age, sex, sentinel frequency (or experience), call rate, and relation to individual meerkats to see what made any particular guardsman respected by the rest of the gang. They then watched the recordings to check for any patterns.
Over the course of the experiment, they noticed that youth and low social status were not barriers to becoming a guardsman. Lookouts could be meerkats of any age and influence, but their fellow meerkats appeared to be more trusting (that is, they looked up less) when a seemingly more experienced guard was on duty.
The meerkats were also less attentive to potential predators when a littermate (aka a close relation) was on duty, showing that they trusted that individual more than those who were not as closely related. Dominance status, sex, and age, on the other hand, did not appear to make much of a difference.
It might sound like an obvious tactic, but oddly it's not one shared by other species that rely on this sentinel behavior – specifically, the dwarf mongoose (Helogale parvula) and pied babblers (Turdoides bicolor), both of which judge an individual guardsman (at least to some extent) on their age, dominance status, and group affiliation.