In mongoose society, immigrants are a bonus—when given time to settle in

December 4, 2017

Researchers studying wild dwarf mongooses have provided insight into what happens when immigrants join a new group. The study in Current Biology on December 4 shows that, initially, recent immigrants rarely serve as lookout, which means they provide little information to help the rest of the group. Even when they do act cooperatively, their new groupmates tend to ignore what they have to offer. But, within five months, the new arrivals become fully integrated and valued members within mongoose society.

"A few months after arriving in a new group, former immigrants are contributing as often as residents and their information is used just as much, but to reach that stage requires a transition period," says Andrew Radford of the University of Bristol, UK.

That's probably because the dispersal process is tough on individuals, notes the lead author of the study, Julie Kern. "Recent immigrants are typically exhausted and run down, as evidenced by a loss of weight," she says. "Even if they tried, they couldn't contribute fully at first because other members don't yet know them."

The study is one of the first to explore the impact of dispersal events on social-information provision and use within groups. It also shows that the expected benefits associated with an increase in group size may not be as straightforward as scientists have often assumed.

Dwarf mongooses within a group depend on each other. For instance, individuals will stand guard, serving as sentinels that keep a watch for predators and call to warn the rest of the group when one is near. Sentinels also issue calls to announce that they're watching. By providing this social information, sentinels allow other group members to concentrate more on foraging. What the researchers wanted to know is how new group members contributed to these tasks and whether the information they provided was used by others.

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