Social animals need each other to live, and sometimes that includes those who aren't close relatives of the rest of the group. If dwarf mongooses (Helogale parvula) are any guide, it takes time for new members to fit in, but eventually they make the pack stronger. Integration of outsiders is a topic that has not been heavily studies in wild animals, so it's not yet clear how relevant this is for other species, ourselves included, but the analogies are hard to miss.
Dwarf mongooses (can we just start calling them mongeese please) have plenty of predators, on account of being so small. They survive by acting as sentries for each other, with some keeping an eye out for danger while others feed. Consequently, as long as they don't exceed the local food supply, larger groups are better, since it means more eyes on the skies.
Sometimes an individual mongoose will lose, or be cast out from, its pack, and join another. Professor Andrew Radford of the University of Bristol was interested in this process of dispersal and integration. In Current Biology, he reports that the new arrivals don't contribute much initially, but eventually play an important role in the success of the group.
New mongoose arrivals don't tend to do much sentry work. This isn't because they are lazy bludgers, as the Mongoose First political party would probably claim, but because they tend to be exhausted and underfed from their time attempting to survive on their own.
When standing guard, a mongoose will make calls to tell others they are on the case and it's safe to eat. Interestingly, even when the new arrivals try to do their bit, they tend to be ignored. However, this too is only temporary. “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,” Radford said in a statement.
To identify this pattern, Radford played calls he and his co-author Dr Julie Kern had previously recorded and watched for responses. Mongooses can recognize individual calls and would stop their own sentry-work when they heard a familiar voice indicating it was on the look-out. They were much less inclined to trust a new arrival's calls, instead continuing to sacrifice eating so they could do their own guard work.
After five months, however, the new arrivals were not only doing as much guardwork as the longstanding members of the group, but being given the same respect for their contribution. Dispersal prevents dwarf mongoose populations from becoming inbred, something other species of mongoose have to address in much more dramatic ways.
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