In wild dwarf mongoose communities, immigrants are always welcome. But a new study shows it takes a little time before newcomers will be trusted with a crucial job: serving on guard duty. A team reports Monday that dwarf mongooses never turn away a newly joined member, but for months, they ignore immigrants who go on sentry duty — even if the outsiders are warning of actual danger.
“But then we also saw that if given enough time to integrate, the new mongooses ultimately became a part of the larger group and the residents saw the benefit of having the immigrants,” Julie Kern, a zoologist at the University of Bristol and lead author of the study, told PBS NewsHour.
Aside from this seemingly disadvantageous behavior of disregarding a basic survival signal, the dwarf mongoose is one of few species to evolve a sense of camaraderie and trust building to outsiders, which might even teach humans a thing or two about how we treat others, some researchers posit.
Being a sentinel happens to be one of the most vital posts in dwarf mongoose societies. While groupmates forage for food, a few mongooses will station themselves atop a tree branch or a tall anthill searching for predators. Those on duty also have a variety of surveillance calls: ones that tell others “I’m on lookout right now!” and others that cry “Run, something’s approaching!”
Kern’s team began watching this behavior in 2011 at the Sorabi Rock Lodge Reserve in Limpopo Province, South Africa. The researchers marked and tracked 165 mongooses, divided among nine groups with about 7 to 12 members each. They found a total of 28 mongooses immigrated from their original groups.
To test the relationship between residents and immigrants, researchers played back pre-recorded mongoose calls. Recent immigrants served less often as sentinels because foraging resident mongooses would ignore their calls. But after about five months living with new group mates, immigrants gained others’ attention just as much as residents on duty. Researchers considered this change as a sign of the newcomers’ acceptance into their new society.
Kern called these five months an “integration period,” where new arrivals have time to get accustomed to new mongooses. And a couple things had to happen for outsiders to gain acceptance. For one, the integration period allows for building a trusting relationship.
“Dwarf mongooses seem to recognize each other’s voices,” said Kay Holekamp, a behavioral ecologist at Michigan State University who did not participate in this study. “They place weight on the information conveyed by the voices they know and seem skeptical of those that they don’t, which means they just need time to get to know the new mongoose.”
Their findings suggest dwarf mongooses are also capable of remembering who’s reliable. “They’re able to keep track of how groupmates contribute, so if they don’t know how reliable a new mongoose is, they won’t want to hear them out,” Kern said.
This integration period is also crucial for the immigrant mongoose’s recuperation. When a mongoose decides to leave its community and join another, the journey can “become energetically costly,” Kern said. The team noticed that immigrants were exhausted and had lost some weight. Essentially, these mongooses weren’t in tip-top shape, so they weren’t quite ready to take on such vigilant roles.
So the integration period proves to be helpful to both parties. And dwarf mongooses have proven to be extremely gregarious mammals.
“As a species, dwarf mongooses are an unusual case due to their ‘friendly acceptance’ of others,” Holekamp explained. “They seem to have outgrown xenophobia, something that so many mammals still experience. Humans, too, have a ways to go.”
But Kern cautions that it’s hard to compare us to mongooses because humans have culture and societal nuances that shape our beliefs and behaviors.
“However, if we are to draw some conclusions from these animals, people should learn to give new residents proper time to integrate to a new place,” Kern said. “Immigrating is tough for any species, so if we allow people time to join a new society, everyone can reap the benefits of having more members just as the mongooses do.”