Birds With Friendly Neighbors Age More Slowly

The Seychelles warbler is a small, monogamous songbird that mates for life. (Photo: Remi Jouan/Wikimedia Commons)

Songbirds who get along with their neighbors are physically healthier and age more slowly, scientists report in a new study. The researchers focused on one species, the Seychelles warbler, but they say the findings could apply to a wide range of wildlife.

This isn't as random as it might sound. Wildlife around the world is increasingly squeezed into fragments of its natural habitat, forcing animals to share much less space than their ancestors did. Habitat loss and fragmentation is now the No. 1 threat for about 85 percent of all endangered species, and on top of protecting those habitats, it's important for scientists to understand how relationships between neighbors can affect the health and longevity of individual animals.

Like humans, many wild animals "own" a private patch of their species' habitat, and will defend it from intruders. If they have friendly neighbors who respect their boundaries, they can save their energy for tasks like foraging or evading predators. But could getting along with neighbors actually give them an edge in survival?

To investigate, the new study looked at Seychelles warblers, small songbirds endemic to their namesake archipelago in the Indian Ocean. Males and females form monogamous pairs, jointly defending a territory until one of them dies.

Aride Island in the Seychelles
Aride Island is one of several habitats where Seychelles warblers still exist. (Photo: Thomas Amler/Shutterstock)

Good neighbors come in two basic varieties, the study's authors say. Some are extended family members who share genes, and thus tend to avoid destructive territorial fights. Others are just friendly non-relatives who have developed mutual trust over time. The latter may not have a genetic incentive to get along, but conflict could create an opening for unfamiliar neighbors, requiring new boundary agreements and potentially raising the risk of even more conflict.

Among Seychelles warblers, the researchers watched some territory owners fight with their neighbors, but never with family members or non-relatives who had been their neighbors in previous years. After studying these conflict patterns, they measured the birds' body conditions and the length of their telomeres — sections of DNA that protect an individual's genetic material, but erode more quickly during times of stress and poor health. Telomere length can reveal the rate at which an animal is aging, the researchers note, and may predict how long it will live.

When living among more relatives or trusted neighbors, territory-owning warblers had better physical health and less telomere loss. If unknown warblers moved into an adjacent territory, however, they showed a decline in health and more telomere shortening. This effect was stronger in densely populated areas, and suggests neighbor relationships are a key factor in how wildlife adapts to limited habitat.

"Defending territory boundaries is crucial if animals are to hold onto valuable food and other resources," says lead author Kat Bebbington, a biologist at the University of East Anglia, in a statement. "Territory owners who are constantly fighting with neighbors are stressed and have little time to do other important things — such as finding food and producing offspring — and their health suffers as a result."

Denis Island, Seychelles
The Seychelles warbler 'appears to prefer dense scrub vegetation or woodland,' according to the International Union for Conservation of Nature, like this forest on Denis Island. (Photo: Kerry Manson/Shutterstock)

As habitats shrink around the world, this kind of infighting could make life even harder for many species. The Seychelles warbler itself has rebounded from a severe decline last century, but it's still listed as Near Threatened by the International Union for Conservation of Nature (IUCN), which attributes its "very limited range" to habitat loss and invasive predators. This study may also be relevant for a broad range of taxa, the authors write, including other wildlife — and maybe even ourselves.

"Interestingly, we show that it's not just relatives that can be trusted, but also neighbors you get to know well over time," Bebbington says. "Something similar probably occurs in human neighborhoods: If you've lived next to your neighbor for years, you are much more likely to trust each other and help each other out now and then." And if you're anything like a Seychelles warbler, you might live longer for it.