By Susan Milius
Even solitary creatures do better when a new place has the same old jerks next door.
Stephens’ kangaroo rats, on the U.S. list of endangered species since 1988, live by themselves most of the time in plots of California grassland that they defend from nearby members of their species. When conservationists moved animals to safer homes away from development, familiar rivals relocated together fared better than kangaroo rats grouped with strangers, says conservation biologist Debra Shier of the San Diego Zoo Institute for Conservation Research.
This boost may come from what’s been called a “dear enemy effect,” Shier and institute colleague Ronald Swaisgood say online October 6 in Conservation Biology. Animals tend not to scrap as aggressively with familiar holders of neighboring territories as with complete strangers. Among the kangaroo rats, the researchers noted that those relocated along with their dear enemies indeed spent less time fighting and more time foraging than kangaroo rats surrounded by unfamiliar neighbors.