RARITY alone does not doom a species to extinction. What matters more for survival is the extent of its range and how its population changes over time.
So says the first detailed study of rare mammals at four North American sites stretching back nearly a million years. They have survived much longer than you would expect had their fate depended purely on random fluctuations in a single population, says Elizabeth Hadly of Stanford University, California.
It’s good news for conservationists. “We don’t have to worry about species that are rare everywhere they live, if they live in lots of places,” says Michael Rosenzweig of the University…
