5. sea otter (Enhydra lutris)
© Only Fabrizio/Fotolia
The luxurious waterproof coat that insulates sea otters from the chilly waters that they inhabit almost led to its extinction. A target of the commercial fur trade, the species was almost wiped out, with only some 2,000 of an estimated 300,000 left by 1911. That year, an international ban on commercial hunting was enacted. Though that ban, along with management and conservation measures taken in the wake of the 1972 Marine Mammal Protection Act, have helped populations recover to perhaps a third of their earlier numbers, they are highly vulnerable to both natural phenomena such as killer whale predation and to anthropogenic factors such as oil spills.
