Which of the following most logically completes the argument below?

The expansion of large-scale farming in Africa and Asia has destroyed much of the natural vegetation on which elephants have historically depended, forcing them to turn to cultivated land to satisfy their enormous appetites. As a result, farmers have lost millions of dollars worth of crops annually. Yet even if elephant sanctuaries were created on a widespread basis to guarantee elephants sufficient natural vegetation, the raiding would likely persist, since

【选项】when elephants forage for food, they typically travel in herds.