Read the following passage about elephants:
Elephants are the largest land animals on Earth. They can weigh between 5,000 to 14,000 pounds and reach heights of 8 to 13 feet. Despite their size, elephants are excellent swimmers and have been known to swim for miles. In the wild, elephants live in large matriarchal herds, led by the oldest female. These herds are typically made up of related females and their offspring, while males will often wander on their own or form bachelor groups.
What can be inferred about the social structure of elephant herds?