Rattlesnakes Scientists have studied rattlesnakes for hundreds of years, yet, there continue to be myths about these snakes. The snake's rattle, which lends it its name, contains hard, loose parts made of the same material found in human nails. When cornered, the snake shakes its tail to make a rattling noise. Researchers used to think that the number of rattles on a snake indicates its age. However, it is now known that each time a rattlesnake sheds its skin, it adds a rattle. These snakes shed their skins about four times a year, and often the rattles break off. Research shows that rattlesnakes have deep social ties. Mothers and babies are known to stay together until babies first shed their skin. Mothers keep their young close to them. If they sense any threat, they shake their rattles and adopt a threatening posture. Studies also show that some rattlesnake young even return to their mother's den after they have grown up. Volumes of literature exist on rattlesnakes. It is clear, however, that more research will continue to be conducted to understand the characteristics of rattlesnakes. 1 What can the reader infer based on the second paragraph of the passage