Animals live in a whole world of smells and sounds and perceptions of their environment that we're not even aware of.
The anaconda, which is a water snake, typically grows to about 20 feet (6 meters) long, weighs several hundred pounds, and can measure more than 12 inches (30 centimeters) in diameter. The females are larger than the males.
They typically feed on large rodents, tapirs, capybaras, deer, peccaries, fish, turtles, birds, sheep, dogs and aquatic reptiles like caiman. They have been known to occasionally prey on jaguars and attacks on humans can be confirmed, although this is rare. Younger anacondas feed on mice, rats, chicks, frogs and fish. Most local people kill these snakes on sight, out of the fear that they are man-eaters. In most instances, if an anaconda senses humans in the area, it will retreat in another direction. Human death by anaconda is quite rare. They themselves are preyed by jaguars, large caimans and by other anacondas. A wounded anaconda can also fall prey to piranhas.
The largest known anaconda measured 10 meters (32.8 feet) long, but unverified reports of much larger snakes have occasionally been made.