Manatees have large ear bones that are well developed at birth. Some scientists have suggested that the main area of sound reception is not the small ear openings, but an area near the cheekbones. A manatee's cheekbones are large and relatively oily, and they are in direct contact with the ear bones. Manatees are adapted for hearing low frequencies, generally between 3 and 5 kHz. Hearing is an important sense for young manatees because mother and calf vocalizations are significant in keeping them together.
Manatees have well-developed eyes.
In clear water, they can detect objects from tens of yards away. A manatee's retinas contain both rod cells and cone cells, indicating that they may have the ability to see in both dim and bright light. We don't know whether or not manatees can distinguish colors. A nictitating membrane acts as an extra eyelid to protect the eye. Touch seems to be very important for manatees.