Hearing
- The hearing capacities of manatees are not well studied, but it is known that manatees are adapted for hearing low frequency sounds.
- Manatees have large ear bones that are well developed at birth. Some scientists have suggested, however, that the main area of sound reception is not the small ear openings but rather an area near the cheekbones. A manatee's cheekbones are large and relatively oily, and they are in direct contact with the ear bones.
- Hearing is an important sense for young manatees because mother and calf vocalizations are significant in keeping them together. The chirps, whistles, and squeaks used by manatees are probably produced in the larynx and are often in the 3-5 kHz range.
- Preliminary studies suggest that manatees have a greater sensitivity to low-frequency sound than any marine mammal studied (U.S. Fish and Wildlife Service, 1995).
Eyesight
- Manatees have well-developed eyes. In the water, they can detect objects from tens of meters away.
- A manatee's retinas contain both rod and cone cells, indicating that they probably have the ability to see both dim and bright light. Recent tests suggest manatees can distinguish between blue and green colors, although the full extent of their color vision is unknown and more studies are needed.
- A nictitating membrane acts as an extra eyelid for protection.
Tactile
Touch seems to be very important for manatees. Body contact is common between mother and calf. Manatees have also occasionally been observed initiating body contact with divers. They have even been seen making contact with inanimate objects such as ropes, buoys, logs, and rocks.
Taste and Smell
- The manatee's chemoreceptive capacities (taste and smell) have not been well studied. They have taste buds on the backs of their tongues and can most likely taste. Studies on manatee food preference at Blue Spring State Park, Florida, indicate that manatees avoid certain plants such as spatter dock, blue-green algae, and waterpennywort that contain natural toxins.
- Manatees have olfactory tissue on small internal nasal bones, and probably have some sense of smell. The capability for scent discrimination is largely unknown.
- Some researchers theorize manatees use smell and/or taste to tell if a female is in estrus or "heat", while other researchers believe males respond to low frequency sounds made by females when they are ready to mate
