Communication and Perception
Dugongs are very social creatures, occurring in mother and calf pairs to herds of 200 individuals. Communication is therefore vital among individuals in this species. The two primary methods of communication this species uses are sound and vision. Much like dolphins, dugongs use chirps, whistles, barks and other sounds that echo underwater in order to communicate. Each sound has its own amplitude and frequency that characterizes the signal, which implies a possible purpose. For example, “chirp-squeaks” have frequencies between 3 and 18 kHz and last for about 60 ms. These "chirp-squeaks" were observed in dugongs foraging on the sea floor for vegetation and when patrolling territories. Barks are used in aggressive behavior and trills in movements that seem to be displays. In order to hear the ranges of sound, dugongs have developed exceptional hearing, which they use more than their sight.
Visual communication is a useful source of communication when dugongs are in close contact. During breeding season, males perform lekking behavior, a physical display in a specific location to draw in females with which to mate. The vision of dugongs, however, is quite poor and they rely on other senses to create a mental map of their surroundings. Dugongs also utilize their sense of smell. They have an elementary olfactory system that allows them to sense chemicals in their environment to a certain degree. This can be used to detect other dugongs, or most likely, for foraging. They can smell aquatic plants and can therefore determine where the next feeding ground should be or where to proceed on their feeding furrow.
Touch is another sense that dugongs use in order to communicate. They have sensatory bristles all over their body, including many on their lip, which help detect vibrations from their surrounds. This allows dugongs to forage more efficiently as they can sense the seagrass against their bristles. This is particularly useful as it complements their poor eyesight. Mothers and calves also engage in physical communication, such as nose touching or nuzzling that strengthens their relationship. Mothers are almost always in physical contact with their calf, the calf either swimming beneath the mother by the fin or riding on top of her. Calve may even on occasion reach out a fin to touch their mother to gain reassurance.
Communication Channels: visual ; tactile ; acoustic
Other Communication Modes: vibrations
Perception Channels: visual ; acoustic ; ultrasound ; vibrations
- Anderson, P., R. Barclay. 1995. Acoustic signals of solitary dugongs : physical characteristics and behavioral correlates. Journal of Mammology, Vol. 76: 1226-1237. Accessed October 11, 2009 at http://cat.inist.fr/?aModele=afficheN&cpsidt=2924260.