Marine Mammal Cognition
Vocal communication in Manatees
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More information concerning Monika Lechermeier
More information concerning Martin Böye
Background / Introduction
Vocalizations in manatees have not been well studied in contrast to many other marine mammal groups. Regarding context and function of manatee sounds there is no evidence for navigational use. These sounds appear to be entirely related to social factors functioning to establish and maintain contact between individuals. Vocalization probably plays an important role in keeping mother and calf together.
During four weeks in June, Flora a twenty years old female manatee had to be separated from her three years old son Pepe. To prevent Pepe from disturbing his ill mother the tank was divided in two pools by use of wooden panels. Sounds were recorded five days a week every morning.
The study is conducted at the Tiergarten Nürnberg where five West Indian manatees are kept in an inside exhibition tank.
Technics
We used a Sony DAT recorder TCD-D7. Sounds were treated on a PC (sound card turtle beach) by Sound forge 5.0b
Results
- A total of 538 calls was recorded
- We found two different categories of sounds (see figures) : pulsed sounds (type A, type B)and short pure modulated sounds (type C, type D).
Conclusion
- Based on observation type A calls seem to be produced by the mother, type B and D calls by the calf.
- Calls of mother and calf are mainly organized in sequence. Call of one animal, when followed by a call of the other one, is so mainly within two seconds.
- Numerous vocalizations are emitted during the first week of separation. Then the rate of emission is decreasing.
Some references
Anderson, P. K., and R. M. R. Barclay. 1995. Acoustic signals of solitary dugongs: Physical characteristics and behavioral correlates. Journal of Mammalogy. 76:1226-1237.
Bengtson, J. L., and S. M. Fitzgerald. 1985. Potential role of vocalizations in West Indian manatees. Journal of Mammalogy. 66:816-819.
Gerstein, E.R., Patton, G.W. & Tavolga, W.N. (1987) Preliminary underwater acoustic thresholds of a captive manatee, Trichechus manatus, a quantitative approach. Proceedings of the 7th Biennial Conference on the Biology of Marine Mammals, Miami, Florida, December 5-9.
Steel, C. 1982. Vocalization patterns and corresponding behavior of the West Indian manatee (Trichechus manatus). Dissertation, Florida Institute of Technology.
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