Individual distinctiveness, short- and long-term comparisons, and context specific rates of Florida manatee vocalizations
- UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
- Lynne Elizabeth Williams (Creator)
- Institution
- The University of North Carolina Wilmington (UNCW )
- Web Site: http://library.uncw.edu/
- Advisor
- Laela Sayigh
Abstract: In the 1980?s, Thomas J. O?Shea recorded captive and wild Florida manatees (Trichechus
manatus latirostris), and statistical analyses of various acoustic features of their calls indicated
possible individual distinctiveness. To further test the hypothesis that manatee calls contain
individually distinctive features and to test the hypotheses that various acoustic features of their
calls are stable over short (1-3 year) and long (19+ year) time periods and that vocal rates vary
depending on behavior, recordings of wild and captive manatees were made between November
2002 and January 2004. Recordings of 31 manatees (21 wild, 10 captive) were obtained and
vocalizations from two additional manatees recorded only in the 1980?s were analyzed, for a
total of 33 individuals. Four of these manatees had been recorded both in the 1980?s and in
2002-2004, and the vocalizations of these individuals were used for long-term comparisons.
Cross-validated linear discriminant analyses using nine different parameters of manatee
vocalizations determined that 1) when using only the most recent recordings, vocalizations were
classified to the correct individual a greater percentage of time than expected by chance for 30
out of 33 animals; 2) an overall higher percentage of calls was correctly assigned to only one of
four animals recorded in the 1980?s when using all recordings versus just the most recent
recordings; 3) when using only adult and calf vocalizations, calls were assigned correctly to both
adults (82.2% of 506 vocalizations) and calves (79.5% of 503 vocalizations) a greater percentage
of time than expected by chance; and 4) when using only calf vocalizations, calls were assigned
correctly to both females (66.0% of 250 vocalizations) and males (58.1% of 253 vocalizations) a
greater percentage of time than expected by chance. ANOVAs were performed on each of the
nine parameters for individual manatees that were recorded: 1) over 19+ years, 2) when less than
one year old and again between the ages of one and three, and 3) as adults in at least two separate field seasons. For three individuals recorded over 19 years, 47% of tested parameters did not
significantly change over that time period; all three individuals were calves in the 1980?s. For
the one individual recorded over 22 years, 33.3% of his parameters did not significantly change
over that time period. For four individuals recorded when they were less than one year old and
then again between the ages of one and three, 71% of tested parameters did not significantly
change. For four individuals recorded as adults in at least two separate field seasons, 76% of
tested parameters did not significantly change. These results indicate that manatee vocalizations
are individually distinctive, and that there are age and sex differences in calls. These results also
suggest that 1) many call parameters are apparently not stable from calf to adulthood in at least
some individuals, 2) some calves, subadults, and adults show variable changes in parameters
over short (1-3 year) time periods, and 3) some calves and adults show stability in all parameters
over short time periods. Florida manatee vocalization rates were not affected by group size at
Blue Spring State Park, Florida, although they were found to differ depending on behavior.
When looking at call rates per minute averaged across group sizes, significantly higher
vocalization rates occurred during social activity than during bottom resting, with boat, and play;
mill had significantly higher rates than bottom rest and with boat; and surface rest had
significantly higher rates than bottom rest. Overall, the hypothesis that Florida manatee
vocalizations are stable over long time periods was not supported, although only one adult was
tested. Conflicting evidence for short-term stability in both calf and adult calls was found, with
the number and type of parameters that changed being highly variable. Results supported the
hypotheses that Florida manatees have individually distinctive vocalizations and that vocal rates
vary depending on behavior. These results add to a growing body of information on manatee
behavior and communication, and could potentially contribute to manatee research and conservation efforts by providing a means to document the presence of specific individuals, the
presence of manatees from different age classes and sexes, or the occurrence of certain behaviors
without having to conduct boat-based surveys.
Individual distinctiveness, short- and long-term comparisons, and context specific rates of Florida manatee vocalizations
PDF (Portable Document Format)
1002 KB
Created on 1/1/2009
Views: 4317
Additional Information
- Publication
- Thesis
- A Thesis Submitted to the University of North Carolina Wilmington in Partial Fulfillment Of the Requirements for the Degree of Master of Science
- Language: English
- Date: 2009
- Keywords
- Manatees--Behavior, Manatees--Florida--Blue Spring State Park, Manatees--Vocalization
- Subjects
- Manatees -- Florida -- Blue Spring State Park
- Manatees -- Vocalization
- Manatees -- Behavior