Despite increased monitoring and wild health assessments, information regarding the relationship between growth and aging of the Florida manatee (Trichechus manatus latirostris) is sparse. The aquatic nature of this mammal makes studying certain aspects of its biology difficult in its natural habitat. Most available age estimations and growth data for manatees has been derived from analyses of individuals postmortem via periotic bones (earbones). Opportunities to collect similar information on living individuals are rare, and individual age estimates are often an integral component of understanding and modeling population dynamics. Accurate age estimates are also critical to effective management and the development of models to predict population trends. For live animals, age estimates are limited to analyses of tissue samples, which is an invasive and requires extensive processing in the lab. As such, there is a strong need for a non-invasive, rapid tool to estimate age in manatees. The present study investigated age distribution and growth parameters (e.g. length, age, and body-mass index) of manatees born at the Miami Seaquarium (n = 16) from 1975 to 1995 in order to create a growth rate chart for manatees born under human care. The Miami Seaquarium recorded the length, weight, and exact day of birth for the manatees, as well as periodic assessments of weight and morphometrics throughout their time in residence. Tables and graphic representations using the age, weight, and length measurements were created in order to illustrate the relationships between size and age. We compared birth weights among both sexes, as well as comparison between sexes. The graphs compare age vs. weight, age vs. body length and lastly age vs. BMI during various life stages. A regression analysis was conducted for each of these comparisons to verify significant relationships and to identify the best predictors of age. From the graphs and related analyses, we generated a growth rate chart for the Florida manatee. The results of this study indicated that the largest rate of growth in length occurred within the first year and then reached a plateau, whereas weight continued to increase over their lifetimes. By pairing the morphometric measurements, we were able to estimate age. These charts can facilitate rapid age estimates for manatees entering rehabilitation, as well as allow for better-specialized care while in rehabilitation.
Blatt, Ariel, "Body weight, length, and age relationship in Florida manatees (Trichechus manatus latirostris) born under human care" (2017). Internship Reports (Restricted). 289.
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