Integration of manatee life-history data and population modeling

Information and Technology Report 1
By:  and 
Edited by: Thomas J. O'SheaB.B. Ackerman, and H. Franklin Percival


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Aerial counts and the number of deaths have been a major focus of attention in attempts to understand the population status of the Florida manatee (Trichechus manatus latirostris). Uncertainties associated with these data have made interpretation difficult. However, knowledge of manatee life-history attributes increased and now permits the development of a population model. We describe a provisional model based on the classical approach of Lotka. Parameters in the model are based on data from'other papers in this volume and draw primarily on observations from the Crystal River, Blue Spring, and Adantic Coast areas. The model estimates X (the finite rate ofincrease) at each study area, and application ofthe delta method provides estimates of variance components and partial derivatives ofX with respectto key input parameters (reproduction, adult survival, and early survival). In some study areas, only approximations of some parameters are available. Estimates of X and coefficients of variation (in parentheses) of manatees were 1.07 (0.009) in the Crystal River, 1.06 (0.012) at Blue Spring, and 1.01 (0.012) on the Atlantic Coast. Changing adult survival has a major effect on X. Early-age survival has the smallest effect. Bootstrap comparisons of population growth estimates from trend counts in the Crystal River and at Blue Spring and the reproduction and survival data suggest that the higher, observed rates from counts are probably not due to chance. Bootstrapping for variance estimates based on reproduction and survival data from manatees at Blue Spring and in the Crystal River provided estimates of X, adult survival, and rates of reproduction that were similar to those obtained by other methods. Our estimates are preliminary and suggestimprovements for future data collection and analysis. However, results support efforts to reduce mortality as the most effective means to promote the increased growth necessary for the eventual recovery of the Florida manatee population.

Additional publication details

Publication type Report
Publication Subtype Federal Government Series
Title Integration of manatee life-history data and population modeling
Series title Information and Technology Report
Series number 1
Year Published 1995
Language English
Publisher National Biological Service
Contributing office(s) Southeast Ecological Science Center
Description 11 p.
Larger Work Type Report
Larger Work Subtype Federal Government Series
Larger Work Title Population Biology of the Florida Manatee (Trichechus manatus latirostris)
First page 269
Last page 279
Online Only (Y/N) N
Additional Online Files (Y/N) N