Estimation of manatee (Trichechus manatus latirostris) places and movement corridors using telemetry data

Effective stewardship of Florida's coast requires, in part, detailed characterizations of ecological components of the marine system. Characterization of one component, manatees (Trichechus manatus latirostris), involves mapping its distribution and abundance and identifying features of the landscape that are intimately associated with its life history. In this study, we developed a raster-based spatial model that transformed radiotelemetry point data to surfaces. illustrating the. areas manatees visited frequently for relatively long periods, called "places," and areas visited frequently for short periods, called "movement corridors." This work involved (1) simulating manatee movement paths between sequential telemetry points using a cost surface based on manatee bathymetric preferences that were derived from empirical associations between telemetry locations and water depth, (2) distributing movement time to cells that were crossed by the simulated movement path, and (3) extracting cells from the movement-path map that qualified as places and those that qualified as corridors. Movement characteristics of wild and rehabilitated animals were similar. Movement rates of males were significantly greater than those of either females with calves or females without calves. Mean number of visits per cell and mean time per visit for the three adult classes were not significantly different. Males had the smallest mean patch size for places, and females without calves had the largest but fewest places. Based on qualitative evaluations by field biologists, we concluded that the model performed well in estimating places. The locations of movement corridors were less certain, although reasonable, given that manatee spatial cognition was considered sufficient to permit directed movement between places.