Degree Granting Department
Henry R. Mushinsky, Ph.D.
John E. Reynolds, III, Ph.D.
Earl D. McCoy, Ph.D.
Habitat selection, Thermoregulation, Temperature, Foraging, Activity Patterns, Human Disturbance
Investigating alternate winter refuges for Florida manatees is increasingly important
as sustained warm-water discharges from industrial and some natural sites becomes more
uncertain. This study examined habitat features of possible importance to manatees by
comparing a winter refuge in Charlotte Harbor, FL (the Matlacha Isles canal system) to
two nearby, seemingly similar sites that are not frequented by manatees during winter.
Water temperature, salinity, boat traffic, canal depth, and tidal flushing were assessed at
these sites. Additionally, this study examined when and how manatees use the Matlacha
Isles refuge by documenting movements, habitat use, and behaviors of manatees during
the winters of 1999/2000 through 2001/2002. Water temperatures had a profound
influence on manatee selection of Matlacha Isles over the two comparison canal systems.
Matlacha Isles did not experience the sudden drops in water temperature following cold
fronts, extreme low temperatures, or long periods of temperatures below manatees’
reported thermal tolerance of 18-20
oC that were recorded in Matlacha Pass (ambient) and
the two comparison canal systems. Heat retention within Matlacha Isles may be
associated with greater water depth and lower tidal flushing. Salinity and boat traffic did
not seem to influence site selection by manatees. During moderately cold weather,
manatees occupying Matlacha Isles forage at night in nearby Matlacha Pass and return
early in the morning to Matlacha Isles, where they primarily rest all day. Neither tidal
state nor boat traffic levels affected manatee travel patterns into or out of Matlacha Isles.
Manatees may passively thermoregulate in the warmer waters of Matlacha Isles during
the day (when they are inactive) and sustain their body temperatures at night through the
heat generated during traveling to feeding sites and during ingestion (chewing) and
digestion. During extreme or prolonged cold weather, Matlacha Isles provides
inadequate warmth for manatees; during such times, most of them travel to a power plant
on the Orange River, approximately 50 kilometers away. Findings from this study may
inform resource managers as they consider attributes manatees find desirable or
necessary in winter. Such information will help managers create new or enhance existing
winter refuges to protect manatees.
Scholar Commons Citation
Barton, Sheri L., "The Influence of Habitat Features on Selection and Use of a Winter Refuge by Manatees (Trichechus manatus latirostris) in Charlotte Harbor, Florida" (2006). USF Tampa Graduate Theses and Dissertations.