Florida manatees are semisocial marine mammals that vocalize when interacting with conspecifics and to maintain contact with offspring. While many aspects of their biology have been studied, there is a dearth of information on the diversity and complexity of vocal behavior during social, nonsocial, and stressful situations. Investigations of vocal communication repertoires which define, categorize, and correlate varied call types with behavior are needed in order to understand the behavioral and social function of associated calls. Arguably the most important social bond in manatees is the period of cow/calf dependency and empirical evidence indicates cows recognize the vocalizations of offspring. Exploration of individually distinctive vocal features can provide insight on which parameters might be salient to facilitate recognition between cows/calves. This study is focused on vocal communication in Florida manatees, how calls are structured, utilized and function while animals are distressed and during social interactions in their shallow water habitats. Hydrophones recorded vocalizations from individual calves and manatees in different behavioral contexts and varying size aggregations. Analysis of the vocal repertoire indicated manatee vocalizations can be parsed into five broadly defined call types which include the hill-shaped high squeak, tonal squeak, noisy squeal, two toned chirp, and the combinatorial squeak-squeal. Furthermore, the high squeak is likely a discrete call whereas the others are graded and do not have strict boundaries between call types (Chapter 2). Broadly defined call types were used to explore call usage with variations in behavior, group size, and group composition (Chapter 3). Manatees vocalized using few call types and altered structural parameters depending on behavioral state. Calls were longer and more frequency modulated when stressed. Vocalizations produced while cavorting were higher in entropy and more frequency modulated than when manatees were resting or feeding. Vocalizations obtained from individual calves suggest that the high squeak is a stereotypical call that is produced by smaller calves. All calves had individually distinctive acoustic features that could potentially be used in recognition (Chapter 4). Lower fundamental frequencies and higher emphasized frequencies from smaller calves suggest that the fundamental frequency may not be a reliable indicator of body size in calves. This research increases our knowledge of the vocal behavior and call characteristics of the Florida manatee. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection

The West Indian manatee (Trichechus manatus) is an herbivorous marine mammal that occupies freshwater, estuarine, and marine habitats. Despite being considered endangered, relatively little is known about the feeding ecology of either of the two recognized subspecies, the Florida manatee (T.m. latirostris) and Caribbean or Antillean manatee (T.m. manatus). A better understanding of their respective feeding preferences and habitat use is essential to establish criteria on which conservation plans can be based. The present study expands on previous work on manatee feeding ecology by both assessing the application of stable isotope analysis to manatee tissue and providing critical baseline parameters for accurate isotopic data interpretation. The present study was the first to calculate stable isotope turnover rate in the skin of any marine mammal. Stable carbon and nitrogen isotope ratios were examined over a period of more than one year in the epidermis of rescued Florida manatees that were transitioning from a diet of aquatic forage to terrestrial forage (lettuce) in captivity. Mean half-life for 13C turnover in manatee epidermis was 55 days and mean half-life for 15N turnover was 42 days. Due to these slow turnover rates, carbon and nitrogen stable isotope analysis in manatee epidermis is useful in summarizing average dietary intake over a long period of time rather than assessing recent diet. In addition to turnover rate, a diet-tissue discrimination value of 2.8‰ for 13C was calculated for long-term captive manatees on a lettuce diet. Turnover and diet-tissue discrimination results were subsequently used to interpret carbon and nitrogen stable isotope data in epidermis samples collected from free-ranging manatees in Florida, Belize, and Puerto Rico. This study was the first application of stable isotope analysis to Antillean manatees. Regional differences in stable isotope ratios in manatee skin were consistent with ratios in plant samples collected in those regions. Signatures in the skin of manatees sampled in Belize and Puerto Rico indicated a diet composed mainly of seagrasses, whereas those of Florida manatees exhibited greater variation. Mixing model results indicated manatees sampled from Crystal River and Homosassa Springs had an overall average intake of primarily freshwater vegetation whereas manatees sampled from Big Bend Power Plant, Ten Thousand Islands, and Warm Mineral Springs fed primarily on seagrasses. Possible diet tissue discrimination values for 15N ranged from 1.0 to 1.5‰. Stable isotope analysis can be successfully applied to interpret manatee feeding behavior over a long period of time, specifically the use of freshwater vegetation vs. seagrasses, and can aid in improving conservation efforts.

The feeding behavior of an animal is based on adaptations to the environment and the animal’s body condition. The Florida manatee (Trichechus manatus latirostris) is an example of a marine mammal that may alter its feeding pattern based on diel and tidal cycles. The increased presence of boats during the day could potentially cause manatees to alter their feeding rates, or the time spent feeding per hour, over the diel cycle. Tide levels may cause manatees to be restricted from areas of preferred vegetation. In addition, the differential reproductive investment between males and females may cause differential time dedicated to feeding between the sexes. This study analyzed sound recordings (lasting up to 24 hr) from manatees tagged in southwest Florida with a digital acoustic recording tag (DTAG) between April and September. Distinctive chewing sounds were indicative of feeding activity. Variation in time spent feeding was analyzed in relation to time of day, sex, female reproductive status, and water level as affected by tides. Manatees dedicated 26% of the time (6 hours) to feeding, on average. During the first year of the study, manatees spent 39% of the time feeding (9 hours), on average, over the course of a 24-hour period; during the second year they spent 15% (2 hours) over the course of a 13-hour daytime period. Adult females fed significantly more, on average, than adult males. Females in late-term pregnancy appeared to spend more time foraging than other non-lactating females, but the sample size was too small to be definitive. Manatee time spent feeding was not correlated with time of day. Increases in feeding activity occurred at mid to high tide levels. This may indicate that manatees had greater access to preferred food sources at this time. An understanding of when manatees 5 are most likely to be feeding and which environmental factors influence this activity may suggest ways to reduce impacts on the endangered population.

The Florida manatee (Trichechus manatus latirostris) is an endangered species that migrates to warm water refuges such as natural springs or power plant effluents during the winter months to escape cold water. The Florida Power and Light (FPL) discharge canal in Port Everglades, Ft. Lauderdale, FL., is utilized as a refuge by overwintering manatees. Construction of a new bridge over the FPL effluent canal had a potential effect on manatee usage of the canal. Discharge is often 10-15° C warmer in the winter season than the surrounding waters of the Intracoastal Waterway. Previous data, including age class and cow/calf abundance from pre-bridge winters (2004-2009), were compared with data from winter 2010, during bridge construction and winter 2011, postbridge construction. No manatees were present at the survey sites during winter until surface water temperatures fell below 22° C. Although monthly mean surface water temperatures were not statistically different between 2008-2009, 2009-2010, and 2010-2011 (21.9±0.4° C, 21.8±1.8° C and 21.4±0.6° C respectively), manatee abundance did vary. 2008-2009 had higher monthly mean numbers of manatees per survey from December through March (29.7, 27.3, 48.1, 2 respectively) than 2009-2010 (0, 30, 10.7, 5 respectively) and 2010-2011 (18.7, 6.7, 0.1, 0 respectively). A Poisson distribution analysis showed a significant difference in adult manatee counts among the study years (α < 0.05). No significant differences were found for juveniles and calves. While I cannot decisively state that bridge construction reduced the number of overwintering adult manatees during 2010, there appears to be the potential for an effect.

The Florida manatee (Trichechus manatus latirostris) is a protected species that is vulnerable to both anthropogenic and natural causes of mortality. The ability of wildlife managers to oversee regulation of this species is based on available abundance estimates and mortality data. Using existing manatee mortality data collected by Florida Fish and Wildlife Conservation Commission (FWC) from 1974-2012, this study focuses on identifying significant spatial clusters of high values or “hotspots” of manatee mortality and the temporal patterns of these hotspots using the novel “emerging hotspot analysis” ArcGIS tool. The categories of manatee mortality included in this analysis were watercraft-related, perinatal, cold-stress, and other natural (which includes red tide) and were classified into five hotspot pattern categories. Of interest were the locations where consecutive or new hotspot patterns were identified among the four categories of manatee mortality included in this analysis. Consecutive hotspot clusters were found near Tampa Bay (which includes parts of Pinellas, Hillsborough, and Manatee Counties) and in the counties of Hernando/Pasco, Monroe, Palm Beach/Broward/Miami-Dade, St. Johns/Flagler, and Citrus. New hotspot clusters were found in Tampa Bay (which includes parts of Pinellas, Hillsborough, and Manatee Counties) and in the counties of Nassau, Wakulla, Charlotte/Lee, St. Lucie/Martin, Levy, Duval, Dixie, Volusia/Seminole, and Citrus. These mortality hotspots frequently overlapped areas of higher manatee and human population densities. These hotspot clusters indicate emerging patterns that highlight areas to focus future research by wildlife managers; specifically, on the relationship between human population density and concentration of watercraft activities in coastal areas, as well as the influence coastal development has on the vital resources utilized by manatees.

The threatened Florida manatee (Trichechus manatus latirostris) migrates seasonally to warm-water refugia throughout the state of Florida due to metabolic requirements from low thermal conductance. Broward County’s two power plant refugia, Port Everglades (PEP) and Lauderdale (LPP), are known heavily-utilized aggregation sites for the Atlantic sub-population. Broward County collected relative abundance counts via aerial surveys from 2004–2013 siting 31,418 manatees during 169 surveys within 18 defined waterway zones. Counts during manatee wintering seasons were significantly different from January 2005-March 2008 and November 2008-March 2013, likely related to flight path and frequency standardization. Mean percentage of adults (90.12%) to calves (9.88%) demonstrates a higher usage by cow-calf pairs than other aggregation sites. Counts of manatees traveling south to Miami-Dade County comprised only 0.83% of all aerial counts, contrary to the theory of the extensive usage of Biscayne Bay foraging grounds. The LPP zone had 57.21% of all manatees with Port Everglades Inlet zone accounting for 23.88% and the South Fork New River zone with 5.95%. This study provided a baseline for pre-construction distributions prior to Port Everglades plant reenergization. With PEP construction now finished and LPP planned for reenergization in the next 10 years, monitoring data studies be compared to these baseline data to better assess the impact of the disruption of Broward County’s main refugia sources.

The seasonal distribution of the Florida manatee (Trichechus manatus latirostris) is influenced predominantly by feeding locations in the summer and proximity to warm-water refuges during colder months. Due to their limited ability to tolerate cold water, when water temperatures drop below 20°C manatees congregate around natural and artificial warm-water refuges, such as warm-water springs or power plant outfalls. Distribution may further be influenced by the tidal cycle through its impact on manatee movement and foraging. Although the importance of tide on manatee distribution and habitat selection has been acknowledged, it has yet to be studied quantitatively in respect to the manatee population in southeast Florida. The purpose of this study was to examine the effect of the tidal cycle on manatee occurrence at the Florida Power & Light (FPL) Port Everglades Power Plant. Walking surveys were conducted in Port Everglades during manatee season, November 15 – March 31, between 2004 and 2008. During the surveys, the number of manatees in four established locations was noted and the animals categorized based on size as either calf, juvenile, or adult. Water temperature data were also collected at four permanent sample locations. Because many surveys yielded zero manatees observed, data were analyzed using the zero-inflated negative binomial model. Although the manatees at the Port Everglades Power Plant must forage away from the warm-water refuge, my findings show no correlation between tidal state and total manatee occurrence at the FPL Port Everglades Power Plant. The results do, however, suggest that the probability of observing a cow/calf pair is greater during high tide when compared to low and mid-tides (P < 0.05). Total manatee occurrence and the presence of cow/calf pairs were both significantly correlated with water temperature (P < 0.05).

The largest Florida manatee (Trichechus manatus latirostris) aggregation at a natural warm-water refuge occurs in Kings Bay, Crystal River, FL. Over the last 32 years, the U.S. Fish and Wildlife Service and the State of Florida have created a network of manatee protection areas within Kings Bay including a year-round refuge designation and seven Federal manatee sanctuaries during the winter manatee season (November 15 – March 31). Aerial survey data collected between 1983 and 2012 was used to examine the seasonal change in manatee distribution within Kings Bay in order to assess the effectiveness of current sanctuary sizes and locations. Regression analysis indicated a significant change in manatee abundance among the winter seasons (p < 0.05). The average winter manatee counts increased by 4.81 animals per year over the 30 year period. In contrast, no significant changes in average or peak manatee abundance was detected among the summer seasons (p = 0.71 and p = 0.45 respectively). The average manatee counts increased by only 0.109 animals per year over the summer periods. Spatially explicit models using Geographic Information System (GIS) analysis revealed a strong correlation between high manatee density and artesian springs during the winter seasons. Highest abundances were identified at three locations: King’s Spring, Three Sisters Springs, and Magnolia Springs. These three locations coincide well with pre-existing sanctuary designations, but additional coverage is needed to support the overflow of manatees outside of sanctuary boundaries. Manatees continued to use Kings Bay in the summer seasons but in lower numbers and densities. Because density patterns were not uniform across summer periods, a heavier reliance on boat speed regulation is recommended to provide adequate protection to the endangered Florida manatee. Within a habitat type, the Magnolia Springs, South Banana Island, and Three Sisters Springs sanctuaries exhibited a significant influence on manatee density, suggesting differences in quality among sanctuaries. Years coinciding with extreme cold weather events also had a significant influence on manatee density. Using GIS to investigate seasonal shifts in manatees can be very informative regarding many issues including habitat selection and may improve the design and management of protected areas.