Group Size 



Mean group size for the pooled sample of all sightings was 1.9 (SE ± 0.12). A two- 

 way ANOVA of group size by month and county would have included missing cells (i.e., 

 specific combinations of month and county for which no data were available). 

 Consequently, a subset of data, including only those counties with sightings in each 

 month (Monroe, Lee, and Sarasota Counties), was analyzed as a two-way ANOVA. This 

 analysis provided no evidence of a month by county interaction (P > 0.85), indicating that 

 any pattern of monthly variation in group size was comparable for those three counties. 

 Monthly variation in average group size, analyzed as a separate one-way ANOVA for 

 each county, was significant (P <0.05) only in Hillsborough County, due to high December 

 counts at warm-water effluents. 



Ninety-four percent of the groups sighted consisted of one to four animals (Figure 

 2). Group sizes were not observed with equal frequency, and more than half of the 297 

 sightings were of single animals (P < 0.005; chi-square). However, 367 (66.2%) of the 554 

 manatees sighted were in groups. Pooled samples of all counties indicated that group- 

 size frequency distributions did not vary significantly between months (P >0.80; chi- 

 square). 



Manatees are usually sighted in small groups when away from warm-water 

 refuges. Eighty-six percent of the sightings during aerial surveys by Odell (1979) and 89% 

 of the sightings by Hartman (1979) were of one to four manatees. Our results and those 

 from other surveys (Hartman 1979, Odell 1979, Reynolds In press) indicate that the. 

 greater percentage of manatees sighted are found in groups, but one is the most common 

 group size. Although Hartman (1979) suggests that manatees are "essentially solitary", 

 solitary manatees are nevertheless a minority of the total numbers sighted. 



Habitat Use 



Substantially more manatees were sighted in marsh-river habitats than in other 

 habitat types, and most were in brackish water (Table 3). Numbers of manatees sighted 

 were not proportional to the amount of survey time in each habitat type or salinity 

 (P < 0.005; chi-square). Pooled samples from all counties indicated that relative numbers 

 of manatees sighted per month varied significantly by salinity and habitat (P < 0.0005; 

 chi-square). 



The preponderance of manatee sightings in brackish water and marsh-river 

 habitats occurred in the Collier and Monroe Counties areas, which are characterized by 

 that combination of habitat and salinity. Inland bays in ENP and the Ten Thousand 

 Islands area of Collier County were classified as "marsh-river" habitat because access to 

 the Gulf of Mexico is restricted by relatively narrow or shallow channels. 



Although these survey results may be general indicators of habitat use, they 

 should be viewed with some caution. All habitat types were not surveyed equally, and 

 local salinities may have varied seasonally due to runoff from rainfall. Irvine and 

 Campbell (1978) reported the relative frequencies of manatee sightings in fresh, brackish, 

 and salt water as 19.1%, 42.5%, and 38.3%, respectively, during winter surveys, and 

 35.2%, 34.9%, and 29.6% during a summer survey of the entire State. In contrast, 80% of 

 the manatees sighted in our surveys were in brackish water (Table 3). 



11 



