Our IJviiii; Rtwimncs— Cixistiil & Murine Ecosyslcms 



267 



StevciiMin. .I.e.. and N.M. Confer. 1478. Siunniary ol avail- 

 able information on Chesapeake Bay submerged vegeta- 

 tion. U.S. Fish and Wildlife Service Biological Rep. 

 FWS/OBS-78/66. 335 pp. 



Tiner, R.W.. and J.T. Finn. 1986. Status and recent trends of 

 wetlands in tfve mid-Atlantic states; Delaware, 



Maryland. Pennsylvania. Virginia, and West Virginia. 

 U.S. Fish and Wildlife Service, Region 5, Newton 

 Comer, MA, and U.S. Environmental Protection Agency, 

 Region 3, Philadelphia. PA. Cooperative Tech. Publ. 411 

 pp. 



For further information: 



Edward Pendleton 



National Biological .Service 



Leetown Science Center 



nOOLeetown Rd. 

 Keameysville, WV 25431) 



The endangered Florida manatee {Triclwcluis 

 mauatus lalimstris) is a survivor. It is one of 

 only tiiree living species of manatees which, 

 along with their closest living relative, the 

 dugong (Diiiioiii^ chii^(in). make up the Order 

 Sirenia. This taxonomic distinctiveness reflects 

 their evolutionary and genetic uniqueness. 

 Sirenians are the only herbivorous marine mam- 

 mals; manatees feed on seagrasses; freshwater 

 plants, including nuisance species such as 

 hydrilla and water hyacinth; and even some 

 shoreline vegetation. Because manatees depend 

 on marine, estuarine. and freshwater ecosys- 

 tems, our efforts to protect them necessitate pro- 

 tection of aquatic resources. 



Life-history Research 



Major efforts have concentrated on better 

 quantification of Florida manatee populations, 

 emphasizing reproduction, population size, and 

 mortality. Most of the information on manatee 



Table. Estimated population traits of the Florida manatee 

 based on long-term life-history research (data are from the 

 National Biological Service and the Florida Department of 

 Environmental Protection). 



Proportion nursing Ist-year calves 

 during winter season 



Blue Spnng 



Crystal River 



Atlantic coast 

 Calf dependency 

 Inlerbirth interval 

 Highest number of births 

 Highest frequency in mating herds 

 No. salvaged carcasses 

 No, documented in ID catalog 

 Highest count (aerial sun/eys) 



36% (mean) 



30% 



36% 



38% 



1 .2 years 



2 5 years 



l^ay-September 



February-July 



2,219 (1974-93) 



>950(1975-February 1994) 



1 ,856 m January 1992 



reproduction (Table) comes from long-term 

 studies based on recognizable individuals at 

 winter aggregation sites (e,g,. Rathbun et al, in 

 press), Florida manatees are at the northern 

 limit of the species' range and must seek 

 warmer waters when water temperatures drop 

 below about 20 °C, Natural springs, such as 

 those found in Crystal River on the west coast 

 and Blue Spring on the St. Johns River, and dis- 

 charges from industrial plants provide warmwa- 

 ter refuges for hundreds of manatees during 

 cold periods. 



Individual manatees are recognized al these 

 sites largely through their unique scar patterns, 

 caused by boat strikes (Figs, la and lb). 

 National Biological Service personnel have cat- 

 aloged almost 1,000 recognizable manatees and 

 maintained their sighting histories in a comput- 

 er-based system (Beck and Reid in press). 



Florida 

 Manatees 



by 



Lynn W. Lefebvre 



Thomas J. O'Shea 



National Biological Service 



Fig. la. Female manatee and calf. 

 Individuals can be identified by 

 their unique scar patterns; scars 

 are usually the result of collisions 

 with boats. 



Fig. lb. A manatee often bears 

 scars from multiple boat colli- 

 sions. 



