The Amy H Remley Foundation  

Manatee and Man

Young Manatee at Black Spring

Sixty years life in the wild is possible for Florida's manatees. Although natural causes such as cold stress, gastrointestinal disease, pneumonia, and other diseases can reduce a manatee's natural life span. We humans can also, albeit sometimes unwittingly, shorten the lives of manatees.

The law prohibits harassment of manatees for good reasons:

Manatee surfaces to breathe
  1. Manatees must breathe at the surface frequently. Should we prevent that by undue attention we induce stress in them. We would not like to be held under water, neither should we do so to manatees.
  2. Manatees devote a long time to feeding and resting each day. Sanctuaries provide safe habitats for wild manatees so that the animals are not disturbed when feeding, resting or nursing young. Consider how you would feel if you were disturbed over a meal or woken up from a much needed nap. Learn how to watch wildlife from a distance so that your presence does not disturb them or change their behavior.
  3. In colder weather manatees need to seek out warm water springs or outfalls for warmth. The last thing we should do is to cause them to leave from a warm water area into colder waters.
  4. How we navigate our watercraft near manatees matters. Watch out continually for manatees swimming – they leave tell tale wave ring disturbances on the surface from their fluke movements. Collisions with watercraft cause most human-related manatee deaths. either through blunt impact, propeller cuts or a combination of both causes. Watercraft operators can help reduce the risk of injuring or killing a manatee by staying within marked channels, obeying posted speed zones, wearing polarized sunglasses, and traveling cautiously in shallow waterways.
  5. Careless navigation destroys seagrass meadows by propeller scarring.
Manatee "footprints" moving away from boat.   Two manatees under a boat propeller   Propeller scarring of seagrass
Manatee Manatee Manatee
Click here for sound Click here for sound  

Actions we take from further afield can also harm manatees:

  1. Red Tide events cause a toxic vapor to ride upon the surface of the Gulf waters. Manatees surfacing to breathe put their nostrils into the vapor and take in toxins sufficient to damage their lungs and cause death. High levels of phosphorous in Gulf waters stimulate the occurrence of Red Tide events. Dumping toxic sludge from the mining of limerock and phosphates into Gulf waters increases the phosphorous concentrations. The spores of the dinoflagellate algae Karenia brevis inhabit the gulf waters naturally. The elevation of ambient water temperatures by sunshine coincident with the presence of sufficient nutrients causes the explosive propagation of the algae and the Red Tide is the result.

  2. Scarcity of available supplies of fodder induce manatee weight loss, stress, disease and behavioral changes. Contaminated groundwater discharging from springs disturbs the ecological balance in river systems promoting increasing algae and invasive plant concentrations which crowd out submersed aquatic vegetative fodder for the manatees. Contamination of the groundwater results from over application of fertilizers to crop land, golf courses and lawns which permeate down into aquifer waters via karstic terrain.

  3. Moreover, over pumping of ground water inland and drought conditions reduces aquifer head levels allowing saltier water to well up from underneath to issue from the spring vents. This stimulates growth of more vigorous marine species of algae and aquatic plants which compete and crowd out the traditional fodder plants.

  4. Other threats to manatees include destruction and degradation of their coastal and freshwater habitat. Also, human carelessness leads manatees to ingest fish hooks, litter, fishing line and to entanglement in crab trap and discarded fishing lines which are also significant causes of harm and even death to manatees.

  5. Entrapment of manatees in culverts, drains and up against guard rails of power plant water up-take conduits, is an additional significant cause of manatee deaths.
Biologists identify this manatee by old propeller scars   Fresh boat propeller wounds on Manatee's peduncle and tail   Sheepshead fish eats manatee festering flesh from a propeller wound
Manatee Manatee Manatee

The U. S. Geological Survey, Sirenia Project
The manatee sound recordings on these pages are property of the United States Government Fish and Wildlife Service and may not be reproduced or analyzed without permission of the Denver Wildlife Research Center.

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