Young are especially susceptible to the effects of cold water. Periodic outbreaks of red tide can cause some manatee deaths. Red tide is a result of a bloom of small microorganisms. Sea squirts, a filter-feeding animal associated with sea grasses, accumulate toxins from the red tide organisms. Manatees accidentally ingest these organisms while feeding on sea grasses.
Biologists count manatees from airplanes.
It is difficult to obtain an exact population figure because poor weather or murky water conditions make it difficult to see manatees clearly. In 1994, aerial surveys counted a minimum of 1,822 manatees. Because the reproductive rate for manatees is so slow, the number of manatees killed by human and natural causes exceeds the number of manatees born. As long ago as 1893, Florida passed a law to protect manatees. Manatees are also protected at the federal level under the Marine Mammal Protection Act of 1972 and the Endangered Species Act of 1973, which makes it illegal to hunt, capture, harm or harass these marine mammals.