In 1741 two Russian ships, St. Peter and St. Paul, from Kamchatka, set sail to explore the island of Bolshaya Zemlya in the explorer Vitus Bering’s last expedition. Following a storm, St. Paul stayed on course but St. Peter got lost and landed on an island that is now known as Bering Island. The ship was too badly damaged to sail again. Upon that ship was Georg Steller, a German born naturalist and trained zoologist who had found work with the Academy of Sciences in Saint Petersburg.
The crew began rebuilding the boat and during that year the food supply ran out. To survive, the crew killed sea otters, various species of birds and seals. Georg Steller was one of the few to survive the winter. He discovered and named a number of new animals including the Steller’s jay (Cyanocitta stelleri), the Steller’s eider (Polysticta stelleri), the Steller’s sea eagle (Haliaeetus pelagicus), the Steller’s sea lion (Eumetopias jubatus), and the Steller’s sea cow (Hydrodamalis gigas). It is speculated that there were only approximately 1,500 Steller’s sea cows in 1741. Their numbers had already dwindled due to overgrowth of sea urchins after aboriginals had removed sea otters from the region. Sea otters eat urchins and when they were removed, sea urchin populations increased and consumed more algae, depriving sea cows of food. While the first Steller’s sea cow killed had been mistaken for a seal, the crew decided to eat it anyway and discovered it to be much like beef. With that, the final extinction event for the Stellar’s sea cow had begun. The crew hunted them aggressively and upon arrival to Kamchatka, spread the word about such tasty eating. Twenty-six years later, the last Steller’s sea cow and the largest and only known cold water sirenian was killed.
The order sirenia has two extant families: Dugondidae, which has only one extant species, the dugong (Dugong dugon) and Trichechidae, which has three species of manatees in the Genus Trichechus including the West Indian manatee (Trichechus manatus), the Amazonian manatee (Trichechus inunguis) and The West African manatee (Trichechus senegalensis). The West Indian manatee can be found in the United States and is divided into 2 subspecies: (1) the Florida manatee (T. m. latirostris) and (2) the Antillean or Caribbean manatee (T. m. manatus). Recent genetic research suggests that the West Indian manatee may have 3, instead of 2 subspecies that are geographically distributed as: (1) Florida and the Greater Antilles; (2) Central and Northern South America; and (3) Northeastern South America (Garcia-Rodriguez 1998 Molecular Ecology 7:1137-1149; Vianna et al. in press Molecular Ecology). The research also discovered West Indian-Amazonian manatee hybrids near the mouth of the Amazonian River.
West Indian manatees are gray aquatic mammals that weigh between 800 and 1,200 pounds and average about 10 feet in length. They have front flippers, a flat-paddle shaped tail and an adorably wrinkled and whiskered face. They live in shallow, slow-moving rivers and other bodies of water where seagrass can be found for grazing. Manatees are concentrated in Florida during the winter but migrate to Texas and as far north as Massachusetts in the summer. West Indian manatees can also be found in the coastal and inland waterways of Central America and along the northern coast of South America. They are gentle and slow-moving animals, spending most of their time eating, resting and traveling. Manatees can swim up to 20 miles per hour in short bursts, but they usually only swim about three to five miles per hour. Manatees are not sexually mature until age five, and only one calf is born every two to five years after a one year gestation. Mothers nurse their young for one to two years, during which time a calf remains dependent on its mother. West Indian manatees in the United States are protected under federal law by the Marine Mammal Protection Act of 1972, and the Endangered Species Act of 1973, which make it illegal to harass, hunt, capture, or kill any marine mammal. West Indian manatees are also protected by the Florida Manatee Sanctuary Act of 1978. Though manatees eat seagrass, it is not thought that they consume enough to otherwise prevent algae overgrowth. However, manatees are Florida’s official marine mammal and provide tourism revenue. There is no documented negative environmental economic impact from the presence of manatees.
November is Manatee Awareness Month in the state of Florida, which is my motivation for writing a positive story of the environment as it pertains to manatees. This presents quite a challenge as 772 manatees have died in 2013, which is already more than double the number of manatee deaths for 2012. The majority of these deaths are due to red tide, an overgrowth of toxic algae. This is certainly not positive news given the 2008 assessment by the International Union for Conservation of Nature and Natural Resources for the American/West Indian manatee estimated a population of 10,000 and a decline rate of 10 percent over three generations due to habitat loss and anthropogenic factors (habitat degradation and loss, hunting, accidental fishing-related mortality, pollution and human disturbance).
The positive aspect of this story is that the situation is not hopeless and we are not helpless when it comes to protecting manatees, which have many champions to show us the way. The Save the Manatee Club has a “Take Action!” page listing current issues and methods of helping. Save the Manatee Club handles injured manatee reports and coordinates rescue and rehabilitation as well as provides funds for equipment both in and outside of Florida, including nets, an isolation pool, a manatee care building, tracking gear, and diving equipment. Save the Manatee Club has also donated seven boats and trailers to various agencies and organizations for manatee rescue and research purposes. There is an elaborate rescue and rehabilitation network headed by the Florida Fish and Wildlife Conservation Commission whose biologists work with SeaWorld Orlando, Homosassa Springs Wildlife State Park, Lowry Park Zoo, Miami Seaquarium, and DolphinResearchCenter to capture, transport and/or treat injured manatees. SeaWorld Orlando, Lowry Park Zoo, and Miami Seaquarium are the only facilities authorized for critical care and rehabilitation of injured or sick manatees or orphaned calves.
The manatee story is just one of many examples of how biologists, veterinarians, keepers and aquarists at zoos and aquariums throughout the world are collaborating with governmental organizations, non-governmental organizations and even corporations to conserve and preserve the natural world.