Manatees are large, fully aquatic mammals that inhabit warm coastal waters and rivers worldwide. These gentle creatures, often called “sea cows” due to their slow, grazing nature, are strict herbivores. They belong to the order Sirenia, a group of aquatic mammals consisting entirely of plant-eaters. This exclusively vegetarian diet dictates their behavior and anatomy.
The Dedicated Herbivorous Diet
Manatees consume a wide variety of aquatic vegetation, encompassing over 60 different species of plants. Their primary food source in marine environments is seagrass, which they graze from the seabed. In freshwater habitats, they feed on plants like water hyacinth, water lettuce, and hydrilla. They also consume mangrove leaves and various forms of algae, adapting to the specific local environment.
The plants manatees eat are low in caloric density and nutritional value, requiring them to spend a significant portion of their day actively foraging. While their diet is strictly plant-based, they may accidentally ingest small invertebrates or fish. This accidental consumption does not change their classification, as their anatomy is dedicated to processing plant matter.
Biological Adaptations for Plant Consumption
The manatee’s body has developed unique features to support its high-fiber, herbivorous diet. One distinctive adaptation is its specialized dentition, featuring only molars used for grinding tough plant material. These cheek teeth are not fixed; instead, manatees possess “marching molars” or hind molar progression. New molars continuously erupt at the back of the jaw and slowly move forward, replacing older, worn-down teeth.
The abrasive nature of their diet, which often includes grit and sand, causes the anterior molars to wear down quickly. As the older teeth reach the front, their roots are resorbed, and they eventually fall out, much like a conveyor belt. This continuous replacement ensures the manatee always has a fresh, effective grinding surface to process the difficult-to-digest cellulose in aquatic plants.
Manatees also possess a digestive system optimized for breaking down large quantities of fibrous plant matter. They are classified as hindgut fermenters, much like horses and elephants, using a large, simple stomach and an exceptionally long intestinal tract. Their intestines can stretch up to 45 meters, which is long for an animal of their size.
This immense digestive capacity includes a capacious large intestine and cecum where symbiotic microbes ferment the cellulose. The prolonged process of digestion, which can take between four and ten days, allows for the efficient extraction of nutrients from their low-quality food source.
The Behavior and Volume of Daily Foraging
The sheer volume of vegetation manatees must consume daily dictates their foraging behavior. They utilize large, highly flexible prehensile lips to grasp and tear off pieces of plants. The upper lip is split, allowing the two sides to move independently, functioning almost like clippers to manipulate food. Manatees also use their flippers to help gather vegetation and scoop it toward their mouth.
To sustain their large body size and low metabolic rate, manatees must consume a significant amount of food daily. They typically eat between 10% and 15% of their body weight in wet vegetation. For a large adult, this translates to well over 100 pounds of plants consumed in a 24-hour period. This constant need means manatees spend between six and eight hours a day actively grazing, a cycle necessary due to the low caloric density of their food.