Manatees are large, gentle aquatic mammals inhabiting coastal waters, rivers, and springs worldwide. Often called “sea cows,” these herbivores feed exclusively on plants in their aquatic environments, making them unique grazers.
Main Dietary Components
Manatees consume a wide variety of aquatic vegetation, with over 60 plant species in their diet. The specific plants vary by habitat. In marine environments, they primarily graze on seagrasses like turtle grass, manatee grass, shoal grass, and widgeon grass. They also consume marine algae and, when accessible, mangrove leaves.
When in freshwater, their diet shifts to plants like hydrilla, water hyacinth, water lettuce, eelgrass, and pickerelweed. Occasionally, they may also eat terrestrial grasses or fallen acorns. Because these plants offer low nutritional value, manatees must eat a substantial amount daily, typically 10% to 15% of their body weight. A 1,000-pound manatee can consume 100 to 150 pounds of vegetation daily.
Feeding Mechanisms
Manatees possess specialized adaptations to efficiently gather and process fibrous plant material. Their most distinctive feature is a large, prehensile upper lip, split and moving independently. This muscular lip acts like pincers, grasping and pulling vegetation towards their mouth. Stiff bristles (vibrissae) on their lips further aid in manipulating food.
Their front flippers also help guide plants to their mouths, pull up submerged vegetation, or anchor them while grazing. Manatees do not have front teeth; instead, they use horny, ridged pads on the roof of their mouth and lower jaw to tear and break down plant material. Behind these pads, they have continuously growing molars, known as “marching molars.” These flat, rough-textured teeth move forward from the back of the jaw as older teeth wear down from their abrasive, often sandy, diet, eventually falling out and being replaced by new ones.
Why Their Diet Matters
The grazing habits of manatees are significant for the health and balance of aquatic ecosystems. By consuming large amounts of vegetation, they act as “aquatic gardeners,” preventing overgrowth and maintaining the structure of seagrass beds. This grazing promotes biodiversity and can stimulate new growth in seagrasses. Manatees also help control invasive plant species, such as hydrilla and water hyacinth, contributing to healthier waterways.
Despite their ecological benefits, manatees and their food sources face threats. Habitat loss, pollution, and the scarring of seagrass beds by boat propellers directly impact food availability. Nutrient pollution from agricultural runoff and sewage can lead to harmful algal blooms, which block sunlight and cause seagrass die-offs. This reduction in their primary food source has led to starvation and increased mortality rates in manatee populations, highlighting the interconnectedness of their diet with broader environmental health and conservation efforts.