Sea otters, marine mammals, are known for their dense fur. They inhabit the coastal waters of the North Pacific Ocean. These aquatic creatures primarily consume marine invertebrates. Sea otters are known to eat sea urchins.
An Ecological Keystone
Sea otters play an important role in marine ecosystems, particularly in kelp forests, where they function as a keystone species. A keystone species is an organism that has a disproportionately large impact on its environment relative to its abundance. Sea otters exert this influence by preying on sea urchins, which are voracious grazers of kelp. Without sea otters to control their populations, sea urchins can multiply rapidly and consume entire kelp forests.
Overgrazing by sea urchins leads to “urchin barrens.” These are areas of the seafloor where kelp has been decimated. Urchin barrens lack the biodiversity and structural complexity of healthy kelp forests. Sea otters prevent or reverse their formation by keeping sea urchin populations in check, allowing kelp forests to flourish.
The presence of sea otters helps maintain healthy kelp forests. These forests provide shelter and food for a diverse array of marine species, including fish and invertebrates. Kelp forests also absorb carbon dioxide, contributing to carbon sequestration and mitigating climate change. Kelp forests protected by sea otters can sequester significantly more carbon, demonstrating their role in coastal marine health.
A Varied Diet
While sea urchins are a component of their diet, sea otters consume a wide variety of other marine invertebrates. Their food choices vary based on geographic location, prey availability, and individual preferences. Sea otters primarily feed on slow-moving invertebrates found on the seafloor.
Other common prey items include crabs, clams, mussels, abalone, snails, sand dollars, and occasionally slow-moving fish. Sea otters often use rocks as tools to crack open the hard shells of their prey. This unique foraging behavior allows them to access the nutritious meat inside shelled organisms.
Sea otters have a high metabolic rate, requiring them to consume 25% to 30% of their body weight in food daily. This high energy demand drives their foraging habits and influences their impact on the marine ecosystem. Individual sea otters can specialize in certain prey items. For example, northern sea otters eat fish, while southern sea otters primarily focus on invertebrates. When preferred prey become scarce, otters expand their diet to include a wider range of available food sources.