Sea otters are charismatic marine mammals with a significant role in coastal ecosystems. Known for their dense fur and tool-using abilities, they help maintain kelp forest balance by consuming sea urchins. As part of a complex food web, sea otters can become prey for other animals.
Apex Ocean Hunters
Adult sea otters face threats from large marine predators like killer whales (Orcinus orca) and great white sharks (Carcharodon carcharias). Killer whales have been observed preying on sea otters, particularly in western Alaska. This behavioral shift is linked to declines in their usual prey, such as seals and sea lions, leading to increased targeting of otters and significant population impacts.
Great white sharks are another documented predator, especially in California waters. Sea otters are not a primary food source for these sharks, which prefer fattier prey like seals and sea lions for their higher caloric value. Encounters often involve “investigatory bites” where sharks may mistake otters for other prey. Though not always intended for consumption, these bites can still be fatal, contributing to mortality rates.
Targeting Young Otters
Sea otter pups are vulnerable to predation due to smaller size and inexperience. Bald eagles (Haliaeetus leucocephalus) are known predators of young sea otters, especially when separated from mothers or left unattended during adult foraging. Eagles can snatch pups weighing several pounds, and nests have been found containing remains of multiple sea otter pups.
Other opportunistic predators, like coyotes and bears, may also target vulnerable pups if they venture too close to shore. Their lack of experience and physical strength makes young otters easier targets compared to adults. Pups are most susceptible when very young, especially when mothers dive for food and leave them floating on the surface.
Factors Limiting Predation Events
Despite the presence of predators, predation events on sea otters are uncommon due to several behavioral and environmental factors. Sea otters possess natural defenses, including agility and the ability to quickly dive underwater or seek refuge. They frequently utilize dense kelp forests, which offer protective cover and a three-dimensional habitat for hiding from threats.
Their dense fur, while insulating, also makes them buoyant and difficult for predators to grasp effectively. Sea otters often engage in social grouping, forming rafts that enhance vigilance and detection of approaching dangers. For many larger predators like great white sharks, sea otters are not an energetically efficient food source due to their lean body mass and thick fur, which lacks the high fat content preferred by these predators. This often results in non-consumptive or investigatory bites rather than full predation.