Marine mammals include pinnipeds (seals, sea lions), cetaceans (dolphins and whales), and sea otters. Because these organisms have fairly advanced cognitive abilities, it is fairly difficult to gauge how offshore renewable energy devices will affect marine mammals. Some of these organisms use echolocation to communicate and navigate themselves through the marine environment, which poses a concern as noise emitted from offshore renewable energy devices can have the potential to mask or hide echolocation of marine mammals. Some marine mammals also have very sensitive hearing, which makes these organisms vulnerable to loud noises generated underwater (i.e. pile driving/construction). With these issues in mind, the stressors that pose the greatest risks to marine mammals are collision, habitat change, and displacement, as well as noise.