Sea otters are highly resilient animals and restoration work has recovered U.S. populations in some regions. However, populations are reestablished in a small fraction of their former range, and modern threats pose new challenges.
Sea otters have no blubber unlike other marine mammals such as whales, dolphins, and seals, and thus depend on their dense fur for insulation against the cold ocean water. Their fur, combined with their high metabolism, helps them maintain their internal temperatures; so they must keep their fur dry and full of air at all times by grooming after each dive for food. Oil spills can compromise this insulation and cause hypothermia and can poison the animals as they ingest oil during grooming.
As residents of the nearshore and estuary environments, sea otters are especiall vulnerable to polluntants. Along the California coast, animals are subjected to a wide range of water-borne pollutants including agricultural and lawn care chemicals contained in river runoff, sewage from coastal communities, pathogens, bacteria and viruses from pets, and harmful algal blooms.
Changes in ocean conditions resulting from climate change pose new threats to sea otters. Warming ocean waters accompanied by increasing acidification can affect the growth and spread of kelp forests, urchins and other shellfish that are food for sea otters. These changing conditions can also promote the growth and spread of toxic algae that cause paralytic shellfish poisoning.
Sea otters are also vulnerable to shark attacks, especially when kelp is absent and sea otters are unable to take cover. Judging by the number of shark-bitten sea otter carcasses found on California beaches, sharks do not appear to target sea otters for food but instead seem to bite, and thus fatally wound sea otters as a possible case of mistaken identity while hunting for seals and sea lions.
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