Sea otter health: Challenging a pet hypothesis

• Do human impacts to the ocean impair sea otter health?
• Spillover of parasites from wildlife explains patterns of parasitism in sea otters.
• Domestic cats play a smaller role in transmission than previously thought.

A recent series of studies on tagged sea otters (Enhydra lutris nereis) challenges the hypothesis that sea otters are sentinels of a dirty ocean, in particular, that pet cats are the main source of exposure to Toxoplasma gondii in central California. Counter to expectations, sea otters from unpopulated stretches of coastline are less healthy and more exposed to parasites than city-associated otters. Ironically, now it seems that spillover from wildlife, not pets, dominates spatial patterns of disease transmission.