The feral cat population has exploded in Hawaii, where they are not native and face no natural predators—and this could spell disaster for the endangered monk seal. That's because cat poop often contains a parasite called Toxoplasmosa gondii, and when sewage and polluted runoff carry the infected feces to the ocean, it can prove lethal, reports Scientific American. The National Oceanic and Atmospheric Administration estimates that eight Hawaiian monk seals have succumbed to the disease since 2001, which is a sizable number given that 1,100 are estimated to be alive today in the wild. The same bacteria have also killed California sea otters and helped send the Hawaiian crow into extinction, reports the Christian Science Monitor.
But while conservationists call for the "humane euthanization" of some feral cats, animal welfare advocates oppose a "hierarchy in which the protection of certain animals comes at the suffering of others," as the president of the Hawaiian Human Society puts it. Monk seals are considered the most endangered pinniped in the country, and their numbers are expected to dip below 1,000 soon, with starvation among the young the largest known problem. Meanwhile, Hawaii's Division of Forestry and Wildlife estimates that 300,000 feral cats live on Oahu and as many as 400,000 on Maui, which is roughly two cats per human resident. NOAA is working with California’s Marine Mammal Center on a monk seal hospital in Kona to try to care for the sick ones before they die. (Humans have hunted Caribbean monk seals to extinction.)