Researchers Focus on Sea Otter Deaths

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Author: A.J.S. RAYL
Date: Feb. 19, 2001
From: The Scientist(Vol. 15, Issue 4)
Publisher: Scientist Inc.
Document Type: Article
Length: 2,625 words

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Could sewage, cat litter, and other terrestrial animal waste be killing some marine animals?

Something is killing sea otters that live along the northern California shoreline of the Pacific Ocean. Nearly 1,000 have been found dead along the coastline over the past five years. Given that the total otter population at any one time is probably well below 3,000 animals, this appears to be a high rate of mortality, especially considering that as many as half of the otters that die are probably never recovered. Veterinary pathologists, in their ongoing research, are finding that some of these marine mammals are dying from parasitic diseases for which the only known egg-shedding or definitive hosts are terrestrial mammals. They cannot yet say with absolute certainty, but they suspect the parasites may be coming through sewage or terrestrial animal waste streaming into their habitats, and perhaps from their prey as well.

"Here on the Pacific Coast, this seems to be a pretty new phenomenon," says David A. Jessup, senior wildlife veterinarian for the California Department of Fish and Game (CDFG) and supervisor of the Marine Wildlife Veterinary Care and Research Center in Santa Cruz. This may be the first land-sea transference of diseases that is proving to be a serious problem in a threatened species.

Sea otters (Enhydra lutris) are more than just furry marine mammals that frolic along the shores of the North Pacific. They are considered by many people, says Jessup, to be "an almost ideal" sentinel species. "The otter is probably the one that's going to be signaling the most to us about problems that we may be the cause of in the environment," explains veterinarian Melissa A. Miller, who works with Jessup as a wildlife pathologist. "As a near-shore species with a high metabolic rate, they consume a lot of prey species, and they're right there where wastewater is coming out both rivers and streams and sewage outfalls. So when we start seeing problems in sea otters that are things you would not expect to see in a healthy marine animal population, it's a serious wake-up call for us."

Patricia A. Conrad, professor of parasitology at the University of California, Davis, who is contributing her expertise to the otter problem, agrees: "It's not true that what you don't know won't hurt you. Sea otters are the bioindicators who [appear now] to be giving us the first indication that something may be going wrong here."


Currently, researchers suspect at least two different parasites are involved in the infections that are killing the otters. "One is Toxoplasma gondii. If the parasite that we're isolating out of these sea otters and harbor seals[1] is the same as that from terrestrial animals and humans, then the only recognized definitive host for that parasite today is felids, basically any type of cat--bobcats, cougars, domestic and feral cats," says Miller. The other isolated parasite and cause of disease and death in these marine animals is Sarcocystis neurona.[2] "This protozoal parasite was...

Source Citation

Source Citation
RAYL, A.J.S. "Researchers Focus on Sea Otter Deaths." The Scientist, vol. 15, no. 4, 19 Feb. 2001, p. 17. Accessed 4 Dec. 2021.

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