Sea otters, opossums and the surprising ways pathogens move from land to sea

19th March 2020

by Kat Kerlin, UC Davis

A parasite known only to be hosted in North America by the Virginia opossum is infecting sea otters along the West Coast. A study from the University of California, Davis, elucidates the sometimes surprising and complex pathways infectious pathogens can move from land to sea to sea otter.

For the study, published in the journal Scientific Reports, researchers tested sea otters ranging from Southern California to Alaska for the presence of Sarcocystis neurona, a parasite and important cause of death in sea otters.

They were surprised to find several infected sea otters in the northern part of Vancouver Island in British Columbia, where Virginia opossums—also known as the North American opossum—are not known to live. They wondered: Could this parasite travel very long distances in water, or is there an additional unknown host for this pathogen?

To answer this question, the scientists examined spatial patterns and previous research into pathogen transmission, diet and movement of otters. Their results suggest the pathogen may be carried by water runoff from land to sea, where it can be concentrated through ocean movement and prey species, such as clams.

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What's killing sea otters? Parasite strain from cats

Genetic link found between deadly pathogen and wild and feral cats on land

Date: August 22, 2019

Source: University of California - Davis

Many wild southern sea otters in California are infected with the parasite Toxoplasma gondii, yet the infection is fatal for only a fraction of sea otters, which has long puzzled the scientific community. A new study identifies the parasite's specific strains that are killing southern sea otters, tracing them back to a bobcat and feral domestic cats from nearby watersheds.

The study, published this week in the journal Proceedings of the Royal Society B, marks the first time a genetic link has been clearly established between the Toxoplasma strains in felid hosts and parasites causing fatal disease in marine wildlife.

The study builds on years of work by a consortium of researchers led by the UC Davis School of Veterinary Medicine's Karen C. Drayer Wildlife Health Center and the California Department of Fish and Wildlife (CDFW). The scientists were called upon in the late 1990s to help decipher the mystery when Toxoplasma caused deaths in sea otters along the California coast.

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Sea otters have low genetic diversity like other threatened species, biologists report

Date:  June 18, 2019

Source:  University of California - Los Angeles

Sea otters have low genetic diversity, which could endanger their health as a species, a UCLA-led team of life scientists has discovered. The findings have implications for the conservation of rare and endangered species, in which low genetic diversity could increase the odds of extinction.

Genetic diversity is a measure of how many differences exist across the genome among individuals in a population. Large populations tend to have high genetic diversity (many differences among individuals), while small populations lose much of this diversity, resulting in individuals that are more genetically similar to one another.

The sea otter's low level of genetic diversity is similar to endangered species, such as the cheetah and Tasmanian devil, said lead author Annabel Beichman, a UCLA graduate student in ecology and evolutionary biology. She and her colleagues reconstructed the otter's evolutionary history and assessed its level of genetic diversity, history of changes in its population size, and levels of potentially harmful genetic variation.

The biologists found evidence of potentially harmful genetic variation and of mating between closely related ancestors in the sea otter genome -- a pattern that is common in endangered species with small population sizes. The team analyzed the genome of Gidget, a female sea otter from the Monterey Bay Aquarium who died this year, as well as the genome of a South American giant otter as an evolutionary point of comparison. There are 13 species of otters, and the sea otter and giant otter live in starkly different environments -- the giant otter in a warm freshwater environment and the sea otter in the frigid coastal waters of the North Pacific Ocean. This study is the first comprehensive genomic analysis of otters.

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Sea otters' tool use leaves behind distinctive archaeological evidence

Researchers used an interdisciplinary approach combining ecology and archaeological methods to study sea otters' past behavior

Date:  March 14, 2019

Source:  Max Planck Institute for the Science of Human History

An international team of researchers has analyzed the use by sea otters of large, shoreline rocks as "anvils" to break open shells, as well as the resulting shell middens. The researchers used ecological and archaeological approaches to identify patterns that are characteristic of sea otter use of such locations. By looking at evidence of past anvil stone use, scientists could better understand sea otter habitat use.

Sea otters are an especially captivating marine mammal, well known for their use of rocks to break open shells. Sea otters are estimated to have once numbered between 150,000-300,000 individuals and their range stretched from Baja California, Mexico, around the northern Pacific Rim to Japan. Their numbers were dramatically reduced by the fur trade. In California, the southern sea otter population was reduced to around 50 individuals, but a massive conservation effort has resulted in increasing their numbers to around 3000 today. However, the southern sea otter is still considered threatened.

Sea otters are unique for being the only marine mammal to use stone tools. They often use rocks to crack open shells while floating on their back, and also sometimes use stationary rocks along the shoreline as "anvils" to crack open mollusks, particularly mussels. A joint project including the Max Planck Institute for the Science of Human History, the Monterey Bay Aquarium and the University of California, Santa Cruz, among others, has resulted in a first-of-its-kind interdisciplinary study published in Scientific Reports, combining ten years of observations of sea otters with archaeological methods to analyze sea otter use of such anvil stones, also known as emergent anvils.

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Shooting deaths of sea otters in California prompt investigation

Bodies of four male sea otters, a federally protected animal whose killing can be punishable with jail time, washed up on beaches over course of eight days

Julia Carrie Wong in San Francisco

Wednesday 31 August 2016 21.59 BSTLast modified on Wednesday 31 August 201622.35 BST

Federal and state officials are investigating the shooting deaths of California sea otters, after the bodies of four male otters were found washed up on beaches near Santa Cruz.

On Monday, the US Fish and Wildlife Service announced a $10,000 reward for information that leads to the arrest and conviction of the person responsible for killing three sea otters that were found between 12-19 August.

A fourth otter carcass was discovered on 20 August with a suspected gunshot wound, Ashley Spratt of the Fish and Wildlife Service said on Wednesday.

“Finding several gunshot sea otters at the same general location during such a short time frame is very unusual,” said Spratt.

“We don’t know why these otters were shot, but what’s important to note is that killing or harassing federally protected wildlife is a crime.”

Sea otters are protected by the Marine Mammal Protection Act, California state law and the Endangered Species Act. Killing a sea otter is punishable by fines up to $100,000 and could result in a jail sentence.

Sea otters were once widespread along the Pacific coast, but the mammals were hunted almost to extinction for their pelts during the 18th and 19th centuries.

In 1977, California’s remaining sea otters were listed as “threatened” under the Endangered Species Act.

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Slime-producing molecules help spread disease from cats to sea otters

8th October 2014 

41 minutes ago by Pat Bailey

(Phys.org) —The spread of diseases from land animals to sea otters and other marine mammals is aided and abetted by gelatinous, sticky polymers produced by seaweed, reports a research team headed by a UC Davis veterinary infectious-disease expert.

These large, complex molecules form slimy biofilms and bind water-borne organic matter into larger particles, in which disease-causing microorganisms can become embedded and introduced to the marine food chain, the researchers discovered.

Using the parasite Toxoplasma gondii as a model, they showed how these sticky polymers increase the chance that disease-causing organisms would be picked up by marine snails, which graze on kelp and are among the common foods of some endangered sea otters.

Findings from the new study will be published Oct. 8 in the journal Proceedings of the Royal Society B.

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Sea otters can get the flu, too: Human H1N1 pandemic virus infected Washington State sea otters

Date:

April 8, 2014

Source:

United States Geological Survey

Summary:

Northern sea otters living off the coast of Washington state were infected with the same H1N1 flu virus that caused the world-wide pandemic in 2009, according to a new study. The researchers discovered antibodies for the 2009 H1N1 flu virus in blood samples from 70 percent of the sea otters studied. None of the otters were visibly sick, but the presence of antibodies means that the otters were previously exposed to influenza.

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Sea Otters Rebound from Exxon Valdez Disaster

By Andrea Thompson, Planet Earth Editor | March 03, 2014 04:04pm ET

Nearly a quarter of a century after the Exxon Valdez disaster dumped 11 million gallons (40 million liters) of oil into Alaska'sPrince William Sound, sea otter numbers have rebounded to levels seen before the spill, the U.S. Geological Survey announced Friday (Feb. 28) with a new study.

Sea otters (Enhydra lutris), found along the Pacific coasts of North America and Northeast Asia, are one of more than 20 types of animals that make their home near the shore affected by the March 1989 oil spill. The disaster occurred in prime sea otter habitat, according to the USGS study. The oil "drastically reduces" the ability of the otters' fur to provide insulation, the report said.

It is estimated that several thousand sea otters perished because of the spill, the USGS said in a statement, and subsequent monitoring showed that the animals were slow to recover, likely because oil lingering in their environment continued to affect them.

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Sea otter return boosts ailing seagrass in California

The return of sea otters to an estuary on the central Californian coast has significantly improved the health of seagrass, new research has found.

Seagrass was deemed to be heading for extinction in this region before the otters returned.

But scientists found that the animals triggered a chain reaction of events that boosted the water-dwelling plants.

The research is published in the journal, PNAS.

The urbanisation of California has led to a huge increase in nutrient pollution in coastal waters, from increasing use of nitrogen-rich fertilizers.

“It's almost like these sea otters are fighting the effects of poor water quality, ”Brent Hughes University of California

This is said to be the reason for the dieback of seagrass, which has also been declining worldwide.

This research suggests that the hunting to near-extinction of sea otters in the late 19th and early 20th Century may have exacerbated the problem, and conversely that their reintroduction is helping revive ailing seagrass populations, even in the face of hugely nutrient-rich water.

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