River Otters Might Be Parasite Dangers

When a North American river otter left behind some bizarre wanting poo on a dock in Maryland and obtained caught by a wildlife digital camera, scientists began to analyze. They discovered river otters residing within the Chesapeake Bay eat a wide range of fish, crabs, and the occasional duck – and that their meals is infested with parasites which generally infect otters. As river otters hunt contaminated prey, they could play an important function inside native meals webs via the culling of sick people, the researchers mentioned.

North American river otters have lived for a very long time in Chesapeake Bay, but comparatively little is thought about how their environment influence them. So what does every day life for river otters on the Atlantic coast of the US appear to be? What do they eat? Where do they socialize? Where do they go to poo? Researchers in Maryland determined to analyze and have now revealed their findings in Frontiers in Mammal Science.

“River otters in the Chesapeake Bay eat a wide range of animals, including those that live in the water and on land. Parasites, too, are crucial parts of their diet,” mentioned senior creator Dr Katrina Lohan, a parasite ecologist and head of the Coastal Disease Ecology Laboratory on the Smithsonian Environmental Research Center (SERC). “We also found that river otters use manmade structures for latrines or choose areas with specific characteristics.”

Poo on the dock of the bay

“We started this research when a colleague sent me an email about some weird-looking, watery poo that she found at the dock on our campus. In the poo was a fire engine red worm,” Lohan mentioned. Eventually wildlife cameras caught a river otter pooing on the dock. Since the worm was most definitely a parasite, Lohan determined to get some samples. The article’s first creator Calli Wise, a graduate researcher on the SERC, collected additional samples from 18 lively otter latrines. Over 11 months, the researchers recovered 28 scats per latrine on common.

“Scats usually smelled strongly of fish and were full of scales or crustacean shells,” Wise mentioned. “We wore gloves and used sterile tools and tubes to collect scat samples, to avoid contamination with other DNA.”

Latrines are central hubs for otters: While they’re primarily used for scent-marking via defecation and urination, river otters additionally use them as spots to eat, play, socialize, and relaxation. Typically, they appear to be areas the place the grass or different vegetation has been flattened with low overhanding vegetation for canopy.

Most latrines on the Chesapeake Bay had been positioned near the shoreline, in areas with woody particles and open entry to the water. Often, onerous to overlook options made them stand out from the encompassing panorama. Such options included man-made constructions and 5 otter latrines had been discovered on docks, boardwalks, and shoreline staircases.

Parasite management

The collected scat was taken to the lab for evaluation. The group used two strategies to determine what the otters had eaten: metabarcoding, a technique that makes use of genetic data, and microscopic examination.

“We collected most scats in the summer, when river otter diet is likely diverse,” Wise unhappy. “We found evidence of invasive species like common carp and white river crayfish in river otters’ diet.” In addition, otters ate extra fish and crustaceans, corresponding to American blue crabs. They additionally included the occasional duck or amphibian on their meal plan.

Otter poo, nonetheless, didn’t solely inform the researchers what the otters had eaten. Using metabarcoding, they had been in a position to decide what parasites had been within the prey. They then matched parasites to the hosts they had been most definitely to contaminate. Many of the parasites are identified to contaminate teleost fish, a particularly numerous group of ray-finned fishes which are the first prey of river otters But a couple of different parasites seemingly contaminated otters instantly. “It is possible that river otters, like other top predators, wouldn’t be able to find enough food to eat without parasites,” Lohan identified.

The group mentioned that they weren’t in a position to clearly determine all parasites, primarily due to lacking sequences in databases that new sequences may be matched to. They additionally couldn’t determine particular person diets or match poo samples to particular person otters.

Nevertheless, the presence of parasites in otter poo would possibly imply river otters are necessary ecosystem engineers. “Since so many of the parasites are actually infecting otters’ prey, it could mean that river otters are culling sick individuals from the populations they are preying upon,” Lohan defined. This may probably alter evolutionary processes for his or her prey, since contaminated people, as soon as eaten, now not contribute to the gene pool.

“Some of the parasites that infect river otters could potentially also infect humans, who also are mammals,” Lohan concluded. “Thus, we could use river otters as ‘disease sentinels,’ and study them to learn about what public health threats occur in certain areas.”

Reference: Wise CM, Serfass TL, Palmer EM, et al. North American river otters eat numerous prey and parasites in a subestuary of the Chesapeake Bay. Front Mamm Sci. 2025. doi: 10.3389/fmamm.2025.1620318

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