Otter poop reveals they may be ecosystem engineers
The expression “this place is a pig” may have to be replaced by “this place is a otter latrine”. In particular the animated latrines of a north American river otter (Longtra canadensis). Small mammals have dubious hygiene with regard to food, eat, play and defecate in the same place.
However, studying their less than impatient habits (and in particular what is in their poop) can help scientists detect future environmental health threats. Their SCAT reveals that they often eat foods that are full of parasites, which can help the greatest ecosystem and be a warning signal for the types of parasites hiding there. The results are detailed in a study published on August 14 in the journal Borders in mammalian science.
“River otters are impressive APEX predators who play a vital role in ecosystems,” said Calli Wise, study co-author and research technician at the Smithsonian Environmental Research Center, in a press release. “The parasites consumed by river otters can also teach us environmental health.”
Rockin ‘around the Otter latrines
This study examined the otters of the river along the bay of Chesapeake in Maryland. They are one of the most elusive creatures in the region: nocturnal, semi-aquatic and generally timid with people. River otters have muscular and rationalized bodies (they can reach up to four feet long), short legs and fully webbed feet that are perfectly suitable for life in and out of the river.
Formerly abundant in North America, their number plunged due to the degradation of habitat and fur trade. In the mid -1990s, the state of Maryland began a reintroduction program which helped their populations to bounce back throughout the state. Even with this success, scientists have no specific estimates as to their number of populations in the Chesapeake Bay watershed of 64,000 square miles. Many other aspects of their behavior, their diets and their daily life remain secret.
“It is shocking to see how little information is on their biology and ecology,” added Katrina Lohan, parasitic ecologist of the Smithsonian and co-author of the study.
Since the otters are difficult to observe in nature, living their lifes of otters, scientists are counting on their excrement for clues. Periodically, the otters will let water come together on the latrines. These latrines are sites on Earth where they socialize, eat and leave fresh excrement as perfume markers so that other otters sniff. The study of the excrement (AKA SCAT) of the Otter latrines can give scientists an idea of what they eat.
A red worm in a strange poop
The study started after a colleague reported a strange water poop in Lohan. It was found on a platform near the Smithsonian Environmental Research Center campus in Edgewater, Maryland and a “red green from the fire engine”, was inside. The wildlife cameras of the region finally spotted a river otter defecating on the platform. Since Lohan thought that the worm was probably a parasite, the team decided to take more samples.
For 11 months, they collected SCAT from 18 active latrines around the campus. They recovered 28 scats by latrine on average. The beaches, the banks and other natural sites were the majority of the latrines, but some artificial structures (walks, quays, etc.) hosted latrines of active otters.
Three otters of the North American river play in the snow on the quays of the Smithsonian Environmental Research Center. Detected with LERC night vision fauna cameras. Credit: Karen McDonald, Smithsonian Environmental Research Center.
“The SCAT generally felt strongly of fish and were full of scales or shells of crustaceans,” said Wise. “We have worn gloves and used sterile tools and tubes to take scat samples, to avoid contamination by other DNA.”
After collecting the samples, the team brought them back to the neighboring laboratory. They studied the SCAT under the microscope and carried out DNA analyzes using a technique called metabcoding, a quick method to identify animal, plant, microbes, etc. species, etc. in a SCAT sample.
The excrement revealed that crabs and fish finish were the basic foods of the otter diets, representing 93% of all prey according to DNA analysis. The otters also dine on amphibians, verses and occasional bird. The small mammals even ate two invasive fish: the common carp and the crayfish in the south of the white river.
However, DNA analyzes have also revealed a multitude of parasites of six different classes in the otters excrement. Most of these parasites were trematodes, or parasitic verses also called dynamics. The other parasites included microscopic dinoflagellates and others known to infect fish branchies, skin or fins. The majority of parasites probably infected the prey of the otters and not the otters themselves.
Ecosystem engineers and “Sentinels of illness”
The presence of parasites in the otter scat could mean that they are important ecosystem engineers. According to Lohan, the otters can help the populations of global prey by eating these animals infected with parasites, as this eliminates the faster fish and crabs. The parasites themselves can also help otters catch more elusive prey.
“Although parasites have negative impacts on individuals, they are extremely important in food networks,” said Lohan. “It is possible that river otters, like other high -level predators, cannot find enough food to eat without parasites.”
Some of the study parasites are known to infect mammals, namely roundworms and single cell apicomplexans. The team believes that these parasites can directly infect the otters themselves instead of their prey.
They have not immediately detected parasites in river otters that can infect humans. However, some of the parasites were closely linked to those who can cause human disease. These include the CystoisOSporase of gastrointestinal disease. While river otters appear more often in urban and suburban areas, the probability that they meet something that could affect human health also increases.
“Some of the parasites that infect the river otters could potentially infect humans, who are also mammals,” concluded Lohan. “Thus, we could use river otters as” Sentinels of illness “and study them to find out what public health threats occur in certain areas.”
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