A recent study found that some Illinois river otters have traces of banned pollutants in their livers.

The study assessed the concentrations of 20 different contaminants and compared their findings to numbers reported about river otters about 25 to 30 years ago, said Samantha Carpenter, a wildlife technical assistant at the Illinois Natural History Survey at the University’s Prairie Research Institute. The University’s Illinois Natural History Survey, College of Veterinary Medicine and Department of Animal Sciences worked in collaboration with Michigan State University’s Diagnostic Center for Population and Animal Health and the Illinois Department of Natural Resources to complete the study.

The goal of the research was not to quantify the effects of the compounds on the otters, said Nohra Mateus-Pinilla, wildlife veterinary epidemiologist at the Illinois Natural History Survey. Rather, the group wanted to establish if the chemicals were present in the otters and if their presence differed from previous studies.

Researchers found the highest concentrations of the pollutants polychlorinated biphenyls; DDE, which is a breakdown of the pesticide DDT; and dieldrin, another pesticide.

The amounts of polychlorinated biphenyls and DDE found in the studied river otters were consistent with the amount found across North America, Carpenter said.

However, she said the dieldrin found in the otters was found in a far higher concentration than in other locations, as dieldrin’s parent product, aldrin, was used intensely on the state’s corn.

These pollutants have been banned for decades but still persist in the environment.

“Depending on the amount of the pesticide that was applied to a particular location, they have long half-lives and are persistent in the environment,” said Jan Novakofski, animal science professor.

Carpenter said research on dieldrin shows that its half-life is between 4 and 25 years, meaning it could take as long as 25 years to halve its presence in the environment.

River otters were used in the study as biomonitors for the situation, Carpenter said, because they are at the top of the food chain.

“They are eating a lot of fish and possibly a lot of the same species of fish that humans in Illinois are also eating,” Carpenter said.

Working up the food chain, chemicals become more concentrated; therefore, otters accumulate more of the banned substances.

“When otters are eating a lot of fatty fish, for example, they are consuming higher concentration of dieldrin than, say, a herbivore would,” Carpenter said.

The concentration of dieldrin was found to be higher when compared with past amounts of dieldrin in river otters, according to the report.

This may be due to the fact the studies compare river otters from different geographical areas of the state, Carpenter said. During the previous study, river otters were limited to the northwest corner of Illinois, but since a reestablishment program by the Department of Natural Resources, their population has expanded.

“We’re comparing otters from different geographical regions of the state so that is one possibility in terms of why there are differences in our results, but there are also other possibilities as well,” Carpenter said.

Going forward, researchers would like to find how often these compounds are present, the species where they are present and the possible effects on the animals where they are present.

“I think more importantly this is a first step to go forward and try to understand what is happening with these compounds,” Mateus-Pinilla said. “It’s really just for us right now, a first step to evaluate these compounds.”

Miranda can be reached at [email protected].