Researchers studying over a decade's worth of dead otters in Britain have concluded that pollution is most likely the cause of penis shrinkage in the water-loving mammals.

According to The Telegraph, scientists from the Cardiff University Otter Project and the Chemicals, Health and Environment Monitoring Trust have been monitoring the otter population for many years, and this month published a report based on 755 otters that died between 1992 and 2009.

According to its website, the Cardiff University Otter Project was founded in 1992 to collect dead otters across England and Wales in order to study tissue samples and monitor aquatic contamination.

Using samples collected from the otters, scientists found that male otters suffered from an increase in a variety of reproductive health issues, including a decrease in penis bone weight, undescended testicles and cysts on sperm-carrying tubes, the BBC reports.

Project manager Dr. Elizabeth Chadwick of the Cardiff University Otter Project said that Endocrine Disrupting Chemicals (EDCs) may be leading to these problems.

"With many of these contaminants, there can be all sorts of different sources," she told the BBC. "So it might be things like drugs that we're taking and they flush through our sewerage systems and end up in the rivers."

Not long ago, British otters were in crisis, according to National Geographic. The native species, Lutra lutra was decimated by toxic insecticides, organochlorines and PCBs that leaked into the water supply. By the late 1970s, only a small fraction remained.

The population has now recovered somewhat, after bans on many of the worst chemicals came into affect, but Anna Jones, director of BBC program Countryfile, said clearly problem has not magically gone away.

"People are very quick to say: otters are in our rivers," Jones told the BBC. "That must mean rivers are perfect, they're so clean, everything's fine again… but it's not really that simple."

Wired notes that while there is no conclusive proof linking otter penis shrinkage to the EDC chemicals, past studies have hinted at such a link, including a 1990 study in mice and 1991 study in sea snails.

On the other hand, a study looking at the affects of EDCs on sperm counts in French males suggested the chemicals caused a drop in sperm concentration that demanded "immediate attention," reports Wired.

Speaking with The Telegraph, Gwynne Lyon, director the CHEM Trust charity that commissioned the study, said the Otter Project's results signal it is time to "end the complacency about the effects of pollutants on male reproductive health."

"This study has raised a warning flag," Lyon said. "In reality humans and wildlife are exposed to a cocktail of many chemicals every day and some may be adding up to cause problems."

Clarification: The text has been changed to specify that otter penis bones are decreasing specifically in weight.

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