The fun-loving otter has gotten a piece of news that might make it put play on pause for a moment: British researchers report that the animal’s penis size is shrinking—more specifically, it’s the weight of the critter’s penis bone, called the baculum, that’s on the decline. And they hypothesize that common chemicals in the environment, to which humans are regularly exposed to, could be to blame.
So should human males be worried? Yes. And no.
Co-authored by the Cardiff University Otter Project and the Chemicals, Health, and Environment Monitoring Trust, the study documents a collection of reproductive health maladies showing up more frequently among male otters, including smaller penises, more cysts on the tubes that funnel sperm, and more cases of undescended testes.
In a press release, the researchers write that "it is not possible to determine exactly what the causes of these changes are, but various studies, both in the laboratory and in wildlife, have suggested links between hormone disrupting chemicals and problems with male reproductive health."
Those "various studies" include a diverse array of research on many different species published over the last 20 years linking increases in male birth defects, testicular cancer, infertility, and even the complete feminization of male sexual organs to exposure to a class of chemicals called endocrine disruptors. EDs include substances like the much-maligned BPA (which also help make us fatter) and phthalates, found in everything from cosmetics, to plastics, to furniture, to pesticides. These chemicals, presumably, could end up in the rivers that otters call home.
The news about the otter fits with the trends endocrine disruptor researchers have noticed for years, including shrinking penises among alligators exposed to toxins in the wild and, more controversially, the feminization of the reproductive systems of male frogs doused with the herbicide atrazine, who, in a lab, even began producing eggs which were fertilized by other male frogs (and hatched healthy young).
In human males, scientists have noticed declining sperm quality, increases in testicular cancer, and a rise in male birth defects since the 1970s. Endocrine disruptors are looked at as a possible explanation.
The challenge is linking these effects with any one cause. In humans, phthalates and BPA show up in more than 90% of the population (!)—presumably, otters are exposed to many as well. The point is that it makes it hard (and often unethical) for researchers to isolate a control population and compare it with a random set of exposed subjects.
While otters and humans aren’t the same (clearly—human males don’t even have penis bones), if endocrine disruptors are causing otter penises to shrink, we probably should worry. Chemicals that affect one mammal often harm another. But the otter penis news is more a call for more research than a reason to sound alarms. Researchers will have to figure out which endocrine disruptors (and in what quantities) the otters are exposed to prove their suspicions.