On the latest installment of HBO’s Last Week Tonight With John Oliver, the wry satirist proposed a new mascot for the ways man-made pollution is endangering wildlife: a male polar bear, crying and clutching his groin.
This darkly amusing image was inspired by a recently published scientific paper that linked unusually brittle polar bear penis bones with high levels of a particular chemical pollutant in their environment.
The riff immediately raised three questions: Is the study real? Are its conclusions valid? Have they been exaggerated for comic effect?
The answers appear to be: yes, maybe, and duh.
The study, published in the February edition of the journal Environmental Research, was conducted by a research team led by Christian Sonne of Aarhus University in Denmark. They proposed that polar bears’ survival—which has been thrown into doubt due to the effects of climate change—may in fact be more threatened by the bone-weakening effects of “endocrine disrupting chemicals,” or EDCs. (EDCs are, to put it simply, chemicals that can disrupt the body’s endocrine system.)
While their findings are legitimate cause for concern, particularly considering the other challenges the polar bear population is facing as Arctic ice shrinks, their use of the term “likely” is certainly questionable.
Endocrine disrupting chemicals include PCBs (polychlorinated biphenyls), a group of highly toxic compounds widely used in protective coating, as lubricants, and in the manufacture of plastics before they were eventually banned due to health and environmental concerns. As New Scientist pointed out, PCBs “are slow to break down” and can be found in “particularly high concentrations” in the Arctic.
“Reduction in penile bone mineral density could lead to an increased risk of species extinction between mating and subsequent fertilization failure as a result of weak penile bones and risk of fractures,” the researchers write.
To determine how real the threat is, Sonne and his colleagues “analyzed penile bone mineral density” in 279 polar bears born between 1990 and 2000, and compared those measurements to levels of PCBs in their immediate environment. The researchers concluded that it is “likely that EDCs directly affect development and bone density in polar bears.”
While their findings are legitimate cause for concern, particularly considering the other challenges the polar bear population is facing as Arctic ice shrinks, their use of the term “likely” is certainly questionable.
The researchers did find a link between higher concentrations of PCBs in the environment and decreased bone mineral density in the animals, but they concede this relationship was only “close to significant.” That’s hardly definitive proof.
Qualifying their findings even further, they go on to write that “PCBs could be in a range that may lead to disruption of normal reproduction and development.”
On her blog Polar Bear Science, zoologist Susan Crockford points out those quite substantial caveats, along with the leaps the researchers had to make to come to their conclusion.*
“They assumed this lessened bone density would make the penis bones weaker and more likely to break, but they did not test this assumption,” she writes. “They did not offer any evidence that penis bones of wild polar bears had been breaking due to this lessened bone density. They did not cite any previous papers or studies in which broken penis bones had been found or studied.”
Not even anything from the Arctic edition of Cosmopolitan, which would surely be all over this trend if it was really happening.
“Their conclusions,” Crockford writes, “are merely possibilities, not certainties of any kind.”
Yes, pollution may be interfering with successful polar bear copulation, but at this point, that’s a matter of informed speculation, not one of actual proof.
Perhaps everyone needs to go back and read our in-depth 2012 article about how polar bears, despite their usefulness as “the fuzzy face of climate change,” may be more resilient than people think.
*UPDATE — April 22, 2015: This post has been updated with the correct title of zoologist Susan Crockford’s blog.
