Environmental pollutants are having a peculiar effect on the penis bones of river otters in Canada.
In a new study, published in the journal Chemosphere, scientists in Canada have discovered that hydrocarbon contaminants linked to oil and gas extraction might contribute to the weakening of the penis bone of North American river otters (Lontra canadensis).
The bone in question is the baculum, a rigid and mineralized bone that runs down the middle of their penis. A wider range of animals possess the bone – not humans, though – and it plays an important role in reproduction and courtships. It might sound like an unusual thing to study when looking at environmental pollution, but the role of the bone in copulation means it’s a surprisingly useful tool for monitoring animal populations.
“It’s akin to taking Mother Nature’s pulse,” Dr Philippe Thomas, lead study author and wildlife biologist at Environment and Climate Change Canada, told IFLScience.
“To identify endpoints, we rely on Indigenous land users, hunters, trappers and fishers that have been connected to the land for centuries,” Thomas continues.
“We were always told how increased mining activities led to decreasing semi-aquatic wildlife numbers in the vicinity of these large industrial projects. Knowing how reproductive endpoints, such as measures of baculum health, helped inform environmental risk to exposure to similar compounds in the past, in wild mink and otter, we put 2 and 2 together and decided to test this for ourselves,” he added.
For the new study, the researchers dissected river otter carcasses in Alberta and closely studied their baculum bone, while also keeping tabs on contaminants in their liver and their surrounding natural environment. The otters were collected in, or downstream of, the Athabasca Oil Sands Region of northern Alberta, a site with rampant crude oil extraction and fracking.
Notably, their livers and environment were found to contain polycyclic aromatic compounds (PACs), a class of chemicals that are produced when coal, oil, gas, wood, and garbage are burned. The more PACs they detected in the environment, the lower the otters’ bone mineral density, suggesting the baculum was weaker. They also found that sites with higher levels of toxic metals, such as thallium and cadmium, were home to otters with weaker baculum. By no coincidence, cadmium is known to affect bone health. It is possible that exposure to PACs could have had an effect on baculum bone health through its impacts on estrogen and androgen levels, which are vital for a sturdy penis bone.
Interestingly, they also identified some metals in the environment, like strontium and iron, that appeared to have protective effects on baculum bone health.
The study explains that North American river otters are a "sentinel species”. Like a canary in a coal mine, these species are able to highlight subtle changes in the ecosystem due to their place in the food chain and their sensitivity to environmental stressors. As such, it’s bad news that this species is already feeling the effects of oil extraction in the area. It’s unclear how this change to the baculum might affect this population, although previous research has suggested that polar bears with stronger baculum have more offspring. If the same holds true for river otters, then a decrease in baculum bone health could lower the local population numbers and have a knock-on effect throughout the ecosystem.
While numbers are officially considered stable, there is not much monitoring of the North American river otter and many fear that the species remains under serious threat in response to changes to their habitat.
This article has been amended to include comments by Dr Philippe Thomas about their work