Male Baby Boom Among Endangered Orcas Causes Concern

First Posted: Apr 02, 2016 05:53 AM EDT

A booming population is usually good news when it concerns an endangered species, but not so much when the new additions are mostly males.

A notable rise in the waning population of Southern Resident Killer Whales or orcas has been more of a concern than a relief due to the accompanying skewed sex ratio, resulting from the birth of more male calves than females. A new scientific research may have some answers to the mystery of the distorted gender balance.

Usually, orcas have a 50-50 ratio between males and females when giving birth. The rise in male offspring has been debated to the quality of the water inhabited by the killer whales. The area where the orcas typically thrive could be high in heavy metals, environmental toxins, Polychlorinated Biphenyls (PCBs) and other pollutants. In addition, the phenomenon can also be linked to dietary habits and a reduced carbohydrate intake of the species.

It has been previously studied that water with a high content of pulp and paper mill discharges, as well as a notable amount of tributyltin, once used for preventing the growth of marine organisms on ship hulls, is associated with more male births in fish. However, it is not yet clear if the impact has the same for marine mammals.

A recent scientific consortium that saw a collaboration between researchers from the National Marine Mammal Foundation, National Oceanic and Atmospheric Administration or NOAA's Marine Fisheries Service, the University of California Davis School of Veterinary Medicine and SeaDoc Society may give us a clearer picture in the future.

These organizations will pool their resources to create an information database and medical chart that will give more insight into the rising male population among endangered Southern Resident orcas. However, the scientists are not ruling out the possibility that at the end of it all it may just come down to pure chance and coincidence. 

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