Dolphins are known for breathing through their blowholes, a well-established fact commonly found in books and articles about dolphin anatomy. However, researchers from the University of Otago in New Zealand have observed a Hector’s dolphin opening its mouth to suck air in, bypassing the blowhole completely.
This strange behaviour, the first documented case of a mouth-breathing dolphin, has raised questions about what we thought we knew about these fascinating marine mammals.
The dolphin in question was first observed off New Zealand’s Banks Peninsula in 2014. Identified by a small “tattoo” lesion near its blowhole, the Hector’s dolphin would jut out of the water, opening its mouth as if to gulp down air.
The same dolphin was seen on multiple occasions, with researchers capturing its surfacing behaviour on video in December 2015. Upon analysis, the footage clearly showed the dolphin breathing through its mouth while never opening its blowhole.
The larynx of a dolphin has evolved to form a plug that reaches into the nasal cavity, creating complete separation of the respiratory and digestive tracts. The plug, sometimes called a goosebeak or epiglottic spout, is located in the air passage leading to the blowhole. The prevailing view among marine mammalogists was that the plug couldn’t be moved, and that dolphins wouldn’t attempt to do so as the risk of drowning was too high.
However, research has shown that the laryngeal plug can be moved when necessary. Veterinarians, for example, sometimes need to reach into a dolphin’s stomach to remove swallowed objects, and will often fight against the plug as the dolphin tenses its muscles to keep it in place.
Experts caution that moving the plug is a risky behaviour that dolphins will only resort to as a last option. There have been cases of dolphins choking to death when they shifted the plug aside to swallow large fish or when a fish tried to escape through their blowhole. Nonetheless, the observation of a dolphin breathing through its mouth provides a valuable insight into the flexibility of their anatomy and behaviour.
Unfortunately, dolphins face numerous threats from human activities, such as pollution, overfishing, and habitat loss. Their intelligence, social nature, and complex behavior make them popular attractions in captivity, with many dolphins living in small tanks in aquariums and amusement parks. These conditions are far from ideal, with significant negative impacts on their wellbeing and lifespans. It is important that we work to mitigate these threats and protect the natural habitats of these remarkable creatures. The discovery of a mouth-breathing dolphin is a reminder of how much more there may be to learn about these magnificent animals.