As a tourist boat made its way through Shark Bay on Australia’s west coast, the passengers on board were unaware of the remarkable sight unfolding just a few metres away. Bubbles were rising from two metres beneath the surface, and the creatures responsible could only be seen by the tour guide, who had an aerial view using his drone camera.
Jake Mason, from Shark Bay Eco Tours, shared with Yahoo News that he was “completely fascinated” by what he witnessed, as it was something he had never encountered before. He was observing the surfacing of dugongs, a mysterious marine mammal that can grow up to three metres in length—roughly the height of a basketball hoop—and weigh 360kg, similar to a polar bear.
Despite being “notoriously hard to spot,” Jake has spent the last three years tracking them, having seen dozens over the years. However, he had never seen them expelling large amounts of bubbles.
Theory emerges as bubbles expelled from multiple dugongs
In this particular instance, the bubbles were primarily coming from the dugongs’ rears, which intrigued both Jake and some of the world’s top dugong experts. The animals were feeding at depths of around eight to nine metres, much deeper than usual for the region.
“It wasn’t all of them, but some were surfacing with a small trail of bubbles coming from their backend,” he explained. “At first, I thought it might have been a coincidence, but the same dugong went down and did the same thing a few minutes later. When a second one did it too, I realized either they had a very gassy seagrass diet or something else was going on.”
Jake speculated that the animals might be using the bubbles to propel themselves through the water.
Other species known to use bubbles for buoyancy
Human locomotion is studied in detail by experts, and recent advancements in sports technology, such as shoes developed by Adidas, have helped athletes break records. Similarly, advanced swimsuits have reduced drag for swimmers. However, when it comes to other aquatic animals, much remains unknown about how they navigate their environment.
There is evidence that manatees, which are related to dugongs, release gas to control their buoyancy and adjust their position in the water. They often use this method to sink again after surfacing. Although Jake couldn’t find any scientific studies on the topic, he wondered if the dugongs he observed were doing the same.
Experts weigh in on strange dugong behaviour
After reviewing images and video of the encounter, Professor Helene Marsh, a dugong specialist at James Cook University, noted that small amounts of bubbles also appeared to come from one animal’s nostrils. As a hind-gut fermenter, a significant amount of gas was likely being expelled from the colon via the anus.
“There are large pressure changes in the first 10 meters of water, and I expect this is affecting the dugong’s release of gases,” she said. “They are certainly known to pass a lot of wind.”
Renee Lambourn, who is researching buoyancy for her PhD, acknowledged that it is still unclear whether dugongs use their digestive system and lungs to manage their movement in the water.
“We have evidence that dugongs control their buoyancy by regulating the volume of air in their lungs before diving, but we don’t have evidence for gas in their digestive system,” she said.
She added that air trapped in the digestive system can expand as an animal reaches the surface, potentially requiring pressure to be released.
“In terms of using their lungs and gas in their digestive system to fine-tune their position in the water like manatees do, it is plausible, but I have no evidence for this,” she concluded.
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