US Navy’s camera-wielding dolphins reveal wild side of the sea-mammal

You won't see them hunt for underwater mines.
Ameya Paleja
dolphins .jpg
Dolphin visually tracking a fish

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Dogs may be used for patrolling purposes on land, but when it comes to the sea, the U.S. Navy relies on bottlenose dolphins and sea lions. Recently, a study published in a scientific journal shared images of these bottlenose dolphins in open waters, Gizmodo reported.

With their abilities to work tirelessly and even wield weapons, robotic dogs may have recently captured the imagination of military forces. However, long before these dogs even came into existence, the U.S. Navy turned to nature for help in its operations.

According to the website of the Marine Mammal Program, the U.S. Navy has been using marine animals since 1959. In the early years of the program, the list of underwater-training species also included sharks, rays, sea turtles as well as marine birds. However, after taking into consideration the trainability and adaptability of the animals, the U.S. Navy settled on training bottlenose dolphins and sea lions.

US Navy’s camera-wielding dolphins reveal wild side of the sea-mammal
US Navy Dolphin sucking a fish

What does the U.S.Navy use sea animals for?

Dolphins naturally possess the best sonar technology known to man, and this can be used used to detect mines on the sea floor that would otherwise go undetected by man-made technology. Additionally, sea animals have excellent low light vision and can dive deep depths without experiencing decompression sickness, as human divers do.

Sea lions trained by the U.S. Navy can locate naval equipment on the ocean floor and can attach recovery lines to them. These animals can also help in detecting and apprehending unauthorized swimmers and divers in naval waters who might posses a risk to the U.S. Navy's personnel or properties.

To understand how these fish behave and communicate in open waters, the U.S. navy attached cameras and audio recording equipment to six of its trained dolphins and recorded data over a period of six months.

What did the researchers find?

The researchers attached the cameras to the backs of some of these animals so that they covered their blowholes, while for others, they attached the cameras to their sides, covering their eyes, jaws, and teeth. Since this is a different perspective to seeing these animals in action, it might be a little startling for some of our readers.

US Navy’s camera-wielding dolphins reveal wild side of the sea-mammal
Images captured by cameras on U.S. Navy dolphins

The researchers published their findings in the journal PLoS One, wherein they stated that the dolphins consumed an array of creatures ranging from bass to croakers, halibut to pipefish, as well as smelt during their open-sea swims. When they caught sea snakes, the dolphins jerked their heads to swallow their catch.

One dolphin under observation caught 69 fish of which 64 were demersal or ground fish while five were near the surface. Another caught 40 fish, of which only four were near the surface while others were demersal. While two other dolphins caught 135 live native fish, one was observed to have consumed eight yellow-bellied sea snakes, the researchers wrote in their report.

The cameras also captured the eye movement of the fish as they tracked their prey. When the prey jumped, the dolphins' eyes continued to track the prey, Gizmodo said in its report.

If fish continued to swim when they entered the dolphin's mouth, the animal appears to use a tactic used by toothed whales and other marine animals, where they expand their throat to suck down their prey.

From the audio recorded, the researchers noted that during the search dolphins clicked at intervals of 20 to 50 ms but as they approached the prey, the click intervals shortened to a buzz and finally a squeal that the dolphin continued till it seized, manipulated,and swallowed the prey.

Other countries like Russia and North Korea are also using dolphins as part of their naval strategies, we have previously reported.

Abstract

For the first time, dolphins wearing video cameras were observed capturing and eating live native fish. While freely swimming in San Diego Bay, one dolphin caught 69 resident fish, 64 demersal, 5 near surface, while the other caught 40, 36 demersal and 4 near the surface. Two other dolphins were observed capturing 135 live native fish in a sea water pool. Two additional dolphins were observed feeding opportunistically during open water sessions in the Pacific Ocean. Notably, one of these dolphins was observed to consume 8 yellow-bellied sea snakes (Hydrophis platurus). Searching dolphins clicked at intervals of 20 to 50 ms. On approaching prey, click intervals shorten into a terminal buzz and then a squeal. Squeals were bursts of clicks that varied in duration, peak frequency, and amplitude. Squeals continued as the dolphin seized, manipulated and swallowed the prey. If fish escaped, the dolphin continued the chase and sonar clicks were heard less often than the continuous terminal buzz and squeal. During captures, the dolphins’ lips flared to reveal nearly all of the teeth. The throat expanded outward. Fish continued escape swimming even as they entered the dolphins’ mouth, yet the dolphin appeared to suck the fish right down.

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