See never-before-seen footage of dolphins hunting under the sea

posted on 08/17/2022 16:38 / updated on 08/17/2022 16:43

(credit: RIDGWAY ET AL., 2022, PLOS ONE, CC-BY 4.0)

For the first time, researchers were able to observe on video the moment when dolphins eat and hunt fish at the bottom of the sea. The cameras, attached to the animals’ bodies, were intended to observe the mammal’s behavior underwater.

In the videos published this Wednesday (17/8) in the scientific journal PLOS One, it is possible to see different dolphins, at different times, hunting different animals. One of them manages to capture 69 resident fish, 64 demersals (which live on the sea floor) and five close to the surface. Another two dolphins were observed catching 135 native fish in the sea. In addition, one of them was observed consuming eight yellow-bellied sea snakes (hydrophis platurus).

Six animals of the species were observed in all and they were identified by the following letters: B, K, S, Y, T and Z.

Watch the moment the S dolphin catches fish in San Diego Bay (USA):

The researchers also looked at eye movements, catching strategies and movements of the dolphins’ lips, tongue, muscles and lower jaw while hunting for food. In addition, they observed the sounds made by the animals during the events.

From this, the scientists were able to see that the animals made “clicks” every 20-50 milliseconds as they searched for prey. According to the researchers, these “clicks” would be a kind of echolocation – the natural sonar sense used by dolphins, porpoises and whales to detect fish emitting sounds.

These sounds became more constant as the dolphins approached their prey and were followed by a victory cry after capture. Another curiosity identified was that the animals used their eyes to closely track prey.

Check experiment details:

  • Capture of dolphins with anatomy showing the relationships of some muscles of the upper and lower lip — A. View of dolphin K as a fish prepared to be swallowed. The lips are opened by the Ob muscles below and LRM above, the tongue (T) is retracted and the gular muscles facilitate the expansion which sucks the fish down. The box shows the directions of B . and C. horizontal cut through the lower jaw. Ob orbicularis oris, muscles of the lower lip, J Jaw, FB, fat body of the mandible, BUL auditory bulla or tympanic bone, EUS Eustachian tube. B. Frontal cut through the mouth immediately anterior to the labial commissure. The dashed line in C. shows the approximate orientation of the B. Ob orbicularis oris muscles of the lower lip, lateral rostral LRM muscle. J, jaw bone, T, tongue.
    RIDGWAY ET AL., 2022, PLOS ONE, CC-BY 4.0

  • Bones and muscles related to the hyolingual apparatus of bottlenose dolphins — A) Ventral view of a dolphin skull. A, articular process; B, basihyal; C, keratohyal; E, epihyal; S, stylohyal; T, tympanohyal; J, jaw. Terminology of the hyoid bone of Reidenberg and Laitman [ 38 ]; B. Horizontal MR image seen at stylohyal level showing heavy (dark) musculature. FB, lower jaw fat body, eye E, jaw JC Frontal magnetic resonance image showing anterior portions of the brain and hyoid apparatus. C, cerebellum; CB, brain; BS, brainstem, Ear, M, muscle masses of the hyoid area. D. Frontal CT scan shows hyoid bones and immense musculature adjacent to M.
    RIDGWAY ET AL., 2022, PLOS ONE, CC-BY 4.0

  • View of the dolphin’s anterior body as it approaches sea snake B. Amplitude of sound recorded when dolphin Z located and captured a sea snake. Head movements (abrupt changes in amplitude at the end of B) are indicative of swallowing prey. C) Audible sound spectrogram.
    RIDGWAY ET AL., 2022, PLOS ONE, CC-BY 4.0

  • Dolphins catch live fish in a pool of seawater — A) The dolphin B sequence (a, b, c, d) shows B sucking a live fish (arrow) into its mouth. B) Dolphin T (a) locates a fish, right eye turned forward. (b) On being captured, the posterior lower lip is pulled down showing the gums and teeth and fish (arrow) inside the mouth. (c) The dolphin reorients the fish while still pulling the lip down and expanding the gular area, apparently causing a reduction in intraoral pressure, but the fish almost escapes. C) Relative amplitude of the recorded sound of dolphin T during capture observed in B . D) Audible sound frequencies recorded from dolphin T during capture observed in B .
    RIDGWAY ET AL., 2022, PLOS ONE, CC-BY 4.0

  • Dolphin S visually tracks fish by rotating its eye. A) During a surface chase, the dolphin visually tracks a fish by turning upside down and rolling the eye forward, displaying the posterior sclera. B) The dolphin rolls the eye backwards displaying the anterior sclera as a fish escapes to the dolphin’s rear. Note the depression under the eyeball accompanying the backward rotation. C) Dolphin eye S without showing a depression.
    RIDGWAY ET AL., 2022, PLOS ONE, CC-BY 4.0

  • K dolphin catches live fish in San Diego Bay. A) View of dolphin K during the capture of fish. B) Relative amplitude of the recorded sound of dolphin K during capture observed in A . C)Audible sound frequencies recorded from dolphin K during capture observed in A . The red bar shows the capture point. Echolocation clicks appear at the end of these recordings as the dolphin searches for another fish.
    RIDGWAY ET AL., 2022, PLOS ONE, CC-BY 4.0

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