Who’s Saying What? Answers from New Tech

While researchers have studied dolphin communication for decades, science has only been able to generalize what signals are used during behaviors. This is because technology has not been available to localize or tell us which individual is talking and what signals they are emitting.

When researchers record communication and behaviors, typically a hydrophone and separate video recording device is used. Acoustic and visual recordings are synced, and while some researchers are able to associate physical behaviors to concurrent acoustic signals – neither video nor acoustic recording give an indication on who spoke the signal. So, it has been difficult to say what animals and signals are meant to act as a back-and-forth conversation. However, slowly but surely technology has advanced, and scientists are one step closer to localizing the ‘whistler‘.

Dr. Herzing from the Wild Dolphin Project began preliminary work using a new localizing device. This custom underwater device uses three hydrophones and camera to simultaneously record audio and video. The recordings are interpreted by a specialized software that will identify a whistle in real time. When watching the recording, the software will mark a ‘whistler’ with either: a yellow star if it emits a whistle, or a red square if it emits a click.

Watch this device in action and learn about Dr. Herzing’s work in the Bahamas.

Scientists have also developed novel technology capable of tracking the strength and projection of a dolphin’s echolocation. Dr. Amundin and colleagues have been working on the ELVIS project.

The ELVIS system includes an array of hydrophones and specialized software that visually tracks a dolphin’s echolocation beam. A dolphin is given the opportunity to choose a symbol on a screen – each symbol representing a food reward. Upon approach, a dolphin can point via their echolocation and ELVIS will follow the beam, showing both the strength of the signals and indicating the choice.

It is truly incredible the advances we have made in our technology and all the new questions we can work to answer!

“I did it!” – Dolphins cheer for themselves

Dolphins may call success and squeal in victory when completing a task correctly or catching prey.

Dolphins emit different types of vocalizations to transmit information about food, location and emotional state. One type of vocalization is called a “burst pulse”. Burst pulse signals are considered rapid click trains and have been observed when dolphins are foraging, as well as socializing.

Victory squeal with a simultaneous whistle. (Ridgway et al., 2015)
Victory squeal. (Ridgway et al., 2014)

Dr. Ridgway and colleagues conducted a unique study that combined simultaneous video and acoustic recordings to investigate what behaviors and vocals dolphins used when attempting to capture prey.

Researchers and trainers used a natural sea pen where a dolphin and trainer stayed at one end of the enclosure, while a fish was baited at the opposite end. Once the trainer cued the dolphin, it would swim across the enclosure in search of the fish.

A unique device was utilized in order to visually record the animal’s physical and acoustic behaviors at the same time. The device was temporarily placed on the melon (i.e., the top of the dolphin’s head) along with an additional hydrophone near the baited fish.

Customized device that simultaneously documented visual and audio recordings.

The researchers found a unique, 3-part vocal pattern during prey capture:

  1. Echolocation clicks were used to search out the fish,
  2. Clicks became closer together as the dolphin neared the fish
  3. A victory squeal (VS) (i.e., burst pulse signal) was emitted at (or just before) the time of capture
(A) As the dolphin eats the fish, head jerks are recorded on the forehead camera microphone. (B) Beginning of approach, echolocation clicks are found; the inter-click-interval became smaller when closing in on fish; at capture, victory squeal was emitted (C) Left to right: (a) view from forehead camera of fish (white arrow) in the distance (b) closing in on fish, TB (c) view of fish in dolphin’s mouth and simultaneous victory squeal (d) view of dolphin rostrum as the animal moves away clicking. (D) spectrogram of vocal pattern emitted during prey capture (from approach to just after capture).

Researchers coined the term “Victory Squeal” to represent the context of when it occurs (when a dolphin knows it has/or is about to succeed in a task), and the vocal being reminiscent of a child-like squeal.

This study was the first of its kind – connecting video and audio at the same time. Researchers were able to confirm dolphins using head jerking behavior when they are consuming a fish. They also presented a particular vocal sequence used when successfully capturing prey. They even extended their research and found that dolphins used a VS when doing a request from their trainer correctly!

Research in the future could potentially use this vocal pattern to assume successful behaviors in managed care or in the wild when people are unable to visualize what the dolphins are doing.

Dive into their study here and find out more about their investigation.