Have you tried to snap your fingers under water? Chances are, you can see the movement and see the waves caused by the movement, but you cannot hear the sound.
It is hard to hear sounds being produced under water.
But it is easy to hear whale song in the seas. We hear it, and other whales hear it too.
If you have never heard a whale song, this video should help.
So far, it was assumed that most elasmobranchs, a type of bony fish – sharks, skates, sting rays, manta rays, etc., do not produce sounds.
They have other sensory organs that help them understand and respond to their environment, including sensors for electrical impulses in water. But no vocal chords.
We just found out that they can hear!
It was only in a 2020 study by Cierra Braga, a doctoral student at the Florida Institute of Technology, that we learnt, for the first time, that Sting Rays can hear, and respond to voices.
It was found that typically, sting rays use sounds only as a stress signal. i.e., when they hear sounds, they respond to it like monkeys in the jungle respond to a warning call of tiger approaching.
And in 2022, the first calls of sting rays were recorded in the wild.
They did produce the clicking sounds in captivity once…
In a study conducted in the 1970s, captive sting rays produced the clicking sound when prodded. This study was not taken to indicate the general sound producing behaviour of sting rays because:
A. The fish were captive.
B. They produced the sound only when prodded – so it was surmised that this was a stress response.
So, What do we know now?
In a study published in the journal Ecology, the authors have observed two species of Sting Ray making clicking sounds in the wild. The video submitted as part of the study is what you have seen in the first part of this report.
The two species are angrove whipray (Urogymnus granulatus) and cowtail stingray (Pastinachus ater), both native to the Indo-West Pacific.
The study was led by Lachlan Fetterplace, a marine ecologist at the Swedish University of Agricultural Sciences.
But they are still stress calls. In both studies, the researchers noted that when a human approached the fish, the sounds were made. When the person increased the distance from the creature, the sound stopped.
Following the publication of the report, some others have also shared their own experiences with sounds. Here is one such video, from 2020.
Why is this interesting?
For starters, sting rays do not have vocal chords. So, we do not know how they produce these sounds.
Secondly, the frequency range of this sound was checked against the range within which sting ray can hear, and the researchers learnt that sting rays can hear these sounds, they are within the hearing frequency.
Further, the sounds are also within the hearing frequency of their predators (hunters) like sharks. So, they can hear these sounds too.
One interesting observation made by one of the researchers is that in 2018 (this footage was filmed off the coast of Indonesia and Australia in 2017-18), when a young (juveline) sting ray made the clicking sound, many adult sting rays surrounded it shortly after. This could be a call for protection or support.
At this time, we are just guessing.