Author: Natasha Hynes
"The fact that these common stingrays have only just been discovered to make sound goes to show how little we know about life beneath the waves.”- Dr. Joni Pini-Fitzsimmons
We know a little bit about how elasmobranchs hear (to learn more about shark hearing, read ARTICLE) Yet, we know very little about the sounds they make. Do they even make sounds? Until recently, there had never been any recorded sounds from elasmobranchs in the wild. The sounds that have been recorded were from captive individuals and the sounds they made were usually associated with eating. Crunching, grumbling, and rumbling - all associated with chowing down - have been recorded from some of these individuals. Aside from a few observations in captivity, there hasn’t been much evidence in the way of recordings to show that elasmobranchs make sounds. This article describes the first recordings of elasmobranch sound production in the wild.
Three observations were recorded. The first was in the Gilli Islands, Indonesia, when a researcher was diving and came across a mangrove whipray (Urogymnus granulatus). When the researcher got within 2 metres of the animal, it began making “clicking” sounds and swimming away. The researcher also noticed that each “clicking” sound happened at the same time the spiracles moved. The researchers think that these “clicking” sounds could be coming from the contractions of the spiracles and gills.
The second observation was in Queensland, Australia. The researcher was snorkeling in shallow waters around mangrove whiprays and noticed one juvenile had been separated from its group. It produced seven “clicks” and it was noted that the spiracles contracted with each “click” in this case as well. After the juvenile made these “clicks” the rest of the group swam to the juvenile and the researcher who was snorkeling near it.
The third observation was also in Queensland, Australia. The researcher was snorkeling with a group of cowtail stringrays (Pastinachus ater), swimming behind one individual that was slowly moving away. Once the researcher got within a disk-width of the animal, it began making loud “clicks” that, once again, happened at the same time the spiracles contracted.
The researchers think that these sounds are “warning signals” to predators. The sounds that the rays produced were all within the known hearing ranges of their shark predators, which could startle and scare them away, but more research needs to be done on this.
This study shows that further research into elasmobranch sound production may be fruitful. However, all three of these observations were made through video collection (check them out here: https://figshare.com/articles/dataset/Sound_in_rays_-_video_files/16929838/1). The researchers suggest that future studies on elasmobranch sound production should use hydrophones to capture recordings.
"This discovery opens up exciting new avenues for elasmobranch research and challenges what we thought we knew about how they communicate.”-Dr. Joni Pini-Fitzsimmons
References:
Fetterplace, L.C., Delgado Esteban, J.J., Pini‐Fitzsimmons, J., Gaskell, J., Wueringer, B.E., 2022. Evidence of sound production in wild stingrays. Ecology. https://doi.org/10.1002/ecy.3812