This last trip to Little Cayman was the first time I ever spent some decent time with Stingrays. We saw them perhaps on 4 or 5 dives – essentially whenever we were diving near a sandy area. One thing I was amazed with is the grace with which they glide over the sand, barely disturbing it at all. Put a human diver kicking near the sand, especially ones that are not conscious of their body movements, and you usually end up with one big sand cloud. With stingrays, hardly a particle was disturbed as they glided over the surface.
However, when they are searching for food, they know how to kick up a pretty good sandstorm! When they are gliding over sand, they rely in their incredible sense of smell, combined with sensory features that allow them to detect changes in water current as well as electrical signals underneath them. Clams and muscles tend to expel water changing the currents around them, as well as give off electrical signals. The stingrays pick up on both of these things and stop when they sense something might be below the sand.
They can then agitate the water and sand beneath them to dig down to find prey. This agitation kicks up quite a bit of sand underneath them as shown in the photo here. I don’t know exactly how they do this. But since they breathe by taking in water from the holes behind their eyes (spiracles), and expel it from their gills underneath, I would guess they also use this to also stir up the sand.
I found them to not mind my presence much. For this photo of the one digging in the sand, I was laying on the bottom right in front of it with my 105 mm lens. It allowed me to photograph from a distance away and not be too close to disturb the rays lunchtime. However, it is really not the optimal lens to use for an animal this large. It means you have to put quite a bit of water between you and your subject, which can result in reduced detail and color. Fortunately southern stingrays are quite gray in color and I didn’t need to worry about using strobe lighting.
I did find another that was nearly completely buried in the sand, and slowly inched my way towards it on the bottom. That enabled me to get this other closeup view of a southern stingray. This is how they are typically found when they are resting.
I really enjoyed the time I had to observe these very interesting animals. Their grace in swimming was another reminder how awkward human beings are in this environment. (Something you are reminded of quite frequently by all sorts of aquatic life.) Nonetheless, we have the ability to go into their world and observe. Our presence is tolerated to some extent as long as we recognize we are in their world and under their rules.