If you want to study a stingray’s strike but you don’t want to use your own tender foot as the test target, where do you turn?
To the Halloween story for a zombie foot, that’s where. At least that was the solution for Cal State Long Beach lecturer Benjamin Perlman, who will soon publish his research on when and how rays typically sting.
It started when a colleague connected Perlman with someone hoping to develop a sting-resistant surf bootie, and he discovered there’s not much research on rays’ striking behavior.
“Everybody’s afraid of the great white shark, but the main risk that you actually run into (at the beach) is getting stung by a stingray,” Perlman said, so “this is pretty low-hanging fruit.”
Perlman and some of his undergraduate students collected round rays (known in science as Urobatis halleri) in Belmont Shore and Seal Beach and brought them to a lab, where the animals were put into an aquarium one at a time and—gently—stepped on with a zombie foot that’s been filled with sand and attached to a length of PVC pipe.
High-speed cameras positioned at the top and on one side of the tank captured the rays’ reactions, and software allowed Perlman to position the images of stingrays within a digital 3-D grid so he could precisely track their movements.
A serrated barb grows near the end of the stingray’s tail and normally lies flat against it, but when the animal’s defense mechanism is triggered, the tail flips up and the barb is exposed.
Shooting at 500 frames per second allowed Perlman to slow down the tail action, but in reality, the sting happens within about a half-second of when the ray is stepped on, he said.
A key takeaway? The ray is by far the most likely to sting when stepped on in the middle of its body and pinned down; if a careless beachgoer steps on the animal’s snout or its side fins, it’s most often going to quickly swim away.
Perlman said he and his students determined a stingray will strike about 85% of the time when pinned down, but only about 5% of the time when stepped on or brushed around its edges.
“The fact that they really just try to escape most of the time, that really surprised us,” he said. “We expected there to be a lot more strikes from other parts of the body.”
The research helps explain why the “stingray shuffle”—sliding your feet along the sand instead of picking them up as you move through the water—works so well.
Stingrays seem to like the warmer water close to the shore, and when the tide is lower they tend to burrow under the sand, so they’re hard to see, Long Beach Marine Safety Capt. Omar Naranjo said.
Rays are “pretty easy to avoid if you shuffle your feet,” because they feel you coming and swim away, he said.
Getting stung is a common injury in Long Beach, with more than 240 reported stings so far this year and more than 1,300 since June 2021, Naranjo said.
The only known treatment is soaking the injured foot or ankle in hot water, which Perlman said helps break down the toxin that is secreted at the base of the ray’s barb (the stinger) and travels into the wound.
When beachgoers run afoul of a stingray, Long Beach lifeguards can get them to a lifeguard station and apply hot water, Naranjo said. He also advised people to try the Watchtower app (scan the QR code on the back of any lifeguard tower) or visit safebeachday.com for information on any stingray hotspots as well as water temperature, wind direction and other data.
Perlman plans to submit his research later this summer to a scientific journal, and he’s already got a number of other questions he and his students can explore: How does water temperature affect rays’ behavior? Are there differences based on the size or sex of the stingray? What muscles are involved in the tail action, and how do they use their pectoral fins to bury themselves in sand?
He’s hoping his work will help improve beach safety, but, “It still kind of blows my mind that here are these stingrays that people get struck by all the time,” he said, and, “we really didn’t understand how the rays were doing it.”