August 6, 2019

Short-Finned Pilot Whales Strand on St. Simons Island

Posted by: Cohen Carpenter

Short-Finned Pilot Whales Strand on St. Simons Island

In case you missed it, a couple weeks back, on July 16, 2019, roughly 50 short-finned pilot whales (Globicephala macrorhynchus) came to St. Simons Island beaches, with several of them stranding themselves onshore.

Dozens of beach-goers quickly moved into the shallow water attempting to push the animals back into the surf. After several hours most of the whales were back in the water, however a few of them beached a few more times in locations south of the original stranding and were again helped by onlookers.

One of the whales had to be euthanized due to its poor health and inability to swim off, and two others washed up later after the pod swam off. The fact that the pod did not return, suggests that one of the three deceased whales could have been the cause of the mass stranding. Many cetaceans (whales and dolphins) have such strong social bonds that groups will often follow a leader, even if the leader is sick or disoriented and leads them away from there preferred habitat and even to shore.

Video footage taken by a charter captain several days later near  Ponce Inlet, FL (just north of Cape Canaveral) shows a pod of short-finned pilot whales in which one individual appears to be one of the whales from the St. Simons stranding. In dolphins and whales, fins are often used in identifying individuals, like fingerprints, because each individual usually acquires a distinct set of nicks and notches through rough play, attacks, hitting obstacles, and unfortunately from boat strikes and entanglement in fishing gear. This sighting holds promise that the pod made it back to deep water safely and the quick action by beach-goers prevented a much larger mortality event.

Necropsies of the three carcasses have did not reveal any direct culprit. Their stomachs were mostly empty, which could suggest poor health or a large amount of time spent out of their normal feeding grounds, according to Clay George, wildlife biologist with the Georgia Department of Natural Resources. Two types of parasites were also found in the inner ear and the sinuses, but it is not clear yet if these had a significant role in the stranding. Work is being done to examine the parasites and tissue from the affected areas. It’s worth noting though, that pilot whales are in a group of cetaceans called odontocetes (along with dolphins), which rely heavily on echolocation for communication and navigation in which sound waves are processed through the inner ear.

For this same reason, naval sonar tests for identifying submarines have been known to cause strandings. The sonar used for these tests occurs at a low frequency that can maintain extremely high decibel ranges up to 300 miles away. These noises can be painful to many species and disorienting to those animals relying on echolocation.

Seismic testing for oil exploration can have the same effect, as decibel ranges are comparable to that of military sonar tests. Luckily, the short-finned pilot whale is not considered an endangered species. However, the North Atlantic Right Whale (Eubalaena glacialis) is, with roughly 400 individuals left. In recent decades it was discovered that the waters off Georgia’s coast serve as this species’ calving grounds. The reception of sound is not the same in right whales as in toothed whales, but extreme noises will be similarly painful and disruptive. Such disruptions in critical habitats like calving grounds could push this species over the brink. Read more on the North Atlantic Right Whale here.

 

*Photos by Guerry Norwood Sr., St. Simons Island Resident

Above: Swimmers helping one of the whales that returned to the beach near the St. Simons Island pier, where a crowd of onlookers gathered.

 

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