Mystery orcas with bulbous heads wash up dead in unexplained mass stranding

The nine Type D orcas were discovered in Chile on a beach, and one of the females was confirmed to be a healthy adult with no evidence of human participation in her demise.

It is the first occurrence of its sort in 67 years and just the second time in recorded history that a bizarre and unusual bunch of orcas has become stranded on a beach in Chile.

The "Type D" sub-group of orcas, which is a unique type of orcas endemic to the Southern Hemisphere, includes orcas (Orcinus orca). Some researchers contend that Type D orcas may potentially be an entirely distinct species since they differ so greatly from other orcas.

Robert Pitman, a marine biologist at Oregon State University, told Live Science, "I think there's a good possibility here that this Type D killer whale could be one of the largest undescribed species left on the planet."

At least nine distinct subgroups, or "types," of orcas exist around the world. However, Type D orcas, which have rounder "melon" heads and smaller white patches by their eyes, are among the most distinctive.

The first Type D orcas were discovered by scientists in 1955 when a group of oddly shaped killer whales washed ashore on a New Zealand beach. But it wasn't until the early 2000s that researchers discovered whales that matched the peculiar face features and body forms of the 1955 New Zealand orcas in images from all throughout the southern oceans that the creatures were recognized as a different group of orcas.

Up to the two most recent cases, the sole reported stranding of a Type D orca occurred in 1955 at a beach. Due to her unique tiny eye patch, rounded skull, and curled dorsal fin, a stranded female orca that was found in November of last year was recognized as a Type D orca by researchers in Punta Arenas (near the extreme southern tip of Chile). The scientists moved the animal's carcass to a museum after taking measurements and images of it.

Eight stranded orcas were discovered later that month, roughly four kilometers (2.5 miles) distant. Despite being much more decrepit, the experts think these animals also belonged to the Type D of orcas. The findings of the study were released by the researchers on June 8 in the journal Polar Biology.

The nine orcas' deaths and beaching remain unknown to the biologists. Although the causes are not well known, whales may become stranded for a number of reasons, such as disease or human use of underwater sonar. The team's examination of the lone female orca revealed that it was an adult in good health. No indications of human participation, such as entanglement or a collision with a boat, were present. The animal was free of parasites, and the heart and all abdominal organs looked to be in good condition. The necropsies on the other eight, more severely decomposed orcas were only measurements.

Pitman asserted that Type D orca strandings are probably uncommon for a good reason. The only significant landmasses in that region of the ocean for orcas to beach on are New Zealand, Tasmania, and the southernmost tip of South America. Type D orcas exclusively inhabit the region between 40 and 60 degrees south.

The new article was examined by Pitman before it was published, and he provided feedback to Live Science through email. "I have to admit, I never thought I would hear about another stranding of Type D killer whales in my lifetime," Pitman said.

As far north as Greenland and as far south as Antarctica, different species of orcas may be found. Although the ranges of several of these kinds overlap, they don't seem to interbreed or even necessarily interact with one another.

Similar to Type D orcas, researchers have hypothesized that additional populations may differ from one another to the point where they may be considered distinct species or subspecies.

Pitman and colleagues conducted some of the earliest genetic studies on Type D orcas and discovered that the population is likely quite tiny and highly inbred.

However, Pitman stated that in order to fully understand Type D orca biology, further biopsies and tissue samples would likely be needed in order to shed light on the puzzle of how these mysterious sea creatures are linked to other orcas.