Rare whale dolphin mysteriously washes ashore

A female northern right whale dolphin washed ashore on the beach in Manzanita, Ore., on June 9. Only four other of these “unique” dolphins have been spotted by the Seaside Aquarium since 1995. (Tiffany Boothe/Seaside Aquarium via AP)

A rare female northern right whale dolphin washed up on an Oregon beach last week, leaving experts guessing as to how the creature, seen only four times on the coastline in the last 20 years, died.

The Seaside Aquarium said the 5-foot-long female was discovered at Manzanita Beach and transferred to Portland State University to undergo a necropsy — an autopsy performed on animals — but the initial results were inconclusive.

“Though sad, this has given us a unique opportunity to learn a little more about this incredible species,” the Seaside Aquarium wrote on Facebook.

First identified in the 19th century, the cetacean species resembles a cross between an orca and a bottlenose dolphin, according to the Oregonian. The dolphin, which lacks a dorsal fin, appears black with a white streak on its underbelly.

The right whale dolphin is known to make its home in waters further south and deeper offshore, ranging across the North Pacific from as far east as Japan to Alaska and Mexico, according to the paper.

Its documented movements correspond with changes in water temperatures, moving south when waters are cold and north when they’re warm, experts said.

“Though sad, this has given us a unique opportunity to learn a little more about this incredible species.”

— Officials of the Seaside Aquarium

The aquarium said the biggest threat these dolphins face are from high-sea drift nets, which were believed to be responsible for a 24 to 73 percent population decline. Drift nets were recently required by law in Oregon and California to issue acoustic warnings into the water to reduce by-catch rates.

The social species normally travels in groups of 200 to 300, though can sometimes be spotted with up to 2,000 other whale dolphins, leaving experts wondering how the lone female came ashore, the aquarium said.

The aquarium was awaiting further test results to narrow down the cause of death.