A rare northern right whale dolphin washed up on Manzanita Beach in Oregon on Saturday — and scientists don’t know why, according to a Facebook post from the Seaside Aquarium.
The aquarium said they’ve only seen four of the dolphins since 1995.
Nehalem Bay State Park staff reported the animal to the Northern Oregon and Southern Washington Marine Mammal Stranding Network, a group that works with stranded animals, the Oregonian reported.
The mammal, a 5-foot 5-inch female, was taken to Portland State University for a necropsy, but the results were inconclusive, the aquarium said.
"We are waiting on more test results to see if we can narrow down the cause of death," the aquarium said.
The dolphins tend to live further south, the aquarium said, and they generally live in the deep, cold waters of the northern Pacific Ocean, from Baja California to the Gulf of Alaska and Japan, according to the National Oceanic and Atmospheric Administration.
The dolphins are sociable and like to travel in groups of about 100 to 200 animals, though they will sometimes swim in herds that total between 2,000 and 3,000 dolphins, NOAA said.
NOAA estimates that there are between 16,000 to 21,000 of the dolphins living off the coasts of California, Oregon and Washington and about 68,000 dolphins total in the northern Pacific Ocean. However, the agency added that they have "insufficient data" on the dolphins' population trends.
The animals were first identified in the 1800s and got their name because they resemble right whales, according to the Oregonian. The biggest threat to the dolphins is from large fishing nets, like high-seas drift nets and gillnets, according to the aquarium and NOAA.
Anyone using a high-seas drift net in Oregon and California is required to use pinger devices to warn unwitting cetaceans away from the net, according to the aquarium.
Because the dolphins are so rare, the aquarium said, the stranding "has given us a unique opportunity to learn a little more about this incredible species."