A 12-foot male Minke whale was found washed ashore on the beach at Robert Moses State Park Wednesday night.
Marine biologists from the Riverhead Foundation are performing a necropsy to see how it died.
The whale is the latest in a string of sea creatures to turn up on Long Island's shores.
Officials say a total of five whales have washed ashore this summer, including one at Davis Park about two weeks ago.
Portuguese man-of-war have also been spotted on beaches from Kismet to Montauk and have stung at least two children.
As News 12 has reported, there were two shark sightings recently off Jones Beach and Overlook Beach. A viewer also sent in a picture of a thresher shark caught yesterday at Cedar Beach.