Marine scientists investigating the mass stranding of five pilot whales on Kauai’s Kalapaki Beach last month have ruled out disease as causing the event, and say something sudden must have triggered the stranding. But it’s still unclear what exactly caused the whales to beach themselves.

Besides ruling out disease, marine mammal experts said the whales did not show signs of trauma from underwater noise impacts, such as gas bubbles in their blood vessels or organs to indicate decompression sickness. The Navy reported it did not conduct sonar work within 24 hours of the event, within 5 nautical miles of the area.

The stranding began in the early morning hours of Oct. 13 in Kalapaki Bay, fronting the Kauai Marriott Resort. The whales were part of a pod of approximately 17. Two of the whales died on the beach that morning, and three more were found dead in the bay that afternoon.

The bodies of the whales — three males and two females — were in “very good” condition, and all five had full stomachs, said Kristi West, stranding director at the University of Hawaii’s Hawaii Institute of Marine Biology, who performed necropsies on the animals.

“We often find animals that are very skinny and look nutritionally stressed, and that was not the case with any of these animals,” West said Tuesday during a joint informational briefing before the House Energy and Environment and Ocean and Marine Resources committees.

The briefing provided an unusual glimpse into the ongoing investigation. West said her work — she responds to roughly 20 marine mammal strandings per year — typically is not reported publicly.

“This was pretty surprising for us for strandings: All five of our animals had full stomachs, and that’s somewhat unusual, because typically if we have a single stranding or an animal is sick, it hasn’t eaten,” West said. “They’ve got to work really hard to eat. They’ve got to dive to potentially hundreds of meters and catch prey.”

West said after the briefing that several test results are still pending, including neurotoxin screenings to test for poisons that affect the nervous system, testing of liver tissue for rodenticides, and microscopic examinations of the whales’ inner ears.

“The fact that all these animals had so much food and the freshness of the food just tells us that something sudden happened that brought them in,” she said. “That’s what we kind of have right now for hints as to what happened to the whales. … This was something sudden.”

State Rep. Dee Morikawa (D, Niihau-Koloa-Kokee) said she’s been researching whether the mass whale stranding is somehow linked to the state’s deployment of rat poison on Lehua Island, a seabird sanctuary off the northern tip of Niihau.

The state Department of Land and Natural Resources in August and September dropped pellets containing diphacinone on the rat-infested island. Social media posts showing dead fish and birds prompted an investigation, but preliminary results were inconclusive as to whether the rodenticide caused the deaths of dozens of mullet and two juvenile booby seabirds.

Morikawa said she’s concerned that any linkage of the whale stranding to the rat poison will be “covered up.”

“There are too many bold statements that say, ‘There is no way that the rat poison could have had any consequence to the whales.’ And maybe it’s true,” Morikawa said. “But it’s just so coincidental. Common sense tells me that if the whales pass Niihau and they see a whole lot of dead fish or sick fish or squid or whatever, they’ll have a field day eating them. And that’s what I’m suspecting happened.”

West said she too is eager to get results back from the liver analyses, and promised to openly report the findings. She said frozen tissue samples can also be further tested along with samples from the fish and squid found in the whales’ stomachs.

“We will absolutely share any information that we get, and if there is request for additional testing … I’ll be happy to send them,” West said. “My goal here is to get answers as well. Lots of information is going to trickle in over the next several months.”

There are an estimated 19,500 pilot whales in the waters surrounding the main Hawaiian Islands, including resident populations that stay in certain areas and open-ocean groups.

David Schofield, regional stranding coordinator with the National Oceanic and Atmospheric Administration, said there were four mass pilot whale strandings in the late 1950s, on Lanai, Kauai and Oahu, and one off of Molokai in 1989.

“Mass strandings are very rare for Hawaii, but they are not uncommon around the world, especially over time with diminished ocean health. We’re seeing more of these across the globe,” Schofield said.

West said that although the Kauai stranding was unfortunate, scientists were able to collect important research data.

“Part of the goal of our program is to maximize the opportunity to learn about these whales. We’re not going to be able to properly protect them unless we understand how they live,” she said. “We’re not going to be able to address threats that they face unless we know exactly what those threats are, and then we can start to address them.”