Cause of death for humpback whale calf found dead in Gastineau Channel this summer inconclusive

Animal still unidentified, tests and analysis yield no definitive evidence 

The necropsy team examines the humpback whale calf. Line from the peduncle of the animal was attached by the response team to help maneuver the animal on to the shore. (NOAA Fisheries, David Gann, taken under NOAA Permit # 24359)

By Ellie Ruel

Juneau Independent

A necropsy of the humpback whale calf found dead in Gastineau Channel in July turned up inconclusive results, according to the National Oceanic and Atmospheric Administration.

“Based on the necropsy findings and subsequent testing, we were able to rule out entanglement, predation, starvation, and major illness. While we were not able to rule out vessel strike as a potential cause of death, we did not find signs of blunt-force trauma on the tissues accessible for examination and sampling,” said Dr. Suzie Teerlink, NOAA Fisheries marine mammal specialist and Alaska Region humpback whale recovery coordinator.

Members of the Alaska Marine Mammal Stranding Network performed an initial examination and collected samples from the whale the day after it was towed ashore south of downtown Juneau. Measurements and samples were taken to establish information about the animal’s health. 

The calf was identified to be male, about six to eight months old, slightly over 30 feet long and weighed over 15,000 pounds. The fluke, or lobes of the tail that have distinctive, fingerprint-like pigmentation that can be used to identify individual whales, did not match any identified animals from regional catalogs, likely due to its age.

The carcass was left resting on its side and the angle made some tissues inaccessible for sampling. The necropsy team did observe bruises and bleeding on the whale’s exterior, but the trauma was not considered extensive enough to be a contributing factor. 

“We don't know if there are injuries that are inaccessible to see or sample,” lead veterinarian Dr. Kate Savage explained in a NOAA article published in late August. “We don’t want to speculate. Laboratory analyses of samples may help shed some light on what happened, but we may not get a clear answer.”

She took samples of the whale’s subcutaneous tissue, lung, muscle, liver, stomach, abdominal tissue, right eye, intestine, abdominal cavity, skin, and blubber, which were analyzed by the Alaska Veterinary Pathology Service. The summary diagnosis was an undetermined cause of death. 

According to Teerlink, this isn’t an uncommon finding. Necropsies can also offer broader insights into marine mammal biology and physiology for a species that is typically difficult to study.

“Field necropsies, in particular, can be challenging due to environmental conditions and limited access to all tissues. Consequently, it is not uncommon for the cause of death to remain inconclusive,” she said.

According to NOAA, no further tests are planned to determine this whale’s cause of death, but some samples were set aside for future research.

• Contact Ellie Ruel at ellie.ruel@juneauindependent.com.