NOAA Team Gets Innovative

How a Bamboo Knife was Altered to Save Entangled Whale Calves

By Clarissa Lam

March 2021

The blade just won’t catch. The whale disentanglement crew has been out on the Pacific under the hot Hawaiian sun for the past two hours tracking a female humpback whale and her calf. The crew huddles on their boat off the shores of Maui, waiting for the whales to return to the surface for air. Finally the whales surface and the crew quickly reaches in with their tools, but the ropes around the calf are just too tight and the blade can’t find a nook or cranny to cut through them. NOAA didn’t have the right tool in the toolbox.

Increased Risk to Whale Calves

Adult whales can be entangled for years until someone reports the entanglement to the right responders. However, the timeline for calves is far shorter, and entanglement can be particularly dangerous for whale calves. Whale calves drink their mothers’ milk, which can be about 50% milk fat, causing calves to grow rapidly and increasing the risk of embedded lines. If a line entangles a whale just a few months before it is discovered by a disentanglement response team, the line can embed into the whale’s blubber layer as the whale continues to grow around the rope. “We were watching these lines around the calves disappear into the blubber,” said Grant Thompson, who serves on the sanctuary-led whale entanglement response team.

The deeper the line is embedded, the greater the lethality, especially in whale calves. Because calves grow so rapidly, embedded lines are far more likely to occur compared to mature whales. By the time the whale disentanglement crew can reach an entangled calf, the ropes can be embedded several inches into the whale’s blubber, making the normal hooked blade useless.

entangled whale with pole blade
The other knives that the response team uses are only sharpened on the inside of the blade so they can run along the whale without cutting it. Those blades then hook onto the lines and use the sharp edge on the inside of the knife to cut the line. Photo: Nicole Davis/USCG, under NOAA Marine Mammal Health and Stranding Response Program Permit # 932-1905-1

A Grassroots Approach

Person sharpening tool with safety goggles
Thompson sharpens the curved knives to help free whale calves. Photo: Ed Lyman/NOAA

The waters around the Hawaiian Islands, including Hawaiian Islands Humpback Whale National Marine Sanctuary, serve as the principal breeding and calving grounds for a majority of the humpback whales in the North Pacific, resulting in the entanglement of newborn whale calves — some even as young as only a few weeks old. After encountering an entangled whale calf in the sanctuary in February 2013, the whale disentanglement crew quickly realized that their existing tools would be unable to get to the embedded wrap. Their hooked blades, which are only sharpened on the inside to protect the animals, simply skipped over the embedded line.

Just seven months later in December 2013, the team encountered another entangled calf with a similar tight wrap around the body that was quickly becoming embedded. This time, one team member, Grant Thompson, set out to create a blade that could free the calf. “This is a constant situation with entanglement in general because there's no store to go to and grab the tools that you need,” Thompson said. Each entanglement is unique and teams sometimes need to develop individualized tools for that particular entanglement. While a few blades have been developed and standardized specifically for disentangling whales, some blades can be altered to do the job.

Thompson bought a curved knife that is commonly used to cut bamboo in Hawai’i and then sharpened the inside as well as the outside of the blade. By sharpening both sides of the knife, the blade can cut into the deeper layer of blubber and reach an embedded line. “Unfortunately it's one of those tools that you have to be cruel to be kind,” Thompson said.

Once the knife was prepared and tested, Thompson brought it to Ed Lyman, NOAA’s regional large whale entanglement response coordinator for Hawaiian Islands Humpback Whale National Marine Sanctuary. Together they added a coupling to the base of the knife so they could attach it to the long pole they use to reach whales from their boat. From then on, Lyman called it the ‘Thompson Blade.’

whale entangled under pole knife
Lyman uses the Thompson Blade to cut the ropes from a calf. Photo: Michael Griffin/USCG, under NOAA Marine Mammal Health and Stranding Response Program Permit # 932-1905-1

Scaling Up Distribution

Although Thompson’s original blade was created in 2013, the story of this blade has reentered the spotlight as Lyman began distributing the tool across Hawaii and Alaska at the start of the whale migration season in the fall of 2020. Lyman also plans to distribute more copies of the knife to Monterey Bay National Marine Sanctuary in preparation for their coming season. Beyond the danger entanglements pose to whale calves, a wide variety of marine animals such as seals, turtles, and manta rays can also become entangled, and the Thompson Blade can be used to save any animal entangled with an embedded line. As the season comes to an end in Hawaii, we celebrate the whale disentanglement response teams and their ongoing creativity and grassroots efforts to protect our beloved marine mammals.

All imagery showing entangled whales and depicting their response was authorized under NOAA Marine Mammal Health and Stranding Response Program Permits 932-1905 and 18786. Do not approach marine wildlife without a permit. The best thing you can do to assist an entangled whale is to contact your local hotline or the U.S. Coast Guard.

Clarissa Lam is a student at Reed College and a Virtual Student Federal Service intern for NOAA's Office of National Marine Sanctuaries.