Understanding what a species eats – and how that changes over time – not only gives us a window into the lives of wild animals, but also gives us the power to be responsible stewards of their ecosystems.
Genetic metabarcoding is changing the way we look at diet and foraging ecology in whales. With each new sample, we gain new insight into the feeding behavior of these enigmatic species. Learn more about how the Whale And Dolphin Ecology Lab (WADE), led by SAFS Assistant Professor Amy Van Cise, is using genetic metabarcoding to understand and conserve southern resident killer whales in the Salish Sea.
Killer whales are the only natural predator of baleen whales – those that have “baleen” in their mouths to sieve their plankton diet from the water. More solitary than toothed whales, baleen whales face predatory attacks from killer whales, especially mother and calf pairs. When attacked, some species fight back, while others choose flight. But whale species also produce loud underwater songs…what stops killer whales from homing in on their calls and attacking them?
In new acoustic research conducted by Trevor Branch, a Professor in the University of Washington School of Aquatic and Fishery Sciences, he found that some baleen whale species call at such deep frequencies that they’re completely undetectable by killer whales—who cannot hear sounds below 100 Hz. These tend to be the whale species that flee in the face of attack. Meanwhile, their high-frequency singing brethren who fight back when attacked, also tend to be slower-moving and more maneuverable. The deep singers are in the flight club and include blue, fin, sei, Bryde’s and minke whales, while the fight club includes right, bowhead, gray and humpback whales. Branch’s research was published in Marine Mammal Science on Jan 31. 2025.
P. Markovic, CETREC, Western Australia
Killer whales charging next to a blue whale calf with visible killer whale toothmarks like a rake and missing chunks of flesh. Location: Bremer Bay, Western Australia.
The fight or flight hypothesis is not new, but research into acoustics is shedding new insights into the behavioral, morphometric, and ecological adaptations of baleen whales. Could this so-called acoustic crypsis, where whales that call at such deep frequencies that they are acoustically invisible to killer whales, have developed as a defense mechanism from attack?
Killer whales are found in every one of the world’s oceans, and their prey ranges from small fish to the largest whales on Earth. The fight species of baleen whales usually migrate and calve closer to the coast in shallow water, a haven of sorts which provides easier defense against killer whale attacks—especially for group defense in aggregations. Combined with their slow-swimming and more navigable bodies, their communication with other whales is often at higher frequencies easily heard by killer whales—above 1500 Hz. In contrast, flight species have streamlined and slender bodies adapted for speed, and typically disperse across wider open ocean regions for mating and calving, where they are able to flee in all directions.
These behaviors also have implications for feeding and mating. Denser congregations in shallow coastal areas leaves less food for fight species, in comparison to the open ocean favored by flight species. However, the opposite is true for finding a mate—it’s easier when you’re all in a similar location, versus spread out over long distances. Where do acoustics fit into this picture?
Singing is a fundamental part of mate attraction and selection for whales. Males of the flight species sing in a way that maximizes the number of females that hear them, producing simple and repeated songs to attract a potential mate, and singing over prolonged periods to allow females to track them down. “But these super loud songs could expose them and their mates to killer whale attack. And this is where acoustic crypsis comes in: singing at low frequencies that are impossible, or very difficult, for killer whales to hear,” Branch said.
J. Daw, CETREC, Western Australia
After a killer whale pod kills a blue whale calf, one dives into the mouth of the blue whale to feast on its tongue. Location: Bremer Bay, Western Australia.
Branch conducted a review of aquarium experiments on killer whale hearing ranges, reviewed the source frequency and source level of populations of all baleen whales, and combined these with knowledge of how sounds move through the ocean, to predict which whale populations can be easily heard by killer whales. It turns out that flight species generally can’t be heard more than 1 km away by killer whales, unlike the calls of fight species.
The research shows that under the sea there is a sound landscape governed by fear, with some whale species choosing to sing their songs to their prospective Valentines at deep levels to avoid attacks; while other whale species compete to sing the most varied and interesting songs, and fight back when attacked. The fight vs. flight differences appear to drive all aspects of the lives of baleen whales, from where they are found, to their communication, to where and when they breed and feed.
Branch said: “It just never occurred to me that some whales sing low to avoid killer whales, but the more I looked at this, the more I realized that every aspect of their behavior is influenced by the fear of predation.”
Alongside two student researchers from her lab, SAFS Assistant Professor Amy Van Cise has been out on the Puget Sound for a few days conducting killer whale research. Working with a team comprised of UW students, Wild Orca, and San Diego Zoo Wildlife Alliance, they’re assisted in locating fecal samples from the whales by Wild Orca’s poop-sniffing dog, Eba.
Eba, the poop-sniffing Wild Orca dog.
Amy Van Cise, with student researchers Sofia Kaiaua and Mollie Ball, were aboard the Wild Orca boat with Research Director Dr. Deborah Giles, who is also a Resident Scientist at Friday Harbor Laboratories, where she teaches Marine Mammals of the Salish Sea in the Spring. Recent UW Marine Biology and Oceanography graduate, Aisha Rashid, was also present, now working for Wild Orca. They were joined by Hendrik Nollens from the San Diego Zoo Wildlife Alliance, and Eba’s handler, Jim Rappold.
NOAA research permit #26288 (Wild Orca)
The research team is collecting fecal samples from Southern Resident killer whales.
To collect samples, Wild Orca drives slowly about 500-1000m downwind of the killer whales (preferably behind them), waiting for Eba to catch a scent. Once she does, one of her trainers (either Giles or Jim Rappold) works with Eba to have her direct the boat to the sample location, where the team then scoops it out of the water and carefully spins it down, pours off the excess sea water, and stores it in a conical tube on ice until they can get it in a freezer.
Hendrik Nollens (San Diego Zoo Wildlife Alliance) holds one of the samples collected during the trip.
From a single sample, the collaborative research team can get hormones (to tell things like pregnancy, stress, or nutritional stress), genetics (to ID the whale, determine diet composition, and/or look a gut microbiome and parasites), and also look at toxins/contaminants.
NOAA Research Permit #26288 (Wild Orca)
A single fecal sample can reveal a wealth of information about a killer whale.
The trip has also been used to collect content to develop an outreach video based on the diet research underway at the WADE lab and how it fits into the broader conservation goals for Southern Resident killer whales. For the video, Mollie and Sofia interviewed Dr. Michael Weiss, who is the Research Director of the Center for Whale Research, and Jay Julius, the former Chairman of the Lummi Nation, full time fisherman and father, and the Founder and President of Se’Si’Le.
The research team aboard the Wild Orca boat.
UW student researchers in the WADE lab interview Dr. Michael Weiss, Research Director of the Center for Whale Research.
All photos of killer whales are taken under NOAA research permit #26288 to Wild Orca
