“Click … buzz … crunch.”
Those are the sounds, as researchers describe them, that get recorded when the endangered southern resident killer whales go hunting for salmon, then zoom in on their prey and finally make a kill.
Meanwhile, underwater acrobatics performed by the orcas — such as twists and turns as they close in on an elusive salmon — were found to be consistently associated with certain echolocation sounds made by the whales while tracking their prey. These and other recently reported findings were discovered by attaching sophisticated sound-and-motion instruments to the whales themselves.
Based on newly discovered connections between sounds and behavior, experts are able to describe the conditions — including noise from boats — that lead to greater success or failure when the whales go hunting for salmon. This information, they say, can be used to better protect the orcas over the long term.
“We’ve been building on technology that’s been available for 20 years,” said Jennifer Tennessen, a research scientist who has focused on the movement aspects of the whales. “As with a lot of research, the capabilities started slowly and then started growing faster and faster.”
Years of fieldwork with the whales and analyses using computer modeling have shown how noise from vessels appears to change the diving patterns of southern resident orcas and interfere with their foraging activities.
By combining so-called “signature movements”— such as deep diving — with corresponding sounds made by the whales, scientists are developing a fairly clear picture of orca hunting practices, said Marla Holt, a researcher with NOAA’s Northwest Fisheries Science Center who has focused on the acoustic aspects of these studies. With echolocation, killer whales send out high-frequency pulses and then listen for echoes, perhaps forming a mental image of their surroundings.
“The rapid echolocation clicks sound like a buzz,” Holt said, noting that such buzzing is often heard during a rapid chase of salmon in deep water. “They are trying to keep the fish within their acoustic gaze,” she explained.
A sudden jerky change of direction, sometimes accompanied by the whale’s rolling over to an upside-down position, has been recorded time and again, she said, particularly just before a whale snatches a fish. “You can hear the crunch sound from tearing the prey apart and sharing among family members.”
Years of fieldwork with the whales and analyses using computer modeling have shown how noise from vessels appears to change the diving patterns of southern resident orcas and interfere with their foraging activities. Since the well-being of the whales is tied strongly to their getting enough food, these studies have implications for whale-watching boats, sport fishers and many commercial operations.
The latest provocative findings, still unpublished but reported by Tennessen at the online Salish Sea Ecosystem Conference in April, involve a behavioral comparison of southern resident orcas with their distant relatives, the northern residents, which frequent British Columbia and Southeast Alaska. The northern resident population, which also eats fish, has been growing at a healthy pace, while the southern resident population is essentially the same as in the 1970s, when numbers were depleted by orca captures for aquariums.
With the help of Canadian researchers, the latest study examined the differing reactions to noise among the two major groups. Among many findings, the researchers learned that northern residents were capturing more fish overall than southern residents. And, while both groups shared food with family members, older females did most of the pursuit and capture among northern residents, while males did most of the hunting among southern residents. Since males are larger, they may be expending more energy for an equivalent amount of food, according to Tennessen.
These and other social differences in foraging may have become ingrained into the cultures of the two groups of orcas, yet questions remain as to how these differing hunting techniques came about and how they may affect the overall populations.
Holt and Tennessen have become close partners in these underwater orca investigations. At the conference, April 26-28, they drew from more than 20 years of studies by various researchers to explain the current state of knowledge. Both researchers work for NOAA. Holt is on the staff of the Northwest Fisheries Science Center, while Tennessen is employed by Lynker, Inc., working for the same agency but under a government contract.
Vessel noise and interference with killer whales were the subject of about 40 conference presentations — a single ongoing track lasting through the three-day event. Discussions ranged from keeping track of vessels in the Salish Sea, to reducing noise in the water, to assessing the health conditions of the orcas.
“Effectively, noise is a problem because lack of Chinook salmon is a problem,” asserted Rob Williams, co-founder and chief scientist of Oceans Initiative, a Seattle-based research group dedicated to the protection of marine life. If it wasn’t for the need to find food, he said, the effects of noise on the whales would be far less severe.
“If there is not enough salmon available in the environment, vessel noise and disturbance will reduce the amount of prey that is accessible to the whales,” he said. “The population consequences of noise will look just like an exaggerated effect of prey limitation.”
The lack of adequate prey can affect body condition, reproduction and survival, Williams said. Those effects are exacerbated by the amount of toxic chemicals consumed when eating contaminated Chinook.
“We have known since the late ‘90s or early 2000s that noise and disturbance affects the behavior of killer whales,” Williams said. “Although the science is progressing quickly, the management actions are lagging a few years behind, and it seems to me we are always playing catchup.”
Acoustic ties to behavior
The key to the Holt and Tennessen behavioral studies is a package of high-tech instruments, called a digital acoustic recording tag or D-tag. These cellphone-sized units are attached to killer whales by reaching out with a long pole. Suction cups are designed to hold the instruments in place for a day or so, then researchers retrieve the tag from the water by following a radio signal.
Listen to the sound of the echolocation behavior of a killer whale recorded on a digital acoustic recording tag or D-tag, including examples of the faster clicks and buzzes the whales make when they are chasing and trying to capture prey. Auido recording courtesy NOAA Fisheries under Permit No. 781-1824/16163
The latest instruments provide a unique point-of-whale perspective by precisely recording depth, changes in direction and speed, and even rolling motions. Besides movement, a pair of stereo hydrophones (underwater microphones) picks up sounds from the whale wearing the tag and from nearby animals, along with ambient sounds, including vessel noise. The result is a rare insight into what the whales are hearing.
By modeling sound and movement variables, Holt and Tennessen have been able to identify distinct patterns of behavior.
For example, the whales typically exhibit slow clicking for echolocation as they move along searching for prey, said Holt. This searching pattern may include dives to 60 feet or so. Without the clicking, the whales are considered to be in a traveling mode — a separate state of nonforaging behavior.
Occasionally, a whale will make a deep dive, often more than 450 feet, accompanied by an increasing rate of clicks that eventually sounds like a buzz to the human ear. This buzzing sound is associated with the hot pursuit of a fish and may involve rapid changes in acceleration and direction, often followed by the victorious sound of crunching when the fish is captured. The crunching generally continues as the whale returns to the surface, often sharing food with family members along the way.
If the whale becomes involved in an apparent pursuit without capturing prey, the behavior is classified as an “in-between” behavioral state for the purposes of modeling.
By understanding these states of behavior, researchers can quantify the effects of vessel noise, as heard by the whales, with less human judgment involved. Timely observations of speed and location of nearby vessels are factored in.
“Importantly, we found that the occurrence of foraging states was highest with farther vessels,” Holt said during her talk. “The largest effect was in the deep-foraging state.”
In other words, the whales made fewer foraging dives and spent less time in productive foraging activity when vessels were closer. The researchers also found that the probability of capturing prey was reduced when vessels were moving faster, although the total number of fish available was another major factor.
With respect to noise, deep dives by the whales tended to last longer when vessels were louder and when boat operators were using echosounders — navigational sonars and the so-called fish-finders that emit sounds in the orcas’ hearing range. This suggests that vessel noise may interfere with the whales hunting abilities, causing them to prolong their hunting efforts.
Statistical analysis showed a significant relationship between noise and foraging behavior. Higher noise levels were associated with increased searching for prey (slow clicking) but reduced pursuit (fast clicking/buzzing) and reduced capture, Tennessen said. Increased noise may be causing the whales to miss opportunities to catch fish.
For each fish they capture, the whales may be spending more time searching for food, “which could lead to reduced overall caloric intake,” Tennessen said.
Higher noise levels were also associated with longer dives, suggesting that the whales were spending more time going after prey without capturing them. Alternatively, longer dives might be a natural “avoidance response” to escape from unwanted sounds, she added.
“I think it is interesting to note that there may be a sex difference in foraging strategies here as well,” she said. “Females may be less likely to pursue prey in noise, whereas males may still chase but potentially miss prey.”
In the study comparing northern resident to southern resident orcas, Tennessen began by pointing out that the difference in population growth is “notable and somewhat baffling.”
“We have two populations with similar histories of extraction (for aquariums), similar social structure, similar diets and food preferences, living in relatively similar and overlapping habitat, yet one has tripled in size while the other has essentially flatlined,” she said, adding that finding a solution to this mystery could offer strategies for recovering the southern resident population.
In studies using sound-and-motion D-tags, researchers from Canada’s Department of Fisheries and Oceans directed their attention on the northern residents while a team of U.S. scientists studied the southern residents in similar fashion.
Social differences were striking. While males were the primary hunters among southern residents, elder females did most of the prey capture among northern residents.
Southern resident males with living mothers caught more fish than southern resident males whose mothers had died. But the situation was opposite to the north, where northern resident males without mothers caught more salmon.
In both populations, whoever catches a fish often shares it with others, but much remains unknown about the social aspects of sharing, Tennessen said. In both populations, females with calves were found to capture less prey than females without calves, demonstrating the social burden of keeping calves alive, especially during periods of famine. When food is difficult to find — such as when salmon are scarce or noise levels are high — females with calves may forego foraging opportunities.
“This may provide insight into the reduced calving and survival rates in southern residents,” Tennessen noted.
Tennessen and Holt have begun to take the next steps in their ongoing studies by using D-tags to examine the activities of the southern residents at night, when conditions are expected to be quieter. A major question is whether their foraging activities at night might make up for their reduced success during the day. By adding in a nighttime prey-capture rate, the researchers hope to produce an estimate of total caloric intake, which could be compared to the caloric needs of the animals.
The researchers are currently analyzing data from their completed nighttime work with tagged whales in the Salish Sea. Results should be coming soon, they say, acknowledging support of many collaborators, both in fieldwork and analysis, in the U.S. and in Canada.
Whale watching comes under scrutiny
Efforts to reduce vessel noise and interference around the southern resident orcas began nearly 30 years ago with common-sense guidelines to avoid disrupting the whales as they feed and socialize with other orcas. Starting in 1993, the volunteer-based Soundwatch program educated boaters in the San Juan Islands about the guidelines as well as the needs and habits of orcas.
Operated by The Whale Museum, Soundwatch also conducts on-the-water research, including reports of boating and orca activities. Since 1998, Soundwatch crews have spent more than 13,000 hours observing and contacting boat operators, according to Alanna Frayne, coordinator of Soundwatch who spoke at the Salish Sea conference.
Last year alone, Soundwatch recorded more than 150 speed violations and more than 120 distance violations around the whales, said Frayne. The vast majority of incursions involved private, recreational boaters. Occasionally, commercial whale-watch boats also were seen to be in violation of distance requirements spelled out in Washington state law.
In Canada, Straitwatch was started in 2002 with boater-education and research goals similar to Soundwatch. Straitwatch operates mostly around Vancouver Island under the Canadian nonprofit Cetus Research and Conservation Society. While the rules for protecting orcas are somewhat different in Canada, Straitwatch has recently reported improved compliance with speed and distance requirements among whale-watching vessels.
Early whale-watching guidelines evolved into “Be Whale Wise,” a collaborative campaign for protecting whales that started in 2001 and involved governmental and other groups in the U.S. and Canada. Since then, both countries have approved laws with strict distance restrictions for boaters around orcas. In Washington state, it is also illegal for boats to go faster than 7 knots within a half mile of orcas. In Canada, a 7-knot guideline is directed at boats within 1,000 meters (0.62 mile) of orcas. Reducing boat speed and increasing distance from the whales has been shown to reduce the amount of noise reaching the animals.
On-the-water enforcement of boating rules by government agencies has increased in recent years, thanks to increased funding. But officials with both Soundwatch and Straitwatch as well as others at the Salish Sea conference agreed that even more enforcement would increase compliance and improve conditions for the whales on both sides of the border.
Commercial shipping asked to help
Because the speed of vessels, both large and small, is known to affect noise levels in the water, a voluntary slow-down program was initiated five years ago for commercial ships coming into the Port of Vancouver in Canada. The effort, a central part of the ECHO Program, has been accompanied by studies to measure the effects of the slowdown, and experts say the noise reduction has been significant.
Over the past two years of summer trials, about 90 percent of the vessels voluntarily slowed down while traveling through Haro Strait and Boundary Pass, which are waterways that separate the U.S. from Canada, according to Ryan Ford, manager of ECHO, which stands for Enhancing Cetacean Habitat and Observation.
Results showed that the slowdown lowered noise levels by more than 3 decibels in the area, or about a 55 percent reduction in sound intensity, Ford said. A more recent slowdown, started in 2020 along Swiftsure Bank, resulted in a 37 percent decrease in sound intensity, based on 2020 data. Swiftsure Bank is a known orca-foraging area near the entrance to the Strait of Juan de Fuca.
As experts study ways to reduce noise from individual ships and boats, they must also confront a growing number of vessels coming into the Salish Sea, a factor that weighs against progress in noise reduction.
By recording underwater noise with hydrophones and studying the type of ships that produce various frequencies of sound, researchers have been able to make some predictions about the levels of sound expected at various speeds.
“Vessel traffic, both large and small, was found to be the greatest contributor to noise,” Ford said. “But other factors — like weather, currents, ocean conditions and even the measurement equipment itself —can play a role.”
Although every ship is different, Ford said, a vessel’s speed and draft (distance from keel to waterline) are key operational factors that affect sound.
“At mid to higher frequencies, cargo ships with deeper draft tend to be louder,” Ford said. “Vessel size is the design characteristic most related to noise emissions; larger vessels tend to be louder.”
The ECHO Program was launched in 2014 by the Vancouver Fraser Port Authority, which brought together government agencies, vessel operators, marine transportation officials, scientists, native communities and environmental groups, all with the goal of improving conditions for the whales.
“Underwater noise is a really, really complex topic,” said Krista Trounce, the program’s research manager. “There are many scientists around the world working on these topics of understanding underwater noise, understanding the impact on whales in our region.”
It is one thing to measure noise levels and determine the noise reduction from slowing down a ship, she said. It is quite another to understand how those noise reductions might help the southern resident killer whales. That will take more research.
The high rate of voluntary participation by ships of all sizes has been attributed to the ECHO Program’s cooperative effort to protect the whales combined with a sense of shared responsibility. Open discussions and shared findings related to the experimental slowdowns have helped create a sense of teamwork. The program operates with clear goals of reducing noise without creating a major burden to the shipping industry, and financial compensation is available for some costs related to the slowdowns.
Ships approaching the Port of Vancouver must be guided by a local pilot generally aware of the slow-down effort, Trounce said. The greater challenge, she added, is to reach the operators of foreign vessels — who may not even speak English —before their ships reach whale-foraging areas along the coast and in the Salish Sea.
By keeping the program voluntary, recommended speeds and transit routes can be adjusted quickly as new findings emerge, she said. While some people have argued for a mandated speed limit, that would require a joint effort between the two countries, including their coast guards.
“How quiet does it need to be for the southern residents?” Trounce asked during her conference presentation. “Both NOAA and DFO are doing amazing work in this area — if you caught the presentations by Marla and Jennifer earlier today. I feel like in the near future there is an opportunity to take all of this amazing science … and bring it together with some sort of transboundary science group to see if there is a magic number.”
Such a “magic number,” based on the foraging needs of killer whales, would provide a meaningful goal for sound levels that could help the whales in their hunt for salmon, she said. While the current goal is a 50 percent reduction in sound intensity, further studies could build support for new goals more protective of the orcas.
Early last year, Transport Canada, a federal agency, formed a working group of international experts to develop noise-reduction targets for all of Canada. Recommendations from that group are expected this fall. Transport Canada also funds a variety of studies that could lead to technological solutions to the problem of noise in marine waters throughout the world.
While the ECHO Program continues with refinements in Canada, a similar program, called Quiet Sound, was launched last year by Washington Maritime Blue, a group of businesses, government entities and organizations dedicated to sustainable use of the marine environment. Funding support comes from the state of Washington, the ports of Seattle and Tacoma, NOAA and others.
Rachel Aronson, director of Quiet Sound, explained how the program grew from recommendations by the Governor’s Southern Resident Killer Whale Task Force in 2018. Upcoming projects are expected to include a voluntary vessel slowdown in Washington state waters, along with research to measure the effects. New studies of the acoustic environment in Puget Sound could involve existing hydrophones and new acoustic equipment.
In addition to those efforts, a “U.S. Navy Challenge” could result in federal grants to Quiet Sound to develop new automated methods of sensing the presence of marine mammals along with new technologies to reduce noise from vessels.
More vessels, more noise
As experts study ways to reduce noise from individual ships and boats, they must also confront a growing number of vessels coming into the Salish Sea, a factor that weighs against progress in noise reduction.
At least 22 marine terminal construction projects are proposed or already under construction in the Salish Sea, with 12 of those projects in Canada and 10 in the U.S., according to a report by Lovel Pratt, marine protection and policy director for the nonprofit group Friends of the San Juans.
The Canadian projects alone would add more than 2,600 vessel transits to and from ports in British Columbia, a 25 percent increase in ocean-going vessel traffic within the Salish Sea when compared to 2020. That does not include additional trips from one port to another within the Salish Sea, nor does it account for vessels that always stay within the waterway, such as tugs, barges and ferries, she said.
“The most glaring finding in this report,” said Pratt, is the lack of any information about potential vessel traffic from terminal projects on the U.S. side of the border. “None of the projects in Washington state identified any vessel-traffic increases — even though the specific purpose of some of these Washington state projects is to increase vessel traffic,” she said during the Salish Sea conference.
Last August, for example, the U.S. Department of Transportation designated the “M-5 Coastal Connector,” which will increase tug and barge traffic from Bellingham in North Puget Sound to Southern Oregon and Southern California. The goal is to reduce truck traffic on Interstate 5 along the eastern side of Puget Sound. The project, funded with a $6.8 million federal grant, will upgrade a barge-loading facility, thus facilitating increased vessel traffic within Puget Sound as well as out to the ocean, according to Pratt.
Last year’s completion of the $57 million South Terminal Modernization Project at the Port of Everett, also under the federal Marine Highway Program, is designed to reduce congestion on I-5 by increasing barge traffic on Puget Sound. The effects of increasing the barge traffic were not studied as part of the project’s environmental review, Pratt said.
The lack of any consideration for the potential environmental impacts of increased vessel traffic “highlights a failure of Washington State’s Environmental Policy Act,” Pratt wrote in her report on the potential increases in vessel traffic.
Potential damage from the increased vessel traffic, both projected and unidentified, goes beyond an increase in underwater noise that affects the foraging ability of the southern resident orcas, Pratt said.
“There are also impacts associated with accidents,” she continued. “Given the southern residents’ small population size, just one southern resident death as a result of a ship strike could have significant population consequences, and a major oil spill could cause extinction of the species.”
The Southern Resident Killer Whale Task Force recommended in 2018 that permit applications for construction in Washington state waters address the potential harms to orcas from increased vessel traffic before a project is approved.
“So far, there has been only preliminary progress on the implementation of the orca task force recommendation,” Pratt said.
Among other possible solutions, she said, is a greater consideration for orcas by federal agencies that oversee shipping, including the addition of vessel impacts during environmental reviews required by the Endangered Species Act and other federal laws. Both the U.S. and Canada should work together to develop what might be considered a “carrying capacity analysis” for various areas within the Salish Sea, she added.
“We need to know how much vessel traffic in the Salish Sea is ecologically and culturally sustainable,” she said. “That needs to include all the associated and cumulative impacts.”
Whale warnings for mariners
One measure to help protect southern resident orcas and other whales is a system that collects reports of whale sightings and quickly transmits them to commercial vessel operators in the vicinity.
Since 2018, the Whale Report Alert System, or WRAS, has sent out more than 20,000 warnings to vessel operators, mostly around Vancouver Island but also along the Northwest Coast and down into Puget Sound, said Jessica Scott of OceanWise, who helps oversee the system managed by the British Columbia Cetacean Sightings Network.
The system takes information from anyone who spots whales from boat or onshore and enters the information into a cellphone app. The system checks to make sure the observer has identified the species and location with certainty or high probably. Vessel operators who are part of the system receive a text message if they are within 10 nautical miles of the observed whales. The system also sends a desktop message to vessel-operations centers, which can then relay the message to vessel operators, particularly those without cellphones or in areas where cellphone reception is poor.
“Mariners can choose any sort of mitigation action,” Scott said, “such as slowing down, diverting course, keeping in mind increased vigilance, or turning off their (echo) sounders.”
So far, about 60 vessel owners and related organizations in British Columbia and Washington are using the system, she said, adding that WRAS officials are working on ways that the messages can be targeted to specific vessels near a whale or group of whales.
A separate system, still under development by university researchers, is designed to forecast where orcas and other whales will be in an hour, two hours or longer, said Ruth Joy, a professor at Simon Fraser University in British Columbia.
“The idea behind it is quite simple,” she said. “If we know where killer whales are now, wouldn’t it be nice to be able to predict into the future — one or two hours — where those killer whales are expected to be? That way, we can reduce both the noise impact and the potential for collision risk by slowing vessels down or rerouting vessels.”
In an article published in April, Marine Randon, a post-doctoral fellow at Simon Fraser, laid out the statistical framework for the system, which factors together the known history of orca movements with real-time observations of whales as they travel. The result is similar to a map of hurricane predictions from the National Weather Service, with a center line that indicates the most likely path surrounded by a bubble of uncertainty that gets wider with more distance from the current location. The predicted pathway of the whales can be updated in real time as new sightings and location information comes in.
Joy said the current system for southern resident orcas, as tested, can forecast future locations about two hours before the whales arrive with an accuracy within about 5 kilometers (3.1 miles).
“If you are a mariner, those two hours give you about 80 nautical miles of warning before you come across a southern resident killer whale,” she said.
As proposed, these predictions of orca locations could be made available to vessel operators through the Whale Report Alert System, operated by the BC Cetacean Sightings Network. Beyond killer whales, the researchers plan to expand the system to cover humpback whales, fin whales and possibly others. Other plans include tracking whale movements with hydrophones and adding that information to the forecasts. Hydrophones, Joy noted, can pick up the sounds of whales at night as well as during the day.
Using a computer to identify orcas and other marine species from the sounds picked up on hydrophones is the focus of a project called HALLO, which stands for Humans and Algorithms Listening for Orcas, Joy said. The project involves “deep learning,” a sophisticated form of artificial intelligence. About 426,000 “species level” sound images are being used to train the deep-learning system to distinguish among different sounds heard in the water.
Emergency actions from research
When orcas fail to get enough food, early signs of nutritional stress can be observed and even measured in photographs taken directly over the whales, according to John Durban, a researcher with SeaLife Response, Rehabilitation and Research, or SR3.
Last September, SR3 researchers observed an orca in such a poor body condition that a state agency responded with an emergency order to keep commercial whale-watching boats at a greater distance from the whales.
The ability to maintain health assessments on the southern residents grew out of research that began 15 years ago, first using helicopters and then drones. Today, the SR3 researchers use an octocopter with eight slow-spinning motors, which is much quieter than typical off-the-shelf drones with high-speed motors, Durban said. The octocopter can stay high over the whales — at least 100 feet — by using a good telephoto lens to capture clear images.
“We can give them a basic health check without them knowing we’re there,” Durban said.
One simple indication of health is the angle — as seen from above — of an orca’s “eye patches,” the elongated white markings on each side of the head. Because of fat deposits behind the skull, a healthy orca will have eye patches that diverge at a greater angle, whereas an orca that has lost a lot of weight will have eye patches that are nearly parallel, even bending inward toward the back, tracing the shape of the skull. This latter condition, commonly called “peanut head,” often is a prelude to death for a whale.
“We can measure body condition before they die, and hopefully allow pro-active management actions,” Durban said, adding that any orca in “poor” body condition — ranked 1 on a scale from one to 5 — is given the designation “whale of concern,” recognizing that studies show a high risk of death associated with this body state.
One example is J56, a female calf born in May 2019 and named Tofino. As early as July of 2020, this young whale was causing concern among orca researchers because her condition was bordering on “poor” and her body color was paler than normal. All southern resident whales are important, Durban noted, but females are of particular importance because of their critical role in rebuilding the population.
“Unfortunately, a year later, in 2021, our fears were confirmed even further.,” Durban said. “She had deteriorated in body condition. She had become very lean and developed a blotchy skin condition.”
Based on a health assessment from SR3 in early September 2021, the Washington Department of Fish and Wildlife acted quickly to issue an emergency order designating J56 as “vulnerable” and ordering commercial whale-watching vessels to stay back a half-mile from the whale and her family group. Recreational boaters also were asked to comply with the increased distance. Normally, the allowed distance is 300 yards alongside a group of traveling orcas.
As stated in the order, “This designation and the additional distance is necessary to ensure that J56’s ability to survive is not hindered by the presence of vessels.” J56 is still alive today but remains a “whale of concern.”
A second emergency order came a few days after the first, when the images from the SR3 drone showed that three other females in J pod were showing a wide mid-body girth indicative of late-stage pregnancy. Designating the whales as vulnerable and in need of extra food, the order imposed a half-mile distance requirement for commercial whale watchers. Two of the whales — J36 and J19 — subsequently lost their pregnancies, but J37 gave birth to her second known offspring, J59, which seems to be a healthy whale. Losing two of three potential births is a fairly typical rate for the southern residents, Durban said.
Using the angle between the eye patches, Holly Fearnbach, another SR3 researcher, developed a body condition index so precise that one can observe changes from one season to the next as the abundance of salmon changes. Winter is known as a lean time for orcas, which require prey all year long to survive.
On a population level, the information about body condition — which is directly influenced by the number of available salmon — can be used to make management decisions about the orcas, Durban said. Studies have shown that when body conditions in general are good, the population tends to increase. But when body conditions are poor, the population tends to decrease. Importantly, the analysis has revealed a “lag time,” Durban said.
“When body condition starts to decline, abundance (orca population) declines a year later,” he explained. “When body condition starts to increase, as in 2018-2019, abundance starts to increase a year later, so our measures of body condition precede changes in population size.
“In other words, it’s an early-warning system — and a powerful one. We can provide information on the relative risk of mortality of the whales in the coming year,” he said.
Discussions are underway with management agencies in the U.S. and Canada to see how body-condition information can be used to direct human activities to protect the whales, Durban said.
“I would echo Rob’s (Williams’) sentiment that there have been incredible strides made in science to support recovery of southern resident killer whales, and I hope we can be creative and precautionary and proactive with our management decisions.”