Southern Resident Killer Whales Research Articles

A comparison of EAR and SoundTrap performance for acoustic monitoring of resident killer whales

Since 2006, a network of hydrophones has been deployed along the outer coasts of Washington, Oregon, and California to improve our understanding of endangered Southern Resident killer whale (SRKW) movements outside the inland waters of the Salish Sea and refine Critical Habitat designation. During this time period, improvements in methods and equipment have resulted in longer deployments, improved ability to detect resident killer whales (RKW) and monitor their acoustic behavior, and added the capability to characterize ambient and ship noise throughout SRKW range. It is important to understand how these changes might impact the results of long term studies on RKW movements and distribution. In this study, we co-located Ecological Acoustic Recorders (EARs) and SoundTraps at five locations along the Washington coast, analyzed each data set separately, and compared the results. Preliminary analysis of these data resulted in a 1.6 to 3.4 times increase in the number of days with RKW detections in the SoundTrap data compared to the EAR data depending on location. We will present the results of this comparison, investigate potential causes of the differences between recorder type, and highlight the implications of these differences to previous knowledge of RKW movements along the Washington coast.

Open-source deep learning models for acoustic detection and classification of orcas

Current efforts to acoustically study and monitor killer whales in British Columbia (BC), including the endangered population of Southern Resident killer whales (SRKW), are hampered by the lack of sufficiently accurate sound detection and classification algorithms. Recently, several research groups have reported significant improvements in algorithm performance utilizing deep neural networks. However, for most practitioners, these novel tools remain out of reach. To bridge this gap, we are developing a set of open-source deep learning models for acoustic detection and classification of BC's killer whales. These models will be made publicly available along with expert-curated training and test sets to facilitate further development and applications. We are collaborating with Orcasound to deploy the models on their live data. We are also working together with the PAMGuard developer team to ensure that our models can be seamlessly imported and used in PAMGuard, a widely used open-source software platform for passive acoustic monitoring. In this contribution, we will provide an overview of our deep learning methodology and present preliminary results on model performance, with particular attention to the model's ability to handle diverse and variable acoustic environments and generalize to new “unseen” environments.

Acoustic localization of resident killer whales for source-level estimation of echolocation clicks

To study the efficacy of resident killer whale echolocation clicks for foraging and other activities requires knowledge of the acoustic characteristics of their clicks, in particular, source levels. To compute apparent source level (ASL) from recordings of killer whales in the wild requires localization of the clicking animals, ideally including rigorous uncertainty estimates, to account for transmission losses from source to receiver. This paper considers acoustic localization of killer whales based on time-of-arrival-differences for clicks recorded at a 2 × 2 m2 array of 23 hydrophones. To quantify uncertainties, a Bayesian localization approach is formulated and two methods of solution are considered, one based on a linearized approximation and the other a nonlinear three-dimensional (3D) grid search. Simulations indicate significant linearization errors in 3D uncertainty (probability) distributions, confirming the superiority of the nonlinear localization. Results of this localization approach are used to calculate ASLs (with uncertainties) for echolocation clicks from Southern and Northern Resident killer whales determined to be directed approximately at the array (i.e., on-axis). Comparison of ASL values across varying ranges indicates a roughly logarithmic range dependence, consistent with whales adjusting their click levels based on distance to the target, approximately accounting for two-way spherical-spreading loss.

Effect of interactive threats on foraging effort by endangered killer whales (Orcinus orca)

Killer whales face many anthropogenic threats including vessel traffic, noise, and reduced prey availability. Here, we use high-resolution suction-cup Dtags to study the behavior of endangered Southern Resident killer whales that rely on biosonar to hunt salmon, and investigate how proximate vessels affect foraging behavior. From tag data, we identified subsurface behavior, including foraging and prey capture events. We then tested several vessel and associated sound, demographic, and environmental variables on behavioral state occurrence, time spent within each state, and foraging effort involving prey capture. Whales made fewer prey capture dives and spent less time in these dives when vessels had an average distance <400 yard (366 m). Lower prey abundance and higher vessel speed reduced prey capture probability, documenting the interplay between these effects. Finally, whales dove to depth more slowly while increasing dive duration to capture prey in the presence of vessel-emitted sonar, but descended more quickly with higher noise levels and closer vessels. Current efforts investigating foraging behavior and noise exposure over the diel cycle aim to better quantify foraging rates and activity budgets in this endangered population. These findings advance awareness of vessels and noise consequences on killer whales to inform conservation and management actions.

Sound and movement data from two overlapping populations of killer whales reveal noise effects on foraging behavior

Understanding ambient noise effects on foraging ecology of endangered killer whales is a necessary step toward predicting population-level consequences of acoustic disturbance. However, this has been limited by the difficulty of identifying prey capture which typically occurs out of sight, and by the challenge of obtaining a sufficient range of noise conditions. We addressed these problems using sound and movement data from suction cup-attached archival tags deployed on 52 Northern resident and endangered Southern resident killer whales sampled during overlapping field efforts. We measured broadband ambient noise levels above low-frequency cut-offs that minimized flow noise, and quantified foraging behavior using established acoustic and movement signatures to detect prey capture events. Statistical models revealed significant effects of noise level on searching, pursuit and capture outcomes, including the likelihood that a prey pursuit dive was aborted. We discuss the utility of broadening the range of noise level conditions available by sampling from multiple populations within overlapping geographic regions, and highlight the implications of noise-induced foraging interference on two killer whale populations with different population trajectories. Finally, we suggest future applications of this comparative approach to foster a greater understanding of the population consequences of acoustic disturbance in killer whales.

A Monte Carlo approach to modelling detection ranges for killer whales in inshore waters of British Columbia, Canada

Passive underwater listening stations are often used to monitor the presence, distribution and movements of marine mammals. This requires an understanding of the distances at which marine mammal sounds can be detected at a location and at different times given varying ambient noise conditions. Here, we describe a Monte Carlo approach for determining call detection probabilities as a function of distance for networked underwater listening stations deployed by Fisheries and Oceans Canada in the Salish Sea to track endangered Southern Resident Killer Whales. We used ambient sound levels measured in situ, modelled propagation losses determined by two acoustic models, and applied Monte Carlo simulations to capture the variability in call source level and animal depth. Given that only some parts of the call frequency spectrum may be responsible for the maximum detection range, the analysis was carried out independently for consecutive 300 Hz frequency bands. Median detection range estimates ranged from 700 m at the noisiest time and location to 8 km at the quietest. A sensitivity analysis revealed that the frequency distribution of source levels used for the analysis was a major factor affecting detection range results, while differences in propagation losses between summer and winter were less important.

Reducing vessel noise increases foraging in endangered killer whales

Disturbance from underwater noise is one of the primary threats to the critically endangered southern resident killer whales (SRKWs). Previous studies have demonstrated that SRKWs spend less time feeding when vessels are present. In 2018, we measured the effects of a voluntary vessel slowdown action in SRKW critical habitat to assess whether ship speed (and related source level) affects foraging behaviour. Observations of SRKWs and ships were collected from land-based sites on San Juan Island, WA, USA, overlooking the Haro Strait slow-down area. Exploratory analyses found little support for a linear relationship between ship speed and SRKW behaviour, but strong support between received noise level from ships and the probability of SRKWs engaging in foraging activity. Reducing ship speed, and therefore ship noise amplitude will help decrease the probability of ship noise disrupting SRKW foraging activity and may help to increase the proportion of accessible salmon.

Destroying and Restoring Critical Habitats of Endangered Killer Whales.

Endangered species legislation in the United States and Canada aims to prevent extinction of species, in part by designating and protecting critical habitats essential to ensure survival and recovery. These strict laws prohibit adverse modification or destruction of critical habitat, respectively. Defining thresholds for such effects is challenging, especially for wholly aquatic taxa. Destruction of critical habitat (e.g., prey reduction and ocean noise) threatens the survival and recovery of the 75 members of the endangered southern resident killer whale population found in transboundary (Canada–United States) Pacific waters. The population's dynamics are now driven largely by the cumulative effects of prey limitation (e.g., the endangered Chinook salmon), anthropogenic noise and disturbance (e.g., reducing prey accessibility), and toxic contaminants, which are all forms of habitat degradation. It is difficult to define a single threshold beyond which habitat degradation becomes destruction, but multiple lines of evidence suggest that line may have been crossed already.

Stereotyped whistles in southern resident killer whales.

The endangered Southern Resident killer whales (Orcinus orca) of the northeast Pacific region use two main types of vocal signals to communicate: discrete calls and whistles. Despite being one of the most-studied cetacean populations in the world, whistles have not been as heavily analyzed due to their relatively low occurrence compared to discrete calls. The aim of the current study is to further investigate the whistle repertoire and characteristics of the Southern Resident killer whale population. Acoustic data were collected between 2006–2007 and 2015–2017 in the waters around San Juan Island, Washington State, USA from boats and from shore. A total of 228 whistles were extracted and analyzed with 53.5% of them found to be stereotyped. Three of the four stereotyped whistles identified by a previous study using recordings from 1979–1982 were still occurring, demonstrating that whistles are stable vocalizations for a period of more than 35 years. The presence of three new stereotyped whistles was also documented. These results demonstrate that whistles share the longevity and vocal tradition of discrete calls, and warrant further study as a key element of Southern Resident killer whale communication and cultural transmission.

An example of DNA methylation as a means to quantify stress in wildlife using killer whales

The cumulative effects of non-lethal stressors on the health of biodiversity are a primary concern for conservation, yet difficulties remain regarding their quantification. In mammals, many stressors are processed through a common stress-response pathway, and therefore epigenetic changes in genes of this pathway may provide a powerful tool for quantifying cumulative effects. As a preliminary assessment of this approach, we investigated epigenetic manifestations of stress in two killer whale populations with different levels of exposure to anthropogenic stressors. We used bisulfite amplicon sequencing to compare patterns of DNA methylation at 25 CpG sites found in three genes involved in stress response and identified large differences in the level of methylation at two sites consistent with differential stress exposure between Northern and Southern Resident killer whale populations. DNA methylation patterns could therefore represent a useful method to assess the cumulative effects of non-lethal stressors in wildlife.

Survival of the fattest: linking body condition to prey availability and survivorship of killer whales

AbstractRecovering small, endangered populations is challenging, especially if the drivers of declines are not well understood. While infrequent births and deaths may be important to the outlook of endangered populations, small sample sizes confound studies seeking the mechanisms underlying demographic fluctuations. Individual metrics of health, such as nutritive condition, can provide a rich data source on population status and may translate into population trends. We examined interannual changes in body condition metrics of endangered Southern Resident killer whales (SRKW) collected using helicopters and remotely operated drones. We imaged and measured the condition of the majority of all three social pods (J, K, and L) in each of seven years between 2008 and 2019. We used Bayesian multi‐state transition models to identify relationships between body condition changes and both tributary‐specific and area‐based indices of Chinook salmon abundance, and K‐fold cross‐validation to compare the predictive power of candidate salmon covariates. We found that Fraser River (tributary‐specific) and Salish Sea (area‐based) Chinook salmon abundances had the greatest predictive power for J Pod body condition changes, as well as the strongest relationships between any salmon covariates and SRKW condition across pods. Puget Sound (tributary‐specific) Chinook salmon abundance had the greatest predictive power for L Pod body condition changes, but a weaker relationship than Fraser River or Salish Sea abundance had with J Pod body condition. The best‐fit model for K Pod included no Chinook covariates. In addition, we found elevated mortality probabilities in SRKW exhibiting poor body condition (reflecting depleted fat reserves), 2–3 times higher than whales in more robust condition. Collectively, these findings demonstrate that (1) fluctuations in SRKW body condition can in some cases be linked to Chinook salmon abundance; (2) the three SRKW pods appear to have distinct patterns of body condition fluctuations, suggesting different foraging patterns; and (3) aerial photogrammetry is a useful early‐warning system that can identify SRKW at higher risk of mortality in the near future.

The Efficacy of Management Measures to Reduce Vessel Noise in Critical Habitat of Southern Resident Killer Whales in the Salish Sea

The inland waters around southern Vancouver Island and northern Washington State, known as the Salish Sea, host critical habitat for endangered southern resident killer whales (SRKW). This is, however, a highly traversed area, with approaches to industrial ports and coastal cities, international shipping lanes, ferry routes, and considerable recreational vessel traffic. Vessel noise is a key threat to SRKW prosperity, and so conservation measures directed to mitigate its effects have been explored annually since 2017. Here, we describe trials undertaken in 2020, which included spatially limited slowdown zones, exclusion areas as Interim whale Sanctuary Zones (ISZs), and a lateral displacement of tug transits to increase the distance between their route and SRKW foraging areas. To assess each of the measures we first considered the level of mariner participation using data from the Automated Identification Systems (AIS), mandatory for commercial vessels. Knowing this, the changes in soundscape were examined, focused on impacts on broadband (10 Hz to 100 kHz) ambient noise and the frequencies used by SRKW for communication (500 Hz to 15 kHz) and echolocation (15 to 100 kHz). A control period of two-months prior to trial initiation was used to quantify the changes. High levels (> 80%) of compliance were found for each measure, except ISZs, where observance was low. Median reduction in speeds ranged from 0.2–3.5 knots. Resulting sound reductions were most notable in the lower frequencies, although reductions were also recorded in SRKW pertinent ranges. Tug displacement also reduced ambient noise in these frequencies, despite making up a small portion of the overall traffic. The management trials were effective in reducing potential impacts singularly and in concert. Greater awareness and stakeholder engagement may increase compliance and, therefore, the efficacy of measures in the future.

How the Lummi Nation Revealed the Limits of Species and Habitats as Conservation Values in the Endangered Species Act: Healing as Indigenous Conservation

ABSTRACT In their recent efforts to protect the Southern Resident killer whale population in the Salish Sea and bring ‘Lolita’ home, the Lummi Nation exposed significant limitations to species and habitats as values in Western conservation models. Where Indigenous conservation falls outside this scope, it is often invisible to or actively suppressed by the settler state. The conservation practices of NOAA, in accordance with the federal policy of the ESA, have amounted to extractive colonial enterprises, treating the whales as educational, economic, and environmental possessions while degrading the relationship of the Lummi to the whales as relatives and attacking Lummi sovereignty.

Vessels and their sounds reduce prey capture effort by endangered killer whales (Orcinus orca)

Vessel traffic is prevalent throughout marine environments. However, we often have a limited understanding of vessel impacts on marine wildlife, particularly cetaceans, due to challenges of studying fully-aquatic species. To investigate vessel and acoustic effects on cetacean foraging behavior, we attached suction-cup sound and movement tags to endangered Southern Resident killer whales in their summer habitat while collecting geo-referenced proximate vessel data. We identified prey capture dives using whale kinematic signatures and found that the probability of capturing prey increased as salmon abundance increased, but decreased as vessel speed increased. When vessels emitted navigational sonar, whales made longer dives to capture prey and descended more slowly when they initiated these dives. Finally, whales descended more quickly when noise levels were higher and vessel approaches were closer. These findings advance a growing understanding of vessel and sound impacts on marine wildlife and inform efforts to manage vessel impacts on endangered populations.

Trade, Competitive Exclusion, and the Slow-Motion Extinction of the Southern Resident Killer Whales

Orcinus Orca is the world's largest predator, and simultaneously a significant tourist asset and cultural icon for much of the Pacific Northwest. In the past two decades, the Southern Resident Killer whales (SRKW) have declined by more than 25 percent, and this population appears on a slow-motion path towards extinction. This paper combines elements from biology and economics to put forward a new methodology for investigating their collapse and presents empirical work supporting its novel explanation - the Orca Conjecture. The key mechanism is ecological - Gause's law of competitive exclusion - combined with a shock coming from booming trade with Asia. Using three different empirical methods drawn from economics, I find the attendant noise disturbance from increased ship traffic post-1998 has lowered births and raised deaths significantly, placing the SRKW on a slow-motion path towards extinction.

Legal Options (and Obligations?) for Enhanced Canada–United States Cooperative Southern Resident Killer Whale Conservation

The critically endangered Southern Resident killer whale (SRKW) population is at a conservation crossroads. The SRKW’s range extends from California to southern Alaska, but the core habitat of the species is the inland Salish Sea. The principal threats to the population are the decline in Chinook salmon abundance, physical and acoustic disturbance, and environmental contamination. Effective management must respond to the cumulative impact of these threats. The SRKW population has been protected as an endangered species in Canadian and U.S. waters for more than a decade, and emergency conservation measures have been produced in both jurisdictions. Unfortunately, these conservation measures have failed to stabilize the population or advance cooperative ecosystem-based conservation. The United Nations Convention on the Law of the Sea (UNCLOS) legally obligates states to cooperate in marine mammal conservation and, with respect to cetaceans, specifically requires states to work through an appropriate institution for their conservation and management. This article examines ongoing efforts by Canada and the United States to stabilize and recover the SRKW population in view of UNCLOS and the objective of long-term stewardship. This assessment includes ad hoc cooperative mechanisms and possible developments under existing cooperative forums. Although the base legal obligations created by UNCLOS are likely met, the objective of institutionalized cooperative cetacean conservation and management in UNCLOS is not met; moreover, existing cooperative forums are insufficient to effect SRKW recovery. Canada and the United States continue to approve projects without properly assessing the cumulative transboundary impact on the SRKW population or quantifying their contribution to important ecosystem-based thresholds, which reveals the true extent of management dissonance in the Salish Sea. This analysis concludes that enhanced bi-lateral cooperation and long-term co-existence with the SRKW population requires the creation of a new institutional forum, analogous to the International Joint Commission, that coordinates SRKW recovery measures and assesses future projects in view of cumulative effects management.

Age and sex influence social interactions, but not associations, within a killer whale pod.

Social structure is a fundamental aspect of animal populations. In order to understand the function and evolution of animal societies, it is important to quantify how individual attributes, such as age and sex, shape social relationships. Detecting these influences in wild populations under natural conditions can be challenging, especially when social interactions are difficult to observe and broad-scale measures of association are used as a proxy. In this study, we use unoccupied aerial systems to observe association, synchronous surfacing, and physical contact within a pod of southern resident killer whales (Orcinus orca). We show that interactions do not occur randomly between associated individuals, and that interaction types are not interchangeable. While age and sex did not detectably influence association network structure, both interaction networks showed significant social homophily by age and sex, and centrality within the contact network was higher among females and young individuals. These results suggest killer whales exhibit interesting parallels in social bond formation and social life histories with primates and other terrestrial social mammals, and demonstrate how important patterns can be missed when using associations as a proxy for interactions in animal social network studies.

A cumulative effects model for population trajectories of resident killer whales in the Northeast Pacific

Like numerous species at risk, the resident killer whale populations of the Northeast Pacific are vulnerable to the cumulative effects of anthropogenic threats. A Pathways of Effects conceptual model summarised the current understanding of each threat (prey availability, acoustic and physical disturbance, and contaminants), threat interactions, and potential impacts to fecundity and mortality. A Population Viability Analysis utilised the most recent available data to quantify impacts of threats on population parameters. The impacts of individual and cumulative threat scenarios on modelled Southern and Northern Resident Killer Whale populations were compared to the observed population demographics to define a model that best captured the real world dynamics. Of the individual and combined threat models tested, the cumulative model incorporating all threats predicted demographic rates closest to those observed for both populations. Recent low Chinook salmon abundance and its interactions with vessel disturbance and contamination strongly influenced modelled killer whale population dynamics. The cumulative effects population viability analysis model projected a mean increase in the modelled Northern Resident Killer Whale population to the carrying capacity within 25 years. In contrast, the mean modelled Southern Resident Killer Whale population trajectory was projected to decline under current conditions, with a 26% probability of population extinction, and in those projections, extinction was estimated to occur after 86 (± 11) years. Our results highlight the importance of considering the collective impact of multiple threats to imperilled species and the necessity of testing management and mitigation measures aimed at recovery using a holistic, validated model.

Integrating physical, chemical and biological data to understand fate, behaviour and effects of diluted bitumen in coastal waters

ABSTRACT: 1141488 Production of bitumen from oil sands is predicted to rise over the next decade. Some of this increased production will be transported to coastal areas for export. While some product will be transported via rail, the majority is likely to be transported through pipelines as diluted bitumen. This unconventional oil product is a mixture of the highly viscous bitumen with differing amounts of diluent, which can include condensates, synthetic crudes or conventional crudes. As a mixture of products, the behaviour of diluted bitumen may differ from conventional heavy crude oils following a spill. This is of concern in Canada as the main transportation route for exporting diluted bitumen will go through the Salish Sea, home to endangered southern resident killer whales, economically important commercial and traditional fisheries including Pacific salmon, and millions of people. Knowing how diluted bitumen products will behave and their potential impacts if a spill occurs in these coastal waters is important in developing an effective response plan. The Centre for Offshore Oil, Gas and Energy Research (COOGER) within Fisheries and Oceans Canada (DFO) has been carrying out research to characterize and predict the fate and behaviour of diluted bitumen products in marine environments over the last seven years. Using a combination of small-scale microcosms, medium-scale mesocosms, large-scale weathering and wave tank studies as well as field experiments, we have collected a broad range of data providing insights into how diluted bitumen might behave following a spill. Our research suggests that diluted bitumen will weather rapidly, with density and viscosity increasing significantly over the first 48 h. Low concentrations of hydrocarbons are typically detected in the water column, even in the presence of high energy breaking waves. The amount of weathering and water column hydrocarbons vary with season, but overall the microbial community shows a small response to the presence of diluted bitumen. Conventional spill response technologies may be used within the first 48 h of a spill, but extensive weathering will further limit their effectiveness. While the studies provide a more complete understanding of the fate and behaviour of diluted bitumen in coastal waters, there are important questions yet to be answered, some of which are presented here.

The development and use of towed hydrophone arrays to inform Southern Resident killer whale Critical Habitat in outer coastal waters

Southern Resident killer whales (SRKW) were listed as endangered in 2005, requiring designation of Critical Habitat. At that time little was known about SRKW distribution in winter/spring along the outer coast. From 2004 to 2016, we conducted nine winter/spring surveys aboard NOAA ocean-class vessels to locate and follow SRKW pods using visual sightings, satellite telemetry, and passive acoustic monitoring using towed hydrophone arrays. We present information on the evolution of the towed hydrophone array system, and insights gained on the movements and acoustic behavior of this population. Beginning with a linear two-element hydrophone array system, operations evolved to include a secondary, five-element array towed in parallel, to resolve left-right bearing ambiguity to vocalizing animals. Acoustic localization allowed tracking of vocalizing whales when visual surveys were not possible (e.g., nighttime/inclement weather). When visual and/or satellite tag position data indicated whales were within acoustic range, vocalizations were detected only 45% of the time, a result that has implications for other PAM efforts. These surveys helped fill important gaps in our understanding of SRKW occurrence to inform Critical Habitat in the outer coastal portion of their range. Despite limited monitoring, we established the importance of this key portion of their range in winter/spring.