Southern Resident Killer Whales Research Articles

Speaking up: Killer whales (Orcinus orca) increase their call amplitude in response to vessel noise

This study investigated the effects of anthropogenic sound exposure on the vocal behavior of free-ranging killer whales. Endangered Southern Resident killer whales inhabit areas including the urban coastal waters of Puget Sound near Seattle, WA, where anthropogenic sounds are ubiquitous, particularly those from motorized vessels. A calibrated recording system was used to measure killer whale call source levels and background noise levels (1-40 kHz). Results show that whales increased their call amplitude by 1 dB for every 1 dB increase in background noise levels. Furthermore, nearby vessel counts were positively correlated with these observed background noise levels.

Spatial confirmation of vocal communication between a killer whale calf and its natal family

We recorded an interchange of vocal signaling between a four‐year‐old Southern Resident killer whale and its natal family members (mother and brother). This information was recorded on a 30‐m‐long linear array of hydrophones that was towed behind our electric motor powered research vessel. Over the course of about 1/2 hour we recorded signals from these isolated orcas about 500 m offshore of San Juan Island, WA. Surface locations of the orcas were documented with visual accounts, photographs, video, and ‐ during the latter portion of the encounter ‐ with a hand‐bearing compass. During a six minute interval of the recording we have localized 70 vocalizations that we can associate with the surface positions of either the juvenile or the mother‐brother pair (they were close together). The central three minutes of this interval document an event in which the juvenile left the family group, swam toward our vessel, approached it within about 10m, turned abruptly away during a rapid call‐response sequence with the mother and/or brother, and then rejoined the natal group. This rare event informs killer whale vocal development, repertoire, communication, and active space.

Investigating noise effects on the call amplitude of endangered Southern Resident killer whales (Orcinus orca)

Anthropogenic sound exposure has been identified as a potential threat to endangered Southern Resident killer whales (SRKWs). Such exposure can mask important biological sounds including those used for social functions. Vocal animals might compensate for increased background noise by calling louder (the Lombard effect). In this study, amplitude compensation was investigated in SRKW communication calls recorded off of San Juan Island, WA, U.S.A. Data were obtained from two calibrated recording systems, a shore-based hydrophone array [V. Veirs, J. Acoust. Soc. Am., 116, 2615 (2004)] and a boat-based vertical array. Calls were localized using time of arrival differences to estimate range and apparent source levels after background levels were subtracted from the signal. Call levels were calculated assuming spreading loss functions determined from sound propagation observations made in situ. Results demonstrated a positive relationship between call levels and background levels. Costs of such vocal flexibility are unknown, but may include changes in energetic demand and/or communicative functionality. Within the data ranges measured in this study, killer whales communicatively adjusted for fluctuating background noise levels. However, other sounds detected during passive listening (e.g. prey sounds) might be more susceptible to masking effects [Work supported by NOAA and Colorado College.]

Killer whales (Orcinus orca) and Bell Laboratories: What can information theory tell us about the communication system of this species

In the 1950's Shannon and Weaver developed information theory as a statistical tool to determine the structure and organization within communication systems. More recently information theory has been applied to the study of animal communication. We gathered acoustic recordings of the Southern Resident killer whales in the inland waters of Washington State, USA, and British Columbia, Canada, from both land based and boat based acoustic arrays. Recorded calls were categorized using the accepted call catalog for this population. In this paper we will present our results from applying various Shannon entropies to the documented call sequences. One notable result is that the call repertoire is more redundant than is ideal to convey the maximum amount of information. This may be a result of their particular social system and behavioral ecology, or may be an indication of the amount of noise present in their acoustic environment. Comparisons will also be made with measures of information theory in other species.

A Brief Review of Known Effects of Noise on Marine Mammals

Marine mammals, especially cetaceans, are highly vocal and dependent on sound for almost all aspects of their lives, e.g. food-finding, reproduction, communication, detection of predators/hazards, and navigation. They are thus likely sensitive to anthropogenic noise. Sound has a large potential area of impact, sometimes covering millions of square kilometers of ocean with levels high enough to cause possible disturbance in marine mammals. There can be great variation in the reaction of marine mammals to noise, depending on such factors as species, individual, age, sex, prior experience with noise, and behavioral state. Species with similar hearing capabilities can respond differently to the same noise. Observed effects of noise on marine mammals include: changes in vocalizations, respiration, swim speed, diving, and foraging behavior; displacement, avoidance, shifts in migration path, stress, hearing damage, and strandings. Responses of marine mammals to noise can often be subtle and barely detectable, and there are many documented cases of apparent tolerance of noise. However, marine mammals showing no obvious avoidance or changes in activities may still suffer important, even lethal, consequences. Acoustically-induced strandings may displace a local beaked whale ( Ziphiidae ) population (for an extended period if not permanently) or even possibly eliminate most of its members. As beaked whales seem to be found in small, possibly genetically isolated, resident populations, even a transient and localized acoustic impact could have prolonged population consequences. Observed reactions to noise in marine mammals could theoretically result in impacts such as decreased foraging efficiency, higher energetic demands, less group cohesion, higher predation, decreased reproduction, and thus seriously impact the population. Alternatively, they may be harmless. However, noise is thought to contribute to at least some species’ declines or lack of recovery (Southern resident killer whales ( Orcinus orca ) , western gray whales ( Eschrichtius robustus ) off Sakhalin).

Environmental noise studies in Puget Sound

The ambient noise environment at a site in North Puget Sound, Washington, depth ∼100 m, located within the nearby Smith Island marine sanctuary, is studied. The measurement system consists of a buoy for which the surface expression houses a microphone at nominal height 2 m above the sea surface, with multiple underwater acoustic sensors suspended in the water column. The recording bandwidth for the air system corresponds to audio band, whereas the underwater system records ambient noise at frequencies up to 50 kHz. The two systems are recorded coherently. One goal of this pilot study is to examine different components of the noise budget, including injection of noise from airplane flyovers, and correlation between pressures above and below water. Another goal relates to properties of the noise field that could possibly impact echolocation by southern resident killer whales; these properties likely being restricted to noise levels at frequencies above 25 kHz. Besides representing an important marine mammal habitat, a key advantage of this site is the availability of meteorological and sea surface wave data, obtained from Smith Island and a nearby NOAA buoy, and vessel and air traffic data. Results from the summer 2007 field work will be presented.

Persistent organic pollutants and stable isotopes in biopsy samples (2004/2006) from Southern Resident killer whales

“Southern Resident” killer whales include three “pods” (J, K and L) that reside primarily in Puget Sound/Georgia Basin during the spring, summer and fall. This population was listed as “endangered” in the US and Canada following a 20% decline between 1996 and 2001. The current study, using blubber/epidermis biopsy samples, contributes contemporary information about potential factors (i.e., levels of pollutants or changes in diet) that could adversely affect Southern Residents. Carbon and nitrogen stable isotopes indicated J- and L-pod consumed prey from similar trophic levels in 2004/2006 and also showed no evidence for a large shift in the trophic level of prey consumed by L-pod between 1996 and 2004/2006. ∑PCBs decreased for Southern Residents biopsied in 2004/2006 compared to 1993–1995. Surprisingly, however, a three-year-old male whale (J39) had the highest concentrations of ∑PBDEs, ∑HCHs and HCB. POP ratio differences between J- and L-pod suggested that they occupy different ranges in winter.

Acoustic monitoring of resident, offshore, and transient killer whales off the Washington coast

Three acoustically distinct populations of killer whales representing each of the known ecotypes (resident, offshore, transient) were recorded in the Summer–Fall of 2004 off the southern Olympic Coast of Washington. Two high-frequency acoustic recording packages (HARPs) continuously recording at 80-kHz sample rate were deployed to assess the seasonal occurrence of vocal odontocetes in this region. From mid-July to early-October the population-specific discrete calls of killer whales were heard on 8 days and were classified to population by Volker Deecke (UBC) and John Ford (DFO-Canada) using an acoustic ID catalogue. West Coast Transient killer whales producing calls of the California dialect were heard on three occasions from August through October. Offshore killer whales were heard twice in August–September, and Northern Resident killer whales were heard once in August. Although Northern Resident killer whales have been extensively studied within Puget Sound and coastal British Columbia, they have been visually sighted only once off the northern Olympic Peninsula, making their detection at this offshore southerly location unique. Endangered Southern Resident killer whales were not heard at this site from July–October. Analysis of year-round data from a site further offshore is underway. [Funded by Chief of Naval Operations- N45.]

The acoustic environment of the southern resident killer whales in Haro Strait: Propagation modeling and analysis of field measurements

We will discuss the complicated shallow water acoustic environments of the southern resident killer whales in the Haro Strait of the Puget Sound through combined analysis of field measurements and acoustic propagation modeling in the frequency range of 1 to 20 kHz. Haro Strait is a highly variable acoustic environment with active commercial shipping, whale watching, and Naval activity. Southern resident killer whales are of unique public concern in this area because of potentially high impact by anthropogenic sound sources, either by auditory masking that may interfere with foraging strategies or annoyance and disorientation due to complicated reverberation. Predictive acoustic modeling in combination with field measurements can aid in understanding the mechanisms of impact and better inform assessment of the risk, providing a critical step towards the quantitative evaluation of impact in the context of complicated environments, changing background sound levels, and emerging management issues. Preliminary results of modeling and analysis of data collected in the summer of 2004 will be presented.

One year of background underwater sound levels in Haro Strait, Puget Sound

Haro Strait, on the west side of San Juan Island, WA, is the home range of the Southern Resident orca whales, a major shipping lane to and from Canada, and a center of private and commercial boating, especially in the summer. Four ITC hydrophones in a near-shore fixed array are used here to localize the underwater vocalizations of Southern Resident orca whales. The system operates 24 hours a day and has a frequency response of 100 Hz 10 kHz. Background sound levels are automatically characterized by half-hour reports that include: statistics and graphics based on mean sound levels (2-min running arithmetic mean pressure); a histogram of mean sound levels binned by frequency; and 2-s sound samples from maximum background events. Sound levels range from ∼90 dB re 1 microPa (quiet conditions) to ∼130 dB re 1 microPa when loud commercial ships are passing in the nearby shipping lane or speedboats are passing close to the hydrophone array. Complete results for one year of continuous monitoring will be presented, segmented by time (season, day of the week, hour in the day), frequency spectrum and dominant noise source class. [Work supported by 35 undergraduate researchers and the Colorado College.]

Source levels of free-ranging killer whale (orcinus orca) social vocalizations

An array of four hydrophones spaced over 200 m near the shore of San Juan Island, WA, has been used to localize the underwater vocalizations of Southern Resident orca whales. The hydrophones (ITC) have home-built pre-amps and amplifiers and signals are digitized simultaneously by two computers. The system has been calibrated with an underwater speaker (J-9). Automatic call detection is used to activate data logging on one computer and real-time localization on a second that directs a video camera to record the water’s surface at the predicted source location. The system requires about 1 s to detect a call, locate it and redirect the video camera. This is the first report of source levels of social vocalizations of free-ranging Southern Resident orcas. To date (July 2004), 160 orca calls have been localized within 200 m of the center of the array. The average acoustic intensity of these calls is 145 dB re 1 μPa@1 m. The range of intensities is from 137 to 157 dB re 1 μPa@1 m. Complete results including intensity angular distributions with respect to the probable direction of whale travel will be presented. [Work supported by 32 undergraduate researchers over 5 years and the Colorado College Physics Department.]

Evaluating potential infectious disease threats for southern resident killer whales, Orcinus orca: a model for endangered species

Infectious diseases have the potential to play a role in the decline of threatened wildlife populations, as well as negatively affect their long-term viability, but determining which infectious agents present risks can be difficult. The southern resident killer whale, Orcinus orca, population is endangered and little is known about infectious diseases in this species. Using available reference literature, we identified 15 infectious agents (bacteria, viruses, and fungi) reported in free-ranging and captive killer whales, as well as 28 additional infectious agents reported in free-ranging and captive odontocete species sympatric to southern resident killer whales. Infectious agents were scored as having a high, medium, or low ability to affect fecundity or reproductive success, to cause disease in individual animals, and to cause epizootics. Marine Brucella spp., cetacean poxvirus, cetacean morbilliviruses, and herpesviruses were identified as high priority pathogens that warrant further study. Using identified pathogens to develop a standardized necropsy and disease testing protocol for southern resident killer whales and sympatric odontocetes will improve future efforts to better understand the impacts of priority and non-priority infectious agents on southern resident killer whales. This model can be used to evaluate potential infectious disease risks in other threatened wildlife populations.