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Cuvier's beaked whales (Ziphius cavirostris) are known as extreme divers, though behavioral data from this difficult-to-study species have been limited. They are also the species most often stranded in association with Mid-Frequency Active (MFA) sonar use, a relationship that remains poorly understood. We used satellite-linked tags to record the diving behavior and locations of eight Ziphius off the Southern California coast for periods up to three months. The effort resulted in 3732 hr of dive data with associated regional movements--the first dataset of its kind for any beaked whale--and included dives to 2992 m depth and lasting 137.5 min, both new mammalian dive records. Deep dives had a group mean depth of 1401 m (s.d. = 137.8, n = 1142) and duration of 67.4 min (s.d. = 6.9). The group mean time between deep dives was 102.3 min (s.d. = 30.8, n = 783). While the previously described stereotypic pattern of deep and shallow dives was apparent, there was considerable inter- and intra-individual variability in most parameters. There was significant diel behavioral variation, including increased time near the surface and decreased shallow diving at night. However, maximum depth and the proportion of time spent on deep dives (presumed foraging), varied little from day to night. Surprisingly, tagged whales were present within an MFA sonar training range for 38% of days locations were received, and though comprehensive records of sonar use during tag deployments were not available, we discuss the effects frequent acoustic disturbance may have had on the observed behaviors. These data better characterize the true behavioral range of this species, and suggest caution should be exercised when drawing conclusions about behavior using short-term datasets.

High‐resolution movement data from Cuvier's beaked, or goose‐beaked whale (Ziphius cavirostris, hereafter Ziphius, n = 8) tag deployments (4.1–19.2 days) were used to estimate blood and tissue O2 and CO2 levels. Acceleration and magnetometry data were used to estimate the locomotion cost (LC) from the relationship between activity and the O2 consumption rate. We estimated that the diving metabolic rate (DMR) decreased with increasing dive duration, ranging from 6.18 mL O2 min−1 kg−1 for very short dives (<1.0 min) to 1.65 mL O2 min−1 kg−1 and 2.06 mL O2 min−1 kg−1 for intermediate (>17.5 and ≤33.3 min) and long dives (>33.3 min), respectively. The calculated aerobic dive limit (cADL), average behavioural ADL (bADL) and dynamic ADL (dADL) were 62.4, 61.3 (44.3–75.4) and 41.7 (2.0–102.5) min, respectively. Despite the physiological and metabolic adjustments assumed by the model, the muscle O2 ran out for many of the stereotypical long, deep dives exhibited by these animals. Based on the model results, we speculate that a large portion of the foraging dives in Ziphius are fuelled by alternative metabolic pathways, for example, phosphocreatine or glycolysis. A reliance on these alternative metabolic pathways during foraging may require long recovery periods, including primarily aerobic dives. Disturbing this normal dive pattern may disrupt this normal dive pattern, leading to behavioural and physiological changes that could cause trauma.

Goose-beaked whales ( Ziphius cavirostris ) are a deep-diving toothed whale species and top predators in deep sea ecosystems. Much is yet to be learned about their social and foraging strategies due to their elusive behavior, but this information is increasingly relevant given their demonstrated behavioral changes in association with anthropogenic sound. This study used direction-of-arrival (DOA) localization to track the position of goose-beaked whales from echolocation clicks recorded on seafloor-mounted hydrophone arrays offshore Southern California. Overall, 2738 tracks of diving goose-beaked whales were processed from acoustic recordings collected at four long-term monitoring sites between 2018 and 2023. Results highlight distinct spatial use patterns driven by bathymetric features at each site, with whales foraging closer to the seafloor at sites with complex bathymetry and showing a preference for certain bathymetric features. Group sizes at depth ranged from 1 to 9 individuals with a mean of 2.34 and exhibited site-specific seasonal variability as well as a strong diel trend at one site. During many of these encounters, individuals exhibited highly coordinated behaviors. This study demonstrates the value of long-term passive acoustic tracking for studying elusive, deep-diving species and provides significant advancements in understanding goose-beaked whale behavior at depth over long time scales.

The Atlantic Behavioral Response Study is a multi-disciplinary collaboration with the U.S. Navy to quantify mid-frequency (1-10 kHz) active sonar (MFAS) effects for marine mammals. We will present baseline behavior and MFAS response results for goose-beaked whales (Ziphius cavirostris). Our study site is a biologically rich area where Navy coordination is possible and MFAS occurs but at lower rates than sonar ranges where many BRS' have occurred. We use multi-scale tagging approaches with strategically programmed satellite-transmitting tags yielding weeks of coarser position and diving data and shorter, fine-scale movement and acoustic tags. Controlled exposure experiments (CEEs) provide exposure-response results for different sound sources, including: no noise controls (n = 20), experimental pulsed active sonar (PAS; n = 53), naval vessel PAS (n = 34) and continuous active sonar (CAS). Responses are evaluated relative to key variables (received level [RL], behavioral state, and horizontal range) and specifically assess spatial avoidance, changes in diving and foraging behavior, and social response. Response results for PAS CEEs will be given; CAS studies are ongoing. We observed subtle behavioral changes in control CEEs at similar, low rates as the lowest (< 100 dB) MFAS RLs but a clear escalation of avoidance and diving responses with increasing RL for 100-140 dB exposures. Results amplify earlier indications of Ziphius sensitivity to MFAS by substantially expanding sample sizes and temporal scales, but suggest differences in aspects of response from studies on ranges.

Beaked whales (Cetacea: Ziphiidea) of the genera Ziphius and Mesoplodon are so difficult to study that they are mostly known from strandings. How these elusive toothed whales use and react to sound is of concern because they mass strand during naval sonar exercises. A new non-invasive acoustic recording tag was attached to four beaked whales (two Mesoplodon densirostris and two Ziphius cavirostris) and recorded high-frequency clicks during deep dives. The tagged whales only clicked at depths below 200 m, down to a maximum depth of 1267 m. Both species produced a large number of short, directional, ultrasonic clicks with no significant energy below 20 kHz. The tags recorded echoes from prey items; to our knowledge, a first for any animal echolocating in the wild. As far as we are aware, these echoes provide the first direct evidence on how free-ranging toothed whales use echolocation in foraging. The strength of these echoes suggests that the source level of Mesoplodon clicks is in the range of 200-220 dB re 1 µPa at 1 m. This paper presents conclusive data on the normal vocalizations of these beaked whale species, which may enable acoustic monitoring to mitigate exposure to sounds intense enough to harm them.

The oceanographic conditions of the Southern California Bight (SCB) dictate the distribution and abundance of prey resources and therefore the presence of mobile predators, such as goose-beaked whales (Ziphius cavirostris). Goose-beaked whales are deep-diving odontocetes that spend a majority of their time foraging at depth. Due to their cryptic behavior, little is known about how they respond to seasonal and interannual changes in their environment. This study utilizes passive acoustic data recorded from two sites within the SCB to explore the oceanographic conditions that goose-beaked whales appear to favor. Utilizing optimum multiparameter analysis, modeled temperature and salinity data are used to identify and quantify these source waters: Pacific Subarctic Upper Water (PSUW), Pacific Equatorial Water (PEW), and Eastern North Pacific Central Water (ENPCW). The interannual and seasonal variability in goose-beaked whale presence was related to the variability in El Niño Southern Oscillation events and the fraction and vertical distribution of the three source waters. Goose-beaked whale acoustic presence was highest during the winter and spring and decreased during the late summer and early fall. These seasonal increases occurred at times of increased fractions of PEW in the California Undercurrent and decreased fractions of ENPCW in surface waters. Interannual increases in goose-beaked whale presence occurred during El Niño events. These results establish a baseline understanding of the oceanographic characteristics that correlate with goose-beaked whale presence in the SCB. Furthering our knowledge of this elusive species is key to understanding how anthropogenic activities impact goose-beaked whales.

Background Acoustic disturbance is increasingly recognized as an ecological concern, particularly at sea. In light of marine mammal stranding events associated with use of naval mid-frequency active sonar (MFAS), which often involve goose-beaked whales ( Ziphius cavirostris ), research has sought to detect and characterize Ziphius behavioral responses to MFAS. Methods We deployed Sound and Motion Recording and Telemetry (SMRT) tags on 13 Ziphius in the Southern California Bight. The study area includes the United States Navy’s Southern California Anti-submarine Warfare Range (SOAR), and deployments overlapped temporally with training exercises including MFAS use. We used hierarchical hidden Markov models (HHMMs), which provided a framework to model whale behavior and putative responses to MFAS at two relevant time scales: foraging dive cycles, which may last hours, and five-minute intervals, where finer-scale changes in movement and behavior are evident. Results We analyzed 70.7 days of tag data (1697.6 h) representing 361 Ziphius foraging dive cycles, 52 with MFAS detections. Cumulative MFAS sound energy level (cSEL) per dive cycle was 69.9–160.3 dB re 1µPa 2 s (median 121.3, inter-quartile range (IQR) 21.7). We identified two dive-cycle states: “Typical” and “Variant.” In Variant state, durations of dive cycles, foraging dives, non-foraging dives, and echolocation periods were shorter on average but more variable, while time spent near the surface and net distance traveled were longer and more variable. According to Akaike’s information criterion (AIC), MFAS cSEL (rather than per-sound maximum received level) increased the probability of switching from Typical to Variant dive-cycle state, with MFAS cSEL also modulating transition rates between four fine-scale behavior states during Variant dive cycles only. Whales transitioned to Variant state in 12 of 52 MFAS-exposed dive cycles (23.1%), with observed Variant state dwell times ranging from 1 to 72.4 h (median 9.0, IQR 9.2). Conclusions This work has relevance for conservation and management, enhancing our understanding of Ziphius behavioral responses to operational MFAS in an area where naval training activities occur regularly. These analysis tools may prove useful in assessing responses to other acoustic disturbance and understanding how shorter-term behavior changes translate to longer-term consequences.

Where’s Whaledo is a software toolkit that uses a combination of automated processes and user interfaces to greatly accelerate the process of reconstructing animal tracks from arrays of passive acoustic recording devices. Passive acoustic localization is a non-invasive yet powerful way to contribute to species conservation. By tracking animals through their acoustic signals, important information on diving patterns, movement behavior, habitat use, and feeding dynamics can be obtained. This method is useful for helping to understand habitat use, observe behavioral responses to noise, and develop potential mitigation strategies. Animal tracking using passive acoustic localization requires an acoustic array to detect signals of interest, associate detections on various receivers, and estimate the most likely source location by using the time difference of arrival (TDOA) of sounds on multiple receivers. Where’s Whaledo combines data from two small-aperture volumetric arrays and a variable number of individual receivers. In a case study conducted in the Tanner Basin off Southern California, we demonstrate the effectiveness of Where’s Whaledo in localizing groups of Ziphius cavirostris . We reconstruct the tracks of six individual animals vocalizing concurrently and identify Ziphius cavirostris tracks despite being obscured by a large pod of vocalizing dolphins.

Depth distributions were analyzed from a study of 19 Cuvier’s beaked whales Ziphius cavirostris that were tagged with satellite transmitting instruments off southern California, USA. Over 113 000 depth measurements were made over the equivalent of ∼200 sampling days. The mean foraging depth was 1182 m (SD = 305 m), and the mean of the maximum depth of all foraging dives was 1427 m (SD = 298 m). Mean foraging depths increased with seafloor depths up to a maximum of ∼1300 m at a seafloor depth of 1900 m, but decreased slightly to a mean of ∼1200 m at seafloor depths of 2000–4000 m. Near-bottom habitat appears to be important for foraging; whales spent ∼30% of their foraging time within 200 m of the bottom at seafloor depths of 1000–2000 m. However, little foraging time was spent near the bottom at seafloor depths greater than 2000 m. The percentage of time spent at near-surface depths (< 50 m) was more than twice as high at night (25%) than during the day (12%). Lunar light also appears to affect diving, with 28% of dark nights and only 17% of brightly moonlit nights spent at these near-surface depths. The apparent avoidance of surface waters during daytime and on brightly moonlit nights is consistent with avoidance of visual predators. A considerably greater fraction of time was spent foraging at night (24.8%) than during the day (15.7%), possibly due to energetic constraints imposed by predator avoidance during the day.

Understanding abundance and trends of beaked whales in the heavily industrialized Gulf of America (formerly Gulf of Mexico), is critical for management but challenging with visual-based distance-sampling due to their elusive surface behavior. Acoustic-based distance-sampling methods rely on accurate modeling of detection probability as a function of distance from a recorder, requiring population-specific diving and acoustic behavior parameters, which is currently lacking for Gulf populations. To address this, we used passive acoustic tracking with two 4-channel High-Frequency Acoustic Recording Packages (HARPs) deployed off Louisiana (~1100 m depth) in 2021. Echolocation clicks detected on both recorders were localized in 3D to characterize acoustic and diving behavior. These data informed a Monte Carlo cue-based simulation to estimate the probability of detection by a near-seafloor single-sensor HARP. A trial-based approach also estimated detection probability as a function of range to a single-channel sensor deployed at the site. Results show species-specific differences. Goose-beaked whales ( Ziphius cavirostris ), were detected for longer periods during foraging dives (n = 24 dives, mean: 20.5 min; range: 7–42) compared with Blainville’s ( Mesoplodon densirostris , n = 2 dives, 13.6 min; 11–16) and Gervais’ ( Mesoplodon europaeus , n = 24 dives, 12.7 min; 7–19) beaked whales. Maximum dive depths also differed, with some goose-beaked whales foraging at or near the seafloor. Descent and ascent rates were similar within species but differed among them (1.34/1.40 m/s for goose-beaked and 1.15/1.19 m/s for Gervais’ beaked whales). Source level and broadband directivity index were estimated at 225 dB pp re 1 μPa-1m and 26 dB for goose-beaked whales, and 218 dB pp re 1 μPa-1m and 20 dB for Gervais’ beaked whales. Estimates were not possible for Blainville’s beaked whales due to limited data. In both the Monte Carlo simulation and trial-based approach, detection probability declined sharply with ranges, reflecting the highly directional beam of beaked whale echolocation clicks.