Ziphius Cavirostris Research Articles

Quantifying deep‐sea predator–prey dynamics: Implications of biological heterogeneity for beaked whale conservation

Abstract Prey distribution and density drive predator habitat usage and foraging behaviour. Understanding ecological relationships is necessary for effective management in any environment but can be challenging in certain contexts. While there has been substantial effort to quantify human disturbance for some protected, deep‐diving marine mammals, there are virtually no direct measurements of deep‐sea predator–prey dynamics. We used recently developed techniques to measure deep‐water squid abundance, size and distribution within foraging habitat areas of deep‐diving Cuvier's beaked whales (Ziphius cavirostris) on and around a Navy training range where sonar is often used. Beaked whales are a management priority as both mortal strandings and sublethal disturbance have occurred in association with Navy mid‐frequency sonar. We found large differences in prey (squid) abundance over small horizontal distances. Highest squid densities occurred within a commonly utilized foraging area on the range. Much lower prey abundance was measured in adjacent, bathymetrically similar areas less commonly used for foraging. By combining prey densities with available behavioural and energetic data, we generate relativistic energetic assessments of foraging habitat quality. This provides a simple, yet quantitative means of evaluating fitness implications of spatial prey heterogeneity and associated consequences of disturbance. Synthesis and applications. Given the challenges deep‐diving predators face with limited foraging time in extreme environments, small‐scale prey heterogeneity can have substantial implications for foraging success. Our results provide fine‐scale data within neighbouring beaked whale foraging habitat areas commonly disturbed by sonars. These results have direct management implications and inform population‐level models of disturbance consequences with empirical data on the foraging ecology of these protected species. These issues have been at the heart of recent debate and litigation over spatial management and proposed sonar exclusion zones, which have previously been based entirely on indirect assumptions regarding habitat quality. While limited in temporal and spatial scope, our novel results provide the first direct ecological data to inform such applied decisions. They also highlight broader regulatory implications of different disturbance consequences in nearby areas and demonstrate the value of empirical, biologically based approaches to spatial management of marine ecosystems generally.

Future Directions in Research on Beaked Whales

Until the 1990s, beaked whales were one of the least understood groups of large mammals. Information on northern bottlenose whales (Hyperoodon ampullatus) and Baird’s beaked whales (Berardius bairdii) was available from data collected during whaling, however, little information existed on the smaller species other than occasional data gleaned from beach-cast animals. Recent research advances have been plentiful. Increasing global survey effort, together with morphometric and genetic analyses have shown at least 22 species in this group. Longitudinal field studies of at least four species (H. ampullatus, B. bairdii, Ziphius cavirostris, Mesoplodon densirostris) have become established over the last three decades. Several long-term studies support photo-identification catalogues providing insights into life history, social structure and population size. Tag-based efforts looking at diving, movements and acoustics have provided detail on individual behaviour as well as population structure and ranges. Passive acoustic monitoring has allowed long-term and seasonal monitoring of populations. Genetic studies have uncovered cryptic species and revealed contrasting patterns of genetic diversity and connectivity amongst the few species examined. Conservation concern for these species was sparked by mass strandings coincident with military mid-frequency sonar use. Fat and gas emboli have been symptomatic indicators of mortalities related to sonar exposure, suggesting that their vulnerability stems from the physiological exertion of extreme diving for medium-sized whales. Behavioural response experiments have now shown that beaked whales appear to cease foraging and delay their return to foraging and/or leave the area in association with exposure to mid-frequency signals at low acoustic levels. Future priorities for these species will be to (1) continue field-studies to better understand smaller-scale habitat use, vital rates and social structure; (2) develop better detection methods for larger-scale survey work; (3) improve methodology for monitoring energetics, individual body condition and health; (4) develop tools to better understand physiology; (5) use recent genetic advances with improved sample databanks to re-examine global and local beaked whale relationships; (6) further quantify anthropogenic impacts (both sonar and other noise) and their population consequences (7) apply acquired data for realistic mitigation of sonar and other anthropogenic impacts for beaked whale conservation.

Living apart together: Niche partitioning among Alboran Sea cetaceans

Co-occurring species are expected to distribute themselves unevenly throughout ecological niche dimensions to avoid competitive exclusion. However, few studies have previously investigated spatial and trophic factors structuring an entire cetacean community. Here, we combined density surface models (DSMs) with two dimension (δ15N and δ13C) isotopic niche spaces in order to identify the mechanistic processes underlying niche partitioning for the most abundant cetacean species inhabiting the Alboran Sea: the long-finned pilot whale (Globicephala melas), the Cuvier’s beaked whale (Ziphius cavirostris), the Risso’s dolphin (Grampus griseus), the bottlenose dolphin (Tursiops truncatus), the striped dolphin (Stenella coeruleoalba), and the short-beaked common dolphin (Delphinus delphis). DSMs provide a spatially-explicit assessment of species distribution through key spatial and environmental gradients, whereas isotopic niches characterize habitat and resource use. Our isotopic niche approach pointed to habitat and/or trophic segregation between the small (striped and short-beaked common dolphins) and large-sized cetacean species (Risso’s and bottlenose dolphins, and long-finned pilot whales). Conversely, DSMs suggested a larger degree of spatial segregation among species by depth, with some overlap for offshore species (long-finned pilot, Cuvier’s beaked whales and Risso’s dolphins) and also between bottlenose and common dolphins. Thus, both components of the ecological niche apparently played an important role in explaining niche partitioning among species, which, in turn, might explain the high abundance and diversity of cetaceans in the Alboran Sea. Further, when both methodologies were applied in isolation, the structure and functioning of this cetacean community was poorly resolved. The combination of both approaches is therefore desirable when investigating niche partitioning among ecologically similar species within communities.

Taxonomic status and epidemiology of the mesoparasitic copepod Pennella balaenoptera in cetaceans from the western Mediterranean.

Pennella balaenoptera is a mesoparasitic copepod that has been reported in at least 17 cetacean species. Subtle morphological differences in the first antennae of adult females have been used to discriminate this species from P. filosa, a species infecting fishes. Other morphological traits are unreliable because of their high plasticity, and no molecular data are available to confirm the taxonomic status of P. balaenoptera as an independent species. We found no consistent morphological differences of the first antennae between P. balaenoptera and P. filosa collected from cetaceans and fish in the western Mediterranean. Molecular data on the mitochondrial cytochrome oxidase subunit I failed to show reciprocal monophyly for the 2 species, and nucleotide divergence between them was low (mean ± SD [range]: 4.1 ± 0.006% [0.5-8.9]). Thus, P. balaenoptera and P. filosa are considered conspecific. We also obtained data on infection parameters of P. balaenoptera based on 450 individuals of 6 cetacean species stranded on the Spanish Mediterranean coast between 1980 and 2017. Prevalence was significantly lowest in the most coastal species, the bottlenose dolphin Tursiops truncatus (3.6%) and highest in the most oceanic species, Cuvier's beaked whale Ziphius cavirostris (100%). This suggests that the life cycle of P. balaenoptera is primarily oceanic. Interestingly, P. filosa also occurs in the oceanic realm infecting large fishes. This ecological similarity further supports the hypothesis that P. balaenoptera and P. filosa are conspecific.

Distribution and abundance of beaked whales (Family Ziphiidae) Off Cape Hatteras, North Carolina, U.S.A.

AbstractBeaked whales are vulnerable to the impacts of disturbance from several sources of anthropogenic sound. Here we report the distribution and abundance of beaked whales off Cape Hatteras, North Carolina, U.S.A., an area utilized by the U.S. Navy for training exercises, and of particular interest for seismic geophysical surveys. From May 2011 through November 2015, monthly aerial surveys were conducted at the site. Beaked whales were encountered 74 times (n = 205 individuals) during these surveys.Ziphius cavirostris, the most commonly encountered species, was observed in every month of the year.Mesoplodonspp. were encountered in ten months of the year. Photographs of adult males with erupted teeth permitted six sightings to be identified conclusively asM. europaeus;M. miruswas also photographed just outside the study area. Beaked whale surface densities stratified by depth (0.005–0.007/km2) were among the highest reported in the world for small ziphiids. A quantitative comparison of sightings and stranding records suggests that strandings do not accurately reflect the relative abundance of beaked whale species in this area. We conclude that Cape Hatteras, at the convergence of the Labrador Current and Gulf Stream, is a particularly important year‐round habitat for several species of beaked whales.

The challenge of habitat modelling for threatened low density species using heterogeneous data: The case of Cuvier’s beaked whales in the Mediterranean

The Mediterranean population of Cuvieŕs beaked whale (Ziphius cavirostris), a deep-diving cetacean, is genetically distinct from the Atlantic, and subject to a number of conservation threats, in particular underwater noise. It is also cryptic at the surface and relatively rare, so obtain robust knowledge on distribution and abundance presents unique challenges. Here we use multiplatform and multiyear survey data to analyse the distribution and abundance of this species across the Mediterranean Sea. We use a novel approach combining heterogeneous data gathered with different methods to obtain a single density index for the region. A total of 594,996km of survey effort and 507 sightings of Cuvier’s beaked whales, from 1990 to 2016, were pooled together from 24 different sources. Data were divided into twelve major groups according to platform height, speed and sea state. Both availability bias and effective strip width were calculated from the sightings with available perpendicular distance data. This was extrapolated to the rest of the sightings for each of the twelve groups. Habitat preference models were fitted into a GAM framework using counts of groups as a response variable with the effective searched area as an offset. Depth, coefficient of variation of depth, longitude and marine regions (as defined by the International Hydrographic Organization) were identified as important predictors. Predicted abundance of groups per grid cell were multiplied by mean group size to obtain a prediction of the abundance of animals. A total abundance of 5799 (CV=24.0%) animals was estimated for the whole Mediterranean basin. The Alborán Sea, Ligurian Sea, Hellenic Trench, southern Adriatic Sea and eastern Ionian Sea were identified as being the main hot spots in the region. It is important to urge that the relevant stakeholders incorporate this information in the planning and execution of high risk activities in these high-risk areas.

Physiological, morphological, and ecological tradeoffs influence vertical habitat use of deep-diving toothed-whales in the Bahamas.

Dive capacity among toothed whales (suborder: Odontoceti) has been shown to generally increase with body mass in a relationship closely linked to the allometric scaling of metabolic rates. However, two odontocete species tagged in this study, the Blainville’s beaked whale Mesoplodon densirostris and the Cuvier’s beaked whale Ziphius cavirostris, confounded expectations of a simple allometric relationship, with exceptionally long (mean: 46.1 min & 65.4 min) and deep dives (mean: 1129 m & 1179 m), and comparatively small body masses (med.: 842.9 kg & 1556.7 kg). These two species also exhibited exceptionally long recovery periods between successive deep dives, or inter-deep-dive intervals (M. densirostris: med. 62 min; Z. cavirostris: med. 68 min). We examined competing hypotheses to explain observed patterns of vertical habitat use based on body mass, oxygen binding protein concentrations, and inter-deep-dive intervals in an assemblage of five sympatric toothed whales species in the Bahamas. Hypotheses were evaluated using dive data from satellite tags attached to the two beaked whales (M. densirostris, n = 12; Z. cavirostris, n = 7), as well as melon-headed whales Peponocephala electra (n = 13), short-finned pilot whales Globicephala macrorhynchus (n = 15), and sperm whales Physeter macrocephalus (n = 27). Body mass and myoglobin concentration together explained only 36% of the variance in maximum dive durations. The inclusion of inter-deep-dive intervals, substantially improved model fits (R2 = 0.92). This finding supported a hypothesis that beaked whales extend foraging dives by exceeding aerobic dive limits, with the extension of inter-deep-dive intervals corresponding to metabolism of accumulated lactic acid. This inference points to intriguing tradeoffs between body size, access to prey in different depth strata, and time allocation within dive cycles. These tradeoffs and resulting differences in habitat use have important implications for spatial distribution patterns, and relative vulnerabilities to anthropogenic impacts.

Impacts of Navy Sonar on Whales and Dolphins: Now beyond a Smoking Gun?

The risks military sonar poses to cetaceans received international attention with a highly-publicized mass stranding of Cuvier’s beaked whales (Ziphius cavirostris), Blainville’s beaked whales (Mesoplodon densirostris) and northern minke whales (Balaenoptera acutorostrata) in the Bahamas in 2000. This was the first time that the US Government determined a stranding to be the result of mid-frequency active sonar use. Subsequently attention has been drawn to other mass strandings coincident with naval exercises, including events preceding the 2000 mass stranding. The list of species for which mass strandings have been linked to naval exercises has also increased to include other beaked whales, dwarf and pygmy sperm whales (Kogia spp.), pilot whales (Globicephala spp.), several dolphin species (Stenella sp. and Delphinus delphis) and harbor porpoises (Phocoena phocoena). In particular, there have been several mass strandings in the northern Indian Ocean coincident with naval exercises - including one of the largest (200-250 dolphins) - which have received little attention. Changes in beaked whale behaviour, including evasive manoeuvring, have been recorded at received levels below <100 dB re 1µPa (rms) and mass stranding may occur at received levels potentially as low as 150–170 dB re 1 µPa. There is strong scientific evidence to suggest that a wide range of whale, dolphin and porpoise species can also be impacted by sound produced during military activities, with significant effects occurring at received levels lower than previously predicted. Although there are many stranding events that have occurred coincident with the presence of naval vessels or exercises, it is important to emphasize that even the absence of strandings in a region does not equate to an absence of deaths, i.e., absence of evidence does not mean evidence of absence. Strandings may be undetected, or be unlikely to be observed because of a lack of search effort or due to coastal topography or characteristics. There may also be “hidden” impacts of sonar and exercises not readily observable (e.g., stress responses). Due to the level of uncertainty related to this issue, ongoing baseline monitoring for cetaceans in exercise areas is important and managers should take a precautionary approach to mitigating impacts.

Using multipath reflections to obtain dive depths of beaked whales from a towed hydrophone array.

Beaked whales are deep divers, emitting echolocation clicks while at depth. Little is known about the dive behavior of most species; however, passive acoustic data collected with towed hydrophone arrays can provide depth information using multipath reflections of clicks coupled with a two-dimensional localization of the individual. Data were collected during a shipboard survey in the western North Atlantic Ocean using a towed linear hydrophone array. Beaked whale tracks were classified as either Cuvier's (Ziphius cavirostris) or Gervais'/True's (Mesoplodon europaeus/Mesoplodon mirus). Weighted species average depths and weighted species standard deviations were 1158 m ± 287 m for Cuvier's (n = 24), and 870 m ± 151 m for Gervais'/True's (n = 15). Depth uncertainties ranged from 3% to 142% of the average depth. Slant ranges were corrected for depth to provide average horizontal perpendicular distance estimates. The average horizontal perpendicular distance distribution exhibited fewer detections in the first bin than the second. This is the first report of dive depths for Gervais'/True's beaked whales and use of this method to obtain depths for beaked whales using a towed linear array.

Diving behaviour of Cuvier's beaked whales exposed to two types of military sonar.

Cuvier's beaked whales (Ziphius cavirostris) have stranded in association with mid-frequency active sonar (MFAS) use, and though the causative mechanism linking these events remains unclear, it is believed to be behaviourally mediated. To determine whether MFAS use was associated with behavioural changes in this species, satellite tags were used to record the diving and movements of 16 Cuvier's beaked whales for up to 88 days in a region of frequent MFAS training off the coast of Southern California. Tag data were combined with summarized records of concurrent bouts of high-power, surface-ship and mid-power, helicopter-deployed MFAS use, along with other potential covariates, in generalized additive mixed-effects models. Deep dives, shallow dives and surface intervals tended to become longer during MFAS use, with some variation associated with the total amount of overlapping MFAS during the behaviour. These changes in dives and surface intervals contributed to a longer interval between deep dives, a proxy for foraging disruption in this species. Most responses intensified with proximity and were more pronounced during mid-power than high-power MFAS use at comparable distances within approximately 50 km, despite the significantly lower source level of mid-power MFAS. However, distance-mediated responses to high-power MFAS, and increased deep dive intervals during mid-power MFAS, were evident up to approximately 100 km away.

Nowhere to go: noise impact assessments for marine mammal populations with high site fidelity

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 32:391-413 (2017) - DOI: https://doi.org/10.3354/esr00820 Theme Section: 21st century paradigms for measuring and managing the effects of anthropogenic ocean noise Nowhere to go: noise impact assessments for marine mammal populations with high site fidelity Karin A. Forney1,*, Brandon L. Southall2,3,4, Elisabeth Slooten5, Steve Dawson6, Andrew J. Read4, Robin W. Baird7, Robert L. Brownell Jr.8 1Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, NOAA, c/o MLML Norte, 7544 Sandholdt Rd, Moss Landing, CA 95039, USA 2Southall Environmental Associates, Inc., 9099 Soquel Dr, Suite 8, Aptos, CA 95003, USA 3University of California, Institute of Marine Science, Long Marine Laboratory, 100 McAllister Way, Santa Cruz, CA 95060, USA 4Nicholas School of the Environment, Duke University, 135 Duke Marine Lab Rd, Beaufort, NC 28516, USA 5Department of Zoology, University of Otago, PO Box 56, Dunedin, 9054, New Zealand 6Department of Marine Science, University of Otago, PO Box 56, Dunedin, 9016, New Zealand 7Cascadia Research Collective, 218 1/2 4th Ave W, Olympia, WA 98501, USA 8Southwest Fisheries Science Center, National Marine Fisheries Service, NOAA, 34500 Highway 1, Monterey, CA 93940, USA *Corresponding author: karin.forney@noaa.gov ABSTRACT: As awareness of the effects of anthropogenic noise on marine mammals has grown, research has broadened from evaluating physiological responses, including injury and mortality, to considering effects on behavior and acoustic communication. Most mitigation efforts attempt to minimize injury by enabling animals to move away as noise levels are increased gradually. Recent experiences demonstrate that this approach is inadequate or even counterproductive for small, localized marine mammal populations, for which displacement of animals may itself cause harm. Seismic surveys within the ranges of harbor porpoise Phocoena phocoena in California and Māui dolphin Cephalorhynchus hectori maui in New Zealand highlight the need to explicitly consider biological risks posed by displacement during survey planning, monitoring, and mitigation. Consequences of displacement are poorly understood, but likely include increased stress and reduced foraging success, with associated effects on survival and reproduction. In some cases, such as the Critically Endangered Māui dolphin, displacement by seismic activities risks exposing the remaining 55 dolphins to bycatch in nearby fisheries. Similar concerns about military and industrial activities exist for island-associated species such as melon-headed whales Peponocephala electra in Hawai'i; shelf-break associated species such as Cuvier’s beaked whales Ziphius cavirostris off the US Atlantic coast, and whales foraging in coastal habitats, such as the Critically Endangered western gray whale Eschrichtius robustus. We present an expanded framework for considering disturbance effects that acknowledges scientific uncertainty, providing managers and operators a more robust means of assessing and avoiding potential harm associated with both displacement and direct effects of intense anthropogenic noise exposure. KEY WORDS: Anthropogenic noise · Marine mammals · Impact assessment · Mitigation · Monitoring · Small populations Full text in pdf format PreviousNextCite this article as: Forney KA, Southall BL, Slooten E, Dawson S, Read AJ, Baird RW, Brownell RL Jr (2017) Nowhere to go: noise impact assessments for marine mammal populations with high site fidelity. Endang Species Res 32:391-413. https://doi.org/10.3354/esr00820 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 32. Online publication date: May 08, 2017 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2017 Inter-Research.

Estimating geo-position and depth of echo-locating beaked whales using an array of drifting recorders

An array of 8 drifting recorders were deployed in the Catalina Basin off Southern California to localize beaked whales. The drifting recorders with hydrophone pairs at 90-135 m were deployed along two parallel lines with ~1 km separation between recorders. The array was re-deployed daily at approximately the same location to maintain this array spacing. Cuvier’s beaked whales (Ziphius cavirostris) were detected on 26 occasions from their distinctive echo-location clicks. On 8 of these occasions, direct-path and surface-reflected signals were received on four or more drifting recorders, which allowed us to estimate location and depth of the whales. Average array tilt during these events was less than 0.2°, and always less than 0.6°. The same echolocation clicks were seldom received on more than two recorders, so we could not use methods that require TDOA measurements between recorders. We develop a novel method of 3-D localization using the vertical bearing angles estimated from the direct- and surface-reflected signals and use optimization methods to find the unique location and depth at which these angles converged. Detection ranges varied from 1.0 to 3.7 km (mean = 2.0, sd = 0.65), and depths of vocalizing animals varied from 696-1150 m (mean = 948, sd = 152).

Spatio-temporal distribution of beaked whales on Canada’s East Coast

Beaked whales represent some of the least understood marine mammals worldwide with the movements and distribution of many species largely unknown. Around eastern Canada current knowledge is limited to the eastern Scotian shelf and northern bottlenose whales. The acoustic signals of the beaked whale species are recognizable and sufficiently unique to be candidates for passive acoustic monitoring. Thirteen deep-water recorders located along the shelf break off Eastern Canada from Bonnécamps Canyon (42.5 N) to Southern Labrador (55.3 N) collected acoustic data near-continuously from Aug 2015 to July 2016. A minimum of one of every 20 minutes were recorded at 250,000 samples per second to monitor for the presence echolocations clicks of odontocetes, including beaked whales. An automated detector, validated by manual analysts, identified the presence of endangered Northern Bottlenose whales (Hyperoodon ampullatus), Cuvier’s (Ziphius cavirostris), and special concern Sowerby’s beaked whales (Mesoplodon bidens). The presence data were analyzed to determine the occurrence and residency durations of beaked whales throughout the geographic range studied. We then studied the influence of currents, sea ice, surface temperatures, chlorophyll, distance to the 1000 m isobath, background noise and anthropogenic noise on the whales’ acoustic occurrence. Acoustic studies such as this allow us to gain further insights on the occurrence of these notoriously difficult to study species.

Encounters with the Cuvier’s beaked whale, Ziphius cavirostris Cuvier, 1823 (Cetacea: Ziphiidae), in waters off eastern Kamchatka and the Commander Islands

The biology of the Cuvier’s beaked whale, Ziphius cavirostris Cuvier, 1823, in Russian waters remains almost unstudied. The species is encountered rarely elsewhere in the seas of Russia, except for the waters off the Commander Islands. Currently, some researchers express doubt about the accuracy of the known Cuvier’s beaked whale records in the region. This report provides information on the confirmed encounters with Cuvier’s beaked whale off the Commander Islands and eastern Kamchatka.

Spatio-temporal variation in click production rates of beaked whales: Implications for passive acoustic density estimation.

Passive acoustic monitoring has become an increasingly prevalent tool for estimating density of marine mammals, such as beaked whales, which vocalize often but are difficult to survey visually. Counts of acoustic cues (e.g., vocalizations), when corrected for detection probability, can be translated into animal density estimates by applying an individual cue production rate multiplier. It is essential to understand variation in these rates to avoid biased estimates. The most direct way to measure cue production rate is with animal-mounted acoustic recorders. This study utilized data from sound recording tags deployed on Blainville's (Mesoplodon densirostris, 19 deployments) and Cuvier's (Ziphius cavirostris, 16 deployments) beaked whales, in two locations per species, to explore spatial and temporal variation in click production rates. No spatial or temporal variation was detected within the average click production rate of Blainville's beaked whales when calculated over dive cycles (including silent periods between dives); however, spatial variation was detected when averaged only over vocal periods. Cuvier's beaked whales exhibited significant spatial and temporal variation in click production rates within vocal periods and when silent periods were included. This evidence of variation emphasizes the need to utilize appropriate cue production rates when estimating density from passive acoustic data.

Dolphin Morbillivirus in a Cuvier's Beaked Whale (Ziphius cavirostris), Italy.

Dolphin morbillivirus (DMV) has caused several mortality events in Mediterranean striped (Stenella coeruleoalba) and bottlenose (Tursiops truncatus) dolphins populations since 19; in the last 5 years, the virus was reported to infect new hosts in this basin, such as fin whales (Balaenoptera physalus), sperm whales (Physeter macrocephalus), and even a harbor seal (Phoca vitulina). Very recently, a calf Cuvier’s beaked whale (Ziphius cavirostris) calf stranded on the Southern Italian coastline with mild pathological findings suggestive of morbilliviral infection, received the first confirmation of DMV infection in this species by biomolecular evidences on lung tissue. This new cross-species infection report, along with 19% of the cetaceans specimens examined by the Italian Stranding Network being found positive to DMV, support the hypothesis of an endemic circulation of this virus among Mediterranean cetaceans.

Two live sightings of Sowerby's beaked whale (Mesoplodon bidens) from the western Mediterranean (Tyrrhenian Sea)

Sowerby's beaked whale (Mesoplodon bidens) was previously known in the Mediterranean Sea from a single live stranding of two individuals in the French Riviera. We report here on two live sightings in the western Mediterranean, central-western Tyrrhenian Sea off eastern Corsica (Montecristo Trough) and off eastern Sardinia (Caprera Canyon) in 2010 and 2012, respectively. In both cases single individuals, possibly the same individual, occurred within groups of Cuvier's beaked whales (Ziphius cavirostris) suggesting inter-specific interactions. Based on our close observations of mixed-species groups of Sowerby's and Cuvier's beaked whales, we hypothesize that some previous long-distance sightings of beaked whales in the Mediterranean may not be reliably attributed to Z. cavirostris. The present sightings and previous live stranding indicate that the western Mediterranean Sea is the easternmost marginal area of M. bidens within the North Atlantic geographic range. Notes on behaviour are also provided.

Key Oceanographic Characteristics of Cuviers Beaked Whale (Ziphius cavirostris) Habitat in the Gulf of Genoa (Ligurian Sea, NW Mediterranean)

Cuvier’s beaked whale presence has been associated worldwide with continental slope and submarine canyons areas. In the Mediterranean Sea, a hot spot of the species presence has been identified in the Genoa Canyon area, located in the Gulf of Genova (Ligurian Sea, NW Mediterranean Sea). Within the framework of the NATO Marine Mammal Risk Mitigation Project, several research cruises have been conducted between 1999 and 2011 in the Ligurian Sea area. During these cruises depth profiles of temperature, salinity, sound velocity, dissolved oxygen, fluorescence and turbidity as a function of depth were collected using a Conductivity, Temperature, Depth (CTD) and auxiliary sensors installed on a Rosette frame. Concurrently, Cuvier’s beaked whale (Ziphius cavirostris) presence was assessed through visual observations. The aim of this study was to investigate the environmental characteristics of a beaked whale habitat in the Genoa canyon area correlating beaked whale presence with the oceanographic variables. A Logistic Regression model was developed using the data collected during the oceanographic campaign carried out in summer 2002. Model accuracy was also evaluated in the same area based on the data collected 9 years later in summer 2011. The depth of the maximum dissolved oxygen (Depth Ox Max) turned out to be a significant predictor of beaked whale presence in the studied area. Higher presence probabilities of beaked whales were found associated to higher turbidities of deep-water layers in both the calibration and evaluation set. Results suggest dynamic predictors may act as proxy of macro-scale features that characterise beaked whale habitats. Particularly the depth the maximum oxygen concentration may be a tracer of the vertical exchanges of water masses (i.e., downwelling), transferring energy from the surface waters to the deep waters where beaked whales feed on their prey.

Mid-frequency active sonar and beaked whale acoustic activity in the Northern Mariana Islands

Mid-frequency active (MFA) sonar has been associated with multiple mass stranding events of beaked whales around the world. A recent increase in military training exercises in the Mariana Archipelago corresponds with the presence of MFA sonar in the surrounding waters. We provide a quantitative report on MFA sonar and beaked whale acoustic activity detected on two autonomous acoustic recording packages deployed near Saipan and Tinian from March 2010 through December 2013. There were no detections of MFA sonar at Saipan during the 5-month deployment in 2010. On August 21, 2011, MFA sonar was detected near Saipan concurrent with a stranding event involving two Cuvier’s beaked whales (Ziphius cavirostris). After one observed day of MFA sonar activity in Saipan and Tinian in 2011, observations increased to 1 month of ongoing activity at Saipan and nearly 3 months ongoing activity at Tinian in 2012. In 2013, MFA sonar events were observed during one day at Saipan and zero days at Tinian. Received levels, sound...

Beaked whale species occurrence in the central Pacific and their relation to oceanographic features

Mesoscale oceanographic features are a major force in structuring the marine environment through processes such as eddy-induced upwelling, and as such effect distribution and aggregation patterns of all organisms along the food chain. It has been shown that top pelagic predators such as cetaceans react to these environmental changes in different ways. We present analysis of frequency-modulated (FM) echolocation pulses of Cuvier’s beaked whale (Ziphius cavirostris), Blainville’s beaked whale (Mesoplodon densirostis), and an unknown beaked whale species producing FM pulse type “BWC,” possibly ginkgo-toothed beaked whale (M. ginkgodens), at five locations in the central Pacific. The recordings were collected at Pearl and Hermes Reef (Northwestern Hawaiian Islands), Kona (Main Hawaiian Islands), Wake Atoll, Tinian, and Saipan (Northern Mariana Islands) between 2008 and 2015, ranging from 4 to 8 years per site. All three beaked whale species were present at all sites in different proportions throughout the recording periods, with a strong nocturnal pattern only for the “BWC” pulse type, yet without seasonal pattern. We examine the varying presence in the context of remotely sensed oceanographic data, including sea surface height deviation, temperature, and salinity, as well as chlorophyll a and derived primary productivity.