Source level estimates for sei whale (Balaenoptera borealis) vocalizations off the Azores.

Sei whale calls have been documented on very few occasions and never in the Azores Archipelago, an area transited by this species during their migration to northern latitudes in spring and early summer. Using a combination of video range tracking (VRT) and acoustic methods, vocalizations are described from an encounter with two sei whales in April 2012 off Pico Island, Azores. Recordings analyzed post-survey revealed 53 low frequency downsweep calls with average maximum frequencies of 100 Hz [standard deviation (SD = 14 Hz)] down to 37 Hz (SD = 8 Hz) over 1.21 s (SD = 0.33 s). Apparent source levels of 177 dB (SD = 5 dB) root-mean-square (rms) re 1 µPa were recorded. Vocalizations were attributed to the pair of sei whales encountered using a combination of the VRT data and differences in arrival time of calls at the hydrophones. These calls are similar to those reported from sei whales off New England and similar to those recorded off Hawaii. The growing body of acoustic data on sei whale vocalizations may contribute to the understanding of this species' distribution and population identity; key information is needed to guide future conservation efforts for this species.

Insights into the distribution and ingestion of prey-like plastic fishing lures in Mediterranean rough-toothed dolphins.

Rough-toothed dolphins (Steno bredanensis) form an isolated subpopulation in the Mediterranean Sea that resides only in the eastern basin. Due to the paucity of records, the conservation threats these dolphins face and their ecology and distribution are poorly understood. While most observations indicate that individuals are found in two isolated clusters in the eastern basin, we hereby present five observations -three visual, one acoustic and one stranding- that possibly extend the range of this subpopulation to the entire offshore waters of the eastern basin. The stomach content remains of the stranded individual revealed a diet based on epipelagic squids and octopods. The stranded dolphin had also consumed seven plastic bags and nine squid-like plastic fishing lures, which had caused a complete gastric blockage and probably led to the stranding. High pollution loads from macroplastics in the Mediterranean Sea may evolve into a new potential threat for this subpopulation.

Australian long-finned pilot whales (Globicephala melas) emit stereotypical, variable, biphonic, multi-component, and sequenced vocalisations, similar to those recorded in the northern hemisphere.

While in the northern hemisphere, many studies have been conducted on the vocal repertoire of long-finned pilot whales (Globicephala melas), no such study has been conducted in the southern hemisphere. Presented here, is the first study on the vocalisations of long-finned pilot whales along the southern coast of mainland Australia. Multiple measures were taken of 2028 vocalisations recorded over five years in several locations. These vocalisations included tonal sounds with and without overtones, sounds of burst-pulse character, graded sounds, biphonations, and calls of multiple components. Vocalisations were further categorised based on spectrographic features into 18 contour classes. Altogether, vocalisations ranged from approximately 200 Hz to 25 kHz in fundamental frequency and from 0.03 s to 2.07 s in duration. These measures compared well with those from northern hemisphere pilot whales. Some call types were almost identical to northern hemisphere vocalisations, even though the geographic ranges of the two populations are far apart. Other call types were unique to Australia. Striking similarities with calls of short-finned pilot whales (Globicephala macrorhynchus) and sometimes sympatric killer whales (Orcinus orca) were also found. Theories for call convergence and divergence are discussed.

Assessing cetacean surveys throughout the Mediterranean Sea: a gap analysis in environmental space.

Heterogeneous data collection in the marine environment has led to large gaps in our knowledge of marine species distributions. To fill these gaps, models calibrated on existing data may be used to predict species distributions in unsampled areas, given that available data are sufficiently representative. Our objective was to evaluate the feasibility of mapping cetacean densities across the entire Mediterranean Sea using models calibrated on available survey data and various environmental covariates. We aggregated 302,481 km of line transect survey effort conducted in the Mediterranean Sea within the past 20 years by many organisations. Survey coverage was highly heterogeneous geographically and seasonally: large data gaps were present in the eastern and southern Mediterranean and in non-summer months. We mapped the extent of interpolation versus extrapolation and the proportion of data nearby in environmental space when models calibrated on existing survey data were used for prediction across the entire Mediterranean Sea. Using model predictions to map cetacean densities in the eastern and southern Mediterranean, characterised by warmer, less productive waters, and more intense eddy activity, would lead to potentially unreliable extrapolations. We stress the need for systematic surveys of cetaceans in these environmentally unique Mediterranean waters, particularly in non-summer months.

Quantifying the acoustic repertoire of a population: the vocalizations of free-ranging bottlenose dolphins in Fiordland, New Zealand.

Quantification of the vocal repertoire of a species is critical for subsequent analysis of signal functionality, geographical variation, social relevance, and transmission. While signal repertoires have been documented for numerous animal species, detailed descriptions for the cetaceans are rare. This study describes the vocalizations of free-ranging bottlenose dolphins resident to the waters of Fiordland, New Zealand. The field recordings presented in this paper were made using both audio band and broadband apparatus. Subsequent classification of vocalizations using multivariate parameters enabled a quantification of the entire vocal output of the focal animals. These results were used to propose a meaningful repertoire of signals employed by this species. A total of 12 individual signal types were described, comprising four broad structural classes: "tonal," "single bursts," "click bursts," and "repeat bursts." The proposed repertoire will allow subsequent investigation into vocal behavior. It appears that the successful description of a species' repertoire is dependent on the use of appropriate recording systems, a high number of representative recordings with good signal-to-noise ratio, and subsequent validation of the original classification system.