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Beaked whales, Family Ziphiidae, occur in deep offshore and oceanic seas, where they are very difficult to study, so that much of our knowledge about them is derived from stranded animals. Most beaked whales (e.g., genera Mesoplodon and Ziphius) have only one pair of mandibular teeth. A reduced dentition is widely regarded as an adaptation to suction feeding, primarily on squid. However, vestigial maxillary and mandibular teeth have been recorded in some species. Here, we describe new records of vestigial teeth in 12 Sowerby's beaked whales, Mesoplodon bidens, and one Cuvier's beaked whale, Ziphius cavirostris, from a total 14 animals of these species, which stranded in 2019–2021 in Scotland. In nine M. bidens some tooth crowns were erupted and mild occlusal wear was visible, whereas pathological teeth were seen in ten individuals. The occurrence of vestigial teeth in Sowerby's beaked whale appears to be significantly under-recorded, suggesting that vestigial teeth form as part of the normal development of the dentition. The reasons for the under-recording of the occurrence and the possible functionality of vestigial teeth in ziphiids are discussed. [ABSTRACT FROM AUTHOR]

Odontocetes possess specialized fat bodies in and around the mandibles for sound reception which have complex topographical distributions of unique endogenous lipids (triacylglycerols and wax esters [WE]). Although there is diversity across species in the fatty acid (FA) and fatty alcohol (FAlc) components of WE, little is understood about the composition and placement of the intact molecules, which will likely impact acoustic function. We aimed to determine the composition and distribution of intact waxes in the jaw fats from five species representative of three odontocete families: delphinids, kogiids, and ziphiids. Total lipid content was similar in all groups, but the WE content of that lipid (21.3%–53.3% of total lipid) and the identity of intact WE molecules showed a high degree of variation, especially in the short‐chain fatty acid components. In contrast, the FAlc elements were surprisingly well conserved. There were 26 intact WE that were common to all species but the delphinids had 12 additional WE with short‐chain fatty acids (i‐5:0 specifically) not found in the other animals examined here. Our study suggests that this highly specialized tissue has evolved several different biochemical pathways, and that there may be multiple strategies for building acoustic fat bodies. [ABSTRACT FROM AUTHOR]

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 catalogs providing insights into life history, social structure and population size. Tag-based efforts looking at diving, movements and acoustics have provided detail on individual behavior 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. Behavioral 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.

In the coast of Galicia an average of 200 stranded cetaceans are reported annually. From 1990 to 2013, 21 individuals of four species of the family Ziphiidae were found: 15 Cuvier's beaked whales (Ziphius cavirostris), two Sowerby's beaked whales (Mesoplodon bidens), one True's beaked whale (Mesoplodon mirus) and one Blainville's beaked whale (Mesoplodon densirostris), as well as two unidentified ones. These were the first records in Galicia for True's beaked whale and Blainville's beaked whale. The study of the distribution of oceanic species considering only stranded animals has limitations, but is a good approach to this not well-known cetacean family. Due to the small number of individuals of the different species, statistical analyses for geographic or seasonal patterns were only carried out for the Cuvier's beaked whales. Between the periods of 1990-2002 and 2003-2013 significant differences were found for geographic and seasonal occurrence patterns. Over the last decade strandings were located only in the north area of the region, mainly during the spring season, while in the previous decade they were located along the three considered areas and only in autumn and winter. [ABSTRACT FROM AUTHOR]

There have been several incidents in which U.S. Navy sonar operations at sea coincided in time and location with a mass stranding of marine mammals, particularly beaked whales. Although a conclusive cause-and-effect relationship has not been established, there is strong evidence and scientific concern that use of military sonar has resulted in beaked whale mass strandings. Most previous attempts to determine whether military sonar use and whale strandings are correlated have looked at mass stranding records of beaked whales and have singled out those instances in which military operations appear to coincide in time and location with a mass stranding event. In this study, historical data on beaked whale mass strandings and military exercises that were likely to include active sonar use were compiled, and statistical analyses were performed to determine the level of correlation between these events for four geographic regions. Strandings were significantly correlated with naval activity in the Mediterranean and Caribbean Seas, but not off the coasts of Japan and southern California. [ABSTRACT FROM AUTHOR]