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Beaked whales (systematic name Ziphiidae) are a family of cetaceans noted as being one of the least-known groups of mammals because of their deep-sea habitat, reclusive behavior and apparent low abundance. Only three or four of the 24 existing species are reasonably well-known. Baird's beaked whales and Cuvier's beaked whales were subject to commercial exploitation, off the coast of Japan, while the northern bottlenose whale was extensively hunted in the northern part of the North Atlantic in the late 19th and early 20th centuries.
Reports emerged in late 2020 of the possible discovery of a new beaked whale species off the coast of Mexico, the taxonomy of which had not been determined .
Individual species may be very difficult to identify in the wild, since many species appear similar. The observer must rely on size, shape, and placement of teeth and often subtle differences in size, color, forehead shape, and beak length. In collected specimens, the expansion of the premaxillary process in the skull can be a key feature to identification.
The blubber of these whales is almost entirely (94%) composed of wax ester instead of the more usual triglyceride, a unique characteristic of this family.
In December 2008, researchers from the Marine Mammal Institute at Oregon State University completed a DNA tree of 13 of 15 known species of Mesoplodon beaked whales (excluding the spade-toothed whale, which was then only known from a skeletal specimen and a few stranded specimens). Among the results of this study was the conclusion that the male's teeth are actually a secondary sexual characteristic, similar to the of male deer. Each species' teeth have a characteristically unique shape. In some cases, these teeth even hinder feeding; in the strap-toothed whale, for example, the teeth curve over the upper jaw, effectively limiting the gape to a few centimeters. Females are presumed to select mates based on the shape of the teeth, because the different species are otherwise quite similar in appearance.
The beaked whales are the second-largest family of after the oceanic dolphin. Beaked whales were one of the first extant clades to diverge from the ancestral lineage. The earliest known beaked whale date to the Miocene, about 15 million years ago.
A 2016 study split the beaked whales into the basal extinct Messapicetus clade and the crown Ziphiidae which include all of the living members of the family as well as other extinct forms. Both clades share some key characteristics of the family including thick skull bones and the trend toward loss of teeth. In 2020, a molecular study further resolved the relationships among the crown Ziphiidae and placed Shepherd's beaked whale, the only living species with a full set of erupted teeth, between Berardiinae, whose extant forms have four erupted teeth, and Ziphiinae, whose extant form has two erupted teeth.
Hyperoodontidae was preferred in a 1968 phylogeny, which stated that Gray's objection did not qualify as an exception under the International Code of Zoological Nomenclature (ICZN). Hyperoodontidae is indeed currently marked as the valid name by the Integrated Taxonomic Information System (ITIS) which states no successful petition for Ziphiidae had been made to the ICZN as of 2023. In contrast, Smithsonian researchers J.G. Mead and Robert Brownell Jr. argued in 1993 that due to being the "name of choice for over 100 years", Ziphiidae should be given exception under the ICZN Article 23.12. In addition, several authorities, including the Society for Marine Mammalogy Committee on Taxonomy and IUCN Red List of Threatened Species among others continue to use Ziphiidae.
A further, unrelated confusion has arisen, as noted on the ITIS, due to the propagation of an incorrect citation of "Gray, 1850" for Ziphiidae.
Deep-diving mammals face a number of challenges related to extended breath-holding and hydrostatic pressure. Cetaceans and pinnipeds that prolong apnea must optimize the size and use of their oxygen stores, and they must deal with the accumulation of lactic acid due to anaerobic metabolism. Beaked whales have several anatomical adaptations to deep diving: large , livers, and body shape. Most cetaceans have small spleens. However, beaked whales have much larger spleens than delphinids, and may have larger livers, as well. These anatomical traits, which are important for filtering blood, could be adaptations to deep diving. Another notable anatomical adaptation among beaked whales is a slight depression in the body wall that allows them to hold their pectoral flippers tightly against their bodies for increased streamlining. However, they are not invulnerable to the effects of diving so deep and so often. Cascadia Research shows that the deeper the whales dive, the less often they dive per day, cutting their efforts by at least 40%.
The challenges of deep diving are also overcome by the unique diving physiology of beaked whales. Oxygen storage during dives is mostly achieved by blood hemoglobin and muscle myoglobin. While the whale is diving, its heart rate slows and blood flow changes. This physiological dive response ensures oxygen-sensitive tissues maintain a supply of oxygen, while those tissues tolerant to hypoxia receive less blood flow. Additionally, lung collapse obviates the exchange of lung gas with blood, likely minimizing the uptake of nitrogen by tissues.
Dietary information is available from stomach contents analyses of stranded beaked whales and from whaling operations. Their preferred diet is primarily deep-water squid, but also benthic and benthopelagic fish and some crustaceans, mostly taken near the sea floor. In a recent study, gouge marks in the sea floor were interpreted to be a result of feeding activities by beaked whales.
To understand the hunting and foraging behavior of beaked whales, researchers used sound and orientation recording devices on two species: Cuvier's beaked whale ( Ziphius cavirostris) and Blainville's beaked whale ( Mesoplodon densirostris). These whales hunt by echolocation in deep water (where the majority of their prey is located) between about and usually catch about 30 prey per dive. Cuvier's beaked whales must forage on average at for 58 minutes and Blainville's beaked whales typically forage at deep for an average of 47 minutes.
Beaked whales are known to congregate in deep waters off the edge of continental shelves, and bottom features, such as seamounts, canyons, escarpments, and oceanic islands, including the Azores and the Canary Islands, and even off the coasts of Hawaii.
Determining group size for beaked whales is difficult, due to their inconspicuous surfacing behavior. Groups of beaked whales, defined as all individuals found in the same location at the same time, have been reported as ranging from one to 100 individuals. Nevertheless, some populations' group size has been estimated from repeated observations. For example, northern and southern bottlenose whales ( H. ampullatus and H. planifrons), Cuvier's beaked whales, and Blainville's beaked whales ( Mesoplodon densirostris) have a reported maximum group size of 20 individuals, with the average ranging from 2.5 to 3.5 individuals. Berardius species and Longman's beaked whales ( Indopacetus pacificus) are found in larger groups of up to 100 individuals.
Not much information is available about group composition of beaked whales. Only four species have been studied in great detail: northern bottlenose whale, Blainville's beaked whale, Baird's beaked whale, and Cuvier's beaked whale. Female northern bottlenose whales appear to form a loose network of social partners with no obvious long-term associations. In contrast to females, some male northern bottlenose whales have been repeatedly recorded together over several years, and possibly form long-term associations. Studies of Blainville's beaked whales have revealed groups usually consist of a number of females, calves, and/or juvenile animals occasionally accompanied by single males. Drawing on similarities with other mammal species, it has been concluded that this species may therefore engage in female-defense polygyny. (2025). 9783030166632, Springer International Publishing. ISBN 9783030166632 Baird's beaked whales are known to occur in multiple male groups, and in large groups consisting of adult animals of both sexes. There has been some evidence from the Commander islands of multi-year stability in these groups. Arnoux's beaked whales have also been observed to form large pods of up to 47 individuals off the Southern Ocean off the coast of Kemp Land, Antarctica. While males may form short-term associations in the Cuvier's beaked whale, there do not appear to be long term bonds in this species and relatively high rates of fission and fusion within and among groups have been observed.
A major conservation concern for beaked whales (family Ziphiidae) is they appear to be vulnerable to modern sonar operations, which arises from recent strandings that temporally and physically coincide with naval sonar exercises. Mid-frequency active sonar (MFAS), developed in the 1950s for submarine detection, is thought to induce panic when experienced by whales at depth. This raises their heart-rates, forcing them to attempt to rapidly ascend toward the surface in search of air. This artificially-induced rapid ascent can cause decompression.
Post mortem examinations of the stranded whales in concurrence with naval exercises have reported the presence of hemorrhaging near the ears or gas and fat emboli, which could have a deleterious impact on beaked whales that is analogous to decompression sickness in humans. Gas and fat emboli have been shown to cause nervous and cardiovascular system dysfunction, respiratory distress, pain, and disorientation in both humans and animals. In the inner ear, gas embolism can cause hemorrhages, leading to disorientation or vestibular dysfunction.
Breath-holding divers, like beaked whales, can develop decompression-related problems (the "bends") when they return to the surface after deep dives. This is a possible hypothesis for the mass strandings of pelagic beaked whales associated with sonar-related activities. To illustrate, a diving beaked whale may be surfacing from a deep dive and must pass vertically through varying received sound levels. Since the whale has limited remaining oxygen supplies at the end of a long dive, it probably has limited abilities to display any normal sound avoidance behavior. Instead, the whale must continue to swim toward the surface to replenish its oxygen stores. Avoiding sonar inevitably requires a change in behavior or surfacing pattern. Therefore, sonar in close proximity to groups of beaked whales has the potential to cause hemorrhaging or to disorient the animal, eventually leading to a stranding.
Current research reveals two species of beaked whales are most affected by sonar: Cuvier's ( Z. cavirostris) and Blainville's ( M. densirostris) beaked whales. These animals have been reported as stranding in correlation with military exercises in Greece, the Bahamas, Madeira, and the Canary Islands. The livers of these animals had the most damage.
In 2019, a review of evidence on the mass strandings of beaked whale linked to naval exercises where sonar was used was published. It concluded that the effects of mid-frequency active sonar are strongest on Cuvier's beaked whales but vary among individuals or populations, and the strength of their response may depend on whether the individuals had prior exposure to sonar. The report considered that the most plausible explanation of the symptoms of decompression sickness such as gas embolism found in stranded whales to be the whales' response to sonar. It noted that no more mass strandings had occurred in the Canary Islands once naval exercises where sonar was used were banned there, and recommended that the ban be extended to other areas where mass strandings continue to occur.
Four species are classified by the IUCN as "lower risk, conservation dependent": Arnoux's and Baird's beaked whales, and the northern and southern . The status of the remaining species is unknown, preventing classification.
The longest time period for a beaked whale living in captivity was 25 days, the record held by a whale named Alexander, one of two presumed Hubbs' beaked whale calves that stranded on August 24, 1989, on a beach in San Francisco, California, USA. Both whales were taken to Marine World Africa USA, in Vallejo, California. The animals were kept in a 9.7 meter diameter by 2.7 meter deep pool. The second whale, named Nicholas, died after 15 days in captivity. Alexander, the smaller of the two whales, died of pneumonia, while the cause of death for Nicholas was not determined.
A small number of other beaked whales have been kept in captivity. Notably, a Cuvier's beaked whale captured on 02 February, 1992 and held at Sea World of Florida was released after nine days about 30 miles offshore into the Atlantic Ocean. Perhaps the only successful release of a beaked whale, the animal was freeze branded for future identification before release. A rare True's beaked whale, later named Hope, the only member of its species known to be held in captivity, was taken after live-stranding on 02 January, 1973. It was held for about two days in a backyard swimming pool which had been pumped full of seawater before being transferred to the Coney Island Aquarium where it died approximately 2 days later. A juvenile female Cuvier's beaked whale was found stranded on a kelp forest off of Santa Catalina Island on 23 February 1956. She was taken to Marineland of the Pacific, where she was named Martha Washington. On 16 June 1969, a Blainville's beaked whale live stranded in St. Augustine. The whale, thought to be a male, was then transported to Marineland of Florida. It is unknown what happened to the whale, but it was still alive on 18 June 1969.
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