Rare whale washes ashore on Plymouth, MA beach.

zn wrote:

This undated photo provided by the New England Aquarium shows the carcass of rarely-seen deep water beaked whale that washed ashore on Jones Beach in Plymouth, Mass. Aquarium biologists and staff from the International Fund for Animal Welfare are performing a necrospy at the Woods Hole Oceanographic Institution on the carcass after it was found Friday, July 24, 2015. (New England Aquarium via AP)

Beaked whale
From Wikipedia, the free encyclopedia

Beaked whales are the members of the family Ziphiidae which consists of 22 species. These toothed whales are notable for their elongated beaks. Among air-breathing animals, beaked whales are some of the most extreme divers: Cuvier’s beaked whales regularly dive for an hour at a depth over 1,000 m (3,300 ft),[1] and the longest and deepest foraging dive recorded is 137.5 minutes and 2,992 m (9,816 ft). This is the greatest dive-depth known for a mammal.[2]

Beaked whales are one of the least known groups of mammals because of their deep-sea habitat, mysterious habits, and apparent low abundance.[3] Only three to four of the 22 species are reasonably well-known. Baird’s 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 late in the 19th and early in the 20th centuries.

Diving

Beaked whales are deep divers with extreme dive profiles.[1] They regularly dive deeper than 500 m (1,600 ft) to echolocate for food, and these deep dives are often followed by multiple shallower dives of less than 500 m.[11] This pattern is not always followed however. Animals have been observed spending more than an hour at or near the surface breathing. Beaked whales are often seen surfacing synchronously, but asynchronous surfacing has also been observed.[12]

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.[1] Beaked whales have several anatomical adaptations to deep diving: large spleens, 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.[5]

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.[11] 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.[5]

Feeding

The throats of all beaked whales have a bilaterally paired set of grooves that are associated with their unique feeding mechanism, suction feeding.[5] Instead of capturing prey with their teeth, beaked whales suck it into their oral cavity. Suction is aided by the throat grooves, which stretch and expand to accommodate food. Their tongue can move very freely. By suddenly retracting the tongue and distending the gular (throat) floor, pressure immediately drops within the mouth sucking the prey in with the water.

Dietary information is available from stomach contents analyses of stranded beaked whales and from whaling operations. Their preferred diet is primarily deep-water squid,[7] but also benthic and benthopelagic fish and some crustaceans, mostly taken near the sea floor.[12] In a recent study, gouge marks in the seafloor were interpreted to be a result of feeding activities by beaked whales.[13]

To understand the hunting and foraging behavior of beaked whales, researchers used sound and orientation recording devices (DTAGs) 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 approximately 200–1,885 m (656–6,184 ft) and usually catch about 30 prey per dive. Cuvier’s beaked whale must forage on average at 1,070 m (3,510 ft) for 58 minutes and Blainville’s beaked whales typically forage at 835 m (2,740 ft) deep for an average of 47 minutes.[1]

Range and habitat

The family Ziphiidae is one of the most widespread families of cetaceans, ranging from the ice edges at both the north and south poles, to the equator in all the oceans.[14] Specific ranges vary greatly by species, though beaked whales typically inhabit offshore waters that are at least 300 meters deep.

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.[12]

Life history

Very little is known about the life histories of beaked whales. The oldest one ever recorded was 84 years for a male Baird’s beaked whale, and the oldest recorded female Baird’s beaked whale is 54 years. For all other beaked whale species studied, the highest recorded age is between 27 and 39 years. Sexual maturity is reached between seven and 15 years of age in Baird’s beaked whales and northern bottlenose whales. Gestation varies greatly between species, lasting 17 months for Baird’s beaked whales and 12 months for the northern bottlenose whale.[15] There are currently no data available on their reproductive rates.

It is difficult to determine group size of beaked whales, 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.[12]

Not much information is available about group composition of beaked whales. Only three species have been studied in any detail: northern bottlenose whales, Blainville’s beaked whales, and Baird’s beaked whales. 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. These whales are assumed to live in “harem-like” groups, where several females and young are accompanied by a single male.[7] Baird’s beaked whales are known to occur in multiple male groups, and in large groups consisting of adult animals of both sexes.
Conservation

For many years, most beaked whale species were insulated from anthropogenic impacts because of their remote habitat. However, there are now several issues of concern:

Studies of stranded beaked whales show rising levels of toxic chemicals in their blubber.[16]
As a top predator, beaked whales, like raptors, are particularly vulnerable to build-up of biocontaminants. They frequently ingest plastic bags (which do not break down and can be lethal).[12]
They more frequently become trapped in trawl nets, due to the expansion of deepwater fisheries.[17]

Decompression sickness

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.[18] Postmortem 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.[11] Gas and fat emboli have been shown to cause nervous and cardiovascular system dysfunction, respiratory distress, pain, and disorientation in both humans and animals.[18] 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.[1] 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 towards the surface to replenish its oxygen stores.[12] 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 beaked whales (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.[19] The livers of these animals had the most damage.[20]

Though some evidence indicates sonar-related activities can actually lead to a form of decompression sickness in beaked whales, the topic is still up for debate. A significant limiting factor in determining the likelihood of bubble formation in whale tissues and the risk of decompression sickness is the lack of information on their normal diving and surfacing patterns.[1] More research is necessary to determine the extent of whale tissue damage caused by sonar exercises.

Four species are classified by the IUCN as “lower risk, conservation dependent”: Arnoux’s and Baird’s beaked whales, and the northern and southern bottlenose whales. The status of the remaining species is unknown, preventing classification.[21]