167-695: Baleen whales ( / b ə ˈ l iː n / ), also known as whalebone whales , are marine mammals of the parvorder Mysticeti in the infraorder Cetacea ( whales , dolphins and porpoises ), which use keratinaceous baleen plates (or "whalebone") in their mouths to sieve planktonic creatures from the water. Mysticeti comprises the families Balaenidae ( right and bowhead whales), Balaenopteridae ( rorquals ), Eschrichtiidae (the gray whale ) and Cetotheriidae (the pygmy right whale ). There are currently 16 species of baleen whales. While cetaceans were historically thought to have descended from mesonychians , molecular evidence instead supports them as
334-473: A clade of even-toed ungulates (Artiodactyla). Baleen whales split from toothed whales (Odontoceti) around 34 million years ago . Baleen whales range in size from the 6 m (20 ft) and 3,000 kg (6,600 lb) pygmy right whale to the 31 m (102 ft) and 190 t (210 short tons) blue whale , the largest known animal to have ever existed. They are sexually dimorphic . Baleen whales can have streamlined or large bodies, depending on
501-620: A dead zone . Estuaries tend to be naturally eutrophic because land-derived nutrients are concentrated where runoff enters the marine environment in a confined channel. The World Resources Institute has identified 375 hypoxic coastal zones around the world, concentrated in coastal areas in Western Europe, the Eastern and Southern coasts of the US, and East Asia, particularly in Japan. In
668-500: A 26% increase in hydrogen ion concentration in the world's oceans (the pH scale is logarithmic, so a change of one in pH units is equivalent to a tenfold change in hydrogen ion concentration). Sea-surface pH and carbonate saturation states vary depending on ocean depth and location. Colder and higher latitude waters are capable of absorbing more CO 2 . This can cause acidity to rise, lowering the pH and carbonate saturation levels in these areas. There are several other factors that influence
835-478: A V-shaped blow. They are surrounded by a fleshy ridge that keeps water away while the whale breathes. The septum that separates the blowholes has two plugs attached to it, making the blowholes water-tight while the whale dives. Like other mammals, the skin of baleen whales has an epidermis , a dermis , a hypodermis , and connective tissue . The epidermis, the pigmented layer, is 5 millimeters (0.2 in) thick, along with connective tissue. The epidermis itself
1002-405: A blunt snout and reduced dentition rely on suction feeding . Though carnivorous, they house gut flora similar to that of terrestrial herbivores, probably a remnant of their herbivorous ancestry. Baleen whales use their baleen plates to sieve plankton, among others, out of the water; there are two types of methods: lunge-feeding and gulp-feeding. Lunge-feeders expand the volume of their jaw to
1169-442: A change to tissue matter, biochemistry, behavior, reproduction, and suppress growth in marine life. Also, many animal feeds have a high fish meal or fish hydrolysate content. In this way, marine toxins can be transferred to land animals, and appear later in meat and dairy products. There are many ways to categorize and examine the inputs of pollution into marine ecosystems. There are three main types of inputs of pollution into
1336-627: A divergence of the Monachinae (monk seals) and Phocinae lineages 22 mya. Fossil evidence indicates the sea otter ( Enhydra ) lineage became isolated in the North Pacific approximately two mya, giving rise to the now-extinct † Enhydra macrodonta and the modern sea otter, Enhydra lutris . The sea otter evolved initially in northern Hokkaidō and Russia, and then spread east to the Aleutian Islands , mainland Alaska , and down
1503-471: A few are specialists. They typically hunt non-schooling fish, slow-moving or immobile invertebrates or endothermic prey when in groups. Solitary foraging species usually exploit coastal waters, bays and rivers. When large schools of fish or squid are available, pinnipeds hunt cooperatively in large groups, locating and herding their prey. Some species, such as California and South American sea lions, may forage with cetaceans and sea birds. The polar bear
1670-501: A few eat other mammals. While the number of marine mammals is small compared to those found on land, their roles in various ecosystems are large, especially concerning the maintenance of marine ecosystems, through processes including the regulation of prey populations. This role in maintaining ecosystems makes them of particular concern as 23% of marine mammal species are currently threatened. Marine mammals were first hunted by aboriginal peoples for food and other resources. Many were also
1837-436: A fiber-reinforced structure made of intermediate filaments (proteins). The degree of calcification varies between species, with the sei whale having 14.5% hydroxyapatite , a mineral that coats teeth and bones, whereas minke whales have 1–4% hydroxyapatite. In most mammals, keratin structures, such as wool , air-dry, but aquatic whales rely on calcium salts to form on the plates to stiffen them. Baleen plates are attached to
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#17327768471632004-426: A growing global population", and the impact billions of pieces of plastic waste are having globally on the health of marine environments. Bjorn Jennssen (2003) notes in his article, "Anthropogenic pollution may reduce biodiversity and productivity of marine ecosystems, resulting in reduction and depletion of human marine food resources". There are two ways the overall level of this pollution can be mitigated: either
2171-425: A large amount of water and sieve the slow-moving prey. Males typically mate with more than one female ( polygyny ), although the degree of polygyny varies with the species. Male strategies for reproductive success vary between performing ritual displays ( whale song ) or lek mating . Calves are typically born in the winter and spring months and females bear all the responsibility for raising them. Mothers fast for
2338-504: A layer of fat, or blubber , under the skin to keep warm in the cold water. Although baleen whales are widespread, most species prefer the colder waters of the Arctic and Antarctic . Gray whales are specialized for feeding on bottom-dwelling crustaceans . Rorquals are specialized at lunge-feeding, and have a streamlined body to reduce drag while accelerating. Right whales skim-feed, meaning they use their enlarged head to effectively take in
2505-467: A lunge-feeding behavior. Lunge-feeding is where a whale rams a bait ball (a swarm of small fish ) at high speed. Rorquals generally have streamlined physiques to reduce drag in the water while doing this. Balaenids rely on their huge heads, as opposed to the rorquals' throat pleats, to feed effectively. This feeding behavior allows them to grow very big and bulky, without the necessity for a streamlined body. They have callosities , unlike other whales, with
2672-698: A number of features for efficient locomotion such as torpedo-shaped bodies to reduce drag; modified limbs for propulsion and steering ; tail flukes and dorsal fins for propulsion and balance. Marine mammals are adept at thermoregulation using dense fur or blubber , circulatory adjustments ( counter-current heat exchange ); and reduced appendages, and large size to prevent heat loss. Marine mammals are able to dive for long periods. Both pinnipeds and cetaceans have large and complex blood vessel systems pushing large volumes of blood rich in myoglobin and hemoglobin , which serve to store greater quantities of oxygen . Other important reservoirs include muscles and
2839-438: A number of terrestrial habitats, both continental and island. In temperate and tropical areas, they haul-out on to sandy and pebble beaches, rocky shores , shoals , mud flats , tide pools and in sea caves . Some species also rest on man-made structures, like piers , jetties , buoys and oil platforms . Seals may move further inland and rest in sand dunes or vegetation, and may even climb cliffs. Most cetaceans live in
3006-629: A period of glaciation in the Pleistocene or from the eastern part of Siberia , (from Kamchatka and the Kolym Peninsula). The oldest known polar bear fossil is a 130,000-to-110,000-year-old jaw bone, found on Prince Charles Foreland in 2004. The mitochondrial DNA (mtDNA) of the polar bear diverged from the brown bear roughly 150,000 years ago. Further, some clades of brown bear, as assessed by their mtDNA, are more closely related to polar bears than to other brown bears, meaning that
3173-413: A relatively high density and are toxic or poisonous at low concentrations. Examples are mercury , lead , copper and cadmium . Some toxicants can accumulate in the tissues of many species of aquatic life in a process called bioaccumulation . They are also known to accumulate in benthic environments , such as estuaries and bay muds : a geological record of human activities of the last century. DDT
3340-566: A relatively long period of time over the period of migration, which varies between species. Baleen whales produce a number of infrasonic vocalizations , notably the songs of the humpback whale . The meat, blubber, baleen, and oil of baleen whales have traditionally been used by the indigenous peoples of the Arctic . Once relentlessly hunted by commercial industries for these products, cetaceans are now protected by international law. These protections have allowed their numbers to recover. However,
3507-444: A relatively small brain compared to their body mass . Like other mammals, their brain has a large, folded cerebrum , the part of the brain responsible for memory and processing sensory information. Their cerebrum only makes up about 68% of their brain's weight, as opposed to human's 83%. The cerebellum , the part of the brain responsible for balance and coordination, makes up 18% of their brain's weight, compared to 10% in humans, which
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#17327768471633674-406: A result of anthropogenic inputs or alternatively may be something that is now more closely monitored and so more frequently reported. The biggest culprit are rivers that empty into the ocean, and with it the many chemicals used as fertilizers in agriculture as well as waste from livestock and humans . An excess of oxygen-depleting chemicals in the water can lead to hypoxia and the creation of
3841-442: A seal to appear. When the seal exhales, the bear smells its breath, reaches into the hole with a forepaw, and drags it out onto the ice. The polar bear also hunts by stalking seals resting on the ice. Upon spotting a seal, it walks to within 100 yards (90 m), and then crouches. If the seal does not notice, the bear creeps to within 30 to 40 feet (9 to 10 m) of the seal and then suddenly rushes to attack. A third hunting method
4008-484: A sensory organ located in the middle of the jaw to regulate these functions. Baleen whales have two flippers on the front, near the head. Like all mammals, baleen whales breathe air and must surface periodically to do so. Their nostrils, or blowholes , are situated at the top of the cranium . Baleen whales have two blowholes, as opposed to toothed whales which have one. These paired blowholes are longitudinal slits that converge anteriorly and widen posteriorly, which causes
4175-412: A significant backlash on the domestic economy . Marine debris , also known as marine litter, is human-created solid material that has deliberately or accidentally been released in seas or the ocean . Floating oceanic debris tends to accumulate at the center of gyres and on coastlines , frequently washing aground, when it is known as beach litter or tidewrack. Deliberate disposal of wastes at sea
4342-439: A spherical lens. The retina is surrounded by a reflective layer of cells ( tapetum lucidum ), which bounces light back at the retina, enhancing eyesight in dark areas. However, light is bent more near the surface of the eye when in air as opposed to water; consequently, they can see much better in the air than in the water. The eyeballs are protected by a thick outer layer to prevent abrasions and an oily fluid (instead of tears) on
4509-516: A third was recycled or composted. In 2015, there was over 8 million tons of plastic that made it into the ocean. The Ocean Conservancy reported that China, Indonesia, Philippines, Thailand, and Vietnam dump more plastic in the sea than all other countries combined. Through more sustainable packing this could lead to; eliminating toxic constituents, using fewer materials, making more readily available recyclable plastic. However, awareness can only take these initiatives so far. The most abundant plastic
4676-643: A translation error in early copies of Aristotle 's Historia Animalium (in Ancient Greek ), in which " ὁ μῦς τὸ κῆτος " ( ho mus to kētos , "the mouse, the whale so called") was mistakenly translated as " ὁ μυστικῆτος " ( ho mustikētos , "the Mysticetus"), which D. W. Rice (of the Society for Marine Mammalogy ) in Rice 1998 assumed was an ironic reference to the animals' great size. An alternate name for
4843-430: A volume bigger than the original volume of the whale itself by inflating their mouth. This causes grooves on their throat to expand, increasing the amount of water the mouth can store. They ram a baitball at high speeds in order to feed, but this is only energy-effective when used against a large baitball. Gulp-feeders swim with an open mouth, filling it with water and prey. Prey must occur in sufficient numbers to trigger
5010-618: A wide variety of products such as firefighting foams , clothing, carpets, and fast food wrappers. These useful properties in manufacturing unfortunately translate to problematic properties in the environment and organisms from plants to people. Because PFAS are not broken down in the environment, they have been circulated through the air and water to essentially all regions of the atmosphere, land, and ocean. These chemicals have many negative effects on marine life, such as significantly inhibited growth of phytoplankton over time and accumulation in seals, polar bears, and dolphins. Current research
5177-458: A wing-like manner similar to penguins and sea turtles . Flipper movement is continuous. While doing this, baleen whales use their tail fluke to propel themselves forward through vertical motion while using their flippers for steering, much like an otter . Some species leap out of the water, which may allow them to travel faster. Because of their great size, right whales are not flexible or agile like dolphins, and none can move their neck because of
Baleen whale - Misplaced Pages Continue
5344-813: A world largely defined by acoustic information. This applies also to many deeper sea fish, who live in a world of darkness. Between 1950 and 1975, ambient noise at one location in the Pacific Ocean increased by about ten decibels (that is a tenfold increase in intensity). Noise also makes species communicate louder, which is called the Lombard vocal response. Whale songs are longer when submarine-detectors are on. If creatures don't "speak" loud enough, their voice can be masked by anthropogenic sounds. These unheard voices might be warnings, finding of prey, or preparations of net-bubbling. When one species begins speaking louder, it will mask other species voices, causing
5511-540: Is silt -bearing surface runoff , which can inhibit the penetration of sunlight through the water column, hampering photosynthesis in aquatic plants. Much anthropogenic pollution ends up in the ocean. The 2011 edition of the United Nations Environment Programme Year Book identifies as the main emerging environmental issues the loss to the oceans of massive amounts of phosphorus , "a valuable fertilizer needed to feed
5678-568: Is PET (Polyethylene terephthalate) and is the most resistant to biodegradables. Researchers have been making great strides in combating this problem. In one way has been by adding a special polymer called a tetrablock copolymer. The tetrablock copolymer acts as a laminate between the PE and iPP which enables for an easier breakdown but still be tough. Through more awareness, individuals will become more cognizant of their carbon footprints. Also, from research and technology, more strides can be made to aid in
5845-467: Is a very toxic chemical that was used as a pesticide in mass quantities throughout the United States and is known to be neurotoxic, a reproductive toxin, an endocrine disruptor, and a carcinogen. DDT is a major focus of the book Silent Spring published by Rachel Carson in 1962. This is often attributed to launching the modern environmental movement and setting the stage for the creation of
6012-559: Is an archaic word for "whale", which came from Old French baleine , derived from the Latin word balæna , derived itself from the Ancient Greek φάλλαινα (phállaina) . Right whales got their name because of whalers preferring them over other species; they were essentially the "right whale" to catch. Rorquals use throat pleats to expand their mouths, which allow them to feed more effectively. However, rorquals need to build up water pressure in order to expand their mouths, leading to
6179-401: Is another source of marine pollution. Most of the pollution is simply soil, which ends up in rivers flowing to the sea. However, some minerals discharged in the course of the mining can cause problems, such as copper , a common industrial pollutant, which can interfere with the life history and development of coral polyps. Mining has a poor environmental track record. For example, according to
6346-495: Is approximated that there is a stock of 86 million tons of plastic marine debris in the worldwide ocean as of the end of 2013, assuming that 1.4% of global plastics produced from 1950 to 2013 has entered the ocean and has accumulated there. Global consumption of plastics is estimated to be 300 million tonnes per year as of 2022, with around 8 million tonnes ending up in the oceans as macroplastics. Approximately 1.5 million tonnes of primary microplastics end up in
6513-400: Is bound to have a hard, sweeping impact on life in the sea." Noise from ships and human activity can damage Cnidarians and Ctenophora, which are very important organisms in the marine ecosystem. They promote high diversity and they are used as models for ecology and biology because of their simple structures. When there is underwater noise, the vibrations in the water damage the cilia hairs in
6680-426: Is called ocean dumping . Naturally occurring debris, such as driftwood and drift seeds , are also present. With the increasing use of plastic , human influence has become an issue as many types of (petrochemical) plastics do not biodegrade quickly, as would natural or organic materials. The largest single type of plastic pollution (~10%) and majority of large plastic in the oceans is discarded and lost nets from
6847-453: Is disturbed by vibrations, it triggers sensory hairs which send electric current to the brain, where vibrations are processed into sound. Baleen whales have a small, yet functional, vomeronasal organ . This allows baleen whales to detect chemicals and pheromones released by their prey. It is thought that 'tasting' the water is important for finding prey and tracking down other whales. They are believed to have an impaired sense of smell due to
Baleen whale - Misplaced Pages Continue
7014-530: Is herding, where a pod squeezes a school of fish into a small volume, known as a bait ball . Individual members then take turns plowing through the ball, feeding on the stunned fish. Coralling is a method where dolphins chase fish into shallow water to catch them more easily. Killer whales and bottlenose dolphins have also been known to drive their prey onto a beach to feed on it. Killer whales have been known to paralyze great white sharks and other sharks and rays by flipping them upside down. Other whales with
7181-427: Is likely due to climate change which caused seasonally shifting accumulations of plankton in various parts of the world, necessitating travel over long distances, as well as the ability to feed on large baitballs to make such trips worthwhile. A 2017 analysis of body size based on data from the fossil record and modern baleen whales indicates that the evolution of gigantism in baleen whales occurred rather recently, within
7348-399: Is mainly discarded human rubbish which floats on, or is suspended in the ocean. Eighty percent of marine debris is plastic . Microplastics and nanoplastics result from the breakdown or photodegradation of plastic waste in surface waters, rivers or oceans. Recently, scientists have uncovered nanoplastics in heavy snow, more specifically about 3,000 tons that cover Switzerland yearly. It
7515-463: Is needed. It is often very difficult to regulate marine pollution because pollution spreads over international barriers, thus making regulations hard to create as well as enforce. Without appropriate awareness of marine pollution, the necessary global will to effectively address the issues may prove inadequate. Balanced information on the sources and harmful effects of marine pollution need to become part of general public awareness, and ongoing research
7682-500: Is only 1 millimeter (0.04 in) thick. The dermis, the layer underneath the epidermis, is also thin. The hypodermis, containing blubber, is the thickest part of the skin and functions as a means to conserve heat. Right whales have the thickest hypodermis of any cetacean, averaging 51 centimeters (20 in), though, as in all whales, it is thinner around openings (such as the blowhole) and limbs. Blubber may also be used to store energy during times of fasting. The connective tissue between
7849-470: Is probably due to the great degree of control necessary for constantly swimming. Necropsies on the brains of gray whales revealed iron oxide particles, which may allow them to find magnetic north like a compass . Unlike most animals, whales are conscious breathers. All mammals sleep, but whales cannot afford to become unconscious for long because they may drown. They are believed to exhibit unihemispheric slow-wave sleep , in which they sleep with half of
8016-952: Is repeated annually. The gray whale has the longest recorded migration of any mammal, with one traveling 23,000 kilometers (14,000 mi) from the Sea of Okhotsk to the Baja Peninsula . Marine mammal Marine mammals are mammals that rely on marine (saltwater) ecosystems for their existence. They include animals such as cetaceans ( whales , dolphins and porpoises ), pinnipeds ( seals , sea lions and walruses ), sirenians ( manatees and dugongs ), sea otters and polar bears . They are an informal group, unified only by their reliance on marine environments for feeding and survival. Marine mammal adaptation to an aquatic lifestyle varies considerably between species. Both cetaceans and sirenians are fully aquatic and therefore are obligate water dwellers. Pinnipeds are semiaquatic; they spend
8183-622: Is required to fully establish, and keep current, the scope of the issues. As expressed in Daoji and Dag's research, one of the reasons why environmental concern is lacking among the Chinese is because the public awareness is low and therefore should be targeted. The amount of awareness on marine pollution is vital to the support of keeping the prevention of trash from entering waterways and ending up in our oceans. The EPA reports that in 2014 Americans generated about 258 million tons of waste, and only
8350-418: Is scarce. West Indian manatees eat up to 60 different species of plants, as well as fish and small invertebrates to a lesser extent. Sea otters are a classic example of a keystone species; their presence affects the ecosystem more profoundly than their size and numbers would suggest. They keep the population of certain benthic (sea floor) herbivores, particularly sea urchins , in check. Sea urchins graze on
8517-401: Is that the degradation of algal blooms can lead to consumption of oxygen in coastal waters, a situation that may worsen with climate change as warming reduces vertical mixing of the water column. Many potentially toxic chemicals adhere to tiny particles which are then taken up by plankton and benthic animals , most of which are either deposit feeders or filter feeders . In this way,
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#17327768471638684-408: Is the development of echolocation in whales and dolphins. Toothed whales emit a focused beam of high-frequency clicks in the direction that their head is pointing. Sounds are generated by passing air from the bony nares through the phonic lips. These sounds are reflected by the dense concave bone of the cranium and an air sac at its base. The focused beam is modulated by a large fatty organ known as
8851-412: Is the fastest among baleen whales, having been recorded travelling as fast as 10 m/s (36 km/h; 22 mph), and sustaining a speed of 2.5 m/s (9.0 km/h; 5.6 mph) for an extended period. While feeding, the rorqual jaw expands to a volume that can be bigger than the whale itself; to do this, the mouth inflates. The inflation of the mouth causes the cavum ventrale, the throat pleats on
9018-428: Is the most carnivorous species of bear, and its diet primarily consists of ringed ( Pusa hispida ) and bearded ( Erignathus barbatus ) seals. Polar bears hunt primarily at the interface between ice, water, and air; they only rarely catch seals on land or in open water. The polar bear's most common hunting method is still-hunting: The bear locates a seal breathing hole using its sense of smell, and crouches nearby for
9185-720: Is the only marine mammal that catches fish with its forepaws rather than with its teeth. Under each foreleg, sea otters have a loose pouch of skin that extends across the chest which they use to store collected food to bring to the surface. This pouch also holds a rock that is used to break open shellfish and clams, an example of tool use . The sea otters eat while floating on their backs, using their forepaws to tear food apart and bring to their mouths. Marine otters mainly feed on crustaceans and fish. Pinnipeds mostly feed on fish and cephalopods , followed by crustaceans and bivalves , and then zooplankton and warm-blooded prey (like sea birds ). Most species are generalist feeders, but
9352-747: Is thought that their size increased with their dependence on baleen. However, the discovery of a skull of the toothed Llanocetus , the second-oldest mysticete, yielded a total length of 8 meters (26 ft), indicating filter feeding was not a driving feature in mysticete evolution. The discovery of Janjucetus and others like it suggests that baleen evolution went through several transitional phases. Species like Mammalodon colliveri had little to no baleen, while later species like Aetiocetus weltoni had both baleen and teeth, suggesting they had limited filter feeding capabilities; later genera like Cetotherium had no teeth in their mouth, meaning they were fully dependent on baleen and could only filter feed. However,
9519-437: Is to raid the birth lairs that female seals create in the snow. They may also feed on fish. Sirenians are referred to as "sea cows" because their diet consists mainly of seagrass. When eating, they ingest the whole plant, including the roots, although when this is impossible they feed on just the leaves. A wide variety of seagrass has been found in dugong stomach contents, and evidence exists they will eat algae when seagrass
9686-427: Is underway investigating the full extent of the harm to marine ecosystems caused by PFAS. Marine life can be susceptible to noise or the sound pollution from sources such as passing ships, oil exploration seismic surveys, and naval low-frequency active sonar . Sound travels more rapidly and over larger distances in the sea than in the atmosphere. Marine animals, such as cetaceans , often have weak eyesight, and live in
9853-411: Is unknown where this occurred, but it is generally believed that they, like their descendants, followed plankton migrations. These primitive baleen whales had lost their dentition in favor of baleen, and are believed to have lived on a specialized benthic, plankton, or copepod diet like modern baleen whales. Baleen whales experienced their first radiation in the mid-Miocene . It is thought this radiation
10020-517: Is usually reversed, with the males being larger, but the females of all baleen whales are usually five percent larger than males. Sexual dimorphism is also displayed through whale song , notably in humpback whales where the males of the species sing elaborate songs. Male right whales have bigger callosities than female right whales. The males are generally more scarred than females which is thought to be because of aggression during mating season. The unique lungs of baleen whales are built to collapse under
10187-719: The Caribbean and Florida during the warm season as the ridge builds and moves northward through the subtropical Atlantic. Dust can also be attributed to a global transport from the Gobi and Taklamakan deserts across Korea , Japan , and the Northern Pacific to the Hawaiian Islands . Since 1970, dust outbreaks have worsened due to periods of drought in Africa. There is a large variability in dust transport to
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#173277684716310354-655: The EPA in 1970. DDT was banned in the U.S. two years later in 1972. Unfortunately, large quantities had already entered the ocean through runoff and had been dumped directly into the ocean. This toxin impacts marine ecosystems by accumulating from lower trophic levels and up the food chain into higher trophic levels such as from arctic cod into seals, from fish then eaten by dolphins, and from cod and eels into seals. Shortly after Rachel Carson's publication of Silent Spring, PCBs were identified as another persistent, toxic chemical that has been released in extensive quantities to
10521-572: The Eocene . Their evolutionary link to terrestrial mammals was unknown until the 2007 discovery of † Puijila darwini in early Miocene deposits in Nunavut , Canada. Like a modern otter, † Puijila had a long tail, short limbs and webbed feet instead of flippers. The lineages of Otariidae (eared seals) and Odobenidae (walrus) split almost 28 mya. Phocids (earless seals) are known to have existed for at least 15 mya, and molecular evidence supports
10688-486: The Indian Ocean . The variation observed in range size is a result of the different ecological requirements of each species and their ability to cope with a broad range of environmental conditions. The high degree of overlap between marine mammal species richness and areas of human impact on the environment is of concern. Most marine mammals, such as seals and sea otters, inhabit the coast. Seals, however, also use
10855-474: The Mammalodontidae ( Mammalodon and Janjucetus ) from Australia . They were small with shortened rostra , and a primitive dental formula ( 3.1.4.3 3.1.4.3 ). In baleen whales, it is thought that enlarged mouths adapted for suction feeding evolved before specializations for bulk filter feeding . In the toothed Oligocene mammalodontid Janjucetus , the symphysis is short and the mouth enlarged,
11022-543: The Muséum National d'Histoire Naturelle ) and colleagues suggested that, based on phylogenic criteria, there are four extant genera of rorquals. They recommend that the genus Balaenoptera be limited to the fin whale, have minke whales fall under the genus Pterobalaena , and have Rorqualus contain the Sei whale, Bryde's whale, Eden's whale (and by extension Rice's whale), the blue whale, and Omura's whale. The gray whale
11189-534: The North Atlantic right whale is ranked critically endangered by the International Union for Conservation of Nature . Besides hunting, baleen whales also face threats from marine pollution and ocean acidification . It has been speculated that man-made sonar results in strandings . They have rarely been kept in captivity, and this has only been attempted with juveniles or members of one of
11356-488: The North Atlantic right whale , are critically endangered . Other than being hunted, marine mammals can be killed as bycatch from fisheries, where for example they can become entangled in nets and drown or starve. Increased ocean traffic causes collisions between fast ocean vessels and large marine mammals. Habitat degradation also threatens marine mammals and their ability to find and catch food. Noise pollution , for example, may adversely affect echolocating mammals, and
11523-551: The North Ronaldsay sheep ( Ovis aries ) which normally eats seaweed outside the lambing season, the Eurasian otter ( Lutra lutra ) which is usually found in freshwater but can be found along coastal Scotland , and others. Marine mammals form a diverse group of 129 species that rely on the ocean for their existence. They are an informal group unified only by their reliance on marine environments for feeding. Despite
11690-574: The Old World (such as cetaceans ). The first known quadrupedal sirenian was † Pezosiren from the early middle Eocene. The earliest known sea cows, of the families † Prorastomidae and † Protosirenidae , were both confined to the Eocene, and were pig-sized, four-legged, amphibious creatures. The first members of Dugongidae appeared by the middle Eocene. At this point, sea cows were fully aquatic. Pinnipeds split from other caniforms 50 mya during
11857-555: The Raritan River in New Jersey , which empty at the northern and southern ends of Staten Island , are a source of mercury contamination of zooplankton ( copepods ) in the open ocean. The highest concentration in the filter-feeding copepods is not at the mouths of these rivers but 70 miles (110 km) south, nearer Atlantic City , because water flows close to the coast. It takes a few days before toxins are taken up by
12024-675: The United States Environmental Protection Agency , mining has contaminated portions of the headwaters of over 40% of watersheds in the western continental US. Much of this pollution finishes up in the sea. Surface runoff from farming, as well as urban runoff and runoff from the construction of roads, buildings, ports, channels, and harbours, can carry soil and particles laden with carbon, nitrogen, phosphorus, and minerals. This nutrient-rich water can cause fleshy algae and phytoplankton to thrive in coastal areas; known as algal blooms , which have
12191-597: The atmosphere is absorbed by the oceans. This chemical reaction produces carbonic acid ( H 2 CO 3 ) which dissociates into a bicarbonate ion ( HCO − 3 ) and a hydrogen ion ( H ). The presence of free hydrogen ions ( H ) lowers the pH of the ocean, increasing acidity (this does not mean that seawater is acidic yet; it is still alkaline , with a pH higher than 8). Marine calcifying organisms , such as mollusks and corals , are especially vulnerable because they rely on calcium carbonate to build shells and skeletons. A change in pH by 0.1 represents
12358-560: The fin whale ( B. physalus ), the Sei whale ( B. borealis ), Bryde's whale ( B. brydei ), Eden's whale ( B. edeni ), Rice's whale ( B. ricei ), the blue whale ( B. musculus ), the common minke whale ( B. acutorostrata ), the Antarctic minke whale ( B. bonaerensis ), Omura's whale ( B. omurai ), the humpback whale ( M. novaeangliae ), and the gray whale ( E. robustus ). In a 2012 review of cetacean taxonomy, Alexandre Hassanin (of
12525-522: The hippopotamuses . Sirenians, the sea cows, became aquatic around 40 million years ago. The first appearance of sirenians in the fossil record was during the early Eocene, and by the late Eocene, sirenians had significantly diversified. Inhabitants of rivers, estuaries, and nearshore marine waters, they were able to spread rapidly. The most primitive sirenian, † Prorastomus , was found in Jamaica, unlike other marine mammals which originated from
12692-469: The ocean and cause harmful effects there. The majority of this waste (80%) comes from land-based activity, although marine transportation significantly contributes as well. It is a combination of chemicals and trash, most of which comes from land sources and is washed or blown into the ocean. This pollution results in damage to the environment, to the health of all organisms, and to economic structures worldwide. Since most inputs come from land, either via
12859-571: The plankton . Pollution is often classed as point source or nonpoint source pollution . Point source pollution occurs when there is a single, identifiable, localized source of the pollution. An example is directly discharging sewage and industrial waste into the ocean. Pollution such as this occurs particularly in developing nations . Nonpoint source pollution occurs when the pollution is from ill-defined and diffuse sources. These can be difficult to regulate. Agricultural runoff and wind blown debris are prime examples. Pollutants enter rivers and
13026-444: The rivers , sewage or the atmosphere, it means that continental shelves are more vulnerable to pollution. Air pollution is also a contributing factor by carrying off iron, carbonic acid, nitrogen , silicon, sulfur, pesticides or dust particles into the ocean. The pollution often comes from nonpoint sources such as agricultural runoff , wind-blown debris , and dust. These nonpoint sources are largely due to runoff that enters
13193-856: The sediment and marine environment. Additionally, bilge pollution can be toxic to the surrounding environment when bilge water is released from a ship's bilge . Oil spills are one of the most emotive of marine pollution events. However, while a tanker wreck may result in extensive newspaper headlines, much of the oil in the world's seas comes from other smaller sources, such as tankers discharging ballast water from oil tanks used on return ships, leaking pipelines or engine oil disposed of down sewers. Discharge of cargo residues from bulk carriers can pollute ports, waterways, and oceans. In many instances vessels intentionally discharge illegal wastes despite foreign and domestic regulation prohibiting such actions. An absence of national standards provides an incentive for some cruise liners to dump waste in places where
13360-643: The spleen which all have the capacity to hold a high concentration of oxygen. They are also capable of bradycardia (reduced heart rate), and vasoconstriction (shunting most of the oxygen to vital organs such as the brain and heart) to allow extended diving times and cope with oxygen deprivation. If oxygen is depleted ( hypoxia ), marine mammals can access substantial reservoirs of glycogen that support anaerobic glycolysis . Sound travels differently through water, and therefore marine mammals have developed adaptations to ensure effective communication, prey capture, and predator detection. The most notable adaptation
13527-430: The 'melon'. This acts like an acoustic lens because it is composed of lipids of differing densities. Marine mammals have evolved a wide variety of features for feeding, which are mainly seen in their dentition. For example, the cheek teeth of pinnipeds and odontocetes are specifically adapted to capture fish and squid. In contrast, baleen whales have evolved baleen plates to filter feed plankton and small fish from
13694-532: The 2018 discovery of the toothless Maiabalaena indicates some lineages evolved toothlessness before baleen. Mystacodon selenensis is the earliest mysticete, dating back to 37 to 33 million years ago ( mya ) in the Late Eocene , and, like other early toothed mysticetes, or "archaeomysticetes", M. selenensis had heterodont dentition used for suction feeding. Archaeomysticetes from the Oligocene are
13861-429: The 60 to 100 bpm in humans. When diving, their heart rate will drop to 4 to 15 bpm to conserve oxygen. Like toothed whales, they have a dense network of blood vessels ( rete mirabile ) which prevents heat-loss. Like in most mammals, heat is lost in their extremities , so, in baleen whales, warm blood in the arteries is surrounded by veins to prevent heat loss during transport. As well as this, heat inevitably given off by
14028-592: The Antarctic circumpolar current and its effects on global climate patterns is excluded as being causal for the same reason. Gigantism also was preceded by divergence of different mysticete lineages, meaning multiple lineages arrived at large size independently. It is possible the Plio-Pleistocene increase in seasonally intense upwellings , causing high-prey-density zones, led to gigantism. When swimming, baleen whales rely on their flippers for locomotion in
14195-516: The Black, Caspian, and Azov seas, were probably transported to the Great Lakes via ballast water from a transoceanic vessel. Meinesz believes that one of the worst cases of a single invasive species causing harm to an ecosystem can be attributed to a seemingly harmless jellyfish . Mnemiopsis leidyi , a species of comb jellyfish that spread so it now inhabits estuaries in many parts of the world,
14362-564: The Caribbean and Florida from year to year; however, the flux is greater during positive phases of the North Atlantic Oscillation . The USGS links dust events to a decline in the health of coral reefs across the Caribbean and Florida, primarily since the 1970s. Climate change is raising ocean temperatures and raising levels of carbon dioxide in the atmosphere . These rising levels of carbon dioxide are acidifying
14529-483: The Coelenterates. In a study, the organisms were exposed to sound waves for different numbers of times and the results showed that damaged hair cells were extruded or missing or presented bent, flaccid or missed kinocilia and stereocilia. Ships can be certified to meet certain noise criteria. There are a variety of secondary effects stemming not from the original pollutant, but a derivative condition. An example
14696-528: The North American coast. In comparison to cetaceans, sirenians, and pinnipeds, which entered the water approximately 50, 40, and 20 mya, respectively, the sea otter is a relative newcomer to marine life. In some respects though, the sea otter is more fully adapted to water than pinnipeds, which must haul out on land or ice to give birth. Polar bears are thought to have diverged from a population of brown bears , Ursus arctos , that became isolated during
14863-482: The North Atlantic right whale ( E. glacialis ). Cetotheriidae consists of only one living member: the pygmy right whale ( Caperea marginata ). The first descriptions date back to the 1840s of bones and baleen plates resembling a smaller version of the right whale, and was named Balaena marginata . In 1864, it was moved into the genus Caperea after a skull of another specimen was discovered. Six years later,
15030-452: The US alone. Another pathway of pollution occurs through the atmosphere. The ocean has long been affected by the passage of chemicals from the atmosphere (e.g. nutrient source; pH influence). Wind-blown dust and debris, including plastic bags , are blown seaward from landfills and other areas. Dust from the Sahara moving around the southern periphery of the subtropical ridge moves into
15197-418: The annual new marine biological production. It has been suggested that accumulating reactive nitrogen in the environment may have consequences as serious as putting carbon dioxide in the atmosphere. One proposed solution to eutrophication in estuaries is to restore shellfish populations, such as oysters. Oyster reefs remove nitrogen from the water column and filter out suspended solids, subsequently reducing
15364-494: The arteries warms blood in the surrounding veins as it travels back into the core . This is otherwise known as countercurrent exchange . To counteract overheating while in warmer waters, baleen whales reroute blood to the skin to accelerate heat-loss. They have the largest blood corpuscles ( red and white blood cells ) of any mammal, measuring 10 micrometers (4.1 × 10 in) in diameter, as opposed to human's 7.1-micrometer (2.8 × 10 in) blood corpuscles. When sieved from
15531-459: The atmosphere-ocean CO 2 exchange, and thus local ocean acidification. These include ocean currents and upwelling zones, proximity to large continental rivers, sea ice coverage, and atmospheric exchange with nitrogen and sulfur from fossil fuel burning and agriculture . Eutrophication is an increase in chemical nutrients , typically compounds containing nitrogen or phosphorus , in an ecosystem . It can result in an increase in
15698-456: The brain while the other half remains active. This behavior was only documented in toothed whales until footage of a humpback whale sleeping (vertically) was shot in 2014. It is largely unknown how baleen whales produce sound because of the lack of a melon and vocal cords . In a 2007 study, it was discovered that the larynx had U-shaped folds which are thought to be similar to vocal cords. They are positioned parallel to air flow, as opposed to
15865-651: The capacity of their throats, allowing them to filter larger volumes of water at once. Gray whales are bottom-feeders, meaning they sift through sand to get their food. They usually turn on their sides, scoop up sediment into their mouths and filter out benthic creatures like amphipods , which leave noticeable marks on their heads. The pygmy right whale is easily confused with minke whales because of their similar characteristics, such as their small size, dark gray tops, light gray bottoms, and light eye patches. Molecular phylogeny suggests Mysticeti split from Odontoceti (toothed whales) between 26 and 17 million years ago between
16032-461: The cetaceans genetically and morphologically fall firmly within the Artiodactyla (even-toed ungulates). The term "Cetartiodactyla" reflects the idea that whales evolved within the ungulates. The term was coined by merging the name for the two orders, Cetacea and Artiodactyla, into a single word. Under this definition, the closest living land relative of the whales and dolphins is thought to be
16199-489: The disposal of untreated or partially treated sewage to rivers and subsequently oceans. These nitrogen and phosphorus nutrients (which are also contained in fertilizers ) stimulate phytoplankton and macroalgal growth, which can lead to harmful algal blooms ( eutrophication ) which can be harmful to humans as well as marine creatures. Excessive algal growth can also smother sensitive coral reefs and lead to loss of biodiversity and coral health. A second major concern
16366-521: The diversity in anatomy seen between groups, improved foraging efficiency has been the main driver in their evolution . The level of dependence on the marine environment varies considerably with species. For example, dolphins and whales are completely dependent on the marine environment for all stages of their life; seals feed in the ocean but breed on land; and polar bears must feed on land. The cetaceans became aquatic around 50 million years ago (mya). Based on molecular and morphological research,
16533-511: The ecosystem's primary productivity (excessive plant growth and decay), and further effects including lack of oxygen and severe reductions in water quality, fish, and other animal populations. Nutrient pollution , a form of water pollution , refers to contamination by excessive inputs of nutrients. It is a primary cause of eutrophication of surface waters, in which excess nutrients, usually nitrates or phosphates , stimulate algae growth. Such blooms are naturally occurring but may be increasing as
16700-430: The end of the mouth. This is probably because they feed on slow or immobile prey, combined with the fact that most sunlight does not pass 9.1 meters (30 ft), and hence they do not need acute vision. A whale's eye is adapted for seeing both in the euphotic and aphotic zones by increasing or decreasing the pupil 's size to prevent damage to the eye. As opposed to land mammals which have a flattened lens , whales have
16867-1027: The environment. PCBs are a very well-studied class of chemicals that are manufactured from oil. These chemicals are banned in the United States under the Toxic Substance Control Act , but are still found in the soil, air, sediments, and biota. PCBs are known to accumulate in the fatty tissues of animals. In particular, PCBs build up and are stored in the blubber of marine mammals including dolphins and killer whales. These chemicals cause reproductive issues for many species. In mud crabs, PCBs have been discovered to be immunotoxic by reducing resistance to bacterial disease, reducing antioxidant enzyme activity, and damaging DNA responsible for immune system functions. PFAS are an important emerging class of man-made persistent toxicants that contain extremely strong carbon-fluorine bonds which make these chemicals extremely difficult to break down. They have unique properties that make them useful for manufacturing
17034-437: The exception of the bowhead whale. Rorquals have a higher proportion of muscle tissue and tend to be negatively buoyant, whereas right whales have a higher proportion of blubber and are positively buoyant. Gray whales are easily distinguished from the other rorquals by their sleet-gray color, dorsal ridges (knuckles on the back), and their gray-white scars left from parasites. As with the other rorquals, their throat pleats increase
17201-484: The feeding behavior, and two limbs that are modified into flippers . The fin whale is the fastest baleen whale, recorded swimming at 10 m/s (36 km/h; 22 mph). Baleen whales use their baleen plates to filter out food from the water by either lunge-feeding or skim-feeding. Baleen whales have fused neck vertebrae , and are unable to turn their heads at all. Baleen whales have two blowholes . Some species are well adapted for diving to great depths. They have
17368-632: The first radiation in the late Oligocene. Eomysticetus and others like it showed no evidence in the skull of echolocation abilities, suggesting they mainly relied on their eyesight for navigation. The eomysticetes had long, flat rostra that lacked teeth and had blowholes located halfway up the dorsal side of the snout. Though the palate is not well-preserved in these specimens, they are thought to have had baleen and been filter feeders. Miocene baleen whales were preyed upon by larger predators like killer sperm whales and megalodon . The lineages of rorquals and right whales split almost 20 mya. It
17535-400: The fishing industry. Waterborne plastic poses a serious threat to fish , seabirds , marine reptiles , and marine mammals , as well as to boats and coasts. Marine plastic pollution is a type of marine pollution by plastics , ranging in size from large original material such as bottles and bags, down to microplastics formed from the fragmentation of plastic material. Marine debris
17702-812: The floor or to stay submerged. Surface-living animals (such as sea otters) need the opposite, and free-swimming animals living in open waters (such as dolphins) need to be neutrally buoyant in order to be able to swim up and down the water column. Typically, thick and dense bone is found in bottom feeders and low bone density is associated with mammals living in deep water. Some marine mammals, such as polar bears and otters, have retained four weight-bearing limbs and can walk on land like fully terrestrial animals. All cetaceans are carnivorous and predatory . Toothed whales mostly feed on fish and cephalopods , followed by crustaceans and bivalves . Some may forage with other kinds of animals, such as other species of whales or certain species of pinnipeds . One common feeding method
17869-556: The fragmentation of plastic material. This material is only very slowly degraded or removed from the ocean so plastic particles are now widespread throughout the surface ocean and are known to be having deleterious effects on marine life . Discarded plastic bags, six-pack rings, cigarette butts and other forms of plastic waste which finish up in the ocean present dangers to wildlife and fisheries. Aquatic life can be threatened through entanglement, suffocation, and ingestion. Fishing nets , usually made of plastic, can be left or lost in
18036-474: The fused cervical vertebrae ; this sacrifices speed for stability in the water. The hind legs are enclosed inside the body, and are thought to be vestigial organs . However, a 2014 study suggests that the pelvic bone serves as support for whale genitalia . Rorquals, needing to build speed to feed, have several adaptions for reducing drag , including a streamlined body; a small dorsal fin, relative to its size; and lack of external ears or long hair. The fin whale
18203-454: The globe, but their distribution is patchy and coincides with the productivity of the oceans. Species richness peaks at around 40° latitude, both north and south. This corresponds to the highest levels of primary production around North and South America , Africa , Asia and Australia . Total species range is highly variable for marine mammal species. On average most marine mammals have ranges which are equivalent or smaller than one-fifth of
18370-910: The health of coastal ecosystems, and similar changes have been observed as sea otter populations recovered in the Aleutian and Commander Islands and the Big Sur coast of California. However, some kelp forest ecosystems in California have also thrived without sea otters, with sea urchin populations apparently controlled by other factors. The role of sea otters in maintaining kelp forests has been observed to be more important in areas of open coast than in more protected bays and estuaries . Marine pollution Marine pollution occurs when substances used or spread by humans, such as industrial , agricultural and residential waste , particles , noise , excess carbon dioxide or invasive organisms enter
18537-519: The human population is reduced, or a way is found to reduce the ecological footprint left behind by the average human. If the second way is not adopted, then the first way may be imposed as the world ecosystems falter. The second way is for humans, individually, to pollute less. That requires social and political will, together with a shift in awareness so more people respect the environment and are less disposed to abuse it. At an operational level, regulations, and international government participation
18704-432: The hypodermis and muscles allows only limited movement to occur between them. Unlike toothed whales, baleen whales have small hairs on the top of their head, stretching from the tip of the rostrum to the blowhole, and, in right whales, on the chin. Like other marine mammals , they lack sebaceous and sweat glands. The baleen of baleen whales are keratinous plates. They are made of a calcified, hard α-keratin material,
18871-529: The ice further north that remains frozen year-round. Seals may also migrate to other environmental changes, such as El Niño , and traveling seals may use various features of their environment to reach their destination including geomagnetic fields, water and wind currents, the position of the sun and moon and the taste and temperature of the water. Baleen whales famously migrate very long distances into tropical waters to give birth and raise young, possibly to prevent predation by killer whales. The gray whale has
19038-505: The jellyfish have exhausted the zooplankton , including fish larvae, their numbers have fallen dramatically, yet they continue to maintain a stranglehold on the ecosystem . Invasive species can take over once occupied areas, facilitate the spread of new diseases, introduce new genetic material, alter underwater seascapes, and jeopardize the ability of native species to obtain food. Invasive species are responsible for about $ 138 billion annually in lost revenue and management costs in
19205-426: The lack of the olfactory bulb , but they do have an olfactory tract . Baleen whales have few if any taste buds, suggesting they have lost their sense of taste. They do retain salt-receptor taste-buds suggesting that they can taste saltiness. Most species of baleen whale migrate long distances from high latitude waters during spring and summer months to more tropical waters during winter months. This migration cycle
19372-411: The last 3 million years. Before 4.5 million years ago, few baleen whales exceeded 10 meters (33 ft) in length; the two largest Miocene species were less than 13 m (43 ft) in length. The initial evolution of baleen and filter feeding long preceded the evolution of gigantic body size, indicating the evolution of novel feeding mechanisms did not cause the evolution of gigantism. The formation of
19539-850: The late Oligocene or middle Miocene , but the earliest Mysticeti fossils date to at least 34 million years ago. Their evolutionary link to archaic toothed cetaceans ( Archaeoceti ) remained unknown until the extinct Janjucetus hunderi was discovered in the early 1990s in Victoria, Australia . While, unlike a modern baleen whale, Janjucetus lacked baleen in its jaw, the anatomy shows sufficient similarity to baleen whales. It appears to have had very limited apparent biosonar capabilities. Its jaw contained teeth, with incisors and canines built for stabbing and molars and premolars built for tearing. These early mysticetes were exceedingly small compared to modern baleen whales, with species like Mammalodon measuring no greater than 3 meters (10 ft). It
19706-1053: The latter. Cetaceans ( whales , dolphins , and porpoises ) and artiodactyls are now classified under the order Cetartiodactyla , often still referred to as Artiodactyla (given that the cetaceans are deeply nested with the artiodactyls). The closest living relatives to baleen whales are toothed whales both from the infraorder Cetacea . Bowhead whale [REDACTED] Southern right whale [REDACTED] North Atlantic right whale [REDACTED] North Pacific right whale [REDACTED] Pygmy right whale [REDACTED] Common minke whale [REDACTED] Southern minke whale [REDACTED] Gray whale [REDACTED] Humpback whale [REDACTED] Fin whale [REDACTED] Blue whale [REDACTED] Omura's whale Eden's whale [REDACTED] Rice's whale [REDACTED] Sei whale [REDACTED] Bryde's whale [REDACTED] Balaenidae consists of two genera: Eubalaena (right whales) and Balaena (the bowhead whale , B. mysticetus ). Balaenidae
19873-432: The likelihood or extent of harmful algal blooms or anoxic conditions. Filter feeding activity is considered beneficial to water quality by controlling phytoplankton density and sequestering nutrients, which can be removed from the system through shellfish harvest, buried in the sediments, or lost through denitrification . Foundational work toward the idea of improving marine water quality through shellfish cultivation to
20040-513: The longest recorded migration of any mammal, with one traveling 14,000 miles (23,000 km) from the Sea of Okhotsk to the Baja Peninsula . During the winter, manatees living at the northern end of their range migrate to warmer waters. Marine mammals have a number of physiological and anatomical features to overcome the unique challenges associated with aquatic living. Some of these features are very species-specific. Marine mammals have developed
20207-406: The lower jaw. The auditory meatus is blocked by connective tissue and an ear plug, which connects to the eardrum . The inner-ear bones are contained in the tympanic bulla , a bony capsule. However, this is attached to the skull, suggesting that vibrations passing through the bone is important. Sinuses may reflect vibrations towards the cochlea . It is known that when the fluid inside the cochlea
20374-401: The lower stems of kelp , causing the kelp to drift away and die. Loss of the habitat and nutrients provided by kelp forests leads to profound cascade effects on the marine ecosystem. North Pacific areas that do not have sea otters often turn into urchin barrens , with abundant sea urchins and no kelp forest. Reintroduction of sea otters to British Columbia has led to a dramatic improvement in
20541-403: The lungs of baleen whales lack lobes and are more sacculated. Like in humans, the left lung is smaller than the right to make room for the heart. To conserve oxygen, blood is rerouted from pressure-tolerant-tissue to internal organs, and they have a high concentration of myoglobin which allows them to hold their breath longer. The heart of baleen whales functions similarly to other mammals, with
20708-434: The major difference being the size. The heart can reach 454 kilograms (1,000 lb), but is still proportional to the whale's size. The muscular wall of the ventricle , which is responsible for pumping blood out of the heart, can be 7.6 to 12.7 centimeters (3 to 5 in) thick. The aorta, an artery , can be 1.9 centimeters (.75 in) thick. Their resting heart rate is 60 to 140 beats per minute (bpm), as opposed to
20875-476: The majority of their time in the water but need to return to land for important activities such as mating , breeding and molting . Sea otters tend to live in kelp forests and estuaries. In contrast, the polar bear is mostly terrestrial and only go into the water on occasions of necessity, and are thus much less adapted to aquatic living. The diets of marine mammals vary considerably as well; some eat zooplankton , others eat fish, squid, shellfish, or seagrass, and
21042-429: The ocean by fishermen . Known as ghost nets , these entangle fish, dolphins , sea turtles , sharks , dugongs , crocodiles , seabirds , crabs , and other creatures, restricting movement, causing starvation , laceration , infection , and, in those that need to return to the surface to breathe, suffocation . There are various types of ocean plastics causing problems to marine life . Bottle caps have been found in
21209-449: The ocean is a type of marine pollution by plastics , ranging in size from large original material such as bottles and bags, down to microplastics formed from the fragmentation of plastic material. Marine debris is mainly discarded human rubbish which floats on, or is suspended in the ocean. Plastic pollution is harmful to marine life . Another concern is the runoff of nutrients (nitrogen and phosphorus) from intensive agriculture , and
21376-775: The ocean through land runoff. This includes sewage discharge and pollution from urbanization and land use. In 2001, more than 66,795 mi of the Chinese coastal ocean waters were rated less than Class I of the Sea Water Quality Standard of China. Much of this pollution came from Ag, Cu, Cd, Pb, As, DDT, PCBs, etc., which occurred from contamination through land runoff. Ships can pollute waterways and oceans in many ways including through their ballast, bilge, and fuel tanks. Oil spills can have devastating effects. In addition to being toxic to marine life, polycyclic aromatic hydrocarbons (PAHs), found in crude oil , are very difficult to clean up, and last for years in
21543-521: The ocean through rivers, but wind-blown debris and dust can also play a role, as these pollutants can settle into waterways and oceans. Pathways of pollution include direct discharge, land runoff, ship pollution , bilge pollution , atmospheric pollution and, potentially, deep sea mining . The types of marine pollution can be grouped as pollution from marine debris , plastic pollution , including microplastics , ocean acidification , nutrient pollution , toxins and underwater noise. Plastic pollution in
21710-446: The ocean, there are frequent red tide algae blooms that kill fish and marine mammals and cause respiratory problems in humans and some domestic animals when the blooms reach close to shore. In addition to land runoff , atmospheric anthropogenic fixed nitrogen can enter the open ocean. A study in 2008 found that this could account for around one third of the ocean's external (non-recycled) nitrogen supply and up to three per cent of
21877-473: The ocean: direct discharge of waste into the oceans, runoff into the waters due to rain, and pollutants released from the atmosphere. One common path of entry by contaminants to the sea are rivers. The evaporation of water from oceans exceeds precipitation. The balance is restored by rain over the continents entering rivers and then being returned to the sea. The Hudson River in New York State and
22044-440: The oceans . This, in turn, is altering aquatic ecosystems and modifying fish distributions, with impacts on the sustainability of fisheries and the livelihoods of the communities that depend on them. Healthy ocean ecosystems are also important for the mitigation of climate change. Some of the potential toxic metals include copper, zinc, cadmium, lead as well as rare earth elements such as lanthanum and yttrium . Following
22211-541: The oceans, which have also evolved several specialized aquatic traits. In addition to the above, several other mammals have a great dependency on the sea without having become so anatomically specialized, otherwise known as "quasi-marine mammals". This term can include: the greater bulldog bat ( Noctilio leporinus ), the fish-eating bat ( Myotis vivesi ), the arctic fox ( Vulpes lagopus ) which often scavenges polar bear kills, coastal gray wolf ( Canis lupus ) populations which predominantly eat salmon and marine carcasses,
22378-858: The ongoing effects of global warming degrade Arctic environments. Procaviidae Elephantidae Dugongidae (dugongs) Trichechus manatus (West Indian manatee) Trichechus senegalensis (African manatee) Trichechus inunguis (Amazonian manatee; freshwater species) Hippopotamidae Mysticeti (baleen whales) Odontoceti (toothed whales, except river dolphins ) Ruminantia Perissodactyla Pholidota Feliformia Canidae Ursus maritimus (polar bear) all other ursids Enhydra lutris (sea otter) Lontra felina (marine otter) † Neogale macrodon (sea mink) all other mustelids Otariidae (eared seals) Odobenidae (walruses) Phocidae (earless seals) The term "marine mammal" encompasses all mammals whose survival depends entirely or almost entirely on
22545-621: The open ocean, and species like the sperm whale may dive to depths of −1,000 to −2,500 feet (−300 to −760 m) in search of food. Sirenians live in shallow coastal waters, usually living 30 feet (9.1 m) below sea level. However, they have been known to dive to −120 feet (−37 m) to forage deep-water seagrasses . Sea otters live in protected areas, such as rocky shores, kelp forests , and barrier reefs , although they may reside among drift ice or in sandy, muddy, or silty areas. Many marine mammals seasonally migrate. Annual ice contains areas of water that appear and disappear throughout
22712-439: The parvorder is "Mystacoceti" (from Greek μύσταξ "mustache" + κῆτος "whale"), which, although obviously more appropriate and occasionally used in the past, has been superseded by "Mysticeti" ( junior synonym ). Mysticetes are also known as baleen whales for their baleen , which they use to sieve plankton and other small organisms from the water. The term "baleen" ( Middle English baleyn, ballayne, ballien, bellane , etc.)
22879-461: The penalties are inadequate. It has been estimated that container ships lose over 10,000 containers at sea each year (usually during storms). Ships also create noise pollution that disturbs natural wildlife, and water from ballast tanks can spread harmful algae and other invasive species . Ballast water taken up at sea and released in port is a major source of unwanted exotic marine life. The invasive freshwater zebra mussels, native to
23046-407: The perpendicular vocal cords of terrestrial mammals. These may control air flow and cause vibrations. The walls of the larynx are able to contract which may generate sound with support from the arytenoid cartilages . The muscles surrounding the larynx may expel air rapidly or maintain a constant volume while diving. The eyes of baleen whales are relatively small for their size and are positioned near
23213-541: The polar bear might not be considered a species under some species concepts . In general, terrestrial amniote invasions of the sea have become more frequent in the Cenozoic than they were in the Mesozoic. Factors contributing to this trend include the increasing productivity of near-shore marine environments, and the role of endothermy in facilitating this transition. Marine mammals are widely distributed throughout
23380-441: The potential to create hypoxic conditions by using all available oxygen. In the coast of southwest Florida, harmful algal blooms have existed for over 100 years. These algal blooms have been a cause of species of fish, turtles, dolphins, and shrimp to die and cause harmful effects on humans who swim in the water. Polluted runoff from roads and highways can be a significant source of water pollution in coastal areas. About 75% of
23547-531: The pressure instead of resisting the pressure which would damage the lungs, enabling some, like the fin whale, to dive to a depth of −470 meters (−1,540 ft). The whale lungs are very efficient at extracting oxygen from the air, usually 80%, whereas humans only extract 20% of oxygen from inhaled air. Lung volume is relatively low compared to terrestrial mammals because of the inability of the respiratory tract to hold gas while diving. Doing so may cause serious complications such as embolism . Unlike other mammals,
23714-526: The pygmy right whale was classified under the family Neobalaenidae. Despite its name, the pygmy right whale is more genetically similar to rorquals and gray whales than to right whales. A study published in 2012, based on bone structure, moved the pygmy right whale from the family Neobalaenidae to the family Cetotheriidae, making it a living fossil ; Neobalaenidae was demoted to subfamily level as Neobalaeninae. Rorquals consist of three genera ( Balaenoptera , Megaptera , and Eschrichtius ) and 11 species:
23881-548: The release of toxins there is an increase of noise, light, sediment le dan plumes and elements that have the potential to impact the ecosystems . Deep sea minerals (DSM) can be extremely beneficial, it can cause wealth, raising living standards as well as economic opportunities for both current and future generations. In addition, if the wealth is poorly managed it can have the potential to cause great economic and social damage . The instability of price and production levels of minerals can cause an external economic shock leading to
24048-446: The rostrum is wide, and the edges of the maxillae are thin, indicating an adaptation for suction feeding. The aetiocetid Chonecetus still had teeth, but the presence of a groove on the interior side of each mandible indicates the symphysis was elastic, which would have enabled rotation of each mandible, an initial adaptation for bulk feeding like in modern mysticetes. The first toothless ancestors of baleen whales appeared before
24215-479: The sea directly from urban sewerage and industrial waste discharges, sometimes in the form of hazardous and toxic wastes , or in the form of plastics. In a study published by Science , Jambeck et al. (2015) estimated that the 10 largest emitters of oceanic plastic pollution worldwide are, from the most to the least, China, Indonesia, Philippines, Vietnam, Sri Lanka, Thailand, Egypt, Malaysia, Nigeria, and Bangladesh. Inland mining for copper, gold, etc.,
24382-527: The seas. Around 98% of this volume is created by land-based activities, with the remaining 2% being generated by sea-based activities. It is estimated that 19–23 million tonnes of plastic leaks into aquatic ecosystems annually. The 2017 United Nations Ocean Conference estimated that the oceans might contain more weight in plastics than fish by the year 2050. Oceans are polluted by plastic particles ranging in size from large original material such as bottles and bags, down to microplastics formed from
24549-503: The smallest species. Baleen whales are cetaceans classified under the parvorder Mysticeti, and consist of four extant families : Balaenidae ( right whales ), Balaenopteridae (rorquals), Eschrichtiidae ( gray whale ) and Cetotheriidae ( pygmy right whale ). Balaenids are distinguished by their enlarged head and thick blubber , while rorquals and gray whales generally have a flat head, long throat pleats, and are more streamlined than Balaenids. Rorquals also tend to be longer than
24716-535: The stomachs of turtles and seabirds, which have died because of the obstruction of their respiratory and digestive tracts . Ghost nets are also a problematic type of ocean plastic as they can continuously trap marine life in a process known as "ghost fishing". A study highlighted by the World Economic Forum warns that ocean plastic pollution could quadruple by 2050, with microplastics potentially increasing fiftyfold by 2100. The study highlighted
24883-432: The surface of the eye. Baleen whales appear to have limited color vision, as they lack S-cones . The mysticete ear is adapted for hearing underwater, where it can hear sound frequencies as low as 7 Hz and as high as 22 kHz , distinct from odontocetes whose hearing is optimized for ultrasonic frequencies. It is largely unknown how sound is received by baleen whales. Unlike in toothed whales, sound does not pass through
25050-474: The target for commercial industry, leading to a sharp decline in all populations of exploited species, such as whales and seals. Commercial hunting led to the extinction of the Steller's sea cow , sea mink , Japanese sea lion and Caribbean monk seal . After commercial hunting ended, some species, such as the gray whale and northern elephant seal , have rebounded in numbers; conversely, other species, such as
25217-437: The third stomach, where it meets fat-digesting enzymes, and is then mixed with an alkaline liquid to neutralize the acid from the fore-stomach to prevent damage to the intestinal tract . Their intestinal tract is highly adapted to absorb the most nutrients from food; the walls are folded and contain copious blood vessels , allowing for a greater surface area over which digested food and water can be absorbed. Baleen whales get
25384-427: The toxic chemicals that flow into Puget Sound are carried by stormwater that runs off paved roads and driveways, rooftops, yards and other developed land. In California, there are many rainstorms that runoff into the ocean. These rainstorms occur from October to March, and these runoff waters contain petroleum, heavy metals, pollutants from emissions, etc. In China, there is a large coastal population that pollutes
25551-404: The toxins are concentrated upward within ocean food chains . When pesticides are incorporated into the marine ecosystem , they quickly become absorbed into marine food webs . Once in the food webs, these pesticides can cause mutations , as well as diseases, which can be harmful to humans as well as the entire food web. Toxic metals can also be introduced into marine food webs. These can cause
25718-412: The underside stretching to the navel , to expand, increasing the amount of water that the mouth can store. The mandible is connected to the skull by dense fibers and cartilage ( fibrocartilage ), allowing the jaw to swing open at almost a 90° angle. The mandibular symphysis is also fibrocartilaginous, allowing the jaw to bend which lets in more water. To prevent stretching the mouth too far, rorquals have
25885-409: The upper jaw and are absent in the mid-jaw, forming two separate combs of baleen. The plates decrease in size as they go further back into the jaw; the largest ones are called the "main baleen plates" and the smallest ones are called the "accessory plates". Accessory plates taper off into small hairs. Unlike other whales (and most other mammals), the females are larger than the males. Sexual dimorphism
26052-565: The urgency of addressing plastic pollution, which threatens marine biodiversity and could push some species to the brink of extinction. Ocean acidification is the ongoing decrease in the pH of the Earth's ocean . Between 1950 and 2020, the average pH of the ocean surface fell from approximately 8.15 to 8.05. Carbon dioxide emissions from human activities are the primary cause of ocean acidification, with atmospheric carbon dioxide (CO 2 ) levels exceeding 422 ppm (as of 2024 ). CO 2 from
26219-433: The water they need from their food; however, the salt content of most of their prey ( invertebrates ) is similar to that of seawater, whereas the salt content of a whale's blood is considerably lower (three times lower) than that of seawater. The whale kidney is adapted to excreting excess salt; however, while producing urine more concentrated than seawater, it wastes a lot of water which must be replaced. Baleen whales have
26386-401: The water, food is swallowed and travels through the esophagus where it enters a three-chambered-stomach. The first compartment is known as the fore-stomach; this is where food gets ground up into an acidic liquid, which is then squirted into the main stomach. Like in humans, the food is mixed with hydrochloric acid and protein-digesting enzymes . Then, the partly digested food is moved into
26553-459: The water. Polar bears, otters, and fur seals have long, oily, and waterproof fur in order to trap air to provide insulation. In contrast, other marine mammals—such as whales, dolphins, porpoises, manatees, dugongs, and walruses—have lost long fur in favor of a thick, dense epidermis and a thickened fat layer (blubber) to prevent drag . Wading and bottom-feeding animals (such as manatees) need to be heavier than water in order to keep contact with
26720-409: The whale's interest, be within a certain size range so that the baleen plates can filter it, and be slow enough so that it cannot escape. Otters are the only marine animals that are capable of lifting and turning over rocks, which they often do with their front paws when searching for prey. The sea otter may pluck snails and other organisms from kelp and dig deep into underwater mud for clams . It
26887-412: The whole ecosystem to eventually speak louder. According to the oceanographer Sylvia Earle , "Undersea noise pollution is like the death of a thousand cuts. Each sound in itself may not be a matter of critical concern, but taken all together, the noise from shipping, seismic surveys, and military activity is creating a totally different environment than existed even 50 years ago. That high level of noise
27054-483: The year as the weather changes, and seals migrate in response to these changes. In turn, polar bears must follow their prey. In Hudson Bay , James Bay , and some other areas, the ice melts completely each summer (an event often referred to as "ice-floe breakup"), forcing polar bears to go onto land and wait through the months until the next freeze-up. In the Chukchi and Beaufort seas, polar bears retreat each summer to
27221-552: Was caused by global climate change and major tectonic activity when Antarctica and Australia separated from each other, creating the Antarctic Circumpolar Current . Balaenopterids grew bigger during this time, with species like Balaenoptera sibbaldina perhaps rivaling the blue whale in terms of size, though other studies disagree that any baleen whale grew that large in the Miocene. The increase in size
27388-471: Was conducted by Odd Lindahl et al., using mussels in Sweden. Apart from plastics, there are particular problems with other toxic pollutants that either do not break down or only very slowly in the marine environment. Examples of persistent toxicants are PCBs , DDT , TBT , pesticides , furans , dioxins , phenols , radioactive waste , and PFAS . Heavy metals are metallic chemical elements that have
27555-489: Was first introduced in 1982, and thought to have been transported to the Black Sea in a ship's ballast water. The population of the jellyfish grew exponentially and, by 1988, it was wreaking havoc upon the local fishing industry . "The anchovy catch fell from 204,000 tons in 1984 to 200 tons in 1993; sprat from 24,600 tons in 1984 to 12,000 tons in 1993; horse mackerel from 4,000 tons in 1984 to zero in 1993." Now that
27722-473: Was formerly classified in its own family. The two populations, one in the Sea of Okhotsk and Sea of Japan and the other in eastern Pacific are thought to be genetically and physiologically dissimilar. However, there is some discussion as to whether the gray whale should be classified into its own family, or as a rorqual, with recent studies favoring the latter. The taxonomic name "Mysticeti" ( / ˌ m ɪ s t ɪ ˈ s iː t aɪ / ) apparently derives from
27889-509: Was thought to have consisted of only one genus until studies done through the early 2000s reported that bowhead whales and right whales are morphologically (different skull shape) and phylogenically different. According to a study done by H. C. Rosenbaum (of the American Museum of Natural History ) and colleagues, the North Pacific ( E. japonica ) and Southern right ( E. australis ) whales are more closely related to each other than to
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