Nature » marine mammals

Ocean Giants: Video: Dolphin Mud Walls

fultonk — Thu, 22 Mar 2012 22:03:37 +0000

Watch a scene from the PBS Nature film, Ocean Giants.

In the shallows of Florida Bay, the fish can be very difficult to catch. Dolphins solve the problem by creating V-shaped walls of mud,a fish trap. Caught in the jaws of the trap, the fish have no where to go, except up. (Video limited to U.S. & Territories.)

Ocean Giants: Video: Bubble Play

fultonk — Thu, 22 Mar 2012 21:26:53 +0000

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Watch a scene from the PBS Nature film, Ocean Giants.

What will a group of dolphins make of the silvery rings of air produced by a bubble machine? (Video limited to U.S. & Territories.)

Ocean Giants: Video: On the Hunt for Herring

fultonk — Thu, 22 Mar 2012 18:53:12 +0000

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Watch a scene from the PBS Nature film, Ocean Giants.

Killer whales use a herding call to cause discomfort and confusion for a school of herring, making the fish easy targets for a meal. (Video limited to U.S. & Territories.)

Ocean Giants: Video: Visit from an Infant Sperm Whale

fultonk — Thu, 22 Mar 2012 15:51:39 +0000

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Watch a scene from the PBS Nature film, Ocean Giants.

An infant sperm whale, separated from its mother, swims remarkably close to cameraman Doug Allan, and as it approaches, calls out with a series of loud coda clicks. (Video limited to U.S. & Territories.)

Ocean Giants: The Whales: A Size Comparison

fultonk — Thu, 22 Mar 2012 14:40:21 +0000

Whales range in size from the blue whale, the largest animal known to have ever lived on the planet to various pygmy species, such as the pygmy sperm whale that reaches a length of around 10 feet. Whales may all be part of the same order, but shapes and sizes vary tremendously depending on species. So, how do right whales size up? A graphic that compares the size of whale species in the order Cetacea. Click image to enlarge.

Ocean Giants: Going Aquatic: Cetacean Evolution

fultonk — Wed, 21 Mar 2012 16:24:12 +0000

All cetaceans, including whales, dolphins, and porpoises, are descendants of land-living mammals. How did these terrestrial ancestors morph over millions of years into the whales and dolphins we are so familiar with today? Dr. Mark Uhen talks with PBS Nature about marine mammal evolution.

What do marine mammals have in common with other mammals? What distinguishes them from other mammals?

Modern marine mammals include: Cetacea (whales, dolphins, and porpoises), Sirenia (sea cows and dugongs) and Pinnipedia (seals, sea lions, and walruses). All of these groups share limbs that are modified into flippers, and an overall streamlined body shape. Like all mammals, marine mammals are warm-blooded, give birth to live young, and mothers produce milk to nurse their young.

Most cetaceans also have some very sparse hair at some time in their development, but it is very much reduced compared to most other mammals. Unlike most other mammals, modern whales do not have external hind limbs, have their forelimbs modified into flippers, have extra vertebrae in their trunk and back, have flukes on their tails for locomotion, and have their nostrils at or near the top of the head rather than the tip of the snout.

Sirenians are similar to whales in that they have only sparse hair on the body. Also like modern whales, modern sirenians lack external hind limbs, have their forelimbs modified into flippers, and have flukes on their tails for locomotion.

Pinnipeds are semi-aquatic and all pinnipeds retain hind limbs. In pinnipeds, both the fore and hindlimbs are modified into flippers. Most pinnipeds retain a substantial coat of hair, although not all.

All cetaceans, including whales, dolphins, and porpoises, are descendants of land-living mammals. What do we know about their terrestrial ancestors?

We know from both studies of DNA and the anatomy of living animals and fossils that whales are part of a mammalian group known as the Artiodactyla. Modern artiodactyls include animals like cows, pigs, sheep, giraffes, camels, and hippos. Artiodactyls have many characteristics that distinguish them from other mammals, but the most distinctive of them are in the foot and ankle. First, artiodactyls reduce the number of toes such that the foot is symmetrical between two digits (a condition called paraxonic). If you think about a cow foot, the hoof seems “split” in two. These animals are often called cloven-hoofed for this reason. The foot actually isn’t split into two at all. Rather, it is actually two toes fused together. Second, artiodactyls have a bone in the ankle called the astragalus (which is found in other mammals as well), but in artiodactyls, it takes on a characteristic form with a pulley shape at each end. Early whales share these characteristics with other artiodactyls. The group of fossil artiodactyls that we think are most closely related to whales is called the Raoellidae, and they lived in Indo-Pakistan, China, and Mongolia during the early and middle Eocene. These animals were probably omnivorous, and some people think they foraged by walking on the bottom of bodies of water.

Around what time period did this terrestrial ancestor begin its transition back into water?

The earliest whales are known from India and Pakistan from around 52.5 million years ago, during the early Eocene.

How long did it take for this land mammal to morph into the whales and dolphins we are familiar with today? What were some of the key adaptations that took place and do we know the order in which these adaptations occurred?

Cetacean Evolution. Graphic by Karen Brazell.
The earliest whales that we think were fully aquatic, that is, they never left the water, are found around 40 million years ago, during the middle Eocene. That means that the transition from terrestrial animals to fully aquatic animals took about 12 million years. The key adaptations are mostly those that still characterize whales today: forelimbs modified into flippers, extra vertebrae in their trunk and back, and flukes on their tails for locomotion. The earliest fully aquatic whales still had tiny external hind limbs, but they were so small they could not support the body on land. Also, their nostrils were far back on the skull from the tip of the snout, but they weren’t all the way back to the top of the head like in modern whales.

How has their evolutionary story driven their behavior, for instance, in developing societies and communication skills?

It is very difficult to answer the question of what drives evolution. It is also probably not the right question to ask if you know how evolution by natural selection works. Basically, many offspring are produced, and only a few survive to adulthood and reproduce. Those that are best able to cope with the living conditions in which they find themselves will be most successful in terms of having the most offspring. Thus, evolution by natural selection is constantly changing species as the conditions in which they live change. So, there usually isn’t some driving force behind evolution, there is just the change in species as a response to changing conditions. That said, some whales, particularly the toothed whales and even more particularly the dolphins have evolved very large brains and are also highly social animals. These large brains and the sociality that appears to be associated with them must offer some kind of advantage over those without it.

When did whales break into the different suborders: Odontoceti and Mysticeti? What are the primary differences between these two suborders?

The earliest known member of the Mysticeti, the modern filter-feeding whales is from the latest Eocene, around 34 million years ago. The earliest known member of the Odontoceti, the modern toothed whales, is from the early Oligocene, around 30 million years ago. This suggests that the split between Mysticeti and Odontoceti occurred during the late Eocene.

What is the whale’s closest living terrestrial relative?

The closest living relatives of whales are the Family Hippopotamidae, which today includes the hippo, Hippopotamus amphibious and the pygmy hippo Choeropsis liberiensis. The fossil record of Hippopotamidae extends from the early Miocene to today.

When did scientists first propose that marine mammals evolved from land-living mammals? What findings led to this conclusion?

Ever since classical times, people knew that marine mammals were different from other sea creatures and they recognized some similarities with terrestrial mammals. Once scientists began to formally classify animals in the 17th century, whales, sirenians, and pinnipeds have all been recognized as mammals, but the placement of some of these groups (particularly whales) within mammals has been controversial until recently.

Were the cetaceans the only land-living mammals to return to water environments? If there were others, did they return to water during the same period and did they morph in similar ways?

There are only two groups of mammals (that we know of) that have become completely aquatic. These are the Cetacea (whales, dolphins, and porpoises) and the Sirenia (sea cows and dugongs). These two groups both originated in the early Eocene, and have followed rather similar evolutionary pathways, particularly in how their limbs and modes of locomotion evolved. This is despite of the fact that cetaceans are carnivorous and sirenians are herbivorous. In addition, the Pinnipedia (seals, sea lions, and walruses) evolved from a group of dog-like Carnivora in the late Oligocene. Pinnipeds are all semi-aquatic, coming ashore to breed and have their young. Another group called the Desmostylia evolved in the early Oligocene and lived until the late Miocene in the North Pacific Ocean. Desmostylians are thought to have been semi-aquatic herbivores.

Why did marine mammals go back to the sea?

It is difficult to answer the question “Why did marine mammals go back to the sea?” Remember that evolution by natural selection facilitates tiny changes generation by generation allowing those that function better in that particular environment to reproduce more often. That said, the earliest changes that we see in whales and some other groups of marine mammals involve feeding and sensory perception. It looks like these early terrestrial ancestors of these groups began feeding in the water and became more adapted to aquatic conditions over time.

What research is happening currently on marine mammal evolution?

New discoveries are continually being made by geologists, paleontologists, and modern biologists about the evolution of marine mammals. Geologists are constantly revising the age estimates of rocks in which we find fossils. New fossils are being described from Indo-Pakistan, North Africa, North And South America, Oceania, and Europe. This is an exciting time to study marine mammal evolution as many of the most important discoveries in this field have been made in the last 10-15 years, and there is no reason to expect that pace of discovery to slow down in the near future.

Mark Uhen is an Assistant Professor of Geology at George Mason University. Previous to working at Mason, Dr. Uhen was Curator of Paleontology at the Alabama Museum of Natural History, and Head of Research and Collections at Cranbrook Institute of Science. Dr. Uhen is also a Research Associate at the United States National Museum of Natural History.

His research focuses on the origin and evolution of cetaceans (whales and dolphins), major evolutionary transitions in general, functional morphology, use of stratigraphic data in phylogenetic analysis, and theoretical aspects of diversification. He has published many papers in scientific journals, contributed chapters to edited books, and presented at numerous scientific conferences.

Ocean Giants: Whale Fact Sheet

fultonk — Wed, 21 Mar 2012 15:32:39 +0000

Class: Mammalia
Order: Cetacea
Suborders: Mysticeti and Odontoceti

The primary difference between the two suborders, Mysticeti and Odontoceti, has to do with the whale’s feeding hardware. Whales in the Mysticeti suborder have baleen plates that serve as a filter-feeding system, while marine mammals in the Odontoceti suborder—which includes dolphins and porpoises as well as whales—have teeth.

Size and weight:
Different species of whales vary drastically in terms of both size and weight. Baleen whales in the Mysticeti suborder are generally larger than those of the Odontoceti suborder. The Mysticeti group includes the blue whale (Balaenoptera musculus)—the largest animal ever to live on the planet. The species can be up to 100 ft long (30m), and weigh as much as 150 tons (136 metric tons)—approximately 300,000 lbs. The sperm whale (Physeter macrocephalus) is the largest toothed-whale, reaching up to 70 ft (21m) in length and 59 tons (54 metric tons) in weight. The smallest baleen whale is the pygmy right (Caperea marginata), which averages a length of only 20 ft and a weight of 4 tons (6m/3.6 metric tons).

Physical Features:
Whales resemble fish because of their fins and hydrodynamic bodies, but have far more in common anatomically with other mammals. Somedistinct physical characteristics include:

Baleen: Also known as whalebone, baleen is a filter-feeder system inside the mouths of whales in the Mysticeti suborder. Plates of keratin grow from the gums of the upper jaw. When the whales feed, they take in large amounts of food-rich water and then use baleen to filter out the water while retaining krill. Baleen is made of keratin, a substance also found in human fingernails and hair. (Baleen is only found in select species of whale.)

Blubber: Blubber is a thick layer of fat under a whale’s skin that helps the warm-blooded animal maintain its body heat under water.

Rostrum: The rostrum is an animal’s beak or a beak-like part of its face. In a whale’s anatomy, it refers to the upper jaw.

Dorsal Fin: A fin located on the back of a wide-variety of aquatic animals including all marine mammals. Its primary purpose is to help the animal maintain balance while it swims.

Pectoral Flippers: The pectoral flippers are the whale’s forelimbs. The flippers have skeletal elements similar to those of terrestrial mammals although, externally, they resemble fish fins.

Flukes: Flukes are the tail fins of whales. Flukes are flat and are responsible for propelling the whale through the water.

Blowhole: Blowholes are nasal openings located at the top of a whale’s head. Similar to nostrils in other mammals, blowholes are used by whales to expel carbon dioxide, mucus, and nitrogen, and to inhale oxygen which is then sent through the trachea to the lungs. After inhalation, blowholes are sealed with a water-resistant muscular flap. Baleen whales have two blowholes while toothed-whales have only one.

Diet:
Mysticeti whales rely on their baleen to feed on relatively small aquatic organisms. Their diet primarily consists on fish, krill, and plankton. Toothed whales are better equipped to grab larger, individual prey animals like fish, squid, and other invertebrates. Some species in the Odontoceti suborder have been known to even eat seabirds and smaller marine mammals.

Geography and Habitat:
Whales are found in all of the world’s oceans. Species often breed and raise calves in warmer tropic or sub-tropic waters, and then migrate to cooler waters at or near the poles to feed. Certain species, like bowheads—that are found exclusively in the Arctic—have a far more limited geographical range.

Lifespan:
The exact lifespan of whales is not known, but it has been estimated at anywhere from 30 to 200 years of age. Bowheads are thought to have an incredibly long lifespan, reaching ages of 200 years or more.

Breeding and Social Structure:
Social behavior varies depending on species, but most whales spend time in groups, primarily during periods of migration. When in groups, whales communicate with each other in a variety of ways including posture, touching, spouting, and above-water movements like breaching and lobstertailing—slapping its tail fluke on the water’s surface. While humpback whales are known for their “songs,” most whales use a variety of vocalizations for communicative purposes.

Reproductive habits also vary from species to species, but on average, mature whales breed every two or three years, with an incubation period of about 9 to 15 months. After giving birth to calves, lactating mothers nurse the babies from nipples concealed in abdominal mammary slits. Calves can swim as soon as they’re born and typically stay with their mother for a year or so.

Risks:
Small or young whales are susceptible to larger ocean predators, including orcas, but whales are most threatened by human activities. Whaling for meat, baleen, oil, and blubber decimated whale populations—particularly after the industry took-off in the 19th century. It wasn’t until 1982 that hunting was officially prohibited by the International Whaling Commission. However, whaling still occurs, hurting current whale numbers. Although some whale populations are recovering, damage to their habitat, caused by pollution and changes in ocean temperatures that negatively impact food sources, remain major threats to the animals.

Additional Facts:

The word cetacean comes from the Greek word for whale, ketos.

The scientific suborder’s name, Mysticeti, most likely derived from the Greek word, mystakos, meaning moustache, possibly referring to the baleen plates attached to the whale’s upper jaw.

Carl Linnaeus humorously gave the blue whale the scientific name Balaenoptera musculus. The first word refers to the whale’s dorsal fin (“whale wing”), and the second, musculus, means “little mouse.”

Sei whales are among the fastest of the baleen whales, reaching speeds up to 34.5 mph.

Most species of toothed whales use echolocation to navigate the ocean. No baleen whales are known to have this ability.

During the embryotic stage, baleen whales develop tooth buds. However, these tooth buds disappear before birth.

The famous narwhal has just two teeth: one in its mouth, and the other jutting out from the front of the male’s head. This unusual protrusion is why the narwhal is nicknamed “unicorn of the sea.”

Whales do not breathe reflexively. They must make a conscious effort to come to the surface to breathe in air.

Like all mammals, whales have body hair, and nurse their young with milk.

Also like all other mammals, whales are warm-blooded. They maintain a temperature around 98-99 degrees Fahrenheit—close to that of humans.

Whales do not have tear ducts but they do have glands near the eyelid that release an oily substance to lubricate and clean the eye.

Whale Species

Blue Whale (Suborder: Mysticeti)
The Blue whale (Balaenoptera musculus) is named for its mottled blue-gray color. Its underside can have a yellowish hue due to the micro-organisms, known as diatoms, which attach to that area of its body. The blue whale, like the humpback, has ventral pleats—creases that run vertically down the underside of a whale’s jaw all the way to its stomach. When feeding, the ventral pleats expand like an accordion to accommodate ahuge amount of food-rich water. This adaptation enables the blue whale to acquire and consume approximately 4 tons (3.6 metric tons) of krill daily. In addition to its enormous size, the blue whale is fast, with the ability to cruise between 5 and 12mph (8-19kmph). In an excited state, the whale can reach speeds of up to 20mph (32kmph). The species produces the loudest and lowest sounds made by any animal—180 decibels and 10-20 hertz—and can be heard underwater for hundreds of miles.

Bowhead Whale (Suborder: Mysticeti)
Living exclusively in the Arctic, the bowhead whale (Balaena mysticetus) has distinctive adaptations to withstand its cold environment. It’s named for its enormous curved upper jaw—which accounts for almost a third of its body length. It relies on its huge skull to smash through ice that covers northern ocean waters. To stay warm, the bowhead has 17-19in (43-50cm) of blubber—the thickest blubber layer of any whale. The bowhead has a dark body with a conspicuous white spot on its chin as well as a white “penduncle patch” on its tail. As the whale ages, its tail grows increasingly whiter. Analysis of one amino acid in the whale’s tissue is revealing astonishing information about their age, leading to estimates that some individuals may be over 200 years old.

Gray Whale (Suborder: Mysticeti)
Instead of dorsal fins, the gray whale (Eschrichtius robustus) has a prominent hump on its back, followed by 6-12 knuckles or small bumps. The whale has dark skin speckled with white and gray patches, barnacles and whale lice. Like other baleen whales, long-term relationships between gray whales are rare, but the whale migrates in pods, swimming 12,430 miles (20,000 km) from northern Pacific waters near Alaska to their breeding and wintering territory off the Mexican coast. Unlike most whales, gray whales are bottom feeders—the animals swim sideways on the ocean floor with their mouths open, then expel sand and water through their baleen without releasing the small crustaceans and tube worms they have scooped up.

Humpback Whale (Suborder: Mysticeti)
The humpback (Megaptera novaeangliae) has bumps around its head and mouth, each sprouting a single hair. Scientists speculate that these hairs may help sense movement in the water. The whales are unusually active for their size: they lobtail, slap the ocean surface with their flippers, and swim on their backs with flippers akimbo. Most impressive, humpbacks can propel themselves completely out of the water when breaching. Humpbacks are best known for singing, which occurs in all-male groups. Their distinct songs can travel for thousands of miles across an entire ocean basin and are communally improvised by large groups of whales from one year to the next.

North Atlantic Right Whale (Suborder: Mysticeti)
The right whale’s (Eubalaena glacialis) head takes up approximately a quarter of its body, and its blubber accounts for about 40% of its weight. This high concentration of fat, as well as the whale’s relatively friendly demeanor, made it an easy target for whalers (who named it for being the “right” whale to hunt). The whale has a black body with distinctive patches of rough skin known as callosities. Each whale can be individually identified by the distinct pattern of their callosities, barnacles, and whale lice on its head. This species of whale has no dorsal fin. The whale feeds by skimming, swimming with a slightly open mouth to catch zooplankton in their baleen. The right whale has the longest baleen of any whale in the Mysticeti suborder.

Sperm Whale (Suborder: Odontoceti)
Besides being the largest of the toothed-whales, the sperm whale (Physeter macrocephalus) is also the most sexually dimorphic: the male can be up to 30 tons heavier than its female counterpart. The whale has the largest brain of any animal, weighing in at around 17lb (7.8 kg) and has the most asymmetrical skull of any animal. Its huge head also houses an oily fluid called spermaceti (after which the whales were named), once used for ointments and candles. Scientists are still unclear what purpose spermaceti serves, but it may help with echolocation or in adjusting its buoyancy for deep dives. The sperm whale spends most of its time in deep water, hunting animals like large squids that live at extreme depths. To reach its prey, a sperm whale can dive as deep as 3280 ft (1km), and stay submerged for over an hour.

Ocean Giants: Additional Resources

fultonk — Sun, 26 Feb 2012 16:01:43 +0000

Voices in the Sea
High-quality images and sound and video recordings of several marine animals from the Scripps Institution of Oceanography UC San Diego Whale Acoustics Lab.

Text of the Marine Mammal Protection Act
Enacted in 1972, this act of the US Congress prohibits, with a few exceptions, the take (“harass, hunt, capture, kill or collect” or to attempt to do so) of marine mammals, and created the Marine Mammal Commission.

Whale and Dolphin Conservation Society
A global charity engaged in a multitude of activities aimed at educating people and protecting whales and dolphins; the site includes links to news, blogs, and games.

Hawaii Whale Research Foundation, Dan R. Salden
A small nonprofit group of dedicated volunteers conducting field research on marine mammals with emphasis on humpback whale social affiliation.

Center for Whale Research, Kenneth C. Balcomb
An organization that conducts annual photo-identification studies of the Southern Resident Killer whale (SRKW) population that frequent the inland waters of Washington State and lower British Columbia.

The Wild Dolphin Project, Denise Herzing
A non-profit scientific research organization that studies and reports on a specific pod of free ranging Atlantic spotted dolphins (Stenella frontalis).

Bowhead Whale Acoustic Project, Outi Tervo
A group of scientists, including Outi Tervo, conducting research on baleen whales in Disko Bay, concentrating on the ecology and behaviour of bowhead whales.

New York Times: Green Blog | Eureka! A Roaming Bowhead Whale
A New York Times blog post on Outi Tervo and her work with bowhead whales.

NPR | A Researcher Asks: Are Dolphins Self-Aware?
Psychologist Diana Reiss discusses communication and cognition in dolphins.

Projecto Boto, Vera M. F. Da Silva
A long-term study of river dolphins in Brazil’s newly-formed Mamirauá Reserve conducted by Dr. Vera da Silva and Dr. Tony Martin.

New York Times | How Far Will Dolphins Go to Relate to Humans?
An article on Dr. Denise L. Herzing’s work with dolphins and dolphin communication off the coast of Florida. Dr. Herzing was featured in the PBS Nature Ocean Giants series.

Doug Allan’s Official Website
The official website for underwater cinematographer Doug Allan.

Didier Noirot’s Official Website
The official website for underwater cinematographer Didier Noirot.

Fellowship of the Whales: Video: Full Episode

tanner vea — Sun, 14 Aug 2011 16:00:26 +0000
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Follow a baby humpback whale as she travels from her birthplace in Hawaii, to feeding grounds off Alaska’s coast. Escorted by her mother, this newborn will learn many things along the way. And when the pair returns to Hawaii, this yearling will be ready to take her place in her own community of whales. Buy the DVD. This film premiered November 15, 2009.

Fellowship of the Whales: Video: Humpback Males Fight

tanner vea — Mon, 08 Aug 2011 17:40:02 +0000

Humpback whales congregate in the waters off Hawaii not only to give birth, but also to mate. This female humpback releases pheromones into the water, indicating that she’s ready to mate. A fight soon breaks out among the humpback bulls that are vying to be her escort.