Opening with an accessible rundown of cetacean biology—including the most recent science on feeding, mating, and communication—Whales, Dolphins, and Porpoises then presents species-specific natural history on a range of topics, from anatomy and diet to distribution and conservation status. Each entry also includes original drawings of the species and its key identifiers, such as fin shape and color, tooth shape, and characteristic markings as they would appear both above and below water—a feature unique to this book.
Figures of myth and—as the debate over hunting rages on—figures of conflict since long before the days of Moby-Dick, whales, dolphins, and porpoises are also ecologically important and, in many cases, threatened. Written for general enthusiasts, emergent cetacean fans, and biologists alike, this stunning, urgently needed book will serve as the definitive guide for years to come.
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Whales, Dolphins & Porpoises
A Natural History and Species Guide
By Annalisa Berta
The University of Chicago PressCopyright © 2015 Ivy Press Limited
All rights reserved.
Phylogeny & Evolution
The majority of marine mammals belong to the order Cetacea, which includes whales, dolphins, and porpoises. The name Cetacea comes from the Greek ketos meaning whale. Two major groups of extant whales are recognized — toothed whales (Odontoceti) and baleen whales (Mysticeti). Toothed whales are much more diverse with 10 families, 34 genera, and 76 extant species (one of which is likely extinct) compared to mysticetes that include 4 families, 6 genera, and 14 extant species. Toothed cetaceans include sperm whales, oceanic whales, river dolphins, monodontids (beluga and narwhal), ocean dolphins, and porpoises. Baleen whales include the right whales, pygmy right whale, gray whale, and blue, fin, sei, Bryde's, humpback, minke, Antarctic minke, and the recently described Omura's whale.
Evolutionary relationships of whales
Cetaceans originated from land mammals and there is strong support for whales being most closely related to artiodactyls (even-toed ungulates), which include cows, goats, camels, and hippos. Because cetaceans and artiodactyls are linked, they are grouped together in the clade Cetartiodactyla. Within cetaceans, relationships among families are still debated. There is general agreement from both molecular and anatomical data for the family level evolutionary history among odontocetes. Basal odontocetes include sperm whales (Physeteridae and Kogiidae). Asiatic river dolphins, Platanistidae, are the next diverging lineage followed by beaked whales (Ziphiidae), Chinese river dolphin (Lipotidae), South American river dolphins (Iniidae and Pontoporiidae), and the latest most recent divergent lineage the Monodontoidea — beluga and narwhal (Monodontidae) and porpoises (Phocoenidae), and oceanic dolphins (Delphinidae).
Unlike odontocetes, higher-level relationships among mysticetes conflict based on molecular (i.e. DNA sequences) versus anatomical data. Using molecular data right whales and the bowhead (Balaenidae) are recognized as basal mysticetes whereas anatomical data positions pygmy right whales (Neobalaenidae) as sister to Balaenidae followed by an alliance of the remaining baleen whales: rorquals (Balaenopteridae) and gray whales (Eschrichtiidae). The position of the gray whale is also debated. Anatomical data places Eschrichtiidae and Balaenopteridae as close relatives whereas molecular data nests gray whales within balaenopterids.
Cetaceans are first found in the fossil record approximately 52.5 million years ago (MYA) during the early Eocene period in current-day India and Pakistan. Recent discoveries in Pakistan and southern India have suggested that extinct artiodactyls, the raoellids, such as Indohyus, are the closet extinct relatives of whales. Indohyus was a cat-sized animal with a long nose, tail, and slender limbs. At the end of each limb were four to five toes that ended in hooves, similar to those of deer. Raoellids also had very thick dense limb bones, an adaptation for buoyancy control. Since raoellids were largely aquatic, this indicates that an aquatic lifestyle arose before whales evolved.
Early whales had legs
The earliest stem cetaceans — such as Pakicetidae (e.g. Pakicetus), Ambulocetidae (e.g. Ambulocetus), and Remingtonocetidae (e.g. Kutchicetus) — are all known from the early and middle Eocene (50 MYA) of current-day India and Pakistan. They are all thought to have been semiaquatic, able to move on land as well as in the water. These stem whales had well-developed forelimbs and hind limbs. Wear on the teeth is consistent with a fish-eating habit. The occurrence of later diverging whales (such as Protocetidae, e.g. Rodhocetus), in Asia, Africa, Europe, and North America) indicates that cetaceans had spread across the globe between 49–42 MYA. They differed from other early cetaceans in having large eyes with the nasal opening that had migrated further back on the skull. Basilosaurids (such as Dorudon) — the closest relatives of modern cetaceans — were widely distributed and lived between 41–35 MYA. Best known is Basilosaurus isis, which had a snake-like body with a maximum length of 56 ft (17 m), with several hundred skeletons reported from the middle-Eocene Valley of Whales in north-central Egypt.
Modern (crown) cetaceans originated from archaic (stem) cetaceans, such as Basilosaurus, approximately 33.7 MYA during the Oligocene period. The diversification of modern cetaceans (Neoceti) has been associated with the breakup of the southern continents and restructuring of ocean circulation patterns — signaled by higher oxygen isotope levels — which resulted in increased food production (indicated by diatoms, a type of tiny algae) and upwelling of nutrient-rich water.
Crown cetaceans differ from stem cetaceans in having a telescoped skull. In "telescoping" the bones of the rostrum are extended and displaced posteriorly and the nostrils have moved to the top of the head where they form the blowholes (see here).
Odontocetes differ from mysticetes by the presence of teeth. Odontocetes acquired echolocation, which enabled them to produce high-frequency sounds that are reflected from objects that surround them — these reflections allow them to pursue individual prey items. Mysticetes acquired a novel feeding mechanism, bulk filter-feeding using baleen plates, strainers in the mouth.
Although most whales today are entirely marine, early fossil members of this lineage, such as pakicetids, likely foraged exclusively in freshwater based on analysis of the carbon and oxygen isotope levels of their teeth and bones.
The oldest named odontocetes are from the North Atlantic (North America). A recently discovered stem odontocete, Cotylocara, has dense bones and air sinuses, features that support the theory that echolocation originated early — between 32–35 MYA. Crown odontocetes, or modern families, diversified in the Miocene, approximately 23–26 MYA. Extant genera of both mysticetes and odontocetes appeared during the Pleistocene, approximately 1.6 MYA. Analysis of the morphology and evolutionary relationships of river dolphins supports the hypothesis that marine odontocetes invaded river systems on multiple occasions. The range and habitat of some whales is much different today than in the past. For example, distant relatives of the South American La Plata River dolphin had a broader range in the past that included southern California. A similar range expansion is indicated for fossil relatives of the beluga that today occupies Arctic waters but inhabited temperate waters as far south as Baja California in the Miocene.
Several fossil odontocetes exhibit unique feeding adaptations. An extinct relative of monodontids (narwhal and beluga), Odobenocetops lived in Peru during the early Pliocene (3–4 MYA). The presence of tusks and a presumed mollusk-eating suction feeding habit are convergences (similarities based on ecology rather than relationship) with the walrus. A recently described fossil porpoise, Semirostrum ceruttii from the Pliocene of California is reconstructed to have employed a form of benthic skim-feeding by using its lower jaw, which extended further beyond the rostrum than in any other known mammal, to probe for and obtain prey.
The earliest named mysticetes are from the South Pacific (Australia and New Zealand). These stem mysticetes, some of which were of large size ranging from 16–40 ft (5–12 m) such as Llanocetus, possessed well-developed teeth with multiple accessory cusps and likely hunted individual prey. Other fossil taxa, such as the Aetiocetus weltoni, were smaller-bodied and may have had both teeth and baleen employed in batch filter-feeding as seen in modern baleen whales.
The earliest known and earliest diverging toothless fossil mysticetes, the eomysticetids, were relatively large bodied at around 33 ft (10 m) in length, with long skulls. They appeared in the Oligocene in both the North and South Pacific and were contemporaneous with some stem-toothed mysticetes. Although the ancestral feeding strategy among crown mysticetes is debated, functional analysis of the late Pliocene (2.5–3.5 MYA) mysticete, Herpetocetus morrowi, suggests a lateral suction-feeding strategy similar to but evolved independently from feeding in living gray whales. As was the case for odontocetes, crown mysticetes underwent an explosive radiation in the Miocene. Whale diversity peaked in the late middle Miocene (14MYA) and fell thereafter, yielding a modern fauna that is much less diverse today than in the past.
Anatomy & Physiology
Cetaceans display considerable diversity in size. Included among the mysticetes or baleen whales are some of the largest species such as the blue whale, the largest animal on earth at 110 ft (33 m) long and weighing 330,000 lb (150,000 kg). Odontocetes show a wider range of sizes, from the sperm whale that is as large as some baleen whales to the vaquita that is about 4¾ ft (1.4 m) in length, weighing 92 lb (42 kg). In odontocetes or toothed whales, males are typically larger, whereas in mysticetes, females are generally larger than males. Since most mysticetes depend upon stored body fat to support their metabolic requirements, particularly during the winter months far from feeding grounds, the extra weight is necessary for their survival, promoting greater reproductive success and aiding females in the nursing of their offspring.
Cetaceans exhibit numerous adaptations for a fully aquatic life. Breathing occurs through blowholes that have migrated to the top of the head. Odontocetes have only a single blowhole instead of the two blowholes of mysticetes. The heads of mysticetes are very large, up to one-third of the body length.
The vertebral region does not contain a sacral region in whales because the pelvic girdle is absent. External hind limbs are very reduced or absent in cetaceans and the forelimbs have been modified into flippers or pectoral fins with an inflexible elbow that functions in steering. The broad flippers of some mysticetes, such as right and bowhead whales, aid in slow turns. The flippers of the humpback are exceptionally long and maintain hydrodynamic efficiency; they are also "waved" during feeding and social displays. The flippers of most odontocetes assist in turning during high-speed maneuvers while chasing prey. In odontocetes that occupy pack ice or rivers, such as the beluga or river dolphins, flipper shapes allow for angled maneuvers in those environments.
The muscular horizontal tail or fluke lacks bony support and is composed of tough, fibrous connective tissue. The tail provides propulsion by vertical movement. Tail shape differs among cetaceans and most provide increased efficiency at high speeds (see Identification). To help minimize drag in the water many smaller odontocetes, for example delphinids, move at high speed and leap and glide (porpoising) above the water's surface. Most whales have a dorsal fin (see also Identification) that provides stability and balance.
The fins, flippers, and flukes of cetaceans have arteries and veins that pass close to one another in opposite directions and function as radiators (counter current exchangers) to control heat balance. The skin of cetaceans is generally smooth and rubbery to the touch. Hair is absent except for sparse bristles (vibrissae) found on the head of some species. The blubber layer, thickest in large baleen whales, enhances streamlining and provides insulation and energy storage.
Mysticetes don't have teeth as adults and have evolved novel feeding structures — baleen plates composed of keratin (the material that makes up the hair, claws, and fingernails of mammals) — that hang down from the upper jaw and strain bulk prey, for example, krill. Rorquals, such as fin whales, can engulf a volume of water that is greater than their body mass. For example, fin whales have been reported to engulf 18,000 gallons (70,000 liters) of water in each gulp, containing 22 lb (10 kg) of krill. Expansion of the mouth and throat in mysticetes is facilitated by external throat grooves or pleats below the mouth and throat. Most odontocetes, especially those with diets of schooling fish, employ their many teeth to obtain prey. Odontocetes are active hunters and pursue prey using echolocation, in which high-frequency sounds are emitted from "phonic lips" near the blowhole. Sounds are focused by the melon, a fatty structure on the top of the head, and returning echoes pass through and under fat bodies on the lower jaw before being transmitted to the ears.
Beaked and sperm whales have fewer or no teeth and are deep divers, feeding primarily on squid. Cuvier's beaked whales hold the diving record and are the longest- and deepest-diving vertebrates, with dives lasting 137 minutes to depths of more than 1.86 miles (2,992 m) on a single breath. Deep-diving cetaceans exhibit a variety of circulatory and respiratory modifications including high blood volume, flexible ribs, and tolerance of complete lung collapse. By contrast with human lungs, large oxygen stores are located in the muscles and blood.
A feature of some whale brains is their large size, especially the cerebrum, the front portion of the brain responsible for movement and mental functions. Brain size relative to body size is large in odontocetes. In comparison to other similar-sized animals most odontocetes have brains that are four to five times larger. Only the human brain is proportionally larger. The high brain:body size ratio of odontocetes, such as dolphins and killer whales, are partly explained by their complex social structure and behavior.
"Behavior" refers to the ways that organisms respond to each other and to environmental cues. Like other mammals, cetacean behavior is driven by the need to obtain food, remain safe from predators, find mates, and rear offspring. However, what makes cetaceans unique is that all of these activities are conducted underwater, yet they are tied to the surface to breathe. This has led to some unique adaptations, particularly in foraging behavior (see here). Unraveling behavior in animals that spend the majority of their lives underwater can be a challenging task, but as long-term studies continue and technology advances, we are gaining a greater understanding of the intricacies of cetacean behavior.
Cetaceans are social animals and so it is important to understand how their behaviors occur within the context of associating with other individuals. The gregariousness of cetaceans varies along a spectrum of being relatively solitary to highly social. In the case of some pelagic dolphins, such as striped and common dolphins, groups may contain hundreds or even thousands of individuals. In general, odontocetes tend to be more gregarious than mysticetes (baleen whales). This is due in part to the larger size of mysticetes, decreased predation risk, and the need to reduce competition for food. However, there are exceptions, as humpback whales can be quite gregarious and river dolphins may be relatively asocial. It is also possible that species typically viewed as being solitary may in fact be socializing acoustically across large distances via low-frequency vocalizations, such as in blue whales.
The group is the primary line of defense against predators. In the ocean, there is no place to hide but individuals can gain safety in numbers — by forming groups. Group members may also actively deter predators, for example by mobbing a predator or arranging themselves in defensive formations.
Excerpted from Whales, Dolphins & Porpoises by Annalisa Berta. Copyright © 2015 Ivy Press Limited. Excerpted by permission of The University of Chicago Press.
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Table of Contents
Phylogeny & Evolution
Anatomy & Physiology
Food & Foraging
Conservation & Management
Identification Tools & Maps
How & Where To Watch
The Species Directory
How to Use the Species Directory
Southern Right Whale
North Atlantic Right Whale
North Pacific Right Whale
Pygmy Right Whale
Rorqual Whales & Gray Whale
Common Minke Whale
Antarctic Minke Whale
Long-Beaked Common Dolphin
Short-Beaked Common Dolphin
Pygmy Killer Whale
Short-Finned Pilot Whale
Long-Finned Pilot Whale
Atlantic White-Sided Dolphin
Pacific White-Sided Dolphin
Northern Right Whale Dolphin
Southern Right Whale Dolphin
Australian Snubfin Dolphin
False Killer Whale
Indo-Pacific Humpback Dolphin
Indian Humpback Dolphin
Australian Humpback Dolphin
Atlantic Humpback Dolphin
Pantropical Spotted Dolphin
Atlantic Spotted Dolphin
Indo-Pacific Bottlenose Dolphin
Common Bottlenose Dolphin
Pygmy Sperm Whale
Dwarf Sperm Whale
Narwhal & Beluga
Arnoux’s Beaked Whale
Baird’s Beaked Whale
Northern Bottlenose Whale
Southern Bottlenose Whale
Longman’s Beaked Whale
Sowerby’s Beaked Whale
Andrews’ Beaked Whale
Hubbs’ Beaked Whale
Blainville’s Beaked Whale
Gervais’ Beaked Whale
Ginkgo-Toothed Beaked Whale
Gray’s Beaked Whale
Hector’s Beaked Whale
Deraniyagala’s Beaked Whale
True’s Beaked Whale
Perrin’s Beaked Whale
Pygmy Beaked Whale
Stejneger’s Beaked Whale
Spade-Toothed Beaked Whale
Shepherd’s Beaked Whale
Cuvier’s Beaked Whale
Amazon River Dolphin
Ganges River Dolphin
Narrow-Ridged Finless Porpoise
Indo-Pacific Finless Porpoise
Classification of Cetaceans
Notes on Contributors