Order Cetacea Suborder Mysticeti (Baleen Whales, 4 Families) Suborder Odontoceti (Toothed Whales, 7+ Families)
Order Cetacea Suborder Mysticeti (baleen whales, 4 Families) Suborder Odontoceti (toothed whales, 7+ Families)
•Streamlined bodies •Mostly hairless, blubber for insulation •Front limbs flippers, hind limbs lost •Horizontal flukes •Genetically related most closely to Artiodactyls (hippos)
Mysticeti Odontoceti
Baleen present instead of teeth, teeth Teeth present, usually homodont, present in fetus but lost before birth monophyodont, exceed typical number for eutherians in some species
Paired external nares located Single opening for external nares, located anterior to eye posterior to eye (except sperm whale)
Skull profile convex, no oil-filled Skull profile concave, depression occupied “melon” present; skull symmetrical by “melon;” skull asymmetrical
Do not echolocate, auditory bullae Echolocate, auditory bullae not attached to attached to skull skull with bony connections
Nasal passages simple Nasal passages complex
Mandibular condyle directed upward, Mandibular condyle directed posteriorly, sternum consists of single bone sternum consists of 3 or more bones Orcinus orca Tursiops truncatus Most Odontocetes are aquatic piscivores, feeding on fish or squid (killer whales eat more). Numerous homodont teeth used for prey capture, not chewing (mostly). Most prey swallowed whole. Use echolocation. Rely on speed. Mysticetes show 3 basic types of feeding behaviors
Right whales (Balaenidae): long baleen plates, large heads, typically graze by skimming near surface, use huge tongue to remove plankton from baleen
Eubalaena glacialis Rorquals (Balaenopteridae): huge mouths and heads, shorter baleen, can swing lower jaw down at 90o angle, furrowed throat and abdomen that can be highly distended, engulf food in swarms, contract throat and squeeze out water, then swallow prey (humpbacks sometimes use bubble nets)
Megaptera novaeanglia upside down...
Eschrichtius robustus
Gray whales (Eschrichtiidae): shortest baleen, scoops up muck from bottom, filters out bottom-dwelling organisms, turns on side to plow through sediments Family Balaenidae (right whales; 2 g, 4 sp)
Eubalaena glacialis
Balaena mysticetus • “Right” whales because they float when dead
• Large and robust, up to 18 m length, 67,000 kg
• Head about 1/3 total length • Over 350 baleen plates on each side of upper jaw
• No furrows on throat or chest
• Rostrum high and arched
• Flippers short and rounded, no dorsal fin
• Surface feeders, near coastlines or pack ice
• Bowhead in Artic, 2 Northern species in N Atlantic or N Pacific; but Southern species migrates Family Neobalaenidae (pygmy right whale; 1 g, 1 sp)
Caperea marginata • Only 5-6 m long
• Southern hemisphere, open marine waters
• Slender, like some rorquals, with small dorsal fin
• Feed near surface, mostly on copepods
• Not much known about ecology, but do not seem to breach or tail slap water like right whales Family Balaenopteridae (rorquals; 2 g, 7 sp)
Balaenoptera musculus
Megaptera novaeangliae B. acutorostrata • Vary in size from minke (11 m, 4,000 kg) to blue (31 m, 160,000 kg)
• Can be streamlined or chunky
• Baleen plates short and broad, skin of throat and chest has many longitudinal furrows
• Feed in cold waters, esp upwelling zones, in summer; eat planktonic crustaceans and small fish
• Migrate toward equatorial regions in winter; live off blubber; breed in wintering areas (N and S hemisphere pops never meet)
• Present in all oceans Family Eschrichtiidae (gray whale; 1 g, 1 sp)
Eschrichtius robustus • Slender, no dorsal fin
• 13-14 m long, 31,500 kg
• Relatively small head with arched rostrum; short baleen plates
• Throat with 2 furrows
• Unusual: bottom feeders
• N. Pacific, mostly on eastern side, migratory, winters in Baja California and Sonora, Mexico ; western population winters near Korea Family Delphinidae (dolphins; 17 g, 34 sp)
Stenella longirostris
Orcinus orca
Cephalorhynchus heavisidii • Range from some small species around 1.5 m, 50 kg to orcas at 9.5 m, 7,000 kg
• Facial depression in skull contains “melon,” lens-shaped fatty deposit that gives forehead characteristic bulge; used in echolocation; may be able to use sound to stun prey (?)
• Color varies from uniform gray to black and white patterns
• Shallow dives, rapid swimmers; mostly eat fish and squid but orcas also take large fish, sharks, seabirds, seals and sea lions, sea otters, other cetaceans
• Gregarious, intelligent; largest relative brain size and encephalization index after humans Family Monodontidae (narwhal, beluga; 2 g, 2 sp)
Monodon Delphinapterus • Arctic Ocean, Bering and Okhotsk Seas, Hudson Bay, St. Lawrence River
• Narwhal: males have long, straight, spiraled tusk (only tooth! an upper incisor), males fence
• Beluga: white, distinct neck, 11/11 teeth
• Both about 6 m, 2,000 kg
• Gregarious, highly vocal, feed on fish Family Phocoenidae (porpoises; 3 g, 6 sp)
Phocoena phocoena • Coastal waters including bays and estuaries, some rivers in SE Asia; Dall’s porpoise (Phocoenoides) inhabits deeper waters
• 1.5 – 2.1 m long, 90 – 118 kg
• Short jaws, no beak, teeth often flattened and spade-like (except Phocoenoides)
• Eat fish, squid, crustaceans
• Dorsal fin low, sometimes absent
• Can form large groups for feeding (over 100 individuals) Family Physeteridae (sperm whales; 2 g, 3 sp) Kogia Physeter • Physeter catodon (Moby Dick) is largest predator at 18 m, 53,000 kg; all but Arctic oceans • Kogia sp only 4 m, 320 kg (not well known)
• Physeter: huge head, 1/3 total body length; facial region with large spermaceti organ dorsally, large quantities of oil; ventral sac has denser, less valuable oil; together, oil-filled organs are 25% body weight; teeth only in lower jaw
• Social, groups of females and calves, usually 1 or a few large males; younger males in bachelor groups, old males solitary
• Deep divers, esp males; use echolocation; feed on deep-water squid (including giant squid), sharks, skates, large fish
• Males migrate, females stay in tropical and temperate waters Family Platanistidae (Ganges and Indus river dolphins; 1 g, 2 sp) Family Iniidae (South American, La Plata, and Chinese river dolphins; 3 g, 3 sp)
Chinese - Lipotes Amazon - Inia
Indus - Platanista Platanistidae: rivers of India and Pakistan • 2 – 2.9 m long, 90 kg • Long, narrow jaws with numerous teeth • Forehead rises abruptly, rounded; eyes reduced, hunts by echolocation and probing muddy river bottom
Iniidae: 3 monotypic genera (Inia: Amazon and Orinoco Rivers; Lipotes: Yangtze River; Pontoporia: coastal rivers of Brazil and Argentina) • Inia not as social, may have good vision above water, can look reddish (boto legends); • Lipotes likely extinct • Pontoporia only river dolphin that can tolerate salt water Family Ziphiidae (beaked whales; 6 g, 21 sp)
Mesoplodon densirostris • Widely distributed in all oceans, deep divers, often in open ocean far from land
• Poorly known, some have never been seen alive
• 4-12 m, up to 11,500 kg
• 1 species has many teeth, but 1 species has only 2 lower teeth on each side and all the rest have only a single lower tooth on each side (battle teeth); lower jaw extends beyond upper jaw and tooth often sticks out on sides
• Most seem highly social and travel in groups, surfacing and diving in synchrony; mostly eat squid, but also deep-sea fish