Marine Mammals
Phylogeny of Marine Mammals Four groups of marine mammals are separate evolutionary lines each entering the marine environment independently Whales share a common ancestor with even-toed ungulates (cattle) Sirenians share a common ancestor with the Proboscidea (elephants) Otters are a separate evolutionary line from the walruses, seals and sea lions all of which share a common ancestor with other carnivores
Whales Pinnipeds Sea Otters Sirenians
Marine mammals, birds,and reptiles are all classified in the Phylum Chordata, Subphylum Vertebrata. Know the Class and Order associated with each of the groups of marine mammals.
Order Cetacea The Whales
The Whales Group of mammals which includes whales, dolphins, and porpoises Natural selection forces have produced convergent evolution for the cetaceans stream-lined body form Cetaceans front flippers have the same bone structure found in other mammals Cetaceans have reduced pelvic girdle 1. lost hind limbs as adults 2. hind limbs are present in the embryonic stage
Natural selection on different marine organisms has produced an efficient, streamlined body form with counter shading in three separate evolutionary lines. This is called convergent evolution.
Fetus of a white-sided dolphin. Two pairs of limbs are present at this stage of development. The limbs will disappear before birth.
The Whales No external ears holes are plugged with wax (in some) Flukes are horizontal on tail (contrast this with the vertical upper and lower caudal fins in fish) Blow holes nose migrated to the top of the head Blow spouts - water condensation in the lungs, sea water, and mucous; exhale when surfacing then inhale Cetaceans can fill a lung volume 3000X larger than a human in one half of the time
The Whales All Cetaceans have a blubber layer 1. increases buoyancy 2. provides insulation against cold water Very little body hair, produce milk, nurse their young Mostly marine (approximately 90 species of marine mammals), 5 species of freshwater dolphins
Whale diversity: Baleen and toothed whales
Great whales can be identified from a distance by their blowing pattern their surface outline at the start of a dive, and how they dive (portion of their body visible at the end of the dive (fin or fluke)).
Baleen Whales Baleen whales have fibrous plates on the upper jaws 1. baleen is made of keratin (protein) 2. there are different types of baleen plates 3. large surface area, strain small planktonic organisms out of the sea water 4. tongue is used to scrape the plankton off of the baleen plates Baleen whales are the largest organisms which have ever lived
Baleen Whales Among the baleen whales, the females are much larger than the males 1. females 110 feet in length 2. males - 80 feet in length 3. weight - 90 to 100 tons (remember that 1 ton = 2000 lbs)
Baleen Whales Humpback Right Bowhead Minke Blue Fin Sei Gray
Baleen Whales Feeding Styles Gulping feeding style - huge gulps of water, accordion pleats on the abdomen (Blue Whale) Skimming feeding style - leave the mouth open, water moves through the baleen as the whale swims (looks like it is smiling!) - Right Whale Bottom feeder - stir up sediment on the bottom, filter out the benthic organisms creates feeding pits on the ocean bottom Gray Whale Humpback Whales make bubble curtains analogous to a net small plankton will not pass through the bubble curtain whales take turns feeding in the enclosed area
Comparison of the diet composition of several great whale species.
Comparison of baleen plate filtering mechanisms in great whales.
Toothed Whales Includes dolphins, porpoises, killer whales (Orcas), sperm whales In contrast to the herbivorous baleen whales, the toothed whales are carnivorous (have teeth) 70-80 species of toothed whales Largest toothed whale is the Sperm Whale
Toothed Whales Dolphins & Porpoises Killer Whale Sperm Whale
Sperm Whale Factoids Eat giant squid Can dive 3000 meters and stay submerged for up to 90 minutes Moby Dick was a sperm whale, based upon a real rouge Sperm Whale which ranged off of the Massachusetts coast in 1830's and 1840's which attacked whalers
Sperm Whale Factoids sperm whales have a substance called spermaceti in their heads which was used for lamp oil ambergris - sticky material found in the gut of sperm whales derived from squid beaks and other undigested proteins; ambergris is used in the manufacture of VERY expensive perfume (Older French scents such as Joy, White Shoulders, etc.)
Toothed Whales Orca s striking black and white pattern - counter shading; common to many marine organisms (light on the bottom, dark on the top) 1. eat seals, penguins, large fish 2. will tip over ice flows to get at the seals on the ice 3. travel in pods (small social groups of related members) 4. mate for life Porpoises have blunter faces than dolphins (extended noses)
Spinner dolphin (Stenella Longirostris) in the eastern Pacific photographed alongside a ship.
Dolphins Highly social Live in pods Ride bow waves from boats and whales allows them to swim fast with very little effort. Dolphins use echolocation to find prey similar to the mechanism used in bats.
Pacific white-sided dolphin (Lagenorhynchus obliguidens) cruises in the bow wake of a research vessel.
Echolocation in dolphins uses a series of clicks created by pushing air through the melon and internal passages.
Naval SONAR research in the Hawaiian islands has negatively affected the ability of whales in the area to hunt and navigate. Whale strandings in areas of SONAR research have increased. Calls for a moratorium on SONAR testing in areas where whales and dolphins feed, breed, and migrate have increased.
Dolphin Beluga Humpback
Day 2
Cetacean Social Interactions Toothed whales are very social and form social groups Killer Whales (Orcas) and Sperm Whales form tight pods ( 10 to 40 individuals) Among Orcas, pods are usually 10 or fewer individuals a. dominant male b. mature females c. calves d. subordinate males
Cetacean Social Interactions Sperm whales pod sizes very in accordance with the season a. harem pods b. nursery pods c. bulls/schools of mature males d. schools of calves and juveniles e. bachelor pods - schools of immature males Sperm whales will surround an injured pod member to protect it
Spying behavior in Orcas (a), Sperm Whales surrounding an injured pod member (b), and bottlenose dolphins carrying a stunned pod member to the surface so that it can breathe.
Cetacean Social Interactions Most whales mate belly to belly this behavior serves other social functions in addition to mating. Humpback whales have long intricate mating songs (10-15 minutes in length). Whales songs appear to be socially transmitted; dialects of the songs are specific to regions of the world s oceans.
Mating behavior in Gray Whales (a) and Humpback Whales (b). Mating pair (a) belly to belly and supported with the assistance of a third whale. Humpbacks actually surface belly to belly, roll, and slap flukes as part of the courtship rituals leading to mating.
Humpback Whale Songs For 10 years, Humpback songs off of the eastern Australian coast were consistent. Two new males appeared from the western Australian coast with a different song pattern. Within three years, the entire 2000 male population had incorporated themes from common to the western dialect. This suggests that Humpback Whale song patterns are learned behavior!
Whale Reproduction whale gestation takes 11-12 months, sperm whales - 16 month gestation born tail first to prevent the calf from breathing in water once the calf is born, swims to the surface to breathe
Commerson s dolphin (Cephalorhynchus commersoni) giving birth in captivity.
Whales feed in colder polar regions during the summer and migrate to warmer tropical areas to give birth during the winter. Note that because the seasons are reversed, northern and southern hemisphere whales never meet.
Whale Reproduction Birth weight/size in whale calves is relatively large compared to the parent in the mammal world, grow very rapidly Blue Whale calves gain 200 lbs/day for the first 17 months. Whale milk is extremely rich, 16-40% fat. Calves nurse for 4-8 months depending upon the species, calves may also nurse from related females. Can drink the equivalent of 400 glasses of milk a day
Whale Reproduction Sperm Whale and Gray Whale mothers are extremely defensive of their calves. Whales have very low reproductive rates; this makes it difficult to replace members removed from the population at rates exceeding natural mortality such as hunting Mature females reproduce every 1 to 4 years, baleen whales every 2 years, dolphins every 3-4 years.
Whale Life History Facts Age at maturity averages 20 years (9 years for female sperm whales, 20 years for male sperm whales) Whale life span: 20 to 40 years on average; may live to 80 years in the larger baleen whales
1. Right, bowhead, blue, fin, and humpback whales remain endangered even though there is an international whaling ban. 2. Seals and sea birds which competed with the great whales for food have all increased in population size as a result of the demise of the great whales.
Whale Strandings Occurs more often among the toothed whales may relate to the social nature of toothed whales 1. injury to a pod member 2. navigational error 3. food 4. toxins 5. parasites 6. percentage returned to the water is very low, they may re-strand themselves
Whale Strandings sperm whales, pilot whales, orcas, bottlenose dolphins, false killer whales are the most commonly stranded toothed whales 20-30 strandings on the GA coast annually, most frequently bottlenose dolphins or pigmy killer whales
Order Pinnipedia Sea Lions, True Seals, Walrus
Order Pinnipedia Streamlined bodies with flippers Excellent swimmers Unlike Cetaceans, must come onshore to rest and mate Restricted to cold water habitats Layers of blubber for buoyancy and insulation as in Cetaceans Predaceous feed on fish and large swimming invertebrates (nekton)
Pinnipeds True Seals Sea Lions Walrus
True Seals Largest group of pinnipeds Hind flippers can not move forward Swim by undulating their entire body No external ears Harbor seals, elephant seals (largest males 20 ft), monk seals (Hawaii, Mediterranean all endangered) Seals have been hunted traditionally for meat, oil, fur hunting has been limited to a few native Inuit tribes, seal populations are recovering
True Seals Weddell Seal Leopard Seal Elephant Seal Munk Seals
Sea Lions Can be distinguished from seals by the presence of external ears Can turn their rear flippers forward, use front flippers for locomotion (in contrast to seals) Includes fur seals and the California Sea Lion Sea lions are killed in fishing nets; killed/shot by fisherman who believe that they are competing with the sea lion for commercial fish. Sea lions practice harem breeding. Large males are territorial and protect a group of reproductively mature cows.
Sea Lions & Eared Seals Steller s Sea Lion California Sea Lion Northern Fur Seal
Walrus Only one species of walrus, found in the Arctic Ocean No external ears Tusks appear to be largely used for mating displays/territorial defense Benthic feeders
Walrus (Odobenus rosmarus) relaxes on Artic ice.
Order Carnivora Sea Otters
Sea Otters spend their entire life in the water (except in the event of severe storm) no blubber, fur which traps air eat sea urchins, abalone, mussels, crabs hold babies on their bellies live in kelp forests, wrap themselves in fronds of kelp which prevents them from being carried away by currents
Sea Otters Abalone fishers protest the protection of the sea otters. Important relationship between the sea otters, the sea urchins, and the kelp (keystone predator). 1. Sea otters decline, feeding on sea urchins decline, sea urchin populations explode. 2. As the sea urchin numbers increase, destruction of the kelp forests increases. 3. Abalone need the kelp forests to survive.
Order Sirenia Manatees and Dugongs
Manatees and Dugongs Four species (all endangered) Dugong in East Africa, Western Pacific Islands and Manatee in Amazon basin, West Africa, and the Southeastern United States. Spend entire life in the water Herbivorous: graze on Manatee Grass (Syringodium)
Manatees and Dugongs Blubber layer present, very wrinkled skin, few hairs present on face Extremely slow moving Nose on top of head at anterior, blow air out when it surfaces (you can hear it if you are close enough). Can reach 15 feet in length, 1300 lbs. Sirenians produce one calf every three years.
Manatees and Dugongs The majority of manatee deaths in the US: boating accidents, especially in Florida as coastal development increases.
Dugong Order Sirenia, Sea Cows Manatee