Download presentation
Presentation is loading. Please wait.
1
Marine Mammals—Cetaceans and Sirenians
Lecture 9
2
Marine Mammals—Cetacean origins
Share a common ancestor with the modern hippopotamus Pakicetus > 50 mya—whale-like skull Mainly terrestrial, foraged in freshwater Ambulocetus < 50 mya—vertebrae suggest undulation swimming Coastal species—still bred on land
3
Marine Mammals—Cetacean origins
Protocetids—a diverse group 45-35 mya Larger global distribution—open water Large nasal openings—higher on head; eyes lower Dorudontids < 40 mya— over 15 feet long Dorsal nasal openings; tail fluke Toes still evident; vestigial hind-legs
4
Order Cetacea Two major groups of cetaceans
Mysticeti—baleen whales 15 species Odontoceti—toothed whales (and dolphins) 75 species—5 freshwater Possess all mammal characteristics— ____________ evolution more fish like
5
Cetacean Characteristics
Well developed tail—undulations dorsoventral Why dorsoventral? Vestigial hind limbs Hair eliminated—streamlining
6
Cetacean Characteristics
Nostrils top of head—blowhole No pharynx Most odontocetes have lost smell Blubber—insulation, buoyancy, energy storage Up to 1 foot thick Capillaries constrictable
7
Blubber Historically, whales hunted for blubber
Food, lamp oil, soap, margarine, cosmetics, candles Harpoon tip (1880) in bowhead whale
8
Echolocation Natural SONAR system
Odontocetes Sounds (clicks, whistles) produced—phonic lips
9
Echolocation Odontocetes vary frequency and duration of clicks
Can produce > 1000 per second Frequency often too high for humans Higher frequency short range & small prey Differences in echo timing density differences Solid structures Fish buried in sand Melon acts as a lens—direction and width of sonic signals can be modified
10
Echolocation—Sperm Whales
11
Cetacean Hearing Inner ear outside skull
Minke Whale Inner ear outside skull External ear canal vestigial Acoustic fats—channel sound toward inner ear Amplified Dolphin
12
Mysticete sound production
Lack phonic lips and melon No echolocation Boat collisions Sound produced with larynx Supported by cartilage and muscles Tissue folds vibrate—resonation chamber Air recycled Variable among species
13
Humpback vocalizations
Whalesong—males on breeding grounds repeat 5-20 minute-long “song” Projects > 20 miles Song is population-specific Evolves over time Bubble-net feeding
14
Mysticete Feeding Baleen—fibrous-keratin plates hang from upper jaw
Inner surface bristled Evolved 25 to 30 mya Embryonic mysticetes have teeth precursors Tongue removes strained prey Largest animals in history
15
Mysticete Feeding—Family Balaenidae
Right Whale
16
Mysticete Feeding Gray whale Rorqual Whales Pleats
17
Odontocete hunting Common odontocete hunting tactics
Coordinated group hunting common Population & individual-specific hunting tactics Learned behavior & innovation Foraging specialists— Reduces competition Pacific & Antarctic Killer whales Dolphins in Florida Bay Common odontocete hunting tactics Chasing, herding, echolocating buried prey, stealing from fisherman
18
Odontocete hunting Strand feeding
19
prey-specific strategy
Odontocete hunting Mud-ring feeding prey-specific strategy
20
Osmoregulation Poorly understood compared to other vertebrates
Water gained from prey Well developed kidneys Seawater is not ingested Unless fasting Concentrated urine eliminates salt Respiration loss minimized efficient O2 extraction Metabolic water—
21
Cetacean diving Oxygen storage ability Some species have large lungs
Large tidal volume—highest among vertebrates Large airways High blood volume concentration of RBCs RBCs with hemoglobin Muscles myoglobin Narwhal ½ O2 in muscles Up to 40’
22
Cetacean diving Breath holding at surface—
Heart rate slows when diving Blood flow to extremities and guts restricted Lungs collapsible, air nonrespiratory areas Rib cage flexible Artery Counter-current heat exchange in tongue Veins
23
Migration More common among mysticetes
Breeding/calving areas in tropical latitudes Feeding in temperate or polar regions
24
Reproduction Poorly documented in most species Internal fertilization
Internal—protrusible penis 10 feet long in blue whale Males aggressive with eachother Courtship displays common Fat-rich milk Blue whale calf up to 200 lbs. per day
25
Reproduction—vulnerable life-history
Age at maturity variable—average 10 years Males later for some species One calf Gestation months Timed with migration for mysticetes Breed every other year at most Some species females 5 year interval 1+ years of infant care Life-span variable 40 to 130+ years
26
The Mighty Manatees Order Sirenia (dugongs & manatees) shares common ancestry with elephants 1rst appear 50 mya Peak diversity ~20 mya Only herbivorous fully aquatic mammals in history Two genera 3 sp. manatee 1 sp. dugong
28
Manatee Characteristics
Dorsal placed nostrils Nails on flippers Vestigial hind limbs
29
Manatee Characteristics
Small brains Manipulative lips Tactile sensory whiskers
30
Manatee Characteristics
Osmoregulation Need to drink freshwater Freshwater springs Effective kidneys Diving physiology Large dorsal lungs Short dive duration < 20 min
31
Manatee Characteristics—feeding
High food intake—5-7% of body wt. per day Aquatic plants—non algae May consume animals—tunicates, entangled fish ~60’ of intestines Gut microbes Tooth replacement throughout life Slow metabolism Marching molars
32
Florida Manatee The largest Sirenian
> 3000 lbs, 12 feet Restricted to Florida during winter Freshwater springs Migrate as far north as Virginia in summer Possess layers of blubber Less developed than cetaceans
33
Manatee Threats Slow population growth Hunted for meat
1 calf per female every 2-3 years Hunted for meat Presently very rare in Florida Habitat loss/deterioration Fishing gear interactions Boat strikes—25% of FL mortality Florida Manatee ~5000 individuals Endangered
Similar presentations
