Exam 2 MM

Balaenoptera bydei

Bryde’s whale

3 prominent ridges

Balaenoptera ricei

Rice’s whale

Gulf of Mexico

Described in 2021 as a unique population of Bryde’s whale

Balaenoptera acutorostrata

Common minke whale

3 subspecies

Distinctive coloration

Standard minke whale

Dwarf minke whale

IUCN: Near Threatened

Balaenoptera bonaerensis

Antarctic minke whale

Megaptera novaeangliae

Humpback whale

Robust body

Long flippers with tubercles

Known for breaching & slapping waters

Feed in summer in polar waters

Give birth in tropical/subtropical waters

Eschritchtius robustus

Gray whale

Most primitive of baleen whales

2-5 throat grooves

No dorsal fin

Crenellations: series of low humps on the back

Stay near the coast, vulnerable

IUCN: critically endangered

Suborder Odontoceti

Toothed whales

Teeth on one or both jaws

Single blowhole

Males are bigger than females

6 families, 72 species

small-medium sized whales

streamlined bodies

echolocation

can stun prey with sonic bursts

Melon: fatty organ in forehead area

Capture individual prey

Echolocation

Sensory system based on hearing

Nature’s version of sonar

Emit sound waves from larynx through ring of muscle (travels 5x faster in water)

Focused & directed by the melon (oval mass of fat/wax)

Listen for echoes back from surrounding objects

Returned signals are picked up by oil-filled jaw & transmitted to ear

Brain analyzes echoes: time it takes echoes to return is how far away the object is, size of prey and direction

Physeter macrocephalus

Sperm Whale

Largest toothed whale

Deep diver

Significant sexual dimorphism

Short wide flippers

Hunted extensively during 20th century

Spermaceti

Spermaceti

Semi-liquid organ in head

Made of waxy esters

2.5 tons of a 30 ton animal

Used for echolocation & buoyancy

Heating & cooling of spermaceti through nasal passage

Monodon monoceros

Narwhal

Lives in arctic

Long straight helical tusk in males

What is the tusk in narwhals

A secondary sex characteristic

Elongated upper left canine

Nerved: hydrodynamic sensory capabilities

Senses Temperature and pressure

Delphinapterus leucas

Beluga whale

White as adults

grey as calf

lack dorsal fin

Most vocal of all whales

IUCN: Critically endangered

Family Ziphiidae

Beaked whales

Distinct beak present, head shape varies

Medium sized whales

No central notch in tail fluke

Not gregarious

Two longitudinal grooves beneath chin

Not well known because of deep-sea habitat low abundance

Family Delphinidae

4ft - 30ft

Large skull that houses melon

Males are usually larger than females

Gregarious: form pods

Altruistic behavior

Benefits of a pod

Enhances food searching effectiveness

Prey capture is increased

Predator avoidance

Increases reproductive efficiency

Orcinus orca

Killer whale

Found in all oceans

Apex predator

IUCN: data deficient

Populations often specialize in type of prey

Tursiops truncates

Common bottlenose dolphin

Most familiar of all cetaceans: coastal habitat, prevalence in captivity, common on TV, etc

Gently curved mouth line

Generic dolphin shape

Light gray to nearly black

“Bridle”

Teeth on top & bottom jaws

Diverse feeding behavior

Stenella attenuate

Pantropical spotted dolphin

Millions killed in tuna purse seines

Coastal & pelagic varieties subspecies

Stenella longirostris

Spinner dolphin

4 subspecies

small, slender, tropical dolphin

Dark gray back, light gray sides, white belly

Acrobatic displays: spinning

IUCN: Low risk

Family Phocoenidae

“Porpoises”

6 species in 3 genera

Coastally distributed

Generally small

Short jaws, no beak

Laterally compressed teeth

Eat fish, cuttle fish, and crustaceans

Gregarious, smaller schools than dolphins

Order Sirenia

4 living species, 1 extinct

Totally aquatic

Herbivores

Large, heavy bones to balance gas produced by gut

Paddle-like pelvic appendages

No blowhole

Sparse hair

Mammary glands under pectoral limbs

Evolved from common ancestor of elephants

Dugongs

Have tusks

Dolphin-like fluke

lack nails on flippers

Rostrum pointed downward to facilitate bottom feeding

Calves nurse upside down

Manatees

No tusk

Rounded paddle fluke

Nails present on flippers

Trichechus manatus

Western Indian manatee

Two subspecies

Florida Manatee

Antillean Manatee

Rotund, broad back

Long forelimbs

Small head

Lots of folds and wrinkles

Mobile lips with stout bristles

Large herds

IUCN: vulnerable

Trichechus inunguis

Amazonian manatee

Freshwater

Smallest, slender manatee

Smooth sking

Long flippers

Dark gray with pink belly

Large herds

IUCN: Vulnerable

Trichechus senegalensis

Similar to West Indian manatee, more slender

Coastal marine waters, lower rivers, and estuaries

IUCN: vulnerable

Dugong dugon

Dugong

Indo-pacific distribution covering 37 countries

Prefer shallow, protected bays

Tusks

Dolphin-like fluke

Lack nails

Hydrodamalis gigas

Stellar’s sea cow

Exterminated in 1768

Large body, small head

6-8 m long

Live in shallow subarctic Bering Sea

Hunted for food, skin, oil

Pre-exploitation: 1500 - 2000 animals

Whaling started

Dates back to 6,000 to 10,000 bc

Sustenance whaling

Hunted for meat and oil

Not organized

Baque whaling

1150’s in bay of Biscay

Seasonal trips to the English Chanel and Ireland

North Atlantic right whales

1600’s Industrial Whaling

Europeans started substantial exploitation of whales in North Atlantic

Late 1600’s Americans hunted off New England

Whales harpooned from small, open boats

Hunted for meat, “trail oil” to make soap and lamp oil

Targeted sperm whales and right whales

Japanese whaling

Archeological evidence for 13 species hunted before 200 bc

1700s whales herded into bays and harpooned

Hunted North Pacific right, humpback, fin, gray whales

Whaling effort was relatively low until 19th, 20th, and 21st

3 major periods of Modern Whaling

Coastal Finnmark Whaling

1864-1904

Concentrated whaling Antarctica

Global Whaling 1905-1924

Floating factories led by Norway & Britain

Open Seas Whaling 1925 - present

Now focuses Rorquals

Blue whales yielded 9000 gallons of oil

200,000 taken worldwide between 1924-1971

Fin whale was next

Pinneped reproduction

Highly seasonal, synchronized reproductive cycles

Usually only one offspring produced

All return to land or ice to give birth

Male Pinniped Reproduction

Penis contains baculum: strengthens penis and protects baculum

Testes: small & nonfunctional when non-mating - streamlining

Scrotum in Otariids

Para-abdominal in Phocids & Odobenids

Female Pinniped Reproduction

No unusual adaptations for aquatic life

Uterus is bicornuate

Ovulate from alternate ovaries at each postpartum estrus

Bicornuate

Upper parts of uterus are separate, lower parts are fused

Resource defense mating systems

Males defend resources used by females

Female defense Mating System

Follow & defend females directly

Harems, multiple, & single male groups

Scramble competition

Find one female, mate, move on to the next

Sequential defense

Sequentially defend single females through mating

Lekking

Aggregations of males engaging in competitive display to try to attract females

Otarid mating system

None are know to use scramble competition

Lekking is controversial

Phocid mating systems

Use all five types of mating systems

Walrus Mating System

Observed using resource defense & lekking

Female Choice

Incites male-male competition

Sperm competition

Otter Reproduction

Do not return to land to give birth

Seasonal reproduction

Delayed implantation

6-8 month gestation: rapid growth period 5-6 months

Can reproduce annually, but don’t always

Pups nurse for 4-8 months

Otter Breeding Behavior

Males defend territories when females are in estrus

Females come into estrus once a year - usually after weaning pup

Females choose a single male

Precopulatory behavior: touching, nuzzling, grooming

Rough treatment during mating to stimulate ovulation

Polar Bear reproduction

Dominated by sea ice cycle, food distribution

Fast during ice-free period July-November

Females come into estrus March-May with yearling or 2 yr old cubs

Delayed implantation for 4-5 months - ends when females den up in September

Gestation 3-4 months: altricial young produced

Produce young every 3-4 years

Sirenian reproduction

Little sexual dimorphism

Tusks grown in male dugongs

Females are sexually mature between 3-6 years

Dugongs sexually mature at 10 years

Mating is seasonal, but not coordinated

Mating is seasonal, but not coordinated

12-14 month gestation period

Usually single young: twins happen ~4%, but often fatal

Calves depend on mom’s for ~1 year, sometimes 2 if mom is young

Females calf once every 2.5-5 years

Females may postpone breeding if: Sea grass is rare, Increased in FL due to exotic weeds & power plants, Decreased in Amazon due to deforestation

Mating concentrate in spring time

Manatees mate in herds: 1 female followed by 25 or more males

Sirenian Males Reproduction

No baculum

Testes are located in abdominal cavity below kidneys same as elephants

Sirenian Females Reproduction

Uterus & ovaries are almost identical to African elephants

Bicornuate uterus

Conspicuous scaring from past pregnancies

Cetacean Reproduction

Some sexual dimorphism: sperm whales, killer whales and belugas

Cetacean Male Reproduction

No baculum

Penis is normally retracted into body

Cetacean Female Reproduction

Bipartite uterus: Fetus develops in one of the horns

Ovaries of baleen whales may weigh several kilograms

Dolphin ovaries weigh a few grams

Baleen Whale Reproduction

Regular migrations geared towards mating

Extremely long-lived produce young well into old age

Produce young every 2-years

1 year gestation

6-8 months of nursing

Minke whales breed annually

Right whales reproduce every 3-4 years

Toothed Whale Reproduction

Gestation periods usually less than a year

Variable lactation period

Few months in dolphins

Several years in pilot and sperm whales

Reproductive interval dependent on resources usually 2-5 yearsC

Cetacean Matting Patterns

Difficult to observe

No monogamy

Females are often promiscuous, which reduce male-male competition and promotes care of all young

Female choice: creates sperm competition, dead end pouches, male-male-aggression, verbal aggression