Marine Mammals

cetaceans and pinnipeds

Baleen whales

order Cetacea, filter feeders (baleens for filter feeding: fringelike plates of keratin that strain water for krill and other plankton), large bodied, 2 blowholes, includes: humpback, minke, fin, sei, bryde’s, right, gray, suborder Mysticeti

Toothed whales

order Cetacea, fish and squid eaters (swallowed whole), medium-bodied, 1 blowhole, includes: porpoises, belugas, beaked, dolphins, pilot, orca, sperm whale, suborder Odontoceti

Phocids (fam Phocidae)

true seals, order Carnivora, no external ear, dense fur, thick blubber, deep dives for hunting, swim with hind flippers, small front flippers used for steering, can’t “stand”, five prominent claws

Otariids (fam Orariidae)

sea lions, and walruses, external ear, swim with foreflippers, hind flippers for steering, less dense fur, thin blubber, can “stand”, shallow dives for hunting

Pinnipeds breeding method

harem (ex: Galapagos sea lion), lekking-like (ex: harbor seals), rich milk, 1 offspring per procution (b/c high weaning costs), long lived, slow population replacement, sexual dimorphism, seasonal breeding

Cetaceans breeding dynamics

physical competition, singing (ex: humpbacks), sexual dimorphism, seasonal breeding, rich milk, high weaning costs (1 offspring per production), long lived, slow population replacement

Pinnipeds

Phocids (true seals), Otariids (sea lions)

Cetaceans

Baleen whales, Toothed whales

Toothed whale communication

use echolocation

Baleen whales communication

use low-frequency vocalizations

SOFAR

sound fixing and ranging channel, naturally occuring ocean “channel” that allows sound to carry great distances

Pinniped diving adaptations - Oxygen

high blood volume, increased hemoglobin concentration (larger red blood cells), muscles with myoglobin, blood shunting, bradycardia: slow heart rate (to 1/10), “mammalian diving reflex”

Mammalian diving reflex

optimizes oxygen use by slowing heart rate (bradycardia), constricts peripheral blood vessels (redirects oxygen to brain and heart), response to cold water immersion

Whale diving adaptation - oxygen

high blood volume and hemoglobin concentrations, low circulation to extremities, increased muscle anaerobia (lactic acid tolerance), bradycardia, increased oxygen transfer efficiency, higher tidal exchange

Diving adaptions - pressure

exhale before diving, decreased nitrogen absorption (makes oxygen less available), Pinnipeds: inner ear sinus swells with blood (blocks air space, no need for equalizing), Whales: middle ear swells with blood, emulsified fat “foam” in whale lungs which absorbs N rather than the blood absorbing it

Pinnipeds diving adaptions - Temperature

low surface area to volume ratio, blubber, dense fur, oil glands make fur waterproof, counter current exchange (artery (hot) surrounded by returning veins (cool))

Whales diving adaptations - temperature

large body size (reduces SA:V ratio and retains heat), blubber, counter current exchange (limits heat loss in dolpin tails)

Diving adaptations - salinity

osmotic balance (mammals lose water to the ocean, hypotonic → hypertonic), metabolic water (90% from fresh food, fasting seals oxidize fat for water), Pinnipeds: highly efficient kidneys, Whales: specialized, large kidneys

Other threats to Cetaceans

bioaccumulation of toxins, ecotourism, climate change

Threats to Pinnipeds

hunting, competition with fisheries, entanglement, climate change