{Marine Mammals

“Adaptations of Mammals in Marine Environments”

Animals well adapted to the extreme temperatures, depths, pressure, darkness and density of the medium in which they live.

Characteristics of Marine Animals include:

Breathe air through lungs.

Are warm-blooded.

Have hair at some time during life.

Bear live young.

Nurture their young.

Marine Mammals

Generally, marine mammal lungs are proportionately smaller than humans but they:

Use oxygen more efficiently.

They fill their lungs and exchange 90% of the air with each breath.

Have high blood volume.

Blood chemistry allows greater oxygen retention. (Myoglobin, an oxygen carrying compound found in the muscles of marine mammals, provides a crucial additional store of oxygen.)

Deep Diving

Have a high tolerance to lactic acid and carbon dioxide.

Their muscles can work anaerobically (without oxygen) while they hold their breath.

Can tolerate tremendous atmospheric pressure at great depths.

Lungs and ribs are collapsible, air spaces are minimized and nitrogen absorption is limited.

Deep Diving continued . . .

Drag is reduced by hydrodynamic body form.

Appendages are modified for maximum propulsion and minimal drag.

Swimming Adaptations

A large body with small surface-to-volume ratio reduces heat loss.

Blubber or thick underfur is used as insulation.

Complex circulatory system in extremities is used to conserve and dissipate heat.

Young Pinnipeds (ex. Seals) and Cetaceans (ex. Whales) grow fast on milk with 40% to 50% fat.

Human milk is 3.3% fat.

Thermoregulation

Most marine mammals rarely drink fresh water, instead they:

Utilize water present in their food, inspired air and blubber.

Have specialized kidneys that produce urine that is saltier than seawater.

Water Conservation

Many marine mammals communicate with sound:

Echolocation – emit sounds or clicks in the environment and wait for the echo of those calls to return to them from various objects around them. (Navigation and Hunting)

Tactile senses are acute.

Pinnipeds (ex. Seals) and Fissipeds (ex. Sea Otter) have well developed facial whiskers.

Sensory Adaptations

Seals – “True Seals”

Lack ear flaps

Rear flippers point backward (Do not aid in walking on land. Very clumsy on land!)

Swim with efficient, undulating whole-body movements

Built for deep and long diving and long distance migration

Communicate by slapping the water and grunting

Order Pinnipedia

Sea Lions – “Fur Seals”

Very vocal and social animals

Have ear flaps

Hind flippers can rotate underneath them

Fore flippers are used as primary source of propulsion

Order Pinnipedia

Found near the Arctic Circle

Extremely sociable and extremely prone to loud bellowing and snorting

Tusks are used to haul their enormous bodies out of frigid waters or to break breathing holes in the ice from below.

Able to slow their heartbeats to withstand polar temperatures.

Feed off of shellfish on the bottom that they detect using their whiskers.

Order Pinnipedia - Walrus

Found along the coasts of the Pacific Ocean in North America and Asia.

Eat, sleep, hunt, mate and give birth in the water.

Entangle themselves in forests of sea kelp to provide anchorage.

Use rocks as tools to crack open mussels.

Have webbed feet, water repellent fur to keep them dry and warm, and nostrils and ears that close in the water.

Order Carnivora - Sea Otter

Roam the Arctic Ice Sheets.

Strong swimmers and front paws are slightly webbed.

Thick white fur to keep warm and blend in with ice and snow.

Black skin to soak up sun’s warming rays.

Prey on seals and sometimes dead whale carcasses.

Give birth in winter to twin cubs that they care for the next 28 months.

Order Carnivora - Polar Bear

Mostly Herbivorous

Up to 12 feet in length and nearly 2 tons

Tropical to subtropical locations

Must have access to fresh water for osmoregulation

Greatest threat is from humans.

Direct impact by boat propellers

Coastal habitat destruction

Thought to have inspired Mermaid myths.

Order Sirenia – Manatees and Dugongs