A Marine mammal is a mammal that has adapted to aquatic life and rely’s on the ocean to maintain a healthy, livable existence.
These amazing animals can be found living in all of the worlds major oceans from the tropical environments in and around the equator to the northern and southern polar hemispheres in and around the Arctic and Antarctic oceans.
Marine mammals share several characteristics that are common among all mammals such as the need to breathe air, being warm-blooded, having mammary glands which produce milk to feed their young, giving birth to live young (pregnancy/gestation periods) and in some cases having hair.
Here are several common characteristics found in marine mammals:
- Marine mammals breathe air – Although marine mammals live in and around the water they must come to the surface to breathe otherwise they’ll drown.
- Marine mammals are warm-blooded – In order to maintain their body heat marine mammals consume large quantities of calories and develop a thick layer of fat or blubber to keep their vital organs from freezing in cold environments.
- Marine mammals give birth to their offspring – Unlike fish and other aquatic animals whales do not lay eggs; instead they carry their children in their womb until they are born.
- Marine mammals produce milk – Marine mammals have mammary glands that produce milk which they use to feed their children. The milk is often full of fat and nutrients to help the child develop.
Marine mammal characteristics
While land mammals are similar in many ways marine mammals have adapted to deal with living in environments that are generally surrounded by water rather than being elusively surrounded by land, and way marine mammals live, hunt for food and navigate the world is largely dependent upon their oceanic environment and physical characteristics.
For example marine mammals such as whales, dolphins and porpoises have streamlined bodies designed to reduce water resistance when swimming, they also have specialized lungs and muscles designed to store oxygen, thick blubber or fat to help maintain body heat in cold environments, large veins to help transfer blood to vital organs in a cold water or when in deep waters where compression can become an issue and fins, flukes, and flippers to assist with swimming.
Other species such as polar bears have thick layers of fat and fur to help them maintain their body heat in cold climates, a large body to help keep them warm and disperse their body heat, thick curved claws for gripping the ice and predators, sharp teeth and strong jaws for tearing apart prey and powerful muscles for fighting and attacking.
Seals have thick layers of fat/blubber to help keep them warm, rounded bodies to help disperse their body heat, limbs designed for walking/waddling on land with webbed feet/flippers to help them swim and teeth which they use to grip onto their prey.
Seals, sea lions and walruses have a number of characteristics that are similar among the separate species but also share a few distinct differences as well.
For example walruses tend to have a stockier build than seals and sea lions and they also possess two large teeth that protrude from their mouth, similar to a saber toothed tiger only larger.
Seals also have separate distinct characteristics from sea lions such as having shorter for limbs with long claws, which requires them to waddle on land rather than walk and their strong rare flippers allow them to propel themselves through the water more effectively than sea lions.
While not all marine mammals share the same biological characteristics, (a clear example would be to compare polar bears to whales) they all live near or in the ocean and need the ocean for its supply of food and water in order to survive.
The distinct types of marine mammals
In terms of the various marine mammal species there are several distinct groups of marine mammals; sirenians (manatees and dugongs) cetaceans (whales, dolphins and porpoises), fissipeds, sea otters, pinnipeds (seals, fur seals, sea lions and walruses) and (as considered by some researchers and biologists) polar bears.
Both cetaceans and sirenians live in the ocean while polar bears, pinnipeds and fissipeds are land dwellers, but rely on the ocean to supply them with food and water.
As a whole there are over 125 recorded species of marine mammal inhibiting the ocean and native aquatic environments of the world.
Here is a list of the of individual sub groups within the marine mammal family:
- Cetaceans (whales, dolphins and porpoises)
- Pinnipeds (seals, fur seals, sea lions and walruses)
- Ursidae (polar bears)
- Sea otters
- Sirenians (manatees and dugongs)
Although these animals can be found throughout the world the highest concentration of marine mammals (about 40%) are found at or around 40° both north and south of the equator.
Marine mammals and the ecosystem
When it comes to survival and the food chain marine mammals play a large role in maintaining a healthy marine ecosystem, however since around 20% – 30% are considered endangered and/or threatened it raises some concerns on the impact of aquatic life and the impact humans have played in contributing to its condition.
The elimination of one species could significant decrease the chances of survival for another species, especially among species that rely on their prey for survival.
If their prey were to become extinct than the predators also face the possibility of extinction.
On the other hand if a predator were to become extinct they their prey could overpopulate and quickly consume their food supply leading to future starvation.
Although these are extreme examples they are important to point out as it is a possibility.
In order to better product these animals all marine mammals in the United States are protected by the Marine Mammal Protection Act created in 1972.
In addition to the Marine Mammal Protection Act other countries have also created laws designed to protect these animals and organizations have been created to bring awareness about the importance of protecting the endangered marine mammals as well as implement programs that are designed to aid in the recovery of certain species.