11. Mammals
What do you already know about aquatic mammals?
Contents
11.1 Mammal characteristics
Mammals are highly developed animals.- Like birds, they are warm-blooded.
- They have efficient respiratory and circulatory systems.
- They have well-developed senses.
- Their well-developed brains enable them to adapt to different circumstances.
- Many mammals are quick learners.
Mammals are found everywhere on the planet. The best-known orders of mammals are Chiroptera (bats), Cetartiodactyla (whales and even-toed ungulates = the animals with hooves), Carnivora (cats, dogs, seals, and others), Rodentia (mice, rats and other gnawing mammals) and primates (apes, monkeys, and others).
List of mammal genera 11.2 Many mammals live near the water
Most of the world's mammals need water only for drinking. However, some mammals species live all of their lives in or near the water. All aquatic mammals have descended from land-dwelling animals that have migrated back to water. Because of this, every aquatic mammal has lungs and needs to come up to the water's surface to breathe.
Beavers are rodents.
Whales have linear bodies that resemble those of sharks and other fish. They are the mammals most fully adapted to aquatic life. Whales give birth and raise their young in the water. The only species of whale found in the Baltic Sea is the endangered harbour porpoise.
Seals are likewise well adapted to aquatic life. Their body shape is ideal for diving and moving in the water, which probvides the seals an advantage when fishing. They only visit the land or the ice to rest and to give birth.
Minks and otters are predators that like to live near the water. Both of these species are mustelids.
Beavers and muskrats are rodents that like to live near lakes and rivers. Dam-building beavers are second only to humans when considering how much the species' actions modify Finnish water environments. Muskrats are rodents that have been brought to Finland from North America.
11.3 Seals are aquatic mammals
The Baltic Sea is home for two seal species. The larger of these two species is the gray seal. The Baltic ringed seal lives mostly in shore waters. However, the most well-known Finnish seal species is an endangered subspecies of the Baltic ringed seal living in Lake Saimaa, the Saimaa ringed seal.
Both the gray seal and the Baltic ringed seal have adapted to life in the water. They are quick swimmers that use their fin-like limbs to change direction quickly when chasing evading fish. Their bodies are streamlined and their skin is covered by a compact fur. A thick fat layer protects the seals from heat loss.
Both seal species have large eyes, which helps them to see in dark water environments. Seals also have sensory whiskers that help them navigate waters in almost complete darkness.
Seals have no gills, which means that they have to regularly come up to the surface for air. However, seals use oxygen very effectively, meaning that they can remain underwater for over 20 minutes at a time.
Grey seals give birth to light-furred pups on land or ice. In contrast, ringed seals give birth to their young in snowy caves. Seal mothers feed their young by giving them nutritious milk through their mammary glands.
A grey seal.