10.22: Mammal Classification

To what group do rats belong?

Rats are mammals, but this class can be divided into more specific groups. Rats are in a group known as rodents. Rodents are gnawing animals that include beavers, mice, and squirrels.

Groups of Mammals

Traditionally, mammals were divided into groups based on their characteristics. Scientists took into consideration their anatomy (body structure), their habitats, and their feeding habits. Mammals are divided into three subclasses and about 26 orders. Some of the groups of mammals include:

1. Lagomorphs include hares and rabbits. Rabbits and hares characteristically have long ears, a short tail, and strong hind limbs that provide for a bouncing method of locomotion. They are all are small to medium-sized terrestrial herbivores.
2. Rodents include rats, mice, and other small gnawing mammals. They have a single pair of continuously growing incisors (teeth) in each of the upper and lower jaws that must be kept short by gnawing.
3. Carnivores include cats and lions and tigers, dogs and wolves, polar bears, and other meat eaters.
4. Insectivores include moles and shrews (Figure below). These mammals eat primarily insects, other arthropods, and earthworms.

Figure \(\PageIndex{1}\): One of the subgroups of mammals is the insectivores, including this shrew.

5. Bats include the vampire bat. These mammals have forelimbs that form webbed wings, making bats the only mammals naturally capable of true and sustained flight.
6. Primates include monkeys, apes and humans. These mammals are characterized by detailed development of the hands and feet, a shortened snout, and a large brain.
7. Ungulates include hoofed animals, such as deer, sheep, goats, pigs, buffalo, elephants and giraffes (Figure below). These mammals use their hoofs to sustain their whole body weight while moving. Hoofs are formed by a thick nail rolled around the tip of the toe.

Figure \(\PageIndex{2}\): The ungulates (hoofed animals), like the giraffe here, is one of the subgroups of mammals.

Mammals can also be grouped according to the adaptations they form to live in a certain habitat. For example, terrestrial mammals with leaping kinds of movement, as in some marsupials and lagomorphs, typically live in open habitats. Other terrestrial mammals are adapted for running, such as dogs or horses. Still others, such as elephants, hippopotamuses, and rhinoceroses, move slowly. Other mammals are adapted for living in trees, such as many monkeys (Figure below). Others live in water, such as manatees, whales, dolphins, and seals. Still others are adapted for flight, like bats.

Figure \(\PageIndex{3}\): This howler monkey shows adaptations for life among the trees.

Summary

• Traditionally, mammals were divided into groups based on their anatomy (body structure), their habitats, and their feeding habits.
• Subgroups of the mammals include rodents, carnivores, insectivores, bats, and primates.

Explore More

Use the resources below to answer the questions that follow.

Explore More I

• Mammal Conservation in Island Ecosystems at http://www.youtube.com/watch?v=JlsbH-MGsMI (5:21)

1. What is the average size of a mammal?
2. What groups of mammals are most abundant?
3. How often does Dr. Healey find new species in his work?
4. How does the diversity of bats compare to the diversity of other mammals in the Philippines? What does this tell you about generalized statements about species diversity?

Explore More II

• Platypus Parts at http://www.youtube.com/watch?v=QNoQvjlmGdk (3:44)

1. Where does the platypus (Ornithorhynchus anatinus) live?
2. What do platypus eat?
3. How do platypus look for food?
4. What is the purpose of the "spur" on males?

Review

1. What are rodents? Give two examples.
2. What are characteristics of primates. Give three examples of primates.
3. What are ungulates? Give four examples.
4. List five examples of carnivores.