Mammals of the World

Mammals are a class of warm-blooded vertebrates defined by several shared traits: they have hair or fur, they nourish their young with milk produced by mammary glands, and most give birth to live young. The class includes several thousand living species, ranging in size from tiny shrews and bats to elephants and whales. Their internal regulation of body temperature allows mammals to remain active across a wide range of climates, from polar regions to deserts and tropical forests.

Mammals are commonly grouped by lifestyle and anatomy. Carnivores such as lions, tigers, bears and jaguars are adapted for hunting, with teeth and claws suited to capturing prey. Primates, including monkeys and apes, have grasping hands and large brains. Hooved animals such as zebras and deer are typically grazing herbivores, while large mammals like elephants and rhinoceros shape the landscapes they inhabit. Many smaller mammals, including rodents and insectivores, fill important roles lower in the food chain. The island of Madagascar is famous for unique mammals such as lemurs that evolved in isolation.

Many mammal species are now under pressure from habitat loss, hunting and climate change, and a number are classified as endangered. Conservation efforts include protected reserves, breeding programmes and anti-poaching work aimed at species such as tigers, rhinos and elephants. The study of mammals draws on anatomy, behaviour, genetics and ecology to understand how these animals live and how they can be protected.

Frequently asked questions

What features define a mammal?

Mammals are warm-blooded, have hair or fur, and feed their young with milk. Most give birth to live offspring rather than laying eggs.

What are the main groups of mammals?

Common groupings include carnivores, primates, rodents, hooved grazing animals, marsupials, and large mammals such as elephants and rhinoceros.

Why are many mammals endangered?

Habitat destruction, hunting and poaching threaten species such as tigers and rhinos, which is why conservation and protected areas are important.