What is a mammal?
A Mammal is a warm-blooded animal that gives birth to live young and nurtures them with milk producing glands.
Mammals are the last major group of animals to appear on the Earth. They have diversified into an amazing array of shapes and sizes which has been the key to their success.
There are around 4,500 – 5,000 species of mammal ranging greatly in appearance from small bats and shrews to huge sea dwelling creatures such as the Giant Blue Whale.
The Giant Blue Whale is around 100 million times larger than the worlds smallest mammal, the Kitti’s Hog-nose Bat.
Most mammals have a bony skeleton which is often covered in fur or hair and functions as protection to delicate skin, insulation for body warmth and camouflage. Mammals also have skin glands, among which are sebaceous glands which allow the animal to sweat. Mammals are endothermic which means they are able to maintain a constant body temperature which is often higher than that of their surroundings and environment.
Mammals breath air into their lungs. The oxygen in the air is required to release energy from food. Aquatic mammals also require oxygen and regularly surface from the water to breath. Small mammals such as Shrews need to move around much faster than large mammals in order to stay warm. They require 20 times more air than larger mammals such as zebras and elephants.
The Ten Characteristics of A Mammal
From the majestic blue whale navigating the vast oceans to the tiniest bat fluttering in the twilight, mammals are a remarkably diverse and fascinating group of animals.
Despite this diversity, all mammals (well almost all of them) share a set of distinct characteristics that set them apart from other members of the animal kingdom. Here are the ten defining characteristics of mammals, offering insights into the unique adaptations and evolutionary paths that have shaped this vibrant class of creatures.
- Warm-Blooded (Endothermy): Mammals are endothermic, meaning they can generate their own body heat and maintain a constant internal temperature regardless of the external environment.
- Hair or Fur: All mammals have some form of hair or fur at some stage of their life. This serves various functions including insulation, camouflage, and sensory perception.
- Mammary Glands: Female mammals have mammary glands that produce milk, which they use to nourish their young. This is where the name “mammal” comes from.
- Live Birth (Mostly): The vast majority of mammals give birth to live young. However, there are exceptions like the monotremes (e.g., the platypus and echidnas) which lay eggs.
- Three Middle Ear Bones: Mammals possess three bones in the middle ear: the malleus, incus, and stapes (also known as the hammer, anvil, and stirrup, respectively).
- Neocortex in Brain: Mammals have a more developed neocortex, a part of the brain responsible for sensory perception, cognition, generation of motor commands, spatial reasoning, and, in higher mammals, language.
- Single Jawbone: Mammals have a single bone on each side of the lower jaw (the dentary), which articulates directly with the skull.
- Specialized Teeth: Most mammals have heterodont dentition, meaning they have different types of teeth (e.g., incisors, canines, premolars, molars) designed for different functions such as cutting, tearing, and grinding.
- Diaphragm: Mammals possess a diaphragm, a sheet of muscle that separates the chest from the abdomen and is crucial for respiration.
- Four-Chambered Heart: Mammals have a heart with four chambers – two atria and two ventricles – which allows for efficient separation of oxygenated and deoxygenated blood.
Mammals are warm blooded animals that feed their young on milk. Milk producing glands are only found in mammals. Their milk provides nourishment to their young, removing the need for infants to initially have to forage for food. The milk also contains anti-bodies which helps prevent diseases in the young.
Mammals are divided into three groups differentiated by their breeding habits. All mammals give birth to live young with the exception of the Monotremes which includes the Duck-billed Platypus and the 7 species of Spiny Anteater or Echidna.
These are the only mammals that lay soft-shelled eggs which hatch after a short incubation period. Monotremes only have a single rear opening called a Cloaca into which the urinary, alimentary and reproductive systems open.
The two main reproductive groups are the placentals and the marsupials. Placentals are animals that have a placenta in which the young are nourished and developed. Most mammal infants in this group are born fairly well developed, although they do still require parental care in which the young remain close to their parent until they are old enough to hunt for food themselves.
Marsupial infants are born after a short gestation period in an almost embryonic form. The young attach themselves to a nipple in their mother’s pouch and suckle milk while they continue to complete their development. Marsupials are divided into seven orders and include Possums, Opossums, Bandicoots, Koala Bears and Kangaroos.
Many mammals live in groups or communities which provides protection and safety in numbers. This is because the most dangerous time in an animals life is just after birth when they are vulnerable and can be preyed upon by other animals.
Mammal Habitats and Movement
Mammals live in a vast range of different habitats such as oceans, tree tops, burrows and on plains. Different mammals have adapted to survive and move around in their chosen habitat. As many need to find food, shelter and breeding mates, they have to be able to move quickly through their habitats to avoid carnivorous predators.
Aquatic mammals have developed flippers instead of legs to enable them to glide and swim through the water in search of prey and to make speedy escapes when being preyed upon. Mammals that live in trees are usually agile creatures that can move from tree to tree quickly and easily such as monkeys. Some monkeys have a prehensile tail which helps them swing and climb.
The slowest mammal in the world is the Sloth who moves around at a mere 15 – 30 centimetres (0.5 – 1 feet) per minute. Some mammals are extremely fast such as the Cheetah who is the fastest mammal on Earth. The Cheetah can reach speeds of over 105 kilometres per hour, however, it can run out of energy in just 30 seconds after a fast sprint.
Most mammals that live on the land walk around on four legs, however, some are adapted to walk on two legs such as kangaroos and humans.
Different mammals have different feeding habits. Some are insect eating animals known as insectivores who forage for slugs, worms, insects and snails. There are around 345 mammal species that are insectivores. Most have long snouts, small eyes and very sharp teeth. Insectivores include Shrews, Moles, Hedgehogs and the Xenarthran group which includes the Anteater, Sloth and Armadillo.
Herbivorous mammals feed upon grass, shoots, leaves, fruits and plants. Many have a preference to certain plant parts or particular fruits or leaf types. Some herbivores require specialized feeding adaptions such as grinding teeth to chew tough plant material. Herbivorous mammals include Deer, Antelope, Elephants, Zebra and Rabbits.
Carnivores are meat eaters. An animal may be considered a carnivore if it prefers feeding on animal matter over plant matter.
Carnivorous mammals feed on other animals and have to locate, kill and then eat their prey. Some have specialized prey detecting adaptations such as stalking and ambushing as in large cats. An apex predator is a carnivore that sits at the top of the food chain such as predators like big cats (lions and tigers), crocodilians, hyenas and wolves.
Omnivores and scavengers feed on a wide variety of foods and are species that eat both plants and animals as their primary food source. Most lack specialized feeding adaptions. Instead, omnivores require behavioural and anatomical flexibility to locate, process and utilize their wide range of food.
Pigs are one well-known example of an omnivore. Humans are also omnivores.
Most bear species are considered omnivores, however, individuals diets can range from almost exclusively herbivorous to almost exclusively carnivorous depending on what food sources are available in their environments and what season of the year it is.