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mammal : any of a class (Mammalia) of warm-blooded higher vertebrates (such as placentals, marsupials, or monotremes) that nourish their young with milk secreted by mammary glands, have the skin usually more or less covered with hair, and include humans — Webster

OneLook, Free Dictionary, Wiktionary


Mammals are the vertebrates within the class Mammalia, a clade of endothermic amniotes distinguished from reptiles (including birds) by the possession of a neocortex (a region of the brain), hair, three middle ear bones, and mammary glands. Females of all mammal species nurse their young with milk, secreted from the mammary glands.

Mammals include the largest animal on the planet, the blue whale. The basic body type is a terrestrial quadruped, but some mammals are adapted for life at sea, in the air, in trees, underground or on two legs. The largest group of mammals, the placentals, have a placenta, which enables the feeding of the fetus during gestation. Mammals range in size from the 30–40 mm (1.2–1.6 in) bumblebee bat to the 30-meter (98 ft) blue whale. With the exception of the five species of monotreme (egg-laying mammals), all modern mammals give birth to live young. Most mammals, including the six most species-rich orders, belong to the placental group. The largest orders are the rodents, bats and Soricomorpha (shrews and allies). The next three biggest orders, depending on the biological classification scheme used, are the Primates (apes and monkeys), the Cetartiodactyla (whales and even-toed ungulates), and the Carnivora (cats, dogs, seals, and allies). — Wikipedia

Encyclopædia Britannica


Mammals – Mammalogy (Martindale’s Reference Desk)








Mammals (Smithsonian National Museum of Natural History)


WorldCat, Library of Congress, UPenn Online Books, Open Library




Introducing the Mammals (Biology4Kids)


OER Commons: Open Educational Resources



Science Daily,, NPR Archives






More News …

Mammals News -- ScienceDaily Mammals in the news, wild mammals, mammal conservation efforts, and domesticated mammals.

  • Data from thousands of cameras confirms protected...
    on January 27, 2022 at 5:01 pm

    Researchers at UBC's faculty of forestry analyzed data from a global data set drawing from 8,671 camera trap stations spanning four continents. They found more mammal diversity in survey areas where habitat had a protected designation -- compared to forests and other wilderness areas that lacked that designation.

  • Gene mutation that makes dogs small existed in...
    on January 27, 2022 at 4:43 pm

    Popular belief has been that small dogs, such as Pomeranians and Chihuahuas, exist because once dogs were domesticated, humans wanted small, cute companions. But researchers now identify a genetic mutation in a growth hormone-regulating gene that corresponds to small body size in dogs that was present in wolves over 50,000 years ago, long before domestication.

  • Microscopic inner ear structures reveal why major...
    on January 26, 2022 at 5:24 pm

    A new article compares the inner ear structures of the two main groups of bats. By examining the microscopic inner ears of bats from 19 of the 21 known bat families, the researchers were able to show that the presence of extra neurons and specialized ear structures align with a split in bat evolution revealed by DNA.

  • Study demonstrates accuracy of less invasive...
    on January 24, 2022 at 4:50 pm

    A recent study finds a technique that uses dried spots of blood to measure health indicators in elephants is comparable to techniques that use larger blood samples and require immediate cold storage -- technology that is not always available when monitoring animals in the wild.

  • New study determines parentage, age, and survival...
    on January 20, 2022 at 5:54 pm

    A new study is providing insight into North Atlantic right whale calf survival, growth rates, and life history, demonstrating the power of genetic sampling for this critically endangered species. - latest science and technology news stories internet news portal provides the latest news on science including: Physics, Nanotechnology, Life Sciences, Space Science, Earth Science, Environment, Health and Medicine.

  • Lighted nets dramatically reduce bycatch of...
    on January 21, 2022 at 4:14 pm

    In a win-win for commercial fisheries and marine wildlife, researchers have found that using lighted nets greatly reduced accidental bycatch of sharks, rays, sea turtles, and unwanted finfish.

  • Sex-typical behavior of male, female mice guided...
    on January 21, 2022 at 4:00 pm

    Male and female mouse brains differ in important ways, according to a new study led by Stanford Medicine investigators.

  • Rare baby elephant twins born in Kenya
    on January 20, 2022 at 2:58 pm

    An elephant in Kenya has given birth to twins, an extremely rare event, conservationists said Thursday.

  • Gene loss due to one-sided diet: Evolutionary...
    on January 20, 2022 at 2:47 pm

    A team of scientists from the Senckenberg Gesellschaft für Naturforschung, the LOEWE Center for Translational Biodiversity Genomics (TBG), and the Leibniz Institute for Zoo and Wildlife Research investigated whether evolutionary changes in diet can result in the loss of genes, using 52 recent and 31 extinct mammal species as examples. In their study, recently published in the Journal of Evolutionary Biology, the researchers conclude that the loss of the PNLIPRP1 gene is associated with a […]

  • Why do mitochondria look like they do?
    on January 19, 2022 at 4:30 pm

    One of the biggest challenges in biology today is to explain the structure of cristae, the inner membranes of mitochondria. An explanation in this case is a set of principles to predict what form the cristae will take after basic metabolic manipulations of the environment the mitochondria are in. These principles will therefore be a description of the true function of mitochondria, something that has so far only been scarcely imagined.


Here are links to pages about closely related subjects.

Knowledge Realm


Sphere Land, Ice, Water (Ocean), Air
Ecosystem Forest, Grassland, Desert, Arctic, Aquatic

Life Cell, Gene, Tree of Life
Plant Flower, Tree
Invertebrate Cuttlefish, Octopus, Ant, Bee, Butterfly, Spider, Lobster
Vertebrate Fish, Seahorse, Ray, Shark, Frog, Turtle, Tortoise, Dinosaur
Bird, Ostrich, Owl, Crow, Parrot
Mammal Bat, Rabbit, Giraffe, Camel, Horse, Elephant, Mammoth
Whale, Dolphin, Walrus, Seal, Polar Bear, Bear, Cat, Tiger, Lion, Dog, Wolf
Monkey, Chimpanzee, Human


1.   The resources on this page are are organized by a classification scheme developed exclusively for Cosma.