Mammals · Primates · Big cats · Marsupials
Mammal Facts Answered
Mammals are warm-blooded vertebrates with fur and milk production — from the 2-gram bumblebee bat to the blue whale. This hub answers 12 common mammal questions with sourced facts and links to 25 WARN wildlife guides.
- ~6,400
- Living mammal species recognised worldwide
- 1,300+
- Mammal species listed as threatened on the IUCN Red List Source: IUCN Red List
- ~60%
- Primate species at risk — highest share of any mammal group Source: IUCN Primate Specialist Group
- 180 t
- Maximum mass of the blue whale — largest mammal ever
Seven mammal questions answered
Direct answers for search and AI Overviews — each links to a full briefing.
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What is a mammal?
Mammals are warm-blooded vertebrates with hair or fur, three middle-ear bones, and females that produce milk to nurse young. Humans, dogs, whales, bats and elephants are all mammals.
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Are bats mammals?
Yes. Bats are mammals — the only mammals capable of true powered flight. They nurse pups with milk and are warm-blooded.
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Do any mammals lay eggs?
Yes. Monotremes — the platypus and four echidna species — lay leathery eggs and are the only egg-laying mammals. They still nurse young with milk.
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What is the largest land mammal?
The African bush elephant (Loxodonta africana) is the largest land mammal — bulls can exceed 6 tonnes and 3.3 metres at the shoulder. Asian elephants are slightly smaller.
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What is the smallest mammal?
The Kitti’s hog-nosed bat (bumblebee bat) of Thailand and Myanmar weighs about 2 grams — the smallest mammal by mass. The Etruscan shrew rivals it for smallest body length.
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Why are big cats endangered?
Big cats — lions, tigers, leopards, jaguars, cheetahs and snow leopards — face habitat loss, prey depletion, poaching for skins and bones, and retaliatory killing after livestock attacks.
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How long do elephants live?
Wild African elephants often live 60–70 years; Asian elephants typically 48–60 years. Captive elephants may live longer with veterinary care but face welfare challenges in inadequate facilities.
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Mammal FAQs
- What defines a mammal?
- Hair or fur, three middle-ear bones, and females that produce milk. Most give live birth; monotremes (platypus, echidnas) lay eggs but still nurse young.
- Which mammal group is most threatened?
- Primates have the highest share of threatened species — about 60% of primate species are at risk on the IUCN Red List, driven by deforestation, bushmeat hunting and the pet trade.
- Are whales and bats mammals?
- Yes. Both are mammals. Whales nurse calves with milk; bats are the only mammals capable of true powered flight.
- How can I help threatened mammals?
- Fund habitat protection and anti-poaching through vetted partners, reduce demand for illegal wildlife products, and support CNVR and sanctuary programmes for species that cannot return to the wild.
Mammal wildlife guides
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Endangered
Elephant
Asian elephants are Endangered; their main threats are habitat loss and human-elephant conflict, while African elephants also face poaching for the illegal ivory trade.
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Critically Endangered
Tiger
A tiger (Panthera tigris) is the largest living cat species, a striped, solitary carnivore native to Asia; the Sumatran tiger of Indonesia and the Malayan tiger of Malaysia are two of the most endangered surviving populations, both listed as Critically Endangered.
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Vulnerable
Lion
The lion (Panthera leo) is classified as Vulnerable on the IUCN Red List, with an estimated 23,000 mature and subadult lions remaining in Africa plus around 670 in India, and the overall population is decreasing.
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Critically Endangered
Gorilla
A gorilla is the largest living primate, a ground-dwelling, mostly plant-eating great ape native to the forests of equatorial Africa. There are two Critically Endangered species — the Western and Eastern gorilla — and gorillas share roughly 98% of their DNA with humans.
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Critically Endangered
Orangutan
Orangutans are Critically Endangered great apes found only in Borneo and Sumatra; all three species — Bornean, Sumatran, and Tapanuli — face extinction driven mainly by habitat loss from palm oil and logging, plus the illegal pet trade.
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Critically Endangered
Pangolin
Pangolins are the world's most heavily trafficked wild mammals; all eight species are threatened by illegal trade in their keratin scales, used in traditional medicine across Asia, with the Chinese and Sunda pangolins now Critically Endangered.
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Not Evaluated
Bat
Bats (order Chiroptera) are the only mammals capable of true flight, with around 1,400 species worldwide that mostly navigate by echolocation and provide vital pest control, pollination, and seed dispersal.
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Near Threatened
Platypus
A platypus is a semi-aquatic, egg-laying mammal (a monotreme) native to eastern Australia and Tasmania. It has a duck-like bill, webbed feet and a beaver-like tail, hunts underwater using electroreception, and males carry venomous ankle spurs. It is listed as Near Threatened on the IUCN Red List.
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Vulnerable
Koala
The koala is a Vulnerable eucalyptus-eating marsupial native only to Australia, where habitat loss, disease and bushfire have made its eastern populations Endangered under national law as of 2022.
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Not Evaluated
Kangaroo
A kangaroo is a large hopping marsupial native to Australia and the world's biggest marsupial, carrying its young, called a joey, in a pouch; the main kangaroo species are widespread and assessed as Least Concern.
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Not Evaluated
Wolf
The grey wolf (Canis lupus) is a Least Concern pack-hunting canid of the Northern Hemisphere and wild ancestor of dogs — regionally extirpated in much of Europe and North America but recovering where reintroduced.
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Not Evaluated
Bear
Bears are eight living species in the family Ursidae across North America, South America, Europe and Asia; conservation status ranges from abundant (American black bear) to Vulnerable (polar bear, sun bear) to dependent on intensive protection (giant panda).
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Not Evaluated
Rhino
Rhinoceroses are five living species of horned megaherbivores in Africa and Asia; all are threatened by poaching for keratin horn, with three species Critically Endangered including the Sumatran rhino with fewer than 50 individuals.
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Near Threatened
Zebra
A zebra is a striped African member of the horse genus Equus; there are three species — plains, mountain, and Grevy's — ranging from Near Threatened to the Endangered Grevy's zebra, of which fewer than about 2,000 mature animals survive.
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Vulnerable
Giraffe
Giraffes are the tallest animals on Earth and are listed as Vulnerable on the IUCN Red List; the group was split into four species in 2025, and while overall numbers are now near 117,000, some subspecies such as the Kordofan and Nubian giraffe are Critically Endangered.
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Vulnerable
Hippopotamus
The hippopotamus (Hippopotamus amphibius) is a large semi-aquatic African mammal listed as Vulnerable by the IUCN, with roughly 115,000-130,000 individuals remaining and a declining population driven by habitat loss and demand for its tooth ivory.
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Not Evaluated
Leopard
Leopards are spotted Panthera cats of Africa and Asia — Vulnerable (Panthera pardus) — plus clouded leopards and snow leopards as distinct species covered in separate WARN guides.
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Near Threatened
Jaguar
A jaguar (Panthera onca) is a large spotted big cat native to the Americas — the largest cat on the continent and the third-largest in the world — known for the strongest bite of any big cat and a habit of killing prey by piercing the skull.
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Vulnerable
Cheetah
The cheetah (Acinonyx jubatus) is the fastest land animal, reaching roughly 100-120 km/h (about 60-75 mph) in short bursts, and is classified as Vulnerable by the IUCN, with the Asiatic cheetah in Iran listed as Critically Endangered.
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Vulnerable
Sloth Bear
The sloth bear (Melursus ursinus) is a Vulnerable myrmecophagous bear of India, Nepal, Sri Lanka and Bhutan — adapted for eating ants and termites with long claws and a tube-like muzzle, threatened by habitat loss and conflict.
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Vulnerable
Sun Bear
Sun bears are the world's smallest bears, native to Southeast Asia, and are listed as Vulnerable by the IUCN; they are threatened by deforestation, the pet trade, and the bear bile industry, in which bears are caged for years and milked for bile used in traditional medicine.
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Endangered
Proboscis Monkey
A proboscis monkey is a large, reddish-brown Old World monkey found only on the island of Borneo (in Indonesia, Malaysia and Brunei), famous for the male's oversized hanging nose and for living in coastal mangrove and riverside forests; the IUCN classes it as Endangered.
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Endangered
Slow Loris
Slow lorises are small nocturnal primates from South and Southeast Asia; every species is threatened with extinction — ranging from Vulnerable to Critically Endangered — largely because of the illegal pet trade, which is fuelled in part by viral social media videos.
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Endangered
Chimpanzee
A chimpanzee (Pan troglodytes) is a great ape from the forests and woodlands of equatorial Africa. Along with the bonobo, it is humans' closest living relative, sharing roughly 98-99% of our DNA. Famous for tool use, complex societies and culture, it is classified as Endangered.
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Not Evaluated
Gibbon
Gibbons are tailless lesser apes of South-east Asian rainforest, brachiating through the canopy in monogamous family groups; most species are Endangered or Critically Endangered due to habitat loss and the illegal pet trade.