Roughly 4,500 species in 19 orders make up the mammals (Nowak 1991). The largest order of mammals is the the Rodentia with over 1840 species, while bats (Chiroptera) are the second largest order with almost 1000 species. Mammals are characterized by homeothermy, hair, relatively large brains, and mammary glands for postnatal maternal nutrition of young.
The primitive Protheria include the Monotremata (the platypus and echidna; McKenna 1975), while the Theria includes all other mammals (Janson and Pope, 1989). The Theria may be further subdivided as the Metatheria (the pouched mammals or Marsupialia) and the Eutheria (placental mammals). Each mammalian order is briefly described with respect to general ecology, life history characteristics, and distribution.
MONOTREMES (echidna and duck-billed platypus)
Native to Australia and New Guinea, monotremes are the only egg-laying mammalian order. The two Monotremata families are the Ornithorhynidae (Duck-billed Platypuses) and Tachyglossidae (Spiny Anteaters). Spiny anteaters are toothless, spine-covered animals with strong clawed feet for digging and a long sticky tongue. They live in solitarily in crevices and burrows, can torpor, and may survive for a month without insects, worms, or other food (Nowak 1991). Broods of one or three spiny anteater young are born and receive extended maternal care.
Platypus live in burrows near lakes and streams where they feed on small invertebrates and fish (Grant and Carrick 1978). Platypus have short limbs with webbed feet, and a broad, flat tail. Males and females pair-bond seasonally and lay clutches of one to three eggs in a nest (Nowak 1991).
MARSUPIALS (opossums, bandicoots and kangaroos)
The marsupials are pouched mammals native to southern North American and South Americancontinents (70 species) as well as Australia (170 species) (Janson and Pope, 1989). The 280 species of marsupials include the American opossums (Didelphidae, 77 species), carnivorous marsupials (Dasyuridae, 58 species), bandicoots (Peramelidae, 21 species), striped opossums (Petauridae, 23 species), phalangers (Phalangeridae, 20 species), and the kangaroos and wallabies (Macropodidae, 56 species)as well as ten other smaller families. Marsupial body size and diet vary widely and many are nocturnal. Marsupial females have a reproductive system of dual vagina and uteri. Females bear altricial young which are protected in the marsupium (with the exception of some smaller marsupials) and, in some species, young of subsequent litters developing simultaneously though at different stages.
INSECTIVORA (shrews, tenrecs, hedghogs and moles)
The Insectivores are the third largest order of mammals, comprised of almost 400 species in 7 families. The Gymnures and Hedghogs (Erinaceidae, 20 species), Solenodons (Solenodontidae, 2 species), Extinct West Indian Shrews (Nesophontidae, 6 species), Tenrecs and Madagascar "Hedgehogs" (Tenrecidae, 23 species), Golden Moles (Chrysochloridae, 18 species), Shrews (Soricidae, 289 species), Shrew-moles, and Desmans (Talpidae, 32 species) are small, clawed, animals with an elongated narrow snouts.
Most insectivores are nocturnal with diets consisting of grubs, insects, snails, and small vertebrates. Insectivores pervade numerous habitats and are highly active. They seek shelter in enclosures, forests, and foliage. Insectivores have a gestation period of one or two months, variable litter size, and an extended period of parental care (Nowak 1991). Most insectivores live for fewer than five years. Hedgehogs and Solenodons, however, may live into their teens. Solenodons are shrew-like animals with toxic saliva potent enough to immobilize larger prey such as small birds, frogs, and lizards.
MACROSCELIDEA (elephant shrews)
Fifteen species of elephant shrews are native to African forests, grasslands, and thickets. They are small (95-315 mm. head and body length) with large eyes and ears, a long, narrow snout that is not retractile but can be moved in a circular motion, and hind limbs adapted for jumping. Elephant shrews are generally solitary insectivores that produce small broods of precocial young after two months of gestation. Lactation is short and sexual maturity is achieved as early as five weeks (Nowak 1991). Some species of genus Elephantulus reside in colonies and are known to communicate through chirps and tapping sounds made using the hind legs (Nowak 1991).
DERMOPTERA (flying lemurs)
There are two species of Dermoptera in one family native to Southeast Asian mountain or lowland forests. Flying Lemurs are 340-420 mm. body length, with long limbs and tail, large eyes, short ears and nocturnal habits. When outstretched, membranes running from the neck to the front feet, back feet, and end of the tail allow flying lemurs to glide between branches and to feed on flowers and fruit high in tree tops or on outermost tree limbs that are out of the reach of most animals. Activity is reduced during the day when Flying Lemurs hang upside down by their claws. Gestation is 60 days, and only one offspring is born per litter. Young receive extended maternal care and several flying lemurs may live together (Nowak 1991).
CHIROPTERA (bats)
More than 900 species of bats live in most tropical and temperate climes. The suborder Megachiroptera (fruit bats) are tropical and homeothermic. The Microchiroptera are tropical and temperate, commonly heterothermic and insectivorous -- though some eat fruit and flowers and a few species prey on vertebrates. Bats are the only mammals engaging in true flight. Bats are found within the limits of tree growth, and find sanctuary in caves and other small crevices in buildings or trees. Temperate zone bats generally mate in the fall and store sperm through hibernation then produce only one offspring per litter in the spring.
Bats are long-lived for their small body size. Maximum life spans for most species exceed 10 years, while those of others are reported to extend into the thirties.
SCANDENTIA (tree shrews)
Scandentia includes one family (Tupaiidae) of Tree Shrews with five species native to Eastern Asia and Southwest China forests. Difficult to classify, this order is now related most closely to Primates, Chiroptera and Dermoptera. Resembling squirrels with long snouts, Tree Shrews are mostly diurnal, small (100-220 mm. head and body length), bushy-tailed, and feed on insects, fruit, and worms. Most Tree Shrews are adept runners, jumpers, and/or tree-climbers. Communication occurs in snarls and other vocalizations. Shrews appear to be solitary and polygynous; litters of 1 to 3 young are nursed about 5 to 6 weeks and are sexually mature at 3 months (Nowak 1991).
PRIMATES (Prosimians, monkeys and apes)
Primates are generally pan-tropical with the exception of humans who live worldwide (Nowak 1991). The suborder Prosimii includes 6 families (tarsiers, lemurs, indris, aye ayes, galagos, pottos, and lorises), and the Anthropoidea including three New World families (Cebidae, Callitrichidae and Callimiconidae) and three Old World families (Cercopithecidae, Pongidae, Hominidae). Anthropoid primates are diurnal, highly dextrous and have fine manipulative skills (Janson and Pope, 1989) as well as the highest brain to body size ratio. Primates range in size from the mouse lemurs (50 g) to gorillas (200 kg.). Primate faces are flat with a short nose and jaw, forward facing eyes, and teeth designed for grinding. The majority of primates are polygynous with annual production of single young and extended maternal (and sometimes paternal) care.
XENARTHRA (armadillos, anteaters and sloths)
Approximately 30 species of Xenarthra include the armadillos native to the Western Hemisphere (Dasypodidae, 20 species), anteaters native to Central and South America (Myrmecophagidae, 4 species), and sloths (Bradypodidae, 5 species). Head and body lengths range from 125 to 1200 mm (Nowak 1991). Armadillos have bony plates, cylindrical teeth for insect consumption, and digging feet for rooting. Anteaters have a long snout sticky tongue and a diet of ants and termites. Socially, most Xenarthra are solitary but some form loose groups (Nowak 1991). Most sloths bear young singly as do most anteaters, while armadillos bear litters of one to three genetically identical young.
PHILODOTA (spiny anteaters)
Philodota includes one family with seven species of Spiny Anteaters native to parts of Asia, Indonesia, and Africa. They range in head to rump length from 300 to 880 millimeters with scales, short limbs, a cone-shaped skull, and a long tail (Nowak 1991). Like the Xenarthra anteaters, Pholidotes have a stomach that grinds the exoskeletons of insects for more complete digestion. Spiny Anteaters roam in forests, brush, and savanna habitats by night, and remain in burrows or tree crevices by day. They are toothless insectivores who pick up ants, termites, and other foodstuffs using their sticky tongues. When attacked, the Spiny Anteater curls into a ball and may roll down a hill to escape predation, or may eject foul-smelling liquid though more generally they lead slow-moving solitary lives of low aggression (Nowak 1991). Litters of one or two young are born and receive extended maternal care.
LAGOMORPHA (rabbits and hares)
The Lagomorpha consist of two families, the Laporidae (about 50 species of hares and rabbits) and the Ochotonidae (14 species of pikas), native to most countries with the exceptions of New Zealand and Australia. They are characterized by long ears, short fur, an upturned tail, strong hind legs for jumping, and a high reproductive rate.
Rabbits generally live in lowland areas and hills where they build underground burrows and congregate in groups often exceeding 100 members (Janson and Pope, 1989). Their food is double-processed by eating plant food, passing this through the system, and re-consuming the excreted pellets. Except during the mating season, hares are solitary. While rabbits dig underground burrows, hares rest in depressions in the grass. Pikas are found in North America and Asia where they live in a wide range of habitats. Litter size in the Lagomorpha generally ranges from 1-5, although some species bear as many as 15 per litter.
RODENTIA (squirrels, mice, marmots and beaver)
Rodentia is the largest mammalian order and includes the suborders Sciuromorpha (7 families of squirrel-like rodents; squirrels, marmots, gophers, and beavers), Myomorpha (1000 species in 9 families of mouse-like rodents), and Hystricomorpha (16 families of porcupine-like rodents; porcupines, guinea pigs, and coypus). Rodents are pandemic and diverse, including over 1800 species in a wide variety of habitats. Rodents have sharp incisors, grinding teeth in the back, and, in some species, cheek pouches. Though their diets are varied, seeds and vegetative plant parts are predominant.
CETACEA (whales and dolphins)
The 79 species of Cetacea are predominantly marine; however, there are riverine and lacustrine dolphins. Whales may be divided into the Odontoceti (7 families of toothed whales), and three families of the Mysticeti (the baleen whales). Cetacea are characterized by a streamlined body, broad flippers, and blubber insulation. Nostrils at the top of the head are used for breathing, with a single or double blow-hole in toothed and baleen whales, respectively. In deep dives, oxygen is directed to the brain and nerves, and some muscles have evolved to function anaerobically. Cetaceans have an absolute brain size larger than that of humans and like humans the surface is highly convoluted (Nowak 1991).
Cetacean olfaction and vision is limited, but touch and hearing are acute. Whales and dolphins communicate through clicks and whistles. Some Odontoceti have the capacity of echolocation for hunting and navigation (Janson and Pope, 1989). The baleen whales have sieve-like plates that filter crustaceans, zooplankton and fish. Toothed whales (Odontoceti) have cone-like teeth for grasping fish, squid, and cuttlefish which are generally swallowed whole; however, Orca may feed more opportunistically on warm-blooded marine life.
Cetacean young mature slowly after a long gestation period (9-17mos). Baleen whales mature at 12 years and produce young only once every two years (Janson and Pope, 1989). Calves receive extended maternal care and in some species there is evidence of allomaternal care (Whitehead 1996).
CARNIVORA (weasels, skunks, otters, dogs and cats)
There are 240 species in 7 families of Carnivores. They live throughout the world and are characterized by a long flexible body, shearing teeth and forward facing eyes. The largest family of Carnivora is the Mustelidae, including 67 species of weasels, martens, minks, skunks, badgers, and otters, although the Canidae (dogs and wolves) and Felidae (cats, tigers and lions) are more prominent. Canine teeth and powerful jaws assist in the ability to hunt successfully, and most carnivores are either ground - dwelling or skilled climbers (Nowak 1991). Annual litters are vary widely in size (Janson and Pope, 1989).
Most carnivores are solitary although some Canidae and Hyaenidae hunt in packs and communicate through barks and growls. Bears (Ursidae), Raccoon-like animals (Procyonidae), weasels and related animals (Mustelidae), and civets and mongooses (Viverridae) are solitary. A few species of Felidae live in prides of several related females and their young along with one or more unrelated males (Janson and Pope, 1989). Extended parental care of young is delivered in most carnivores.
PINNIPEDIA (seals and sea lions)
Pinnipeds include the ear-less seals (Phocidae, 18 species), the eared-seals, sea lions and fur seals (Otariidae, 16 species), and the walrus (Odobenidae, 1 species). One of the two orders of marine mammals, they are a monophyletic group most closely related to the Carnivora (Nowak 1991). They have streamlined bodies with both hair and sub-dermal blubber . The forelimbs provide the power for underwater movement in the Otariidae and Odobenidae who are also able to move quickly across land. The Phocidae use the hindlimb flippers for forward impulsion and are clumsy on land. Sexual dimorphism is common in the Otariids and Odobenids with some males (e.g. southern elephant seals) weighing as much as four times as much as females (Janson and Pope, 1989). Walruses are native to the Arctic Ocean, from which they migrate in the winter, and are characterized by a thick durable skin and tusks in both males and females. Male walrus may measure up to 13 feet and may weigh as much as 3000 pounds (Janson and Pope, 1989).
Pinnipeds eat fish, crustaceans, molluscs, and other invertebrates. They exhibit highly seasonal mating, delayed implantation and gestation periods of 8-11 months (Eisenberg 1981). They bear a single pup that can swim almost from birth (Janson and Pope, 1989).
TUBULIDENTATA (aardvarks)
Aardvarks feed nocturnally on termites and ants and sleep inside burrows by day. The aardvark is found on African savannas where they sometimes travel long distances in search of food (Janson and Pope, 1989). Most aardvarks bear single offspring (Nowak 1991).
PROBOSCIDEA (elephants)
There are only two species in this order, the African and the Indian Elephants, remnants of a much more diverse order in the Pliocene. African elephants are the larger and both males and females bear tusks (continuously growing upper incisors). Indian elephants have one more toe on the hindfoot and only the males have tusks. Both feed for much of the day on grasses, bark, roots, and leaves to support their massive bodies (Janson and Pope, 1989). Using the trunk to lift food and water, elephants rely on grinding teeth to masticate woody fibers.
Both species have a social organization based on matriarchal groups of females and their young with males associated for shorter lengths of time. Gestation in the Indian elephant is approximately 646 days in the Indian elephant; young nurse for 18 months and females first give birth at 15-16 years (Nowak 1991). Female African elephants appear to select older "musth" males for mating, have a 22 month gestation, and young usually nurse 6-18 months with observations as long as 6 years. Young are produced about every 5 years.
HYRACOIDEA (hyraxes)
The highly sociable Hyraxes look like large guinea pigs, but are most closely related to elephants. As in elephants, grinding teeth serve to assist in digestion of plants, and long incisors are externally visible. Rock-dwelling species tend to be more social than arboreal species (Janson and Pope, 1989). Homeothermic control is poor (Nowak 1991). Social groups include a territorial male and several females. Gestation is somewhat over 200 days and young nurse for 1 to 5 months. All hyraxes engage in an elaborate system of communication consisting of noises and cries including predator alerts.
SIRENIA (manatees, dugongs and sea cows)
Sirenia are tropical and subtropical herbivorous aquatic animals of coastal waters and rivers. Sirenia predate the related Proboscidea, with their maximal abundance in the Oligocene to Pliocene. They are characterized by a large body with a thick layer of blubber, may weigh up to 650 kg and grow to lengths of 4 meters (Janson and Pope, 1989). Young use forelimbs for propulsion but adults use the fluke-like tail. All Sirenia have cheek teeth for grinding and some species (eg. Dugong) also have incisors. Sirenians are generally solitary or found in small groups. Females give birth to a solitary young after a gestation of 13 to 14 months. Lactation lasts for 18 months and sexual maturity occurs between 10 and 15 years (Nowak 1991).
PERISSODACTYLA (odd toed ungulates)
Ungulates are horned and hoofed herbivores which are characterized by their ability to chew and digest fibrous plants, and to run swiftly. Most ungulates breed annually and bear single offspring (Janson and Pope, 1989). Gestation requires roughly a year.
The Perissodactyla are single or three-toed ungulates native to Africa, parts of Asia and Central and South America. Seventeen recent species are included in three families of horses (Equidae), tapirs (Tapiridae) and rhinoceroses (Rhinocerotidae), while an additional family became extinct in the Pleistocene (Nowak 1991). They are grazers of fibrous plant material digested by grinding teeth and simple stomachs. Some Equiidae live in migratory herds on the plains in single male, multi-female groups. These horses, zebras and asses have interbirth intervals of 1 to 3 years. Tapiridae are shorter-legged herbivores native to Malaysia, Asia, Sumatra, Java, and Central and South America where they live in dense underbrush. Rhinocerotidae are native to Africa, Asia, Sumatra, and Borneo; they feed on vegetation in savanna and wooded areas (Janson and Pope, 1989). Gestation exceeds one year and adults have few predators beyond humans.
ARTIODACTYLA (even toed ungulates).
Nine families of Artiodactyls include the hog-like animals (Sulidae), peccaries (Tayassuidae), hippopotamuses (Hippopotamidae), camels and llamas (Camelidae), chevrotains (Tragulidae), giraffes (Giraffidae), deer-like animals (Cervidae), cattle, antelope, goats, and sheep (Bovidae), and pronghorn (Antilocapridae). The Artiodactyla have four toes.
Artiodactyla are predominantly herbivores (though the Suidae are omnivores) with a two-chambered stomach. Suidae tend to live in forest habitats, feeding on roots, plants, bird eggs, and small animals nocturnally. Artiodactyls tend to travel in groups or herds of up to 50 individuals. Artiodactyl species inhabit savannah, forest, riverene and desert habitats.
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