Like many farm animals, horses possess all the major attributes that place them into the mammal category. Read on to find out how our equine friends fit into the mammal world.
Mammals are a class of animals that share a variety of common characteristics, including the fact that they have mammary glands. Mammals create milk using their mammary glands and use it to feed their young.
Thanks to this ability, mammals form unique bonds with their offspring that animals in other categories do not. Mammals are all ‘warm-blooded’ animals that also have three bones in their middle ears which allow them to hear sound effectively.
Apart from these specific characteristics, mammals also tend to be very intelligent, are often capable of domestication and can communicate in unique and intricate ways. Female horses also nurse their foals with milk they produce using their own mammary glands.
Horses also have coats comprised of hair that comes in a variety of beautiful colors and unique patterns. Their hair helps to keep them safe from outdoor elements including harsh rain, wind, and extreme temperatures.
Horses have 3 middle ear bones called the hammer, anvil and stirrup. In prehistoric times, most mammal animals served only as a food source for humans.
The ability of many mammals to be domesticated helped to turn a hunting and often nomadic way of life into a more settled, agricultural lifestyle. Being a mammal creates a unique bonding experience for animals, especially horses.
The fact that mammals have mammary glands and personally feed their own young creates a maternal bond that begins at birth. While there are rare exceptions, most mares that give birth to a foal will quickly begin to bond with them.
Horses, unlike some mammals, like to keep their babies very close and this begins immediately after they are born. Shortly after birthing a foal, mares will instinctively begin to lick off the amniotic fluid that covers their baby.
The mare will continue to lick, nuzzle and help push their baby to stand up and nurse. This bonding helps to ensure that the foal will continue to have a source of food and protection throughout their young lives.
It is easy to see that horses have the largest eyes out of all the mammals that live on land. The horse’s large eyes sit on each side of their head, creating only a couple blind spots but also allowing them to see more of what is around them.
Draft horses are most often called cold-bloods due to their calm demeanor and easy-going personalities. Some racing and competition horse breeds including Arabians and Thoroughbreds can be referred to as hot-bloods.
Rabies is a frequently fatal disease that rapidly spreads to the animal’s brain and causes damage that cannot be repaired. Thankfully, there are annual vaccines available to keep our domesticated animals, including horses, safe.
Horses are unique, but they are still grouped into the larger category of mammals thanks to their backbones, mammary glands, temperature regulation, bonding capabilities, middle ear design and their coats of hair. Now that horses are no longer needed for transportation and farm work, they are often regarded as companion animals.
The ASPCA also specifies “species suitable to be companion animals include dogs, cats, horses, rabbits, ferrets, birds, guinea pigs, and select other small mammals, small reptiles and fish. The Missouri Horse Council maintains that horses are livestock and “supports the legal definition of all domesticated equines to remain as livestock and opposes the current social trend of referring to them as pets or companion animals.” This is a stance taken by many similar associations in the United States and Canada.
Those who make their living as trainers, breeders, dealers and running boarding stables and schools may lose the benefit of being an agricultural endeavor if a horse were regarded solely as a companion animal. A good deal of research into equine diseases, vaccines and husbandry is government funded.
Husbandry and humane treatment laws might not apply if horses were designated companion animals. Many states are passing limited liability laws, which protect livestock owners and livestock event organizers (like cattle and horse shows) from lawsuits from anyone who is injured by a potentially large and dangerous animal such as a cattle-beast or horse.
Considering that most of us do regard our horses not just as companions, but family members, our ultimate goal should be the best possible care, in addition to protecting ourselves. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today.
Horses are herd animals, with a clear hierarchy of rank, led by a dominant individual, usually a mare. They are also social creatures that are able to form companionship attachments to their own species and to other animals, including humans.
They communicate in various ways, including vocalizations such as nickering or whinnying, mutual grooming and body language. When confined with insufficient companionship, exercise, or stimulation, individuals may develop stable vices, stereotypes of psychological origin, that include wood chewing, wall kicking, “weaving” (rocking back and forth), and other problems.
Their first reaction to threat is to startle and usually flee, although they will stand their ground and defend themselves when flight is impossible or if their young are threatened. They also tend to be curious; when startled they will often hesitate an instant to ascertain the cause of their fright, and may not always flee from something that they perceive as non-threatening.
Related to this need to flee from predators is an unusual trait: horses are able to sleep both standing up and lying down. In an adaptation from life in the wild, horses are able to enter light sleep by using a “stay apparatus” in their legs, allowing them to doze without collapsing.
If a horse is never allowed to lie down, after several days it will become sleep-deprived, and in rare cases may suddenly collapse as it involuntarily slips into REM sleep while still standing. Horses are grazing animals, and their major source of nutrients is good-quality forage from hay or pasture.
Horses have an advanced sense of taste, which allows them to sort through fodder and choose what they would most like to eat. They reach full adult development by age five, and have an average lifespan of between 25 and 30 years.
They perform a number of cognitive tasks on a daily basis, meeting mental challenges that include food procurement and identification of individuals within a social system. The Przewalski's Horse was saved from the brink of extinction and reintroduced successfully to the wild.
Commercial horse racing is a ruthless industry motivated by financial gain and prestige. The racing industry breeds thousands of horses looking for its next champion, contributing to an overpopulation crisis.
Loosing and winning horses are commonly sent to the slaughterhouse when their careers have ended. Horses suffer horribly on the way to and during slaughter, often shipped for more than 24 hours at a time without food, water or rest.
Horses are often injured even before arrival due to overcrowded conditions during transport. The methods used to kill horses rarely results in quick deaths: they often endure repeated stuns or blows, and sometimes remain conscious during their slaughter.
Horses are forced to pull oversized loads by the animal entertainment industry. The horses suffer from respiratory ailments from exhaust fumes, and develop debilitating leg problems.
Carriage horses also face the threat of heatstroke from summer heat and humidity. When the horses grow too old, tired, or ill they may be slaughtered and turned into food for dogs or zoo animals, or shipped overseas for human consumption.
They are abused with electrical prods, sharp spurs and “bucking straps” that pinch their sensitive flank area. During bucking events, horses may suffer broken legs or run into the sides of the arena causing serious injury and even death.
Each year, hundreds of wild (feral) horses are rounded up by United States government agencies using inhumane methods. The horses are put in holding pens where, for a small fee, anyone can “adopt” them.
The lucky ones are adopted by people who love and care for them, but many are traded or sold at auctions. Click to download the free sample version Download sample The horse evolved over 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today.
They are a remarkably fast and well-balanced animal which helps them to escape predators in the wild. See the fact file below for more information on Horses or alternatively download our comprehensive worksheet pack to utilize within the classroom or home environment.
The third group contains Przewalski’s wild horse, which is now found only in captivity. Most mares give birth in the spring to a single foal although twins are not uncommon.
Mares produce milk for their young and will feed them for several months. When foals are born their legs are almost the same length as they are when they are fully grown.
This means their legs are so long they find it difficult to reach down to the grass to eat. Foals can focus their eyes almost as soon as they are born and cut their first teeth within a week.
He stood 7 feet 2 inches tall (21.2 and a half hands). Measurement is taken from the ground up to the withers, the highest point on the horse’s shoulder.
Beware of a horse that has flared nostrils and their ears back. The four natural paces for the horse are the walk, trot, canter and gallop.
Horses that work or travel on hard roads need their feet (hooves) protected by metal shoes. Horses hooves, like our finger and toe nails, also grow continuously and need to be trimmed.
To do this, the horses shoes need to be removed and their hooves trimmed every 4 -6 weeks. The person who cares for a horse’s feet is called a farrier, or blacksmith.
Horses are herbivores and love to eat short, juicy grass. Extra high energy food such as barley, oats, maize, chaff, bran or processed pony nuts are good for working horses.
Horses can drink up to ten gallons of water a day. Horses are said to have good memory and are able to communicate through their facial expression.
You can use these worksheets as-is, or edit them using Google Slides to make them more specific to your own student ability levels and curriculum standards. Mammals (from Latin mamma “breast”) are a group of vertebrate animals constituting the class Mammalian (), and characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or hair, and three middle ear bones.
These characteristics distinguish them from reptiles and birds, from which they diverged in the late Carboniferous, approximately 300 million years ago. The largest orders are the rodents, bats and Eulipotyphla (hedgehogs, moles, shrews, and others).
The next three are the Primates (apes including humans, monkeys, and others), the Artiodactyla (cetaceans and even-toed ungulates), and the Carnivora (cats, dogs, seals, and others). In terms of statistics, which reflects evolutionary history, mammals are the only living members of the Synaptic ; this clade, together with Sauropod (reptiles and birds), constitutes the larger Anita clade.
The early synaptic mammalian ancestors were sphenacodontpelycosaurs, a group that included the non-mammalian Dimetrodon. At the end of the Carboniferous period around 300 million years ago, this group diverged from the sauropod line that led to today's reptiles and birds.
All modern mammals give birth to live young, except the five species of honorees, which are egg-laying mammals. The most species-rich group of mammals, the cohort called placentals, have a placenta, which enables the feeding of the fetus during gestation.
Most mammals are intelligent, with some possessing large brains, self-awareness, and tool use. Mammals can communicate and vocalize in several ways, including the production of ultrasound, scent-marking, alarm signals, singing, and echolocation.
This led to a major restructuring of human societies from nomadic to sedentary, with more co-operation among larger and larger groups, and ultimately the development of the first civilizations. Domesticated mammals provided, and continue to provide, power for transport and agriculture, as well as food (meat and dairy products), fur, and leather.
Mammals are also hunted and raced for sport, and are used as model organisms in science. Mammals have been depicted in art since Paleolithic times, and appear in literature, film, mythology, and religion.
Decline in numbers and extinction of many mammals is primarily driven by human poaching and habitat destruction, primarily deforestation. Mammal classification has been through several iterations since Carl Linnaeus initially defined the class.
No classification system is universally accepted; McKenna & Bell (1997) and Wilson & Reader (2005) provide useful recent compendiums. George Gaylord Simpson's “Principles of Classification and a Classification of Mammals (AMH Bulletin v. 85, 1945) provides systematic of mammal origins and relationships that were universally taught until the end of the 20th century.
Since Simpson's classification, the pale ontological record has been recalibrated, and the intervening years have seen much debate and progress concerning the theoretical underpinnings of systematization itself, partly through the new concept of statistics. Though field work gradually made Simpson's classification outdated, it remains the closest thing to an official classification of mammals.
Most mammals, including the six most species-rich orders, belong to the placental group. The three largest orders in numbers of species are Rodentia : mice, rats, porcupines, beavers, cabanas and other gnawing mammals ; Chiroptera : bats; and Soricomorpha : shrews, moles and solenoids.
The next three biggest orders, depending on the biological classification scheme used, are the Primates including the apes, monkeys and lemurs ; the Cetartiodactyla including whales and even-toed ungulates ; and the Carnivora which includes cats, dogs, weasels, bears, seals and allies. These were grouped into 1,229 genera, 153 families and 29 orders.
In 2008, the International Union for Conservation of Nature (IUCN) completed a five-year Global Mammal Assessment for its IUCN Red List, which counted 5,488 species. According to research published in the Journal of Mamma logy in 2018, the number of recognized mammal species is 6,495 including 96 recently extinct.
The word mammal is modern, from the scientific name Mammalian coined by Carl Linnaeus in 1758, derived from the Latin mamma (“teat, pap”). In an influential 1988 paper, Timothy Rowe defined Mammalian phylogenetically as the crown group of mammals, the clade consisting of the most recent common ancestor of living honorees (echidna and platypuses) and Thermal mammals (marsupials and placentals) and all descendants of that ancestor.
Since this ancestor lived in the Jurassic period, Rowe's definition excludes all animals from the earlier Triassic, despite the fact that Triassic fossils in the Haramiyida have been referred to the Mammalian since the mid-19th century. If Mammalian is considered as the crown group, its origin can be roughly dated as the first known appearance of animals more closely related to some extant mammals than to others.
The earliest known synaptic satisfying Kemp's definitions is Tikitherium, dated 225 Ma, so the appearance of mammals in this broader sense can be given this Late Triassic date. In 1997, the mammals were comprehensively revised by Malcolm C. McKenna and Susan K. Bell, which has resulted in the McKenna/Bell classification.
Their 1997 book, Classification of Mammals above the Species Level, is a comprehensive work on the systematic, relationships and occurrences of all mammal taxa, living and extinct, down through the rank of genus, though molecular genetic data challenge several of the higher level groupings. The authors worked together as paleontologists at the American Museum of Natural History, New York.
McKenna inherited the project from Simpson and, with Bell, constructed a completely updated hierarchical system, covering living and extinct taxa that reflects the historical genealogy of Mammalian. In the following list, extinct groups are labelled with a dagger (†).
Super order: Euarchontoglires (Supra primates) Super order: Laurasiatheria Order Eulipotyphla : shrews, hedgehogs, moles, solenoids Clade Scrotifera Order Chiroptera : bats (cosmopolitan) Clade Fereuungulata Clade Feral Order Pholidota : pangolins or scaly anteaters (Africa, South Asia) Order Carnivora : carnivores (cosmopolitan), including cats and dogs Synaptic, a clade that contains mammals and their extinct relatives, originated during the Pennsylvanian subperiod (~323 million to ~300 million years ago), when they split from reptilian and avian lineages.
Crown group mammals evolved from earlier mammaliaforms during the Early Jurassic. The cladogram takes Mammalian to be the crown group.
The original synaptic skull structure contains one temporal opening behind the orbitals, in a fairly low position on the skull (lower right in this image). This opening might have assisted in containing the jaw muscles of these organisms which could have increased their biting strength. The first fully terrestrial vertebrates were amniotic.
Like their amphibious tetra pod predecessors, they had lungs and limbs. Amniotic eggs, however, have internal membranes that allow the developing embryo to breathe but keep water in.
Hence, amniotic can lay eggs on dry land, while amphibians generally need to lay their eggs in water. The first amniotic apparently arose in the Pennsylvanian subperiod of the Carboniferous.
They descended from earlier reptiliomorph amphibious tetra pods, which lived on land that was already inhabited by insects and other invertebrates as well as ferns, mosses and other plants. Within a few million years, two important amnion lineages became distinct: the synopsis, which would later include the common ancestor of the mammals ; and the sauropods, which now include turtles, lizards, snakes, crocodiles and dinosaurs (including birds).
Synopsis have a single hole (temporal finest) low on each side of the skull. One synaptic group, the pelycosaurs, included the largest and fiercest animals of the early Permian.
Non mammalian synopsis are sometimes (inaccurately) called “mammal-like reptiles”. Therapies, a group of synopsis, descended from pelycosaurs in the Middle Permian, about 265 million years ago, and became the dominant land vertebrates.
They differ from basal eupelycosaurs in several features of the skull and jaws, including: larger skulls and incisors which are equal in size in therapies, but not for eupelycosaurs. The therapist lineage leading to mammals went through a series of stages, beginning with animals that were very similar to their pelycosaur ancestors and ending with probainognathiancynodonts, some of which could easily be mistaken for mammals.
The gradual development of a bony secondary palate. Progression towards an erect limb posture, which would increase the animals stamina by avoiding Carrier's constraint.
But this process was slow and erratic: for example, all herbivorous nonmammaliaform therapies retained sprawling limbs (some late forms may have had semi erect hind limbs); Permian carnivorous therapies had sprawling forelimbs, and some late Permian ones also had semi sprawling hind limbs. In fact, modern honorees still have semi sprawling limbs.
The century gradually became the main bone of the lower jaw which, by the Triassic, progressed towards the fully mammalian jaw (the lower consisting only of the century) and middle ear (which is constructed by the bones that were previously used to construct the jaws of reptiles). The Permian–Triassic extinction event about 252 million years ago, which was a prolonged event due to the accumulation of several extinction pulses, ended the dominance of carnivorous therapies.
In the early Triassic, most medium to large land carnivore niches were taken over by archosaurs which, over an extended period (35 million years), came to include the crocodylomorphs, the stegosaurus and the dinosaurs; however, large confronts like Trucidocynodon and traversodontids still occupied large sized carnivorous and herbivorous niches respectively. By the Jurassic, the dinosaurs had come to dominate the large terrestrial herbivore niches as well.
The first mammals (in Kemp's sense) appeared in the Late Triassic epoch (about 225 million years ago), 40 million years after the first therapies. They expanded out of their nocturnal insectivore niche from the mid-Jurassic onwards; The Jurassic Castorocauda, for example, was a close relative of true mammals that had adaptations for swimming, digging and catching fish.
The majority of the mammal species that existed in the Mesozoic Era were multituberculates, eutriconodonts and spalacotheriids. The earliest known Metatheria is Sinodelphys, found in 125 million-year-old Early Cretaceous shale in China's northeastern Liaoning Province.
The fossil is nearly complete and includes tufts of fur and imprints of soft tissues. The oldest known fossil among the Eutheria (“true beasts”) is the small shrew like Jamaica kinesis, or “Jurassic mother from China”, dated to 160 million years ago in the late Jurassic.
A later Eutheria relative, Domain, dated to 125 million years ago in the early Cretaceous, possessed some features in common with the marsupials but not with the placentals, evidence that these features were present in the last common ancestor of the two groups but were later lost in the placental lineage. In particular, the epidemic bones extend forwards from the pelvis.
These are not found in any modern placental, but they are found in marsupials, honorees, other northern mammals and Ukhaatherium, an early Cretaceous animal in the Eutheria order Asioryctitheria. They are apparently an ancestral feature, which subsequently disappeared in the placental lineage.
These epidemic bones seem to function by stiffening the muscles during locomotion, reducing the amount of space being presented, which placentals require to contain their fetus during gestation periods. A narrow pelvic outlet indicates that the young were very small at birth and therefore pregnancy was short, as in modern marsupials.
Hadrocodium, whose fossils date from approximately 195 million years ago, in the early Jurassic, provides the first clear evidence of a jaw joint formed solely by the squamous and century bones; there is no space in the jaw for the articular, a bone involved in the jaws of all early synopsis. The earliest clear evidence of hair or fur is in fossils of Castorocauda and Megatons, from 164 million years ago in the mid-Jurassic.
In the 1950s, it was suggested that the foramina (passages) in the maxillae and maxillae (bones in the front of the upper jaw) of confronts were channels which supplied blood vessels and nerves to vibrissae (whiskers) and so were evidence of hair or fur; it was soon pointed out, however, that foramina do not necessarily show that an animal had vibrissae, as the modern lizard Tupinambá has foramina that are almost identical to those found in the nonmammalian confront Thrinaxodon. Popular sources, nevertheless, continue to attribute whiskers to Thrinaxodon.
Studies on Permian composites suggest that non-mammalian synopsis of the epoch already had fur, setting the evolution of hairs possibly as far back as dicynodonts. When endotherm first appeared in the evolution of mammals is uncertain, though it is generally agreed to have first evolved in non-mammalian therapies.
Modern honorees have lower body temperatures and more variable metabolic rates than marsupials and placentals, but there is evidence that some of their ancestors, perhaps including ancestors of the Athenians, may have had body temperatures like those of modern Athenians. Likewise, some modern Athenians like brothers and xenarthrans have secondarily developed lower body temperatures.
The parasagittal (nonsprawling) limb posture appeared sometime in the late Jurassic or early Cretaceous; it is found in the Eutheria Domain and the Metatheria Sinodelphys, both dated to 125 million years ago. Epidemic bones, a feature that strongly influenced the reproduction of most mammal clades, are first found in Tritylodontidae, suggesting that it is a synapomorphy between them and mammaliformes.
They are omnipresent in non-placental mammaliformes, though Megazostrodon and Erythrotherium appear to have lacked them. It has been suggested that the original function of lactation (milk production) was to keep eggs moist.
Much of the argument is based on honorees, the egg-laying mammals. Thermal mammals took over the medium- to large-sized ecological niches in the Cenozoic, after the Cretaceous–Paleogene extinction event approximately 66 million years ago emptied ecological space once filled by non-avian dinosaurs and other groups of reptiles, as well as various other mammal groups, and underwent an exponential increase in body size (megafauna).
For example, the earliest known bat dates from about 50 million years ago, only 16 million years after the extinction of the non-avian dinosaurs. Molecular phylogenetic studies initially suggested that most placental orders diverged about 100 to 85 million years ago and that modern families appeared in the period from the late Eocene through the Miocene.
However, no placental fossils have been found from before the end of the Cretaceous. The earliest undisputed fossils of placentals comes from the early Paleocene, after the extinction of the non-avian dinosaurs.
In particular, scientists have identified an early Paleocene animal named Protungulatum Donna as one of the first placental mammals. Recalibrations of genetic and morphological diversity rates have suggested a Late Cretaceous origin for placentals, and a Paleocene origin for most modern clades.
The earliest known ancestor of primates is Architects Achilles from around 55 million years ago. This tiny primate weighed 20–30 grams (0.7–1.1 ounce) and could fit within a human palm.
Nearly all mammaliaforms possess an epidemic bone, the exception being modern placentals. On average, male mammals are larger than females, with males being at least 10% larger than females in over 45% of investigated species.
Most mammalian orders are also exhibited male-biased sexual dimorphism, although some orders do not show any bias or are signicantly female-biased (Lagomorpha). Sexual size dimorphism increases with body size across mammals (Mensch's rule), suggesting that there are parallel selection pressures on both male and female size.
Male-biased dimorphism relates to sexual selection on males through male–male competition for females, as there is a positive correlation between the degree of sexual selection, as indicated by mating systems, and the degree of male-biased size dimorphism. The degree of sexual selection is also positively correlated with male and female size across mammals.
Further, a parallel selection pressure on female mass is identied in that age at weaning is signicantly higher in more polygamous species, even when correcting for body mass. Also, reproductive rate is lower for larger females, indicating that fecundity selection selects for smaller females in mammals.
Although these patterns hold across mammals as a whole, there is considerable variation across orders. Breathing is mainly achieved with the diaphragm, which divides the thorax from the abdominal cavity, forming a dome convex to the thorax.
Contraction of the diaphragm flattens the dome, increasing the volume of the lung cavity. Air enters through the oral and nasal cavities, and travels through the larynx, trachea and bronchi, and expands the alveoli.
Relaxing the diaphragm has the opposite effect, decreasing the volume of the lung cavity, causing air to be pushed out of the lungs. During exercise, the abdominal wall contracts, increasing pressure on the diaphragm, which forces air out quicker and more forcefully.
The rib cage is able to expand and contract the chest cavity through the action of other respiratory muscles. Consequently, air is sucked into or expelled out of the lungs, always moving down its pressure gradient.
The heart has four valves, which separate its chambers and ensures blood flows in the correct direction through the heart (preventing backflow). After gas exchange in the pulmonary capillaries (blood vessels in the lungs), oxygen-rich blood returns to the left atrium via one of the four pulmonary veins.
Blood flows nearly continuously back into the atrium, which acts as the receiving chamber, and from here through an opening into the left ventricle. Most blood flows passively into the heart while both the atria and ventricles are relaxed, but toward the end of the ventricular relaxation period, the left atrium will contract, pumping blood into the ventricle.
The heart also requires nutrients and oxygen found in blood like other muscles, and is supplied via coronary arteries. The integumentary system (skin) is made up of three layers: the outermost epidermis, the dermis and the hypodermis.
The epidermis is typically 10 to 30 cells thick; its main function is to provide a waterproof layer. Its outermost cells are constantly lost; its bottom most cells are constantly dividing and pushing upward.
The middle layer, the dermis, is 15 to 40 times thicker than the epidermis. The dermis is made up of many components, such as bony structures and blood vessels.
The hypodermis is made up of adipose tissue, which stores lipids and provides cushioning and insulation. The thickness of this layer varies widely from species to species; :97 marine mammals require a thick hypodermis (blubber) for insulation, and right whales have the thickest blubber at 20 inches (51 cm).
Although other animals have features such as whiskers, feathers, STAE, or cilia that superficially resemble it, no animals other than mammals have hair. Herbivores have developed a diverse range of physical structures to facilitate the consumption of plant material.
To break up intact plant tissues, mammals have developed teeth structures that reflect their feeding preferences. For instance, drugstores (animals that feed primarily on fruit) and herbivores that feed on soft foliage have low-crowned teeth specialized for grinding foliage and seeds.
Grazing animals that tend to eat hard, silica -rich grasses, have high-crowned teeth, which are capable of grinding tough plant tissues and do not wear down as quickly as low-crowned teeth. Most carnivorous mammals have carnassialiforme teeth (of varying length depending on diet), long canines and similar tooth replacement patterns.
The stomach of even-toed ungulates (Artiodactyla) is divided into four sections: the lumen, the reticulum, the oakum and the aromas (only ruminants have a lumen). After the plant material is consumed, it is mixed with saliva in the lumen and reticulum and separates into solid and liquid material.
The solids lump together to form a bolus (or cud), and is regurgitated. When the bolus enters the mouth, the fluid is squeezed out with the tongue and swallowed again.
Ingested food passes to the lumen and reticulum where cellulitis microbes (bacteria, protozoa and fungi) produce cellulose, which is needed to break down the cellulose in plants. Perissodactyls, in contrast to the ruminants, store digested food that has left the stomach in an enlarged cecum, where it is fermented by bacteria.
Carnivora have a simple stomach adapted to digest primarily meat, as compared to the elaborate digestive systems of herbivorous animals, which are necessary to break down tough, complex plant fibers. The cecum is either absent or short and simple, and the large intestine is not calculated or much wider than the small intestine.
The mammalian excretory system involves many components. Like most other land animals, mammals are ureteric, and convert ammonia into urea, which is done by the liver as part of the urea cycle.
Bilirubin, a waste product derived from blood cells, is passed through bile and urine with the help of enzymes excreted by the liver. The passing of bilirubin via bile through the intestinal tract gives mammalian feces a distinctive brown coloration.
Distinctive features of the mammalian kidney include the presence of the renal pelvis and renal pyramids, and of a clearly distinguishable cortex and medulla, which is due to the presence of elongated loops of Hence. Only the mammalian kidney has a bean shape, although there are some exceptions, such as the multilobed geniculate kidneys of pinnies, cetaceans and bears.
Most adult placental mammals have no remaining trace of the cloaca. In the embryo, the embryonic cloaca divides into a posterior region that becomes part of the anus, and an anterior region that has different fates depending on the sex of the individual: in females, it develops into the vestibule that receives the urethra and vagina, while in males it forms the entirety of the penile urethra.
However, the genres, golden moles, and some shrews retain a cloaca as adults. In marsupials, the genital tract is separate from the anus, but a trace of the original cloaca does remain externally.
Honorees, which translates from Greek into “single hole”, have a true cloaca. A diagram of ultrasonic signals emitted by a bat, and the echo from a nearby objects in all other tetra pods, mammals have a larynx that can quickly open and close to produce sounds, and a supra laryngeal vocal tract which filters this sound.
The lungs and surrounding musculature provide the air stream and pressure required to folate. The larynx controls the pitch and volume of sound, but the strength the lungs exert to exhale also contributes to volume.
More primitive mammals, such as the echidna, can only hiss, as sound is achieved solely through exhaling through a partially closed larynx. The movement or tenseness of the vocal folds can result in many sounds such as purring and screaming.
Mammals can change the position of the larynx, allowing them to breathe through the nose while swallowing through the mouth, and to form both oral and nasal sounds; nasal sounds, such as a dog whine, are generally soft sounds, and oral sounds, such as a dog bark, are generally loud. Some mammals have a large larynx and thus a low-pitched voice, namely the hammer-headed bat (Hypsignathus monstrous) where the larynx can take up the entirety of the thoracic cavity while pushing the lungs, heart, and trachea into the abdomen.
Small mammals with small larynges have the ability to produce ultrasound, which can be detected by modifications to the middle ear and cochlea. Ultrasound is inaudible to birds and reptiles, which might have been important during the Mesozoic, when birds and reptiles were the dominant predators.
This private channel is used by some rodents in, for example, mother-to-pup communication, and by bats when echo locating. Toothed whales also use echolocation, but, as opposed to the vocal membrane that extends upward from the vocal folds, they have a melon to manipulate sounds.
Some mammals, namely the primates, have air sacs attached to the larynx, which may function to lower the resonances or increase the volume of sound. The primary function of the fur of mammals is thermoregulation.
Thermoregulation Hair length is not a factor in thermoregulation: for example, some tropical mammals such as sloths have the same length of fur length as some arctic mammals but with less insulation; and, conversely, other tropical mammals with short hair have the same insulating value as arctic mammals. The denseness of fur can increase an animal's insulation value, and arctic mammals especially have dense fur; for example, the musk ox has guard hairs measuring 30 cm (12 in) as well as a dense underfur, which forms an airtight coat, allowing them to survive in temperatures of 40 °C (40 °F).
:162–163 Some desert mammals, such as camels, use dense fur to prevent solar heat from reaching their skin, allowing the animal to stay cool; a camel's fur may reach 70 °C (158 °F) in the summer, but the skin stays at 40 °C (104 °F). :188 Aquatic mammals, conversely, trap air in their fur to conserve heat by keeping the skin dry.
Coloration Camouflage is a powerful influence in many mammals, as it helps to conceal individuals from predators or prey. In arctic and subarctic mammals such as the arctic fox (Alone lag opus), collared lemming (Dicrostonyx Greenlandic), stoat (Muster ermine), and snowshoe hare (Lepus Americans), seasonal color change between brown in summer and white in winter is driven largely by camouflage.
Some arboreal mammals, notably primates and marsupials, have shades of violet, green, or blue skin on parts of their bodies, indicating some distinct advantage in their largely arboreal habitat due to convergent evolution. Aposematic, warning off possible predators, is the most likely explanation of the black-and-white place of many mammals which are able to defend themselves, such as in the foul-smelling skunk and the powerful and aggressive honey badger.
Coat color is sometimes sexually biomorphic, as in many primate species. Differences in female and male coat color may indicate nutrition and hormone levels, important in mate selection.
Coat color may influence the ability to retain heat, depending on how much light is reflected. Mammals with a darker colored coat can absorb more heat from solar radiation, and stay warmer, and some smaller mammals, such as voles, have darker fur in the winter.
The white, pigmentless fur of arctic mammals, such as the polar bear, may reflect more solar radiation directly onto the skin. :166–167 The dazzling black-and-white striping of zebras appear to provide some protection from biting flies.
Goat kids stay with their mother until they are weaned. In male placentals, the penis is used both for urination and copulation. Depending on the species, an erection may be fueled by blood flow into vascular, spongy tissue or by muscular action.
Marsupials typically have forked penises, while the echidna penis generally has four heads with only two functioning. The testes of most mammals descend into the scrotum which is typically posterior to the penis but is often anterior in marsupials.
Female mammals generally have a clitoris, labia major and labia minor on the outside, while the internal system contains paired oviducts, 1-2 uteri, 1-2 cervices and a vagina. The “vagina” of honorees is better understood as an “urogenital sinus”.
The uterine systems of placental mammals can vary between a duplex, were there are two uteri and cervices which open into the vagina, a bipartite, were two uterine horns have a single cervix that connects to the vagina, a biconcave, which consists where two uterine horns that are connected distally but separate medially creating a Y-shape, and a simplex, which has a single uterus. The ancestral condition for mammal reproduction is the birthing of relatively undeveloped, either through direct military or a short period as soft-shelled eggs.
The oldest demonstration of this reproductive style is with Kayentatherium, which produced undeveloped terminates, but at much higher litter sizes than any modern mammal, 38 specimens. Most modern mammals are viviparous, giving birth to live young.
The honorees have a sex determination system different from that of most other mammals. In particular, the sex chromosomes of a platypus are more like those of a chicken than those of a thermal mammal.
Viviparous mammals are in the subclass Their; those living today are in the marsupial and placental infra classes. Marsupials have a short gestation period, typically shorter than its estrous cycle and gives birth to an undeveloped newborn that then undergoes further development; in many species, this takes place within a pouch-like sac, the marsupial, located in the front of the mother's abdomen.
This is the plesiomorphic condition among viviparous mammals ; the presence of epidemic bones in all non-placental mammals prevents the expansion of the torso needed for full pregnancy. The placentals give birth to relatively complete and developed young, usually after long gestation periods.
They get their name from the placenta, which connects the developing fetus to the uterine wall to allow nutrient uptake. In placental mammals, the epidemic is either completely lost or converted into the vacuum; allowing the torso to be able to expand and thus birth developed offspring.
The mammary glands of mammals are specialized to produce milk, the primary source of nutrition for newborns. The young lick the milk from a mammary patch on the mother's belly.
Compared to placental mammals, the milk of marsupials changes greatly in both production rate and in nutrient composition, due to the underdeveloped young. In addition, the mammary glands have more autonomy allowing them to supply separate milks to young at different development stages.
Lactose is the main sugar in placental mammal milk while Montreal and marsupial milk is dominated by oligosaccharides. Weaning is the process in which a mammal becomes less dependent on their mother's milk and more on solid food.
Most mammals also have hair to help keep them warm. Like birds, mammals can forage or hunt in weather and climates too cold for ectothermic (“cold-blooded”) reptiles and insects.
Endotherm requires plenty of food energy, so mammals eat more food per unit of body weight than most reptiles. Small insectivorous mammals eat prodigious amounts for their size.
A rare exception, the naked mole-rat produces little metabolic heat, so it is considered an operational poikilotherm. Birds are also endothermic, so endotherm is not unique to mammals.
Among mammals, species maximum lifespan varies significantly (for example the shrew has a lifespan of two years, whereas the oldest towhead whale is recorded to be 211 years). Although the underlying basis for these lifespan differences is still uncertain, numerous studies indicate that the ability to repair DNA damage is an important determinant of mammalian lifespan.
In a 1974 study by Hart and Set low, it was found that DNA excision repair capability increased systematically with species lifespan among seven mammalian species. Species lifespan was observed to be robustly correlated with the capacity to recognize DNA double-strand breaks as well as the level of the DNA repair protein Ku80.
In a study of the cells from sixteen mammalian species, genes employed in DNA repair were found to be up-regulated in the longer-lived species. The cellular level of the DNA repair enzyme poly ADP ribose polymerase was found to correlate with species lifespan in a study of 13 mammalian species.
Many mammals, such as cats and dogs, are digitigrade, walking on their toes, the greater stride length allowing more speed. Digitigrade mammals are also often adept at quiet movement.
Some animals such as horses are unguligrade, walking on the tips of their toes. A few mammals, namely the great apes, are also known to walk on their knuckles, at least for their front legs.
Some mammals are bipeds, using only two limbs for locomotion, which can be seen in, for example, humans and the great apes. Bipedal species have a larger field of vision than quadrupeds, conserve more energy and have the ability to manipulate objects with their hands, which aids in foraging.
For example, horses show four natural gaits, the slowest horse gait is the walk, then there are three faster gaits which, from slowest to fastest, are the trot, the canter and the gallop. Animals may also have unusual gaits that are used occasionally, such as for moving sideways or backwards.
For example, the main human gaits are bipedal walking and running, but they employ many other gaits occasionally, including a four-legged crawl in tight spaces. Mammals show a vast range of gaits, the order that they place and lift their appendages in locomotion.
Gaits can be grouped into categories according to their patterns of support sequence. Walking is the most common gait, where some feet are on the ground at any given time, and found in almost all legged animals.
Running is considered to occur when at some points in the stride all feet are off the ground in a moment of suspension. Arboreal Gibbons are very good radiators because their elongated limbs enable them to easily swing and grasp on to branches. Arboreal animals frequently have elongated limbs that help them cross gaps, reach fruit or other resources, test the firmness of support ahead and, in some cases, to brachial (swing between trees).
Many arboreal species, such as tree porcupines, silky anteaters, spider monkeys, and possums, use prehensile tails to grasp branches. In the spider monkey, the tip of the tail has either a bare patch or adhesive pad, which provides increased friction.
Claws can be used to interact with rough substrates and reorient the direction of forces the animal applies. This is what allows squirrels to climb tree trunks that are so large to be essentially flat from the perspective of such a small animal.
However, claws can interfere with an animal's ability to grasp very small branches, as they may wrap too far around and prick the animal's own paw. Frictional gripping is used by primates, relying upon hairless fingertips.
Squeezing the branch between the fingertips generates frictional force that holds the animal's hand to the branch. However, this type of grip depends upon the angle of the frictional force, thus upon the diameter of the branch, with larger branches resulting in reduced gripping ability.
To control descent, especially down large diameter branches, some arboreal animals such as squirrels have evolved highly mobile ankle joints that permit rotating the foot into a 'reversed' posture. This allows the claws to hook into the rough surface of the bark, opposing the force of gravity.
Small size provides many advantages to arboreal species: such as increasing the relative size of branches to the animal, lower center of mass, increased stability, lower mass (allowing movement on smaller branches) and the ability to move through more cluttered habitat. Size relating to weight affects gliding animals such as the sugar glider.
Some species of primate, bat and all species of sloth achieve passive stability by hanging beneath the branch. Both pitching and tipping become irrelevant, as the only method of failure would be losing their grip.
They fly through the air at a constant speed by moving their wings up and down (usually with some fore-aft movement as well). Because the animal is in motion, there is some airflow relative to its body which, combined with the velocity of the wings, generates a faster airflow moving over the wing.
This generates a lift force vector pointing forwards and upwards, and a drag force vector pointing rearwards and upwards. The upwards components of these counteract gravity, keeping the body in the air, while the forward component provides thrust to counteract both the drag from the wing and from the body as a whole.
The wings of bats are much thinner and consist of more bones than those of birds, allowing bats to maneuver more accurately and fly with more lift and less drag. By folding the wings inwards towards their body on the upstroke, they use 35% less energy during flight than birds.
The membranes are delicate, ripping easily; however, the tissue of the bat's membrane is able to regrow, such that small tears can heal quickly. The surface of their wings is equipped with touch-sensitive receptors on small bumps called Merkel cells, also found on human fingertips.
These sensitive areas are different in bats, as each bump has a tiny hair in the center, making it even more sensitive and allowing the bat to detect and collect information about the air flowing over its wings, and to fly more efficiently by changing the shape of its wings in response. A tonsorial (from Latin fossil, meaning “digger”) is an animal adapted to digging which lives primarily, but not solely, underground.
Many rodent species are also considered tonsorial because they live in burrows for most but not all the day. Species that live exclusively underground are subterranean, and those with limited adaptations to a tonsorial lifestyle sub-fossorial.
Some organisms are tonsorial to aid in temperature regulation while others use the underground habitat for protection from predators or for food storage. Tonsorial mammals have a uniform body, thickest at the shoulders and tapering off at the tail and nose.
Unable to see in the dark burrows, most have degenerated eyes, but degeneration varies between species; pocket gophers, for example, are only semi-fossorial and have very small yet functional eyes, in the fully tonsorial marsupial mole the eyes are degenerated and useless, Tampa moles have vestigial eyes and the cape golden mole has a layer of skin covering the eyes. External ears flaps are also very small or absent.
The front paws are broad and have strong claws to help in loosening dirt while excavating burrows, and the back paws have webbing, as well as claws, which aids in throwing loosened dirt backwards. Most have large incisors to prevent dirt from flying into their mouth.
Many tonsorial mammals such as shrews, hedgehogs, and moles were classified under the now obsolete order Insectivora. Aquatic Fully aquatic mammals, the cetaceans and Iranians, have lost their legs and have a tail fin to propel themselves through the water.
Whales swim by moving their tail fin and lower body up and down, propelling themselves through vertical movement, while their flippers are mainly used for steering. Their skeletal anatomy allows them to be fast swimmers.
Most species have a dorsal fin to prevent themselves from turning upside-down in the water. The flukes of Iranians are raised up and down in long strokes to move the animal forward, and can be twisted to turn.
The forelimbs are paddle-like flippers which aid in turning and slowing. Semi-aquatic mammals, like pinnies, have two pairs of flippers on the front and back, the fore-flippers and hind-flippers.
In addition to their streamlined bodies, they have smooth networks of muscle bundles in their skin that may increase laminar flow and make it easier for them to slip through water. They also lack arrestor pile, so their fur can be streamlined as they swim.
They rely on their fore-flippers for locomotion in a wing-like manner similar to penguins and sea turtles. Fore-flipper movement is not continuous, and the animal glides between each stroke.
Compared to terrestrial carnivorous, the fore-limbs are reduced in length, which gives the loco motor muscles at the shoulder and elbow joints greater mechanical advantage; the hind-flippers serve as stabilizers. Other semi-aquatic mammals include beavers, hippopotamuses, otters and platypuses.
Hippos are very large semi-aquatic mammals, and their barrel-shaped bodies have graviportal skeletal structures, adapted to carrying their enormous weight, and their specific gravity allows them to sink and move along the bottom of a river. Vocal communication serves many purposes, including in mating rituals, as warning calls, to indicate food sources, and for social purposes.
Males often call during mating rituals to ward off other males and to attract females, as in the roaring of lions and red deer. The songs of the humpback whale may be signals to females; they have different dialects in different regions of the ocean.
Social vocalizations include the territorial calls of gibbons, and the use of frequency in greater spear-nosed bats to distinguish between groups. The velvet monkey gives a distinct alarm call for each of at least four different predators, and the reactions of other monkeys vary according to the call.
For example, if an alarm call signals a python, the monkeys climb into the trees, whereas the eagle alarm causes monkeys to seek a hiding place on the ground. Prairie dogs similarly have complex calls that signal the type, size, and speed of an approaching predator.
Elephants communicate socially with a variety of sounds including snorting, screaming, trumpeting, roaring and rumbling. Some rumbling calls are infrasonic, below the hearing range of humans, and can be heard by other elephants up to 6 miles (9.7 km) away at still times near sunrise and sunset.
Other mammals, called herbivores, eat plants, which contain complex carbohydrates such as cellulose. The digestive tract of a herbivore is host to bacteria that ferment these complex substances, and make them available for digestion, which are either housed in the multichambered stomach or in a large cecum.
Some mammals are coprophagous, consuming feces to absorb the nutrients not digested when the food was first ingested. :131–137 An omnivore eats both prey and plants.
Carnivorous mammals have a simple digestive tract because the proteins, lipids and minerals found in meat require little in the way of specialized digestion. Exceptions to this include baleen whales who also house gut flora in a multi-chambered stomach, like terrestrial herbivores.
The size of an animal is also a factor in determining diet type (Allen's rule). Mammals that weigh less than about 18 ounces (510 g; 1.1 lb) are mostly insectivorous because they cannot tolerate the slow, complex digestive process of a herbivore.
They can therefore tolerate either a slower collection process (carnivores that feed on larger vertebrates) or a slower digestive process (herbivores). Furthermore, mammals that weigh more than 18 ounces (510 g; 1.1 lb) usually cannot collect enough insects during their waking hours to sustain themselves.
The only large insectivorous mammals are those that feed on huge colonies of insects (ants or termites). Some mammals are omnivores and display varying degrees of carnivory and herbivory, generally leaning in favor of one more than the other.
Since plants and meat are digested differently, there is a preference for one over the other, as in bears where some species may be mostly carnivorous and others mostly herbivorous. The dentition of hypo carnivores consists of dull, triangular carnassial teeth meant for grinding food.
Hyper carnivores, however, have conical teeth and sharp carnassials meant for slashing, and in some cases strong jaws for bone-crushing, as in the case of hyenas, allowing them to consume bones; some extinct groups, notably the Machairodontinae, had saber-shaped canines. From a behavioral aspect, this would make them omnivores, but from the physiological standpoint, this may be due to zoopharmacognosy.
Physiologically, animals must be able to obtain both energy and nutrients from plant and animal materials to be considered omnivorous. Thus, such animals are still able to be classified as carnivores and herbivores when they are just obtaining nutrients from materials originating from sources that do not seemingly complement their classification.
For example, it is well documented that some ungulates such as giraffes, camels, and cattle, will gnaw on bones to consume particular minerals and nutrients. Also, cats, which are generally regarded as obligate carnivores, occasionally eat grass to regurgitate indigestible material (such as hairballs), aid with hemoglobin production, and as a laxative.
Many mammals, in the absence of sufficient food requirements in an environment, suppress their metabolism and conserve energy in a process known as hibernation. In the period preceding hibernation, larger mammals, such as bears, become polyphonic to increase fat stores, whereas smaller mammals prefer to collect and stash food.
The slowing of the metabolism is accompanied by a decreased heart and respiratory rate, as well as a drop in internal temperatures, which can be around ambient temperature in some cases. For example, the internal temperatures of hibernating arctic ground squirrels can drop to 2.9 °C (26.8 °F), however the head and neck always stay above 0 °C (32 °F).
A few mammals in hot environments estimate in times of drought or extreme heat, for example the fat-tailed dwarf lemur (Cheirogaleus medium). In intelligent mammals, such as primates, the cerebrum is larger relative to the rest of the brain.
Intelligence itself is not easy to define, but indications of intelligence include the ability to learn, matched with behavioral flexibility. Rats, for example, are considered to be highly intelligent, as they can learn and perform new tasks, an ability that may be important when they first colonize a fresh habitat.
In some mammals, food gathering appears to be related to intelligence: a deer feeding on plants has a brain smaller than a cat, which must think to outwit its prey. Tool use by animals may indicate different levels of learning and cognition.
The sea otter uses rocks as essential and regular parts of its foraging behavior (smashing abalone from rocks or breaking open shells), with some populations spending 21% of their time making tools. Other tool use, such as chimpanzees using twigs to “fish” for termites, may be developed by watching others use tools and may even be a true example of animal teaching.
Tools may even be used in solving puzzles in which the animal appears to experience a “Eureka moment”. Other mammals that do not use tools, such as dogs, can also experience a Eureka moment.
Brain size was previously considered a major indicator of the intelligence of an animal. Since most of the brain is used for maintaining bodily functions, greater ratios of brain to body mass may increase the amount of brain mass available for more complex cognitive tasks.
Cliometric analysis indicates that mammalian brain size scales at approximately the 2 3 or 3 4 exponent of the body mass. Comparison of a particular animal's brain size with the expected brain size based on such cliometric analysis provides an encephalization quotient that can be used as another indication of animal intelligence.
Sperm whales have the largest brain mass of any animal on earth, averaging 8,000 cubic centimeters (490 in 3) and 7.8 kilograms (17 lb) in mature males. Female elephants live in stable groups, along with their offspring. Dolphins are known for their intelligence and travel in groups Socialite is the highest level of social organization.
These societies have an overlap of adult generations, the division of reproductive labor and cooperative caring of young. Usually insects, such as bees, ants and termites, have social behavior, but it is demonstrated in two rodent species: the naked mole-rat and the Maryland mole-rat.
Personality is when animals exhibit more than just sexual interactions with members of the same species, but fall short of qualifying as social. That is, prosocial animals can display communal living, cooperative care of young, or primitive division of reproductive labor, but they do not display all the three essential traits of social animals.
Humans and some species of Callitrichidae (marmosets and tamarind) are unique among primates in their degree of cooperative care of young. Harry Harlow set up an experiment with rhesus monkeys, prosocial primates, in 1958; the results from this study showed that social encounters are necessary in order for the young monkeys to develop both mentally and sexually.
A fission-fusion society is a society that changes frequently in its size and composition, making up a permanent social group called the “parent group”. Permanent social networks consist of all individual members of a community and often varies to track changes in their environment.
In a fission–fusion society, the main parent group can fracture (fission) into smaller stable subgroups or individuals to adapt to environmental or social circumstances. For example, a number of males may break off from the main group in order to hunt or forage for food during the day, but at night they may return to join (fusion) the primary group to share food and partake in other activities.
Many mammals exhibit this, such as primates (for example orangutans and spider monkeys), elephants, spotted hyenas, lions, and dolphins. Solitary animals defend a territory and avoid social interactions with the members of its species, except during breeding season.
This is to avoid resource competition, as two individuals of the same species would occupy the same niche, and to prevent depletion of food. A solitary animal, while foraging, can also be less conspicuous to predators or prey.
In a hierarchy, individuals are either dominant or submissive. Dominant individuals, or alphas, have a high chance of reproductive success, especially in harems where one or a few males (resident males) have exclusive breeding rights to females in a group.
Non-resident males can also be accepted in harems, but some species, such as the common vampire bat (Demons rotundas), may be more strict. Some mammals are perfectly monogamous, meaning that they mate for life and take no other partners (even after the original mate's death), as with wolves, Eurasian beavers, and otters.
It is much more common for polygamous mating to happen, which, excluding less, are estimated to occur in up to 90% of mammals. Led mating occurs when males congregate around females and try to attract them with various courtship displays and vocalizations, as in harbor seals.
All higher mammals (excluding honorees) share two major adaptations for care of the young: live birth and lactation. These imply a group-wide choice of a degree of parental care.
They may build nests and dig burrows to raise their young in, or feed and guard them often for a prolonged period of time. Many mammals are K-selected, and invest more time and energy into their young than do r-selected animals.
When two animals mate, they both share an interest in the success of the offspring, though often to different extremes. Mammalian males may play a role in child rearing, as with genres, however this varies species to species, even within the same genus.
For example, the males of the southern pig-tailed macaque (Maraca pedestrian) do not participate in child care, whereas the males of the Japanese macaque (M. Muscat) do. Non-human mammals play a wide variety of roles in human culture.
They are the most popular of pets, with tens of millions of dogs, cats and other animals including rabbits and mice kept by families around the world. Mammals such as mammoths, horses and deer are among the earliest subjects of art, being found in Upper Paleolithic cave paintings such as at Lascaux.
Major artists such as Albrecht Durer, George Stubby and Edwin Land seer are known for their portraits of mammals. Many species of mammals have been hunted for sport and for food; deer and wild boar are especially popular as game animals.
Mammals such as horses and dogs are widely raced for sport, often combined with betting on the outcome. There is a tension between the role of animals as companions to humans, and their existence as individuals with rights of their own.
Mammals further play a wide variety of roles in literature, film, mythology, and religion. Domestic mammals form a large part of the livestock raised for meat across the world.
Working domestic animals including cattle and horses have been used for work and transport from the origins of agriculture, their numbers declining with the arrival of mechanized transport and agricultural machinery. In 2004, they still provided some 80% of the power for the mainly small farms in the third world, and some 20% of the world's transport, again mainly in rural areas.
In mountainous regions unsuitable for wheeled vehicles, pack animals continue to transport goods. Mammal skins provide leather for shoes, clothing and upholstery.
Wool from mammals including sheep, goats and alpacas has been used for centuries for clothing. Mammals serve a major role in science as experimental animals, both in fundamental biological research, such as in genetics, and in the development of new medicines, which must be tested exhaustively to demonstrate their safety.
Millions of mammals, especially mice and rats, are used in experiments each year. A knockout mouse is a genetically modified mouse with an inactivated gene, replaced or disrupted with an artificial piece of DNA.
They enable the study of sequenced genes whose functions are unknown. A small percentage of the mammals are non-human primates, used in research for their similarity to humans.
Hybrids are offspring resulting from the breeding of two genetically distinct individuals, which will usually result in a high degree of heterozygosity, though hybrid and heterozygous are not synonymous. The deliberate or accidental hybridizing of two or more species of closely related animals through captive breeding is a human activity which has been in existence for millennia and has grown for economic purposes.
Natural hybrids will occur in hybrid zones, where two populations of species within the same genera or species living in the same or adjacent areas will interbreed with each other. Some hybrids have been recognized as species, such as the red wolf (though this is controversial).
Purebred wild species evolved to a specific ecology can be threatened with extinction through the process of genetic pollution, the uncontrolled hybridization, retrogression genetic swamping which leads to homogenization or out-competition from the hetero sic hybrid species. When new populations are imported or selectively bred by people, or when habitat modification brings previously isolated species into contact, extinction in some species, especially rare varieties, is possible.
Interbreeding can swamp the rarer gene pool and create hybrids, depleting the purebred gene pool. For example, the endangered wild water buffalo is most threatened with extinction by genetic pollution from the domestic water buffalo.
Such extinctions are not always apparent from a morphological standpoint. Some degree of gene flow is a normal evolutionary process, nevertheless, hybridization threatens the existence of rare species.
Biodiversity of large mammal species per continent before and after humans arrived thereVarious species are predicted to become extinct in the near future, among them the rhinoceros, primates, pangolins, and giraffes. According to the WWF's 2020 Living Planet Report, vertebrate wildlife populations have declined by 68% since 1970 as a result of human activities, particularly overconsumption, population growth and intensive farming, which is evidence that humans have triggered a sixth mass extinction event.
Hunting alone threatens hundreds of mammalian species around the world. Scientists claim that the growing demand for meat is contributing to biodiversity loss as this is a significant driver of deforestation and habitat destruction ; species-rich habitats, such as significant portions of the Amazon rainforest, are being converted to agricultural land for meat production.
Another influence is over-hunting and poaching, which can reduce the overall population of game animals, especially those located near villages, as in the case of peccaries. The effects of poaching can especially be seen in the ivory trade with African elephants.
Marine mammals are at risk from entanglement from fishing gear, notably cetaceans, with discard moralities ranging from 65,000 to 86,000 individuals annually. Attention is being given to endangered species globally, notably through the Convention on Biological Diversity, otherwise known as the Rio Accord, which includes 189 signatory countries that are focused on identifying endangered species and habitats.
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Euarchontoglires Rodentia (Rats, guinea pigs, squirrels, beavers, chinchillas, porcupines, cabanas and relatives) Lagomorpha (Rabbits and pikes) Scandinavia (Tree shrews) Vermonter (Columns) Primates (lorises, carriers, lemurs, monkeys, apes, humans) © Provided by IndiatimesDiscoveries from mines in Gujarat have recently revealed a deep link between hoofed animals and India.
The discovery of the remains of the creature in India proves that the origin of the group of animals linked to it, including horses and rhinos that we know today, was from the region. It was when land connection formed with India (earlier an island) that the group dispersed to the rest of the known world.
© Provided by India times (Representative Image: Reuters) Indian fossils support new hypothesis for origin of hoofed mammals. “In 2004, our team was able to return to the mine, where our Belgian collaborator Thierry Smith found the first mammal fossils, including Cambaytherium,” Rose said.