88-434: Rabbits are small mammals in the family Leporidae (which also includes the hares ), which is in the order Lagomorpha (which also includes pikas ). They are familiar throughout the world as a wild prey animal, a domesticated form of livestock, and a pet, having a widespread effect on ecologies and cultures. The most widespread rabbit genera are Oryctolagus and Sylvilagus . The former, Oryctolagus , includes
176-407: A common ancestor between lagomorphs and rodents and place them in the clade Glires . Rabbit physiology is suited to escaping predators and surviving in various habitats , living either alone or in groups in nests or burrows. As prey animals, rabbits are constantly aware of their surroundings, having a wide field of vision and ears with high surface area to detect potential predators. The ears of
264-506: A borrowing from the Walloon robète , which was a diminutive of the French or Middle Dutch robbe ("rabbit"), a term of unknown origin. The term coney is a term for an adult rabbit used until the 18th century; rabbit once referred only to the young animals. More recently, the term kit or kitten has been used to refer to a young rabbit. The endearing word bunny is attested by
352-481: A broad range of coat colors and patterns, some of which are produced via dyeing . Some breeds are raised for their wool, such as the Angora rabbit breeds; their fur is sheared, combed or plucked , and the fibers are spun into yarn . The earliest ancestor of rabbits and hares lived 55 million years ago in what is now Mongolia . Because the rabbit's epiglottis is engaged over the soft palate except when swallowing,
440-688: A cellular standpoint, is directly correlated to hind limb muscles. Action pressure from muscles creates force that is then distributed through the skeletal structures. Rabbits that generate less force, putting less stress on bones are more prone to osteoporosis due to bone rarefaction . In rabbits, the more fibers in a muscle, the more resistant to fatigue. For example, hares have a greater resistance to fatigue than cottontails . The muscles of rabbit's hind limbs can be classified into four main categories: hamstrings , quadriceps , dorsiflexors , or plantar flexors . The quadriceps muscles are in charge of force production when jumping. Complementing these muscles are
528-526: A large stray dog in Lazo, Russia . Squirrel attacks on humans are exceedingly rare, but do occur. Whitaker examined the stomachs of 139 thirteen-lined ground squirrels and found bird flesh in four of the specimens and the remains of a short-tailed shrew in one; Bradley, examining the stomachs of white-tailed antelope squirrels , found at least 10% of his 609 specimens' stomachs contained some type of vertebrate, mostly lizards and rodents. Morgart observed
616-409: A layer of tissue sits over the opening of the glottis, which blocks airflow from the oral cavity to the trachea. The epiglottis functions to prevent the rabbit from aspirating on its food. Further, the presence of a soft and hard palate allow the rabbit to breathe through its nose while it feeds. Rabbits' lungs are divided into four lobes: the cranial, middle, caudal, and accessory lobes. The right lung
704-448: A lifespan of 5 to 10 years in the wild. Some can survive 10 to 20 years in captivity. Premature death may occur when a nest falls from the tree, in which case the mother may abandon her young if their body temperature is not correct. Many such baby squirrels have been rescued and fostered by a professional wildlife rehabilitator until they could be safely returned to the wild, although the density of squirrel populations in many places and
792-430: A more digitigrade posture. Rabbits use their strong claws for digging and (along with their teeth) for defense. Each front foot has four toes plus a dewclaw . Each hind foot has four toes (but no dewclaw). Most wild rabbits (especially compared to hares ) have relatively full, egg-shaped bodies. The soft coat of the wild rabbit is agouti in coloration (or, rarely, melanistic ), which aids in camouflage . The tail of
880-629: A near-cosmopolitan distribution. This further supports the hypothesis that the common ancestor of all squirrels, living and fossil, lived in North America, as these three most ancient lineages seem to have radiated from there; if squirrels had originated in Eurasia , for example, one would expect quite ancient lineages in Africa , but African squirrels seem to be of more recent origin. The main group of squirrels can be split into five subfamilies:
968-713: A period of diurnality during the summer. During hot periods, squirrels have been documented to sploot , or lay their stomachs down on cool surfaces. Squirrels, like other rodents, employ species-specific strategies to store food, buffering against periods of scarcity. In temperate regions, squirrels commonly cache nuts beneath leaf litter, inside hollow trees, or underground. However, in subtropical and humid environments, traditional caching can lead to mold growth, decomposition, or premature germination. To counteract these challenges, some squirrels, particularly in subtropical zones, hang nuts or mushrooms on tree branches. This behavior, believed to minimize fungal infections and reduce
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#17327660097071056-501: A rabbit are essential for thermoregulation and contain a high density of blood vessels . The bone structure of a rabbit's hind legs, which is longer than that of the fore legs, allows for quick hopping, which is beneficial for escaping predators and can provide powerful kicks if captured. Rabbits are typically nocturnal and often sleep with their eyes open. They reproduce quickly, having short pregnancies , large litters of four to twelve kits, and no particular mating season ; however,
1144-473: A white-tailed antelope squirrel capturing and eating a silky pocket mouse . The living squirrels are divided into five subfamilies , with about 58 genera and some 285 species . The oldest squirrel fossil, Hesperopetes , dates back to the Chadronian (late Eocene , about 40–35 million years ago ) and is similar to modern flying squirrels. A variety of fossil squirrels, from the latest Eocene to
1232-438: A wide gap, or diastema . The typical dental formula for sciurids is 1.0.1.3 1.0.1.3 . The purposes of squirrels' tails, to benefit the squirrel, include: The hairs from squirrel tails are prized in fly fishing when tying fishing flies . Squirrel hair is very fine, making it better for tying fishing flies. When the squirrel sits upright, its tail folded up its back may stop predators looking from behind from seeing
1320-592: A wide variety of plants, as well as nuts , seeds , conifer cones , fruits , fungi , and green vegetation . Some squirrels, however, also consume meat, especially when faced with hunger. Squirrels have been known to eat small birds , young snakes , and smaller rodents, as well as bird eggs and insects . Some tropical squirrel species have shifted almost entirely to a diet of insects. Squirrels, like pigeons and other fauna, are synanthropes , in that they benefit and thrive from their interaction in human environments. This gradual process of successful interaction
1408-470: Is Lepus , the hares. There are 32 extant species within Lepus . The cladogram is from Matthee et al., 2004, based on nuclear and mitochondrial gene analysis. The term rabbit is typically used for all Leporidae species, excluding the genus Lepus . Members of that genus are known as hares or jackrabbits . Lepus species are precocial , born relatively mature and mobile with hair and good vision out in
1496-675: Is a vertebrate animal of the class Mammalia ( / m ə ˈ m eɪ l i . ə / ). Mammals are characterized by the presence of milk -producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair , and three middle ear bones . These characteristics distinguish them from reptiles and birds , from which their ancestors diverged in the Carboniferous Period over 300 million years ago. Around 6,400 extant species of mammals have been described and divided into 27 orders . The largest orders of mammals, by number of species , are
1584-529: Is below their mouth and rely on their lips and whiskers to determine what they are eating. Blinking occurs 2 to 4 times an hour. The anatomy of rabbits' hind limbs is structurally similar to that of other land mammals and contributes to their specialized form of locomotion. The bones of the hind limbs consist of long bones (the femur , tibia , fibula , and phalanges ) as well as short bones (the tarsals ). These bones are created through endochondral ossification during fetal development. Like most land mammals,
1672-544: Is called a doe , derived from the Old English dā , related to dēon ("to suck"). Rabbits and hares were formerly classified in the order Rodentia (rodents) until 1912, when they were moved into the order Lagomorpha (which also includes pikas ). Since 1945, there has been support for the clade Glires that includes both rodents and lagomorphs, though the two groups have always been closely associated in taxonomy; fossil, DNA , and retrotransposon studies in
1760-744: Is called synurbanization, wherein squirrels lose their inherent fear of humans in an urban environment. When squirrels were almost completely eradicated during the Industrial Revolution in New York , they were later re-introduced to "entertain and remind" humans of nature. The squirrel blended into the urban environment so efficiently that when synanthropic behavior stops (i.e. people do not leave trash outside during particularly cold winters), they can become aggressive in their search for food. Aggression and predatory behavior has been observed in various species of ground squirrels, in particular
1848-444: Is divided into three main parts: foot, thigh, and leg. The hind limbs of a rabbit are an exaggerated feature. They are much longer and can provide more force than the forelimbs, which are structured like brakes to take the brunt of the landing after a leap. The force put out by the hind limbs is contributed by both the structural anatomy of the fusion of the tibia and fibula, and by the muscular features. Bone formation and removal, from
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#17327660097071936-402: Is made up of all four lobes, while the left lung only has two: the cranial and caudal lobes. To provide space for the heart, the left cranial lobe of the lungs is significantly smaller than that of the right. The diaphragm is a muscular structure that lies caudal to the lungs and contracts to facilitate respiration. Rabbits are strict herbivores and are suited to a diet high in fiber, mostly in
2024-703: Is not as frequently used); the Norwegian ikorn / ekorn ; the Dutch eekhoorn ; the Swedish ekorre and the Danish egern . A group of squirrels is called a "dray" or a "scurry". Squirrels are generally small animals, ranging in size from the African pygmy squirrel and least pygmy squirrel at 10–14 cm (3.9–5.5 in) in total length and just 12–26 g (0.42–0.92 oz) in weight, to
2112-572: Is primarily driven by human poaching and habitat destruction , primarily deforestation . Over 70% of mammal species are in the orders Rodentia , Chiroptera , and Eulipotyphla . Mammal classification has been through several revisions since Carl Linnaeus initially defined the class, and at present , no classification system is universally accepted. McKenna & Bell (1997) and Wilson & Reeder (2005) provide useful recent compendiums. Simpson (1945) provides systematics of mammal origins and relationships that had been taught universally until
2200-498: Is processed in the gastrointestinal tract and expelled as regular feces. To get nutrients out of hard to digest fiber, rabbits ferment fiber in the cecum (part of the gastrointestinal tract) and then expel the contents as cecotropes , which are reingested (cecotrophy). The cecotropes are then absorbed in the small intestine to use the nutrients. Soft cecotropes are usually consumed during periods of rest in underground burrows. Rabbits cannot vomit; and therefore if buildup occurs within
2288-467: Is that the ears function as shock absorbers that could aid and stabilize rabbits' vision when fleeing predators, but this has typically only been seen in hares. The rest of the outer ear has bent canals that lead to the eardrum or tympanic membrane . The middle ear, separated by the outer eardrum in the back of the rabbit's skull, contains three bones: the hammer, anvil, and stirrup, collectively called ossicles , which act to decrease sound before it hits
2376-426: Is the viviparous placental mammals , so named for the temporary organ ( placenta ) used by offspring to draw nutrition from the mother 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 , echolocation ; and, in
2464-522: The Bhutan giant flying squirrel at up to 1.27 m (4 ft 2 in) in total length, and several marmot species, which can weigh 8 kg (18 lb) or more. Squirrels typically have slender bodies with very long very bushy tails and large eyes. In general, their fur is soft and silky, though much thicker in some species than others. The coat color of squirrels is highly variable between—and often even within—species. In most squirrel species,
2552-644: The Callosciurinae , 60 species mostly found in South East Asia ; the Ratufinae , 4 cat-sized species found in south and southeast Asia ; the Sciurinae , which contains the flying squirrels (Pteromyini) and the tree squirrels , 83 species found worldwide; Sciurillinae , a single South American species; and Xerinae , which includes three tribes of mostly terrestrial squirrels, including
2640-473: The Cretaceous . The relationships between these three lineages is contentious, and all three possible hypotheses have been proposed with respect to which group is basal . These hypotheses are Atlantogenata (basal Boreoeutheria), Epitheria (basal Xenarthra) and Exafroplacentalia (basal Afrotheria). Boreoeutheria in turn contains two major lineages— Euarchontoglires and Laurasiatheria . Estimates for
2728-674: The Eocene epoch, and among other living rodent families, the squirrels are most closely related to the mountain beaver and dormice . The word squirrel , first attested in 1327, comes from the Anglo-Norman esquirel which is from the Old French escurel , the reflex of a Latin word sciurus , which was taken from the Ancient Greek word σκίουρος ( skiouros ; from σκία-ουρος ) 'shadow-tailed', referring to
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2816-547: The European hare and European or cottontail rabbits , but scientific literature since 1956 has found no evidence of aggression or undue competition between rabbits and hares. When they appear in the same habitat, rabbits and hares can co-exist on similar diets. Hares will notably force other hare species out of an area to control resources, but are not territorial. When faced with predators, hares will escape by outrunning them, whereas rabbits, being smaller and less able to reach
2904-470: The European rabbit , Oryctolagus cuniculus , which is the ancestor of the hundreds of breeds of domestic rabbit and has been introduced on every continent except Antarctica . The latter, Sylvilagus , includes over 13 wild rabbit species, among them the cottontails and tapetis . Wild rabbits not included in Oryctolagus and Sylvilagus include several species of limited distribution , including
2992-564: 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 Mammalogy in 2018, the number of recognized mammal species is 6,495, including 96 recently extinct. The word " mammal " is modern, from the scientific name Mammalia coined by Carl Linnaeus in 1758, derived from
3080-556: The Latin mamma ("teat, pap"). In an influential 1988 paper, Timothy Rowe defined Mammalia phylogenetically as the crown group of mammals, the clade consisting of the most recent common ancestor of living monotremes ( echidnas and platypuses ) and therian 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
3168-495: The Miocene , have not been assigned with certainty to any living lineage. At least some of these probably were variants of the oldest basal "protosquirrels" (in the sense that they lacked the full range of living squirrels' autapomorphies ). The distribution and diversity of such ancient and ancestral forms suggest the squirrels as a group may have originated in North America. Apart from these sometimes little-known fossil forms,
3256-529: The New Zealand white . As livestock, European rabbits are bred for their meat and fur . The earliest breeds were important sources of meat, and so were bred to be larger than wild rabbits at younger ages, but domestic rabbits in modern times range in size from dwarf to giant . Rabbit fur, produced as a byproduct of meat production but occasionally selected for as in the case of the Rex rabbit , can be found in
3344-606: The biological classification scheme used, are the primates : apes , monkeys , and lemurs ; the Cetartiodactyla : whales and even-toed ungulates ; and the Carnivora which includes cats , dogs , weasels , bears , seals , and allies. According to Mammal Species of the World , 5,416 species were identified in 2006. These were grouped into 1,229 genera , 153 families and 29 orders. In 2008,
3432-406: The dominant terrestrial animal group from 66 million years ago to the present. The basic mammalian body type is quadrupedal , with most mammals using four limbs for terrestrial locomotion ; but in some, the limbs are adapted for life at sea , in the air , in trees or underground . The bipeds have adapted to move using only the two lower limbs, while the rear limbs of cetaceans and
3520-496: The family Sciuridae ( / s ɪ ˈ j uː r ɪ d eɪ , - d iː / ), a family that includes small or medium-sized rodents . The squirrel family includes tree squirrels , ground squirrels (including chipmunks and prairie dogs , among others), and flying squirrels . Squirrels are indigenous to the Americas, Eurasia, and Africa, and were introduced by humans to Australia. The earliest known fossilized squirrels date from
3608-496: The genital tubercle and penis . The Sertoli cells triggers the production of Anti-Müllerian duct hormone , which absorbs the Müllerian duct. In an adult male rabbit, the sheath of the penis is cylinder-like and can be extruded as early as two months of age. The scrotal sacs lay lateral to the penis and contain epididymal fat pads which protect the testes. Between 10 and 14 weeks, the testes descend and are able to retract into
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3696-637: The hispid hare is a rabbit. Rabbits, specifically the European rabbit ( Oryctolagus cuniculus ) species, have long been domesticated. The European rabbit has been widely kept as livestock, starting in ancient Rome from at least the first century BC. Selective breeding , which began in the Middle Ages, has generated a wide variety of rabbit breeds , of which many (since the early 19th century) are also kept as pets. Some strains of European rabbit have been bred specifically as research subjects , such as
3784-563: The larynx , and into the lungs. The larynx functions as the rabbit's voice box, which enables it to produce a wide variety of sounds. The trachea is a long tube embedded with cartilaginous rings that prevent the tube from collapsing as air moves in and out of the lungs. The trachea then splits into a left and right bronchus, which meet the lungs at a structure called the hilum . From there, the bronchi split into progressively more narrow and numerous branches. The bronchi branch into bronchioles, into respiratory bronchioles, and ultimately terminate at
3872-465: The phylogeny of the living squirrels is fairly straightforward. The three main lineages are the Ratufinae (Oriental giant squirrels), Sciurillinae and all other subfamilies. The Ratufinae contain a mere handful of living species in tropical Asia . The neotropical pygmy squirrel of tropical South America is the sole living member of the Sciurillinae. The third lineage, by far the largest, has
3960-589: The pygmy rabbit , volcano rabbit , and Sumatran striped rabbit . Rabbits are a paraphyletic grouping, and do not constitute a clade , as hares (belonging to the genus Lepus ) are nested within the Leporidae clade and are not described as rabbits. Although once considered rodents , lagomorphs diverged earlier and have a number of traits rodents lack, including two extra incisors . Similarities between rabbits and rodents were once attributed to convergent evolution , but studies in molecular biology have found
4048-428: The rodents , bats , and Eulipotyphla (including hedgehogs , moles and shrews ). The next three are the primates (including humans , monkeys and lemurs ), the even-toed ungulates (including pigs , camels , and whales ), and the Carnivora (including cats , dogs , and seals ). Mammals are the only living members of Synapsida ; this clade , together with Sauropsida (reptiles and birds), constitutes
4136-439: The sea cows are mere internal vestiges . Mammals range in size from the 30–40 millimetres (1.2–1.6 in) bumblebee bat to the 30 metres (98 ft) blue whale —possibly the largest animal to have ever lived. Maximum lifespan varies from two years for the shrew to 211 years for the bowhead whale . All modern mammals give birth to live young, except the five species of monotremes , which lay eggs. The most species-rich group
4224-402: The thirteen-lined ground squirrel . For example, Bernard Bailey, a scientist in the 1920s, observed a thirteen-lined ground squirrel preying upon a young chicken . Wistrand reported seeing this same species eating a freshly killed snake . There has also been at least one report of squirrels preying on atypical animals, such as an incident in 2005 where a pack of black squirrels killed and ate
4312-589: The 1680s as a diminutive of bun , a term used in Scotland to refer to rabbits and squirrels . Coney is derived from cuniculus , a Latin term referring to rabbits which has been in use from at least the first century BCE in Hispania . The word cuniculus may originate from a diminutive form of the word for " dog " in the Celtic languages . A group of rabbits is known as a colony, nest , or warren , though
4400-809: The 2000s have solidified support for the clade. Studies in paleontology and molecular biology suggest that rodents and lagomorphs diverged at the start of the Tertiary period. Nesolagus (striped rabbits) Poelagus (Bunyoro rabbit) Pronolagus (red rock hares) Romerolagus (volcano rabbit) Sylvilagus (cottontails) [REDACTED] Brachylagus (pygmy rabbit) Caprolagus (hispid hare) Oryctolagus (European rabbit) [REDACTED] Bunolagus (riverine rabbit) Pentalagus (Amami rabbit) Lepus (hares) [REDACTED] The extant species of family Leporidae, of which there are more than 70, are contained within 11 genera , one of which
4488-466: The European rabbit have been developed to suit each of these products; the practice of raising and breeding rabbits as livestock is known as cuniculture . Rabbits are seen in human culture globally, appearing as a symbol of fertility, cunning, and innocence in major religions , historical and contemporary art. The word rabbit derives from the Middle English rabet ("young of the coney"),
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#17327660097074576-518: The European rabbit will form large social groups in burrows , which are grouped together to form warrens . Burrowing by hares varies by location, and is more prominent in younger members of the genus; many rabbit species that do not dig their own burrows will use the burrows of other animals. Rabbits and hares have historically not occupied the same locations, and only became sympatric relatively recently; historic accounts describe antagonistic relationships between rabbits and hares, specifically between
4664-412: The alveolar ducts. The branching that is typically found in rabbit lungs is a clear example of monopodial branching, in which smaller branches divide out laterally from a larger central branch. The structure of the rabbit's nasal and oral cavities necessitates breathing through the nose. This is due to the fact that the epiglottis is fixed to the backmost portion of the soft palate. Within the oral cavity,
4752-420: The brain, allowing it to recognize different sound frequencies. Within the vestibular apparatus three semicircular canals help detect angular motion . The pinnae, which contain a vascular network and arteriovenous shunts, aid in thermoregulation. In a rabbit, the optimal body temperature is around 38.5–40.0 °C (101.3–104.0 °F). If their body temperature exceeds or does not meet this optimal temperature,
4840-492: The case of humans, complex language . Mammals can organize themselves into fission–fusion societies , harems , and hierarchies —but can also be solitary and territorial . Most mammals are polygynous , but some can be monogamous or polyandrous . Domestication of many types of mammals by humans played a major role in the Neolithic Revolution , and resulted in farming replacing hunting and gathering as
4928-409: The characteristic shape of a small mammal. Squirrels live in almost every habitat, from tropical rainforest to semiarid desert , avoiding only the high polar regions and the driest of deserts . They are predominantly herbivorous , subsisting on seeds and nuts, but many will eat insects and even small vertebrates. Many juvenile squirrels die in the first year of life. Adult squirrels can have
5016-812: The clade originating with the last common ancestor of Sinoconodon and living mammals. The earliest-known synapsid 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. However, this animal may have actually evolved during the Neogene. As of the early 21st century, molecular studies based on DNA analysis have suggested new relationships among mammal families. Most of these findings have been independently validated by retrotransposon presence/absence data . Classification systems based on molecular studies reveal three major groups or lineages of placental mammals— Afrotheria , Xenarthra and Boreoeutheria —which diverged in
5104-569: The class Glires ; later, they were separated as the scientific consensus is that many of their similarities were a result of convergent evolution . DNA analysis and the discovery of a common ancestor have supported the view that they share a common lineage, so rabbits and rodents are now often grouped together in the clade or superorder Glires. Since speed and agility are a rabbit's main defenses against predators, rabbits have large hind leg bones and well-developed musculature. Though plantigrade at rest, rabbits are on their toes while running, assuming
5192-444: The closest thing to an official classification of mammals, despite its known issues. 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 , capybaras , and other gnawing mammals; Chiroptera : bats; and Eulipotyphla : shrews , moles , and solenodons . The next three biggest orders, depending on
5280-435: The constant care required by premature squirrels means that few rehabilitators are willing to spend their time doing this and such animals are routinely euthanized instead. Squirrels mate either once or twice a year and, following a gestation period of three to six weeks, give birth to a number of offspring that varies by species. The young are altricial , being born naked, toothless, and blind. In most species of squirrel,
5368-1323: The divergence times between these three placental groups range from 105 to 120 million years ago, depending on the type of DNA used (such as nuclear or mitochondrial ) and varying interpretations of paleogeographic data. Monotremata Marsupialia Xenarthra Afrotheria Glires Euarchonta [REDACTED] Eulipotyphla Chiroptera Pholidota Carnivora [REDACTED] Perissodactyla [REDACTED] Artiodactyla [REDACTED] Monotremata [REDACTED] Paucituberculata [REDACTED] Didelphimorphia [REDACTED] Microbiotheria Notoryctemorphia [REDACTED] Peramelemorphia [REDACTED] Dasyuromorphia [REDACTED] Diprotodontia [REDACTED] Cingulata [REDACTED] Pilosa [REDACTED] Hyracoidea [REDACTED] Sirenia [REDACTED] Proboscidea [REDACTED] Tubulidentata [REDACTED] Macroscelidea [REDACTED] Afrosoricida [REDACTED] Eulipotyphla [REDACTED] Chiroptera [REDACTED] Pholidota [REDACTED] Carnivora [REDACTED] Perissodactyla [REDACTED] Artiodactyla [REDACTED] Scandentia [REDACTED] Lagomorpha [REDACTED] Squirrel Squirrels are members of
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#17327660097075456-585: The earlier Triassic , despite the fact that Triassic fossils in the Haramiyida have been referred to the Mammalia since the mid-19th century. If Mammalia 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. Ambondro is more closely related to monotremes than to therian mammals while Amphilestes and Amphitherium are more closely related to
5544-451: The end of the 20th century. However, since 1945, a large amount of new and more detailed information has gradually been found: The paleontological 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 cladistics . Though fieldwork and lab work progressively outdated Simpson's classification, it remains
5632-493: The female alone looks after the young, which are weaned at six to ten weeks and become sexually mature by the end of their first year. In general, the ground-dwelling squirrel species are social, often living in well-developed colonies, while the tree-dwelling species are more solitary. Ground squirrels and tree squirrels are usually either diurnal or crepuscular , while the flying squirrels tend to be nocturnal —except for lactating flying squirrels and their young, which have
5720-415: The form of cellulose . They will typically graze grass upon waking up and emerging from a burrow, and will move on to consume vegetation and other plants throughout the waking period; rabbits have been known to eat a wide variety of plants, including tree leaves and fruits, though consumption of fruit and lower fiber foods is common for pet rabbits where natural vegetation is scarce. Easily digestible food
5808-625: The hamstrings, which aid in short bursts of action. These muscles play off of one another in the same way as the plantar flexors and dorsiflexors, contributing to the generation and actions associated with force. Within the order of lagomorphs , the ears are used to detect and avoid predators. In the family Leporidae , the ears are typically longer than they are wide, and are in general relatively long compared to other mammals. According to Allen's rule , endothermic animals adapted to colder climates have shorter, thicker limbs and appendages than those of similar animals adapted to warm climates. The rule
5896-401: The hard and soft palate. The nasal cavity itself is separated into a left and right side by a cartilage barrier, and it is covered in fine hairs that trap dust before it can enter the respiratory tract . As the rabbit breathes, air flows in through the nostrils along the alar folds. From there, the air moves into the nasal cavity, also known as the nasopharynx , down through the trachea, through
5984-606: The high speeds of longer-legged hares, will try to seek cover. Descendants of the European rabbit are commonly bred as livestock and kept as pets, whereas no hares have been domesticated , though populations have been introduced to non-native habitats for use as a food source. The breed known as the Belgian hare is actually a domestic rabbit which has been selectively bred to resemble a hare, most likely from Flemish Giant stock originally. Common names of hare and rabbit species may also be confused; "jackrabbits" refer to hares, and
6072-433: The hind limbs are longer than the forelimbs, while all species have either four or five toes on each foot. The feet, which include an often poorly developed thumb , have soft pads on the undersides and versatile, sturdy claws for grasping and climbing . Tree squirrels , unlike most mammals, can descend a tree headfirst. They do so by rotating their ankles 180 degrees, enabling the hind feet to point backward and thus grip
6160-464: The inner ear; in general, the ossicles act as a barrier to the inner ear for sound energy. Inner ear fluid, called endolymph , receives the sound energy. After receiving the energy. The inner ear comprises two parts: the cochlea that uses sound waves from the ossicles, and the vestibular apparatus that manages the rabbit's position in regard to movement. Within the cochlea a basilar membrane contains sensory hair structures that send nerve signals to
6248-516: The intestines (due often to a diet with insufficient fibre), intestinal blockage can occur. The adult male reproductive system forms the same as most mammals with the seminiferous tubular compartment containing the Sertoli cells and an adluminal compartment that contains the Leydig cells . The Leydig cells produce testosterone , which maintains libido and creates secondary sex characteristics such as
6336-668: The larger Amniota clade. Early synapsids are referred to as " pelycosaurs ." The more advanced therapsids became dominant during the Guadalupian . Mammals originated from cynodonts , an advanced group of therapsids, during the Late Triassic to Early Jurassic . Mammals achieved their modern diversity in the Paleogene and Neogene periods of the Cenozoic era, after the extinction of non-avian dinosaurs , and have been
6424-466: The latter term more commonly refers to where the rabbits live. A group of baby rabbits produced from a single mating is referred to as a litter and a group of domestic rabbits living together is sometimes called a herd . A male rabbit is called a buck , as are male goats and deer , derived from the Old English bucca or bucc , meaning "he-goat" or "male deer", respectively. A female
6512-515: The long bushy tail which many of its members have. Sciurus is also the name of one of its genuses. The native Old English word for the squirrel, ācweorna , only survived into Middle English (as aquerne ) before being replaced. The Old English word is of Common Germanic origin, cognates of which are still used in other Germanic languages , including the German Eichhörnchen (diminutive of Eichhorn , which
6600-435: The mortality rate of rabbit embryos is high, and there exist several widespread diseases that affect rabbits, such as rabbit hemorrhagic disease and myxomatosis . In some regions, especially Australia , rabbits have caused ecological problems and are regarded as a pest. Humans have used rabbits as livestock since at least the first century BC in ancient Rome , raising them for their meat, fur and wool. The various breeds of
6688-496: The mortise-tenon joint in carpentry. Because squirrels cannot digest cellulose , they must rely on foods rich in protein , carbohydrates , and fats . In temperate regions, early spring is the hardest time of year for squirrels because the nuts they buried are beginning to sprout (and thus are no longer available to eat), while many of the usual food sources are not yet available. During these times, squirrels rely heavily on tree buds. Squirrels, being primarily herbivores , eat
6776-401: The open air, while rabbit species are altricial , born hairless and blind in burrows and buried nests. Hares are also generally larger than rabbits, and have longer pregnancies . Hares and some rabbits live relatively solitary lives above the ground in open grassy areas, interacting mainly during breeding season. Some rabbit species group together to reduce their chance of being preyed upon, and
6864-530: The pelvic cavity to thermoregulate. Furthermore, the secondary sex characteristics, such as the testes, are complex and secrete many compounds. These compounds include fructose , citric acid , minerals, and a uniquely high amount of catalase , all of which affect the characteristics of rabbit semen; for instance, citric acid is positively correlated with agglutination , and high amounts of catalase protect against premature capacitation . Mammal A mammal (from Latin mamma 'breast')
6952-716: The primary source of food for humans. 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, kept as pets and working animals of various types, 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
7040-407: The rabbit (with the exception of the cottontail species ) is dark on top and white below. Cottontails have white on the top of their tails. As a result of the position of the eyes in its skull and the size of the cornea, the rabbit has a panoramic field of vision that encompasses nearly 360 degrees. However, there is a blind spot at the bridge of the nose, and because of this, rabbits cannot see what
7128-406: The rabbit is an obligate nasal breather . As lagomorphs, rabbits have two sets of incisor teeth, one behind the other, a manner in which they differ from rodents, which only have one set of incisors. Another difference is that for rabbits, all of their teeth continue to grow, whereas for most rodents, only their incisors continue to grow. Carl Linnaeus originally grouped rabbits and rodents under
7216-434: The rabbit must make efforts to return to homeostasis . Homeostasis of body temperature is maintained by changing the amount of blood flow that passes through the highly vascularized ears, as rabbits have few to no sweat glands . Rabbits may also regulate their temperature by resting in depressions in the ground, known as forms. The rabbit's nasal cavity lies dorsal to the oral cavity, and the two compartments are separated by
7304-414: The risk of food loss, also inadvertently aids certain trees, like Cyclobalanopsis , in expanding their range, with forgotten or dislodged nuts sprouting in new locations, influencing forest ecology. Two species of flying squirrel, the particolored flying squirrel and Hainan flying squirrel aid such cacheing by carving grooves into the nuts to fix the nuts tightly between small intersecting twigs, akin to
7392-955: The round head of the femur articulates with the acetabulum of the os coxae , the hip bone. The femur articulates with the tibia, but not the fibula, which is fused to the tibia. The tibia and fibula articulate with the tarsals of the pes , commonly called the foot. The hind limbs of the rabbit are longer than the front limbs. This allows them to produce their hopping form of locomotion. Longer hind limbs are more capable of producing faster speeds. Hares, which have longer legs than cottontail rabbits , are able to move considerably faster. The hind feet have four long toes that allow for digitigrade movement, which are webbed to prevent them from spreading when hopping. Rabbits do not have paw pads on their feet like most other animals that use digitigrade locomotion. Instead, they have coarse compressed hair that offers protection. Rabbits have muscled hind legs that allow for maximum force, maneuverability, and acceleration that
7480-548: The therians; as fossils of all three genera are dated about 167 million years ago in the Middle Jurassic , this is a reasonable estimate for the appearance of the crown group. T. S. Kemp has provided a more traditional definition: " Synapsids that possess a dentary – squamosal jaw articulation and occlusion between upper and lower molars with a transverse component to the movement" or, equivalently in Kemp's view,
7568-446: The tree bark from the opposite direction. As their large eyes indicate, squirrels have excellent vision , which is especially important for the tree-dwelling species. Many also have a good sense of touch , with vibrissae on their limbs as well as their heads. The teeth of sciurids follow the typical rodent pattern, with large incisors (for gnawing) that grow throughout life, and cheek teeth (for grinding) that are set back behind
7656-481: The way the outer, middle, and inner ear muscles coordinate with one another. The ear muscles also aid in maintaining balance and movement when fleeing predators. The auricle , also known as the pinna, is a rabbit's outer ear. The rabbit's pinnae represent a fair part of the body surface area. It is theorized that the ears aid in dispersion of heat at temperatures above 30 °C (86 °F), with rabbits in warmer climates having longer pinnae due to this. Another theory
7744-456: Was originally derived by comparing the ear lengths of Lepus species across the various climates of North America. Subsequent studies show that this rule remains true in the Leporidae for the ears specifically, in that the surface area of rabbits' and hares' ears are enlarged in warm climates; the ears are an important structure to aid thermoregulation as well as in detecting predators due to
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