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106-620: Porcupines are large rodents with coats of sharp spines , or quills, that protect them against predation . The term covers two families of animals: the Old World porcupines of the family Hystricidae , and the New World porcupines of the family Erethizontidae . Both families belong to the infraorder Hystricognathi within the profoundly diverse order Rodentia and display superficially similar coats of rigid or semi-rigid quills, which are modified hairs composed of keratin. Despite this,
212-442: A 20–25 cm (8–10 in) long tail. Weighing 5–16 kg (12–35 lb), they are rounded, large, and slow, and use an aposematic strategy of defence. Porcupines' colouration consists of various shades of brown, grey and white. Porcupines' spiny protection resembles that of the only distantly related erinaceomorph hedgehogs and Australian monotreme echidnas as well as tenrecid tenrecs . The word porcupine comes from
318-414: A burrow and one male defending a territory around the burrow. At high population densities, this system breaks down and males show a hierarchical system of dominance with overlapping ranges. Female offspring remain in the colony while male young disperse. The prairie vole is monogamous and forms a lifelong pair bond. Outside the breeding season, prairie voles live with others in small colonies. A male
424-491: A colony of their own. Rodents use scent marking in many social contexts including inter- and intra-species communication, the marking of trails and the establishment of territories. Their urine provides genetic information about individuals including the species, the sex and individual identity, and metabolic information on dominance, reproductive status and health. Compounds derived from the major histocompatibility complex (MHC) are bound to several urinary proteins. The odor of
530-406: A distinct "chirping", has been likened to laughter , and is interpreted as an expectation of something rewarding. In clinical studies, the chirping is associated with positive emotional feelings, and social bonding occurs with the tickler, resulting in the rats becoming conditioned to seek the tickling. However, as the rats age, the tendency to chirp declines. Like most rat vocalizations, the chirping
636-776: A dramatic impact on aging. For instance, Pacific Ocean rockfishes have widely varying lifespans. The species Sebastes minor lives a mere 11 years while its cousin Sebastes aleutianus can live for more than 2 centuries. Similarly, a chameleon , Furcifer labordi , is the current record holder for shortest lifespan among tetrapods , with only 4–5 months to live. By contrast, some of its relatives, such as Furcifer pardalis , have been found to live up to 6 years. There are studies about aging-related characteristics of and aging in long-lived animals like various turtles and plants like Ginkgo biloba trees. They have identified potentially causal protective traits and suggest many of
742-485: A few are predators. The field vole is a typical herbivorous rodent and feeds on grasses, herbs, root tubers, moss, and other vegetation, and gnaws on bark during the winter. It occasionally eats invertebrates such as insect larvae. The plains pocket gopher eats plant material found underground during tunneling, and also collects grasses, roots, and tubers in its cheek pouches and caches them in underground larder chambers. The Texas pocket gopher avoids emerging onto
848-588: A few have become specialized to rely on a diet of animal matter. A functional-morphological study of the rodent tooth system supports the idea that primitive rodents were omnivores rather than herbivores. Studies of the literature show that numerous members of the Sciuromorpha and Myomorpha, and a few members of the Hystricomorpha, have either included animal matter in their diets or been prepared to eat such food when offered it in captivity. Examination of
954-444: A high-fiber diet; their molars have no roots and grow continuously like their incisors. In many species, the molars are relatively large, intricately structured, and highly cusped or ridged. Rodent molars are well equipped to grind food into small particles. The jaw musculature is strong. The lower jaw is thrust forward while gnawing and is pulled backwards during chewing. Gnawing uses incisors and chewing uses molars, however, due to
1060-539: A means of intra-specific communication during courtship among the Cape mole rat . Footdrumming has been reported to be involved in male-male competition; the dominant male indicates its resource holding potential by drumming, thus minimizing physical contact with potential rivals. Some species of rodent are monogamous, with an adult male and female forming a lasting pair bond . Monogamy can come in two forms; obligate and facultative. In obligate monogamy, both parents care for
1166-686: A part in social communication between dormice and are used when the individuals are out of sight of each other. House mice use both audible and ultrasonic calls in a variety of contexts. Audible vocalizations can often be heard during agonistic or aggressive encounters, whereas ultrasound is used in sexual communication and also by pups when they have fallen out of the nest. Laboratory rats (which are brown rats, Rattus norvegicus ) emit short, high frequency, ultrasonic vocalizations during purportedly pleasurable experiences such as rough-and-tumble play, when anticipating routine doses of morphine , during mating, and when tickled. The vocalization, described as
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#17327650743971272-530: A population, whereas life expectancy is defined statistically as the average number of years remaining at a given age. For example, a population's life expectancy at birth is the same as the average age at death for all people born in the same year (in the case of cohorts ). Longevity studies may involve putative methods to extend life. Longevity has been a topic not only for the scientific community but also for writers of travel , science fiction , and utopian novels. The legendary fountain of youth appeared in
1378-412: A porcupine: (in order from least to most aggressive) quill erection, teeth clattering, odour emission, and attack. A porcupine's colouring aids in part of its defence as most of the predators are nocturnal and colour-blind. A porcupine's markings are black and white. The dark body and coarse hair of the porcupine are dark brown/black and when quills are raised, present a white strip down its back mimicking
1484-458: A predator depresses scent-marking behavior. Rodents are able to recognize close relatives by smell and this allows them to show nepotism (preferential behavior toward their kin) and also avoid inbreeding. This kin recognition is by olfactory cues from urine, feces and glandular secretions. The main assessment may involve the MHC, where the degree of relatedness of two individuals is correlated to
1590-499: A predator warning or defensive action. It is used primarily by fossorial or semi-fossorial rodents. The banner-tailed kangaroo rat produces several complex footdrumming patterns in a number of different contexts, one of which is when it encounters a snake. The footdrumming may alert nearby offspring but most likely conveys that the rat is too alert for a successful attack, thus preventing the snake's predatory pursuit. Several studies have indicated intentional use of ground vibrations as
1696-653: A promising candidate for further research within the field. Their study suggests that high levels of iron in the blood likely reduce, and genes involved in metabolising iron likely increase healthy years of life in humans. Longevity is a highly plastic trait, and traits that influence its components respond to physical (static) environments and to wide-ranging life-style changes: physical exercise, dietary habits, living conditions, and pharmaceutical as well as nutritional interventions. A 2012 study found that even modest amounts of leisure time physical exercise can extend life expectancy by as much as 4.5 years. As of 2021, there
1802-412: A quill that has pierced the skin. The shape of the barbs makes the quills effective for penetrating the skin and for remaining in place. The quills have inspired research for such applications as the design of hypodermic needles and surgical staples. In contrast to the current design for surgical staples, the porcupine quill and barb design would allow easy and painless insertion, as the staple would stay in
1908-551: A rocky environment. Porcupines can be found on rocky areas up to 3,700 m (12,100 ft) high. They are generally nocturnal but are occasionally active during daylight. Porcupines are distributed into two evolutionarily independent groups within the suborder Hystricomorpha of the Rodentia. Rodent Rodents (from Latin rodere , 'to gnaw') are mammals of the order Rodentia ( / r oʊ ˈ d ɛ n ʃ ə / roh- DEN -shə ), which are characterized by
2014-403: A single female monopolizes mating from at least three males. In most rodent species, such as brown rats and house mice, ovulation occurs on a regular cycle while in others, such as voles, it is induced by mating . During copulation, males of some rodent species deposit a mating plug in the female's genital opening, both to prevent sperm leakage and to protect against other males inseminating
2120-678: A single pair of continuously growing incisors in each of the upper and lower jaws . About 40% of all mammal species are rodents. They are native to all major land masses except for Antarctica , and several oceanic islands, though they have subsequently been introduced to most of these land masses by human activity. Rodents are extremely diverse in their ecology and lifestyles and can be found in almost every terrestrial habitat, including human-made environments. Species can be arboreal , fossorial (burrowing), saltatorial /ricochetal (leaping on their hind legs), or semiaquatic. However, all rodents share several morphological features, including having only
2226-412: A single upper and lower pair of ever-growing incisors. Well-known rodents include mice , rats , squirrels , prairie dogs , porcupines , beavers , guinea pigs , and hamsters . However, rabbits , hares , and pikas , which also have incisors that grow continuously (but have two pairs of upper incisors instead of one), were once included with rodents, but are now considered to be in a separate order,
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#17327650743972332-549: A small part of its diet is plant material. It has a chunky body with short legs and tail, but is agile and can easily overpower prey as large as itself. Rodents exhibit a wide range of types of social behavior ranging from the mammalian caste system of the naked mole-rat , the extensive "town" of the colonial prairie dog , through family groups to the independent, solitary life of the edible dormouse . Adult dormice may have overlapping feeding ranges, but they live in individual nests and feed separately, coming together briefly in
2438-399: Is aided by the hollow quills at the back end of the porcupine. The use of odour is when the sight and sound have failed. An unpleasant scent is produced from the skin above the tail in times of stress and is often seen with a quill erection. If these processes fail, the porcupine will attack by running sideways or backwards into predators. A porcupine's tail can also be swung in the direction of
2544-404: Is at frequencies too high for humans to hear without special equipment, so bat detectors have been used for this purpose. Rodents, like all placental mammals except primates, have just two types of light receptive cones in their retina, a short wavelength "blue-UV" type and a middle wavelength "green" type. They are therefore classified as dichromats ; however, they are visually sensitive into
2650-641: Is evident in particular subgroups of rodents like kangaroo rats , hamsters, chipmunks and gophers which have two bags that may range from the mouth to the front of the shoulders. True mice and rats do not contain this structure but their cheeks are elastic due to a high degree of musculature and innervation in the region. While the largest species, the capybara , can weigh as much as 66 kg (146 lb), most rodents weigh less than 100 g (3.5 oz). Rodents have wide-ranging morphologies, but typically have squat bodies and short limbs. The fore limbs usually have five digits, including an opposable thumb, while
2756-402: Is mostly driven by the brain stem, which is itself provoked by the cortex. However Legg et al. 1989 find an alternate circuit between the cortex and whiskers through the cerebellar circuits, and Hemelt & Keller 2008 the superior colliculus. Some rodents have cheek pouches , which may be lined with fur. These can be turned inside out for cleaning. In many species, the tongue cannot reach past
2862-527: Is no clinical evidence that any dietary practice contributes to human longevity. Four well-studied biological pathways that are known to regulate aging, and whose modulation has been shown to influence longevity are Insulin/IGF-1 , mechanistic target of rapamycin ( mTOR ), AMP-activating protein kinase ( AMPK ), and Sirtuin pathways. Autophagy plays a pivotal role in healthspan and lifespan extension . In preindustrial times, deaths at young and middle age were more common than they are today. This
2968-915: Is not aggressive towards other males until he has mated, after which time he defends a territory, a female, and a nest against other males. The pair huddles together, grooms one another, and shares nesting and pup-raising responsibilities. Among the most social of rodents are the ground squirrels, which typically form colonies based on female kinship, with males dispersing after weaning and becoming nomadic as adults. Cooperation in ground squirrels varies between species and typically includes making alarm calls, defending territories, sharing food, protecting nesting areas, and preventing infanticide. The black-tailed prairie dog forms large towns that may cover many hectares. The burrows do not interconnect, but are excavated and occupied by territorial family groups known as coteries. A coterie often consists of an adult male, three or four adult females, several nonbreeding yearlings, and
3074-562: Is not due to genetics, but because of environmental factors such as disease, accidents, and malnutrition, especially since the former were not generally treatable with pre-20th-century medicine. Deaths from childbirth were common for women, and many children did not live past infancy. In addition, most people who did attain old age were likely to die quickly from the above-mentioned untreatable health problems. Despite this, there are several examples of pre-20th-century individuals attaining lifespans of 85 years or greater, including John Adams , Cato
3180-400: Is not understood why this pattern occurs, but in the case of yellow-pine chipmunks , males may have selected larger females due to their greater reproductive success. In some species, such as voles , sexual dimorphism can vary from population to population. In bank voles , females are typically larger than males, but male-bias sexual dimorphism occurs in alpine populations, possibly because of
3286-402: Is so rare is that certain categories of gene expression that are beneficial in youth become deleterious at an older age. Longevity myths are traditions about long-lived people (generally supercentenarians ), either as individuals or groups of people, and practices that have been believed to confer longevity, but for which scientific evidence does not support the ages claimed or the reasons for
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3392-538: Is some question as to whether these mothers can distinguish which young are theirs. In the Patagonian mara , young are also placed in communal warrens, but mothers do not permit youngsters other than their own to nurse. Infanticide exists in numerous rodent species and may be practiced by adult conspecifics of either sex. Several reasons have been proposed for this behavior, including nutritional stress, resource competition, avoiding misdirecting parental care and, in
3498-431: Is sometimes positively correlated to its structural complexity. It suggests that while biological complexity increases individual lifespan, it is counteracted in nature since the survivability of the overall species may be hindered when it results in a prolonged development process , which is an evolutionarily vulnerable state. According to the antagonistic pleiotropy hypothesis , one of the reasons biological immortality
3604-406: The Cape ground squirrel , the male's testes can be 20 percent of its head-body length. Several rodent species have flexible mating systems that can vary between monogamy, polygyny and promiscuity. Female rodents play an active role in choosing their mates. Factors that contribute to female preference may include the size, dominance and spatial ability of the male. In the eusocial naked mole rats,
3710-605: The Great Plains of North America, the burrowing activities of prairie dogs play important roles in soil aeration and nutrient redistribution, raising the organic content of the soil and increasing the absorption of water. They maintain these grassland habitats, and some large herbivores such as bison and pronghorn prefer to graze near prairie dog colonies due to the increased nutritional quality of forage. Extirpation of prairie dogs can also contribute to regional and local biodiversity loss , increased seed depredation, and
3816-803: The Hystricognathi branch of the vast order Rodentia , they are not closely related. The 11 Old World porcupines tend to be fairly large and have spines grouped in clusters. The two subfamilies of New World porcupines are mostly smaller (although the North American porcupine reaches about 85 cm or 33 in in length and 18 kg or 40 lb), have their quills attached singly rather than grouped in clusters, and are excellent climbers, spending much of their time in trees. The New World porcupines evolved their spines independently (through convergent evolution ) and are more closely related to several other families of rodents than they are to
3922-811: The Lagomorpha . Nonetheless, Rodentia and Lagomorpha are sister groups , sharing a single common ancestor and forming the clade of Glires . Most rodents are small animals with robust bodies, short limbs, and long tails. They use their sharp incisors to gnaw food, excavate burrows, and defend themselves. Most eat seeds or other plant material, but some have more varied diets. They tend to be social animals and many species live in societies with complex ways of communicating with each other. Mating among rodents can vary from monogamy , to polygyny , to promiscuity . Many have litters of underdeveloped, altricial young, while others are precocial (relatively well developed) at birth. The rodent fossil record dates back to
4028-463: The Latin porcus ' pig ' + spina ' spine, quill ' , from Old Italian porcospino , ' thorn-pig ' . A regional American name for the animal is quill-pig . A baby porcupine is a porcupette. When born, a porcupette's quills are soft hair; they harden within a few days, forming the sharp quills of adults. Fossils belonging to the genus Hystrix date back to the late Miocene of
4134-488: The Native American "porky roach" headdress. The main quills may be dyed and then applied in combination with thread to embellish leather accessories, such as knife sheaths and leather bags. Lakota women would harvest the quills for quillwork by throwing a blanket over a porcupine and retrieving the quills left stuck in the blanket. The presence of barbs, acting like anchors, causes increased pain when removing
4240-585: The Paleocene on the supercontinent of Laurasia . Rodents greatly diversified in the Eocene , as they spread across continents, sometimes even crossing oceans . Rodents reached both South America and Madagascar from Africa and, until the arrival of Homo sapiens , were the only terrestrial placental mammals to reach and colonize Australia. Rodents have been used as food, for clothing, as pets , and as laboratory animals in research. Some species, in particular,
4346-408: The brown rat , the black rat , and the house mouse , are serious pests , eating and spoiling food stored by humans and spreading diseases. Accidentally introduced species of rodents are often considered to be invasive and have caused the extinction of numerous species, such as island birds, the dodo being an example, previously isolated from land-based predators. The distinguishing feature of
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4452-410: The eastern grey squirrel , have a large deep masseter , making them efficient at biting with the incisors. The Myomorpha , such as the brown rat, have enlarged temporalis and masseter muscles, making them able to chew powerfully with their molars. In rodents, masseter muscles insert behind the eyes and contribute to eye boggling that occurs during gnawing where the quick contraction and relaxation of
4558-890: The 1901 and 1911 British censuses. Time magazine considered that, by the Soviet Union, longevity had been elevated to a state-supported "Methuselah cult". Robert Ripley regularly reported supercentenarian claims in Ripley's Believe It or Not! , usually citing his own reputation as a fact-checker to claim reliability. Longevity in other animals can shed light on the determinants of life expectancy in humans, especially when found in related mammals . However, important contributions to longevity research have been made by research in other species, ranging from yeast to flies to worms . In fact, some closely related species of vertebrates can have dramatically different life expectancies, demonstrating that relatively small genetic changes can have
4664-542: The DNA repair protein PARP ( Poly ADP ribose polymerase ) than cell lines from younger (20 to 70 year old) individuals. The lymphocytic cells of centenarians have characteristics typical of cells from young people, both in their capability of priming the mechanism of repair after H 2 O 2 sublethal oxidative DNA damage and in their PARP gene expression. These findings suggest that elevated PARP gene expression contributes to
4770-516: The Elder , Thomas Hobbes , Christopher Polhem , and Michelangelo . This was also true for poorer people like peasants or laborers . Genealogists will almost certainly find ancestors living to their 70s, 80s and even 90s several hundred years ago. For example, an 1871 census in the UK (the first of its kind, but personal data from other censuses dates back to 1841 and numerical data back to 1801) found
4876-621: The MHC genes they have in common. In non-kin communication, where more permanent odor markers are required, as at territorial borders, then non-volatile major urinary proteins (MUPs), which function as pheromone transporters, may also be used. MUPs may also signal individual identity, with each male house mouse ( Mus musculus ) excreting urine containing about a dozen genetically encoded MUPs. House mice deposit urine, which contains pheromones, for territorial marking, individual and group recognition, and social organization. Territorial beavers and red squirrels investigate and become familiar with
4982-481: The Old World porcupines. Porcupines have a relatively high longevity and hold the record for being the longest-living rodent, with one individual named Cooper living over 32 years. The North American porcupine is a herbivore and often climbs trees for food; it eats leaves, herbs, twigs, and green plants such as clover . In the winter, it may eat bark. The African porcupine is not a climber; instead, it forages on
5088-441: The amount of UV that is reflected decreases with time, which in some circumstances can be disadvantageous; the common kestrel can distinguish between old and fresh rodent trails and has greater success hunting over more recently marked routes. Vibrations can provide cues to conspecifics about specific behaviors being performed, predator warning and avoidance, herd or group maintenance, and courtship. The Middle East blind mole rat
5194-554: The average male life expectancy as being 44, but if infant mortality is subtracted, males who lived to adulthood averaged 75 years. The present life expectancy in the UK is 77 years for males and 81 for females, while the United States averages 74 for males and 80 for females. Studies have shown that black American males have the shortest lifespans of any group of people in the US, averaging only 69 years (Asian-American females average
5300-524: The breeding season to mate. The pocket gopher is also a solitary animal outside the breeding season, each individual digging a complex tunnel system and maintaining a territory. Larger rodents tend to live in family units where parents and their offspring live together until the young disperse. Beavers live in extended family units typically with a pair of adults, this year's kits, the previous year's offspring, and sometimes older young. Brown rats usually live in small colonies with up to six females sharing
5406-713: The case of males, attempting to make the mother sexually receptive. The latter reason is well supported in primates and lions but less so in rodents. Infanticide appears to be widespread in black-tailed prairie dogs, including infanticide from invading males and immigrant females, as well as occasional cannibalism of an individual's own offspring. To protect against infanticide from other adults, female rodents may employ avoidance or direct aggression against potential perpetrators, multiple mating, territoriality or early termination of pregnancy. Feticide can also occur among rodents; in Alpine marmots , dominant females tend to suppress
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#17327650743975512-666: The claims. A comparison and contrast of "longevity in antiquity" (such as the Sumerian King List , the genealogies of Genesis , and the Persian Shahnameh ) with "longevity in historical times" (common-era cases through twentieth-century news reports) is elaborated in detail in Lucian Boia 's 2004 book Forever Young: A Cultural History of Longevity from Antiquity to the Present and other sources. After
5618-622: The continent of Africa. A porcupine is any of 30 species of rodents belonging to the families Erethizontidae (genera: Coendou , Erethizon , and Chaetomys ) or Hystricidae (genera: Atherurus , Hystrix , and Trichys ). Porcupines vary in size considerably: Rothschild's porcupine of South America weighs less than a kilogram (2.2 lb); the crested porcupine found in Italy , North Africa , and sub-Saharan Africa can grow to well over 27 kg (60 lb). The two families of porcupines are quite different, and although both belong to
5724-479: The cranial anatomy of rodents these feeding methods cannot be used at the same time and are considered to be mutually exclusive. Among rodents, the masseter muscle plays a key role in chewing, making up 60% – 80% of the total muscle mass among masticatory muscles and reflects rodents' herbivorous diet. Rodent groups differ in the arrangement of the jaw muscles and associated skull structures, both from other mammals and amongst themselves. The Sciuromorpha , such as
5830-412: The current year's offspring. Individuals within coteries are friendly with each other, but hostile towards outsiders. Perhaps the most extreme examples of colonial behavior in rodents are the eusocial naked mole rat and Damaraland mole rat . The naked mole rat lives completely underground and can form colonies of up to 80 individuals. Only one female and up to three males in the colony reproduce, while
5936-693: The death of Juan Ponce de León , Gonzalo Fernández de Oviedo y Valdés wrote in Historia General y Natural de las Indias (1535) that Ponce de León was looking for the waters of Bimini to cure his aging. Traditions that have been believed to confer greater human longevity also include alchemy , such as that attributed to Nicolas Flamel . In the modern era, the Okinawa diet has some reputation of linkage to exceptionally high ages. Longevity claims may be subcategorized into four groups: "In late life, very old people often tend to advance their ages at
6042-594: The degu less visible to predators. Ultraviolet light is abundant during the day but not at night. There is a large increase in the ratio of ultraviolet to visible light in the morning and evening twilight hours. Many rodents are active during twilight hours (crepuscular activity), and UV-sensitivity would be advantageous at these times. Ultraviolet reflectivity is of dubious value for nocturnal rodents. The urine of many rodents (e.g. voles, degus, mice, rats) strongly reflects UV light and this may be used in communication by leaving visible as well as olfactory markings. However,
6148-489: The establishment and spread of invasive shrubs. Burrowing rodents may eat the fruiting bodies of fungi and spread spores through their feces, thereby allowing the fungi to disperse and form symbiotic relationships with the roots of plants (which usually cannot thrive without them). As such, these rodents may play a role in maintaining healthy forests. In many temperate regions, beavers play an essential hydrological role. When building their dams and lodges, beavers alter
6254-821: The female. Females can remove the plug and may do so either immediately or after several hours. Metabolism of thyroid hormones and iodine in the mediobasal hypothalamus changes in response to photoperiod . Thyroid hormones in turn induce reproductive changes. This is found by Watanabe et al. 2004 and 2007, Barrett et al. 2007, Freeman et al. 2007, and Herwig et al. 2009 in Siberian hamsters , Revel et al. 2006 and Yasuo et al. 2007 in Syrian hamsters , Yasuo et al. 2007 and Ross et al. 2011 in rats, and Ono et al. 2008 in mice. Rodents may be born either altricial (blind, hairless and relatively underdeveloped) or precocial (mostly furred, eyes open and fairly developed) depending on
6360-498: The females that live within the territories are known as "resident" females. In the case of marmots, resident males do not appear to ever lose their territories and always win encounters with invading males. Some species are also known to directly defend their resident females and the ensuing fights can lead to severe wounding. In species with non-defense polygyny, males are not territorial and wander widely in search of females to monopolize. These males establish dominance hierarchies, with
6466-517: The few animal groups that can break open the large capsules of the Brazil nut fruit. Too many seeds are inside to be consumed in one meal, so the agouti carries some off and caches them. This helps dispersal of the seeds as any that the agouti fails to retrieve are distant from the parent tree when they germinate. Other nut-bearing trees tend to bear a glut of fruits in the autumn. These are too numerous to be eaten in one meal and squirrels gather and store
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#17327650743976572-600: The finding that rodents entirely lack the ability to vomit. In many species, the penis contains a bone, the baculum ; the testes can be located either abdominally or at the groin. Sexual dimorphism occurs in many rodent species. In some rodents, males are larger than females, while in others the reverse is true. Male-bias sexual dimorphism is typical for ground squirrels , kangaroo rats, solitary mole rats and pocket gophers ; it likely developed due to sexual selection and greater male–male combat. Female-bias sexual dimorphism exists among chipmunks and jumping mice . It
6678-468: The fore to the hind limbs. The agouti is fleet-footed and antelope -like, being digitigrade and having hoof-like nails. The majority of rodents have tails, which can be of many shapes and sizes. Some tails are prehensile , as in the Eurasian harvest mouse , and the fur on the tails can vary from bushy to completely bald. The tail is sometimes used for communication, as when beavers slap their tails on
6784-457: The ground. It is mostly nocturnal but will sometimes forage for food during the day, eating bark, roots, fruits, berries, and farm crops. Porcupines have become a pest in Kenya and are eaten as a delicacy. Defensive behaviour displays in a porcupine depend on sight, scent, and sound. Often, these displays are shown when a porcupine becomes agitated or annoyed. There are four main displays seen in
6890-444: The high-ranking males having access to the most females. This occurs in species like Belding's ground squirrels and some tree squirrel species. Promiscuity , in which both males and females mate with multiple partners, also occurs in rodents. In species such as the white-footed mouse, females give birth to litters with multiple paternities. Promiscuity leads to increased sperm competition and males tend to have larger testicles. In
6996-690: The hind limbs have three to five digits. The elbow gives the forearms great flexibility. The majority of species are plantigrade , walking on both the palms and soles of their feet, and have claw-like nails. The nails of burrowing species tend to be long and strong, while arboreal rodents have shorter, sharper nails. Rodent species use a wide variety of methods of locomotion including quadrupedal walking, running, burrowing, climbing, bipedal hopping ( kangaroo rats and hopping mice ), swimming and even gliding. Scaly-tailed squirrels and flying squirrels , although not closely related, can both glide from tree to tree using parachute-like membranes that stretch from
7102-413: The immune system, and women tend to mount a stronger immune response to pathogens than men. However, the idea that men have weaker immune systems due to the supposed immuno-suppressive actions of testosterone is unfounded. There is debate as to whether the pursuit of longevity is a worthwhile health care goal. Bioethicist Ezekiel Emanuel , who is also one of the architects of ObamaCare , has argued that
7208-442: The incisors. Rodents have efficient digestive systems, absorbing nearly 80% of ingested energy. When eating cellulose , the food is softened in the stomach and passed to the cecum , where bacteria reduce it to its carbohydrate elements. The rodent then practices coprophagy , eating its own fecal pellets, so the nutrients can be absorbed by the gut. Rodents therefore often produce a hard and dry fecal pellet. Horn et al. 2013 makes
7314-818: The lack of predators and greater competition between males. One of the most widespread groups of mammals, rodents can be found on every continent except Antarctica. They are the only terrestrial placental mammals to have colonized Australia and New Guinea without human intervention. Humans have also allowed the animals to spread to many remote oceanic islands (e.g., the Polynesian rat ). Rodents have adapted to almost every terrestrial habitat, from cold tundra (where they can live under snow) to hot deserts. Some species such as tree squirrels and New World porcupines are arboreal , while some, such as gophers , tuco-tucos , and mole rats, live almost completely underground, where they build complex burrow systems. Others dwell on
7420-502: The leaves, buds, and inner bark of growing trees, as well as aquatic plants. They store food for winter use by felling small trees and leafy branches in the autumn and immersing them in their pond, sticking the ends into the mud to anchor them. Here, they can access their food supply underwater even when their pond is frozen over. Although rodents have been regarded traditionally as herbivores, most small rodents opportunistically include insects, worms, fungi, fish, or meat in their diets and
7526-516: The longest). This reflects overall poorer health and greater prevalence of heart disease, obesity, diabetes, and cancer among black American men. Women normally outlive men. Theories for this include smaller bodies that place lesser strain on the heart (women have lower rates of cardiovascular disease ) and a reduced tendency to engage in physically dangerous activities. Conversely, women are more likely to participate in health-promoting activities. The X chromosome also contains more genes related to
7632-519: The longevity of centenarians, consistent with the DNA damage theory of aging . In July 2020 , scientists used public biological data on 1.75 m people with known lifespans overall and identified 10 genomic loci which appear to intrinsically influence healthspan , lifespan, and longevity – of which half have not been reported previously at genome-wide significance and most being associated with cardiovascular disease – and identified haem metabolism as
7738-421: The look of a skunk. This, along with the raising of the sharp quills, deters predators. Along with the raising of the quills, porcupines clatter their teeth to warn predators not to approach. The incisors vibrate against each other, the strike zone shifts back, and the cheek teeth clatter. This behaviour is often paired with body shivering, which is used to further display the dangerous quills. The rattling of quills
7844-760: The males do not provide direct parental care and stay with one female because they cannot access others due to being spatially dispersed. Prairie voles appear to be an example of this form of monogamy, with males guarding and defending females within their vicinity. In polygynous species, males will try to monopolize and mate with multiple females. As with monogamy, polygyny in rodents can come in two forms; defense and non-defense. Defense polygyny involves males controlling territories that contain resources that attract females. This occurs in ground squirrels like yellow-bellied marmots , California ground squirrels , Columbian ground squirrels and Richardson's ground squirrels . Males with territories are known as "resident" males and
7950-451: The muscle causes the eyeballs to move up and down. The Hystricomorpha , such as the guinea pig, have larger superficial masseter muscles and smaller deep masseter muscles than rats or squirrels, possibly making them less efficient at biting with the incisors, but their enlarged internal pterygoid muscles may allow them to move the jaw further sideways when chewing. The cheek pouch is a specific morphological feature used for storing food and
8056-521: The nature of the precise threat. The urgency of the threat is also conveyed by the acoustic properties of the call. Social rodents have a wider range of vocalizations than do solitary species. Fifteen different call-types have been recognized in adult Kataba mole rats and four in juveniles. Similarly, the common degu , another social, burrowing rodent, exhibits a wide array of communication methods and has an elaborate vocal repertoire comprising fifteen different categories of sound. Ultrasonic calls play
8162-675: The nest a few days after they have opened their eyes and initially keep returning regularly. As they get older and more developed, they visit the nest less often and leave permanently when weaned. In precocial species, the mothers invest little in nest building and some do not build nests at all. The female gives birth standing and the young emerge behind her. Mothers of these species maintain contact with their highly mobile young with maternal contact calls. Though relatively independent and weaned within days, precocial young may continue to nurse and be groomed by their mothers. Rodent litter sizes also vary and females with smaller litters spend more time in
8268-564: The nest than those with larger litters. Mother rodents provide both direct parental care, such as nursing, grooming, retrieving and huddling, and indirect parenting, such as food caching, nest building and protection to their offspring. In many social species, young may be cared for by individuals other than their parents, a practice known as alloparenting or cooperative breeding . This is known to occur in black-tailed prairie dogs and Belding's ground squirrels, where mothers have communal nests and nurse unrelated young along with their own. There
8374-437: The offspring and play an important part in their survival. This occurs in species such as California mice , oldfield mice , Malagasy giant rats and beavers. In these species, males usually mate only with their partners. In addition to increased care for young, obligate monogamy can also be beneficial to the adult male as it decreases the chances of never finding a mate or mating with an infertile female. In facultative monogamy,
8480-518: The paths of streams and rivers and allow for the creation of extensive wetland habitats. One study found that engineering by beavers leads to a 33 percent increase in the number of herbaceous plant species in riparian areas . Another study found that beavers increase wild salmon populations. Meanwhile, some rodents are seen as pests , due to their wide range. Most rodents are herbivorous , feeding exclusively on plant material such as seeds, stems, leaves, flowers, and roots. Some are omnivorous and
8586-623: The porcupine shakes its body. New quills grow to replace lost ones. Despite what is commonly believed, porcupines cannot launch their quills at range. There are some possible antibiotic properties within the quills, specifically associated with the free fatty acids coating the quills. The antibiotic properties are believed to aid a porcupine that has suffered from self-injury. Porcupines are seldom eaten in Western culture but are eaten often in Southeast Asia , particularly Vietnam , where
8692-420: The postponement of senescence as well as happiness and wisdom in old age. Most biological organisms have a naturally limited longevity due to aging , unlike a rare few that are considered biologically immortal . Given that different species of animals and plants have different potentials for longevity, the disrepair accumulation theory of aging tries to explain how the potential for longevity of an organism
8798-560: The predator; if contact is made, the quills could be impaled into the predator causing injury or death. Porcupines' quills, or spines , take on various forms, depending on the species, but all are modified hairs coated with thick plates of keratin , and embedded in the skin musculature. Old World porcupines have quills embedded in clusters, whereas in New World porcupines, single quills are interspersed with bristles, underfur, and hair. Quills are released by contact or may drop out when
8904-438: The present. A life annuity is a form of longevity insurance . Various factors contribute to an individual's longevity. Significant factors in life expectancy include gender , genetics , access to health care , hygiene , diet and nutrition , exercise , lifestyle , and crime rates . Below is a list of life expectancies in different types of countries: Population longevities are increasing as life expectancies around
9010-470: The prominent use of them as a food source has contributed to declines in porcupine populations. Naturalist William J. Long reported the taste of the North American porcupine as "vile" and "malodorous" and delightful only to a lover of strong cheese. More commonly, their quills and guard hairs are used for traditional decorative clothing; for example, their guard hairs are used in the creation of
9116-501: The pursuit of longevity via the compression of morbidity explanation is a "fantasy" and that longevity past age 75 should not be considered an end in itself. This has been challenged by neurosurgeon Miguel Faria , who states that life can be worthwhile in healthy old age, that the compression of morbidity is a real phenomenon, and that longevity should be pursued in association with quality of life. Faria has discussed how longevity in association with leading healthy lifestyles can lead to
9222-416: The rate of about 17 years per decade .... Several celebrated super-centenarians (over 110 years) are believed to have been double lives (father and son, relations with the same names or successive bearers of a title) .... A number of instances have been commercially sponsored, while a fourth category of recent claims are those made for political ends ...." The estimate of 17 years per decade was corroborated by
9328-539: The reproduction of subordinates by being antagonistic towards them while they are pregnant. The resulting stress causes the fetuses to abort. Rodents have advanced cognitive abilities. They can quickly learn to avoid poisoned baits, which makes them difficult pests to deal with. Guinea pigs can learn and remember complex pathways to food. Squirrels and kangaroo rats are able to locate caches of food by spatial memory , rather than just by smell. Longevity Longevity may refer to especially long-lived members of
9434-414: The rest of the members are smaller and sterile, and function as workers. Some individuals are of intermediate size. They help with the rearing of the young and can take the place of a reproductive if one dies. The Damaraland mole rat is characterized by having a single reproductively active male and female in a colony where the remaining animals are not truly sterile, but become fertile only if they establish
9540-408: The rodents is their pairs of continuously growing, razor-sharp, open-rooted incisors . These incisors have thick layers of enamel on the front and little enamel on the back. Because they do not stop growing, the animal must continue to wear them down so that they do not reach and pierce the skull. As the incisors grind against each other, the softer dentine on the rear of the teeth wears away, leaving
9646-798: The scents of their neighbors and respond less aggressively to intrusions by them than to those made by non-territorial "floaters" or strangers. This is known as the " dear enemy effect ". Many rodent species, particularly those that are diurnal and social, have a wide range of alarm calls that are emitted when they perceive threats. There are both direct and indirect benefits of doing this. A potential predator may stop when it knows it has been detected, or an alarm call can allow conspecifics or related individuals to take evasive action. Several species, for example prairie dogs, have complex anti-predator alarm call systems. These species may have different calls for different predators (e.g. aerial predators or ground-based predators) and each call contains information about
9752-441: The sharp enamel edge shaped like the blade of a chisel . Most species have up to 22 teeth with no canines or anterior premolars . A gap, or diastema , occurs between the incisors and the cheek teeth in most species. This allows rodents to suck in their cheeks or lips to shield their mouth and throat from wood shavings and other inedible material, discarding this waste from the sides of their mouths. Chinchillas and guinea pigs have
9858-438: The skin using the anchored barb design rather than being bent under the skin like traditional staples. Porcupines are also sometimes kept as exotic pets . Porcupines occupy a small range of habitats in tropical and temperate parts of Asia, Southern Europe, Africa, and North and South America. They live in forests and deserts, rocky outcrops, and hillsides. Some New World porcupines live in trees, but Old World porcupines prefer
9964-665: The species have "slow or [times of] negligible senescence" (or aging). The jellyfish T. dohrnii is biologically immortal and has been studied by comparative genomics . Honey bees ( Apis mellifera ) are eusocial insects that display dramatic caste-specific differences in longevity. Queen bees live for an average of 1-2 years, compared to workers who live on average 15-38 days in summer and 150-200 days in winter. Worker honey bees with high amounts of flight experience exhibit increased DNA damage in flight muscle, as measured by elevated 8-Oxo-2'-deoxyguanosine , compared to bees with less flight experience. This increased DNA damage
10070-422: The species. The altricial state is typical for squirrels and mice, while the precocial state usually occurs in species like guinea pigs and porcupines. Females with altricial young typically build elaborate nests before they give birth and maintain them until their offspring are weaned . The female gives birth sitting or lying down and the young emerge in the direction she is facing. The newborns first venture out of
10176-588: The stomach contents of the North American white-footed mouse , normally considered to be herbivorous, showed 34% animal matter. More specialized carnivores include the shrewlike rats of the Philippines, which feed on insects and soft-bodied invertebrates, and the rakali or Australian water-rat, which devours aquatic insects, fish, crustaceans, mussels, snails, frogs, birds' eggs, and water birds. The grasshopper mouse from dry regions of North America feeds on insects, scorpions, and other small mice, and only
10282-536: The surface of the ground, but may have a burrow into which they can retreat. Beavers and muskrats are known for being semiaquatic, but the rodent best adapted for aquatic life is probably the earless water rat from New Guinea. Rodents have also thrived in human-created environments such as agricultural and urban areas . Though some species are common pests for humans, rodents also play important ecological roles. Some rodents are considered keystone species and ecosystem engineers in their respective habitats. In
10388-435: The surface to feed by seizing the roots of plants with its jaws and pulling them downwards into its burrow. It also practices coprophagy. The African pouched rat forages on the surface, gathering anything that might be edible into its capacious cheek pouches until its face bulges out sideways. It then returns to its burrow to sort through the material it has gathered and eats the nutritious items. Agouti species are one of
10494-484: The surplus in crevices and hollow trees. In desert regions, seeds are often available only for short periods. The kangaroo rat collects all it can find and stores them in larder chambers in its burrow. A strategy for dealing with seasonal plenty is to eat as much as possible and store the surplus nutrients as fat. Marmots do this, and may be 50% heavier in the autumn than in the spring. They rely on their fat reserves during their long winter hibernation . Beavers feed on
10600-817: The two groups are distinct from one another and are not closely related to each other within the Hystricognathi. The largest species of porcupine is the third-largest living rodent in the world, after the capybara and beaver . The Old World porcupines (Hystricidae) live in Italy , Asia (western and southern), and most of Africa . They are large, terrestrial, and strictly nocturnal. The New World porcupines (Erethizontidae) are indigenous to North America and northern South America . They live in wooded areas and can climb trees, where some species spend their entire lives. They are less strictly nocturnal than their Old World counterparts and generally smaller. Most porcupines are about 60–90 cm (25–36 in) long, with
10706-469: The ultraviolet (UV) spectrum and therefore can see light that humans can not. The functions of this UV sensitivity are not always clear. In degus , for example, the belly reflects more UV light than the back. Therefore, when a degu stands up on its hind legs, which it does when alarmed, it exposes its belly to other degus and ultraviolet vision may serve a purpose in communicating the alarm. When it stands on all fours, its low UV-reflectance back could help make
10812-472: The variation in human lifespan can be related to genetics , with the rest due to individual behaviors and environmental factors which can be modified. Although over 200 gene variants have been associated with longevity according to a US-Belgian-UK research database of human genetic variants these explain only a small fraction of the heritability. Lymphoblastoid cell lines established from blood samples of centenarians have significantly higher activity of
10918-474: The water surface or house mice rattle their tails to indicate alarm. Some species have vestigial tails or no tails at all. In some species, the tail is capable of regeneration if a part is broken off. Rodents generally have well-developed senses of smell , hearing, and vision. Nocturnal species often have enlarged eyes and some are sensitive to ultraviolet light. Many species have long, sensitive whiskers or vibrissae for touch or "whisking" . Whisker action
11024-484: The work of the Ancient Greek historian Herodotus . There are difficulties in authenticating the longest human life span , owing to inaccurate or incomplete birth statistics. Fiction, legend, and folklore have proposed or claimed life spans in the past or future vastly longer than those verified by modern standards, and longevity narratives and unverified longevity claims frequently speak of their existence in
11130-412: The world grow: The Gerontology Research Group validates current longevity records by modern standards, and maintains a list of supercentenarians ; many other unvalidated longevity claims exist. Record-holding individuals include: Evidence-based studies indicate that longevity is based on two major factors: genetics and lifestyle . Twin studies have estimated that approximately 20-30% of
11236-412: Was the first mammal for which seismic communication was documented. These fossorial rodents bang their head against the walls of their tunnels. This behavior was initially interpreted as part of their tunnel building behavior, but it was eventually realized that they generate temporally patterned seismic signals for long-distance communication with neighboring mole rats. Footdrumming is used widely as
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