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68-567: Cubs may refer to: The young of certain large predatory animals such as bears and big cats ; analogous to a domestic puppy or kitten Chicago Cubs , a baseball team of the National League of Major League Baseball (United States) Iowa Cubs , a minor league baseball team of the International League South Bend Cubs , a minor league baseball team of

136-408: A common proto-hibernating ancestor of birds and mammals, the ability to hibernate or go through torpor would have been lost in most larger mammals and birds. Hibernation would be less favored in larger animals because as animals increase in size, the surface area to volume ratio decreases, and it takes less energy to keep a high internal body temperature, and thus hibernation becomes unnecessary. There

204-448: A form of seed dormancy . There is a variety of definitions for terms that describe hibernation in mammals, and different mammal clades hibernate differently. The following subsections discuss the terms obligate and facultative hibernation. The last two sections point out in particular primates, none of whom were thought to hibernate until recently, and bears, whose winter torpor had been contested as not being "true hibernation" during

272-519: A large amount of food and storing the energy in their bodies in the form of fat deposits. In many small species, food caching replaces eating and becoming fat. Some species of mammals hibernate while gestating young, which are born either while the mother hibernates or shortly afterwards. For example, female black bears go into hibernation during the winter months in order to give birth to their offspring. The pregnant mothers significantly increase their body mass prior to hibernation, and this increase

340-406: A later point. This difference in development is evidence, though inconclusive, that they evolved by slightly different mechanisms and thus at different times. As reptiles are ectothermic, having no system to deal with cold temperatures would be deadly in many environments. Reptilian winter dormancy, or brumation, likely evolved to help reptiles survive colder conditions. Reptiles that are dormant in

408-505: A means to survive in their shoreline habitat, where water and oxygen levels vary with the tide. Other animals able to survive long periods with very little or no oxygen include goldfish , red-eared sliders , wood frogs , and bar-headed geese . The ability to survive hypoxic or anoxic conditions is not closely related to endotherm hibernation. Some animals can literally survive winter by freezing. For example, some fish , amphibians , and reptiles can naturally freeze and then "wake" up in

476-529: A modest decline in body temperature (3–5 °C) compared with the much larger decreases (often 32 °C or more) seen in other hibernators. Many researchers thought that their deep sleep was not comparable with true, deep hibernation, but this theory was refuted by research in 2011 on captive black bears and again in 2016 in a study on brown bears . Hibernating bears are able to recycle their proteins and urine, allowing them to stop urinating for months and to avoid muscle atrophy . They stay hydrated with

544-533: A periodic internal clock, which is likely triggered by cooler outside temperatures, as shown in the Texas horned lizard ( Phrynosoma cornutum ). One mechanism that reptiles use to survive hibernation, hypercapnic acidosis (the buildup of carbon dioxide in the blood), is also present in mammal hibernation. This is likely an example of convergent evolution . Hypercapnic acidosis evolved as a mechanism to slow metabolism and also interfere with oxygen transport so that oxygen

612-418: A physiological state wherein the body temperature drops to near ambient temperature, and heart and respiration rates slow drastically. The typical winter season for obligate hibernators is characterized by periods of torpor interrupted by periodic, euthermic arousals, during which body temperatures and heart rates are restored to more typical levels. The cause and purpose of these arousals are still not clear;

680-415: A response to stressors from the environment. A good example of the differences between these two types of hibernation can be seen in prairie dogs . The white-tailed prairie dog is an obligate hibernator, while the closely related black-tailed prairie dog is a facultative hibernator. While hibernation has long been studied in rodents (namely ground squirrels ), no primate or tropical mammal

748-442: A seasonal diapause, where many of their biological functions end up paired with a seasonal rhythm within the organism. This is a very similar mechanism to the evolution of insect migration, where instead of bodily functions like metabolism getting paired with seasonal indicators, movement patterns would be paired with seasonal indicators. While most animals that go through winter dormancy lower their metabolic rates, some fish, such as

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816-414: Is different from Wikidata All article disambiguation pages All disambiguation pages Bear Bears are carnivoran mammals of the family Ursidae ( / ˈ ɜːr s ɪ d iː , - d aɪ / ). They are classified as caniforms , or doglike carnivorans. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of habitats throughout most of

884-462: Is driven by environmental cues, but arousal is driven by physiological cues. Ancient people believed that swallows hibernated, and ornithologist Gilbert White documented anecdotal evidence in his 1789 book The Natural History of Selborne that indicated the belief was still current in his time. It is now understood that the vast majority of bird species typically do not hibernate, instead utilizing shorter periods of torpor . One known exception

952-402: Is evidence that hibernation evolved separately in marsupials and placental mammals, though it is not settled. That evidence stems from development, where as soon as young marsupials from hibernating species are able to regulate their own heat, they have the capability to hibernate. In contrast, placental mammals that hibernate first develop homeothermy , only developing the ability to hibernate at

1020-533: Is from the Proto-Indo-European word *ǵʰwḗr- ~ *ǵʰwér "wild animal". This terminology for the animal originated as a taboo avoidance term: proto-Germanic tribes replaced their original word for bear— arkto —with this euphemistic expression out of fear that speaking the animal's true name might cause it to appear. According to author Ralph Keyes , this is the oldest known euphemism . Bear taxon names such as Arctoidea and Helarctos come from

1088-457: Is further reflected in the weight of the offspring. The fat accumulation enables them to provide a sufficiently warm and nurturing environment for their newborns. During hibernation, they subsequently lose 15–27% of their pre-hibernation weight by using their stored fats for energy. Ectothermic animals also undergo periods of metabolic suppression and dormancy , which in many invertebrates is referred to as diapause. Some researchers and members of

1156-469: Is mostly herbivorous , the remaining six species are omnivorous with varying diets. With the exception of courting individuals and mothers with their young, bears are typically solitary animals . They may be diurnal or nocturnal and have an excellent sense of smell . Despite their heavy build and awkward gait, they are adept runners, climbers, and swimmers. Bears use shelters, such as caves and logs, as their dens; most species occupy their dens during

1224-477: Is not available. To achieve this energy saving, an endothermic animal decreases its metabolic rate and thereby its body temperature. Hibernation may last days, weeks, or months—depending on the species, ambient temperature, time of year, and the individual's body-condition. Before entering hibernation, animals need to store enough energy to last through the duration of their dormant period, possibly as long as an entire winter. Larger species become hyperphagic , eating

1292-433: Is not used up and can still reach tissues in low oxygen periods of dormancy. Seasonal diapause, or arthropod winter dormancy, seems to be plastic and quickly evolving, with large genetic variation and strong effects of natural selection present as well as having evolved many times across many clades of arthropods. As such, there is very little phylogenetic conservation in the genetic mechanism for diapause. Particularly

1360-492: Is the common poorwill ( Phalaenoptilus nuttallii ), for which hibernation was first documented by Edmund Jaeger . Because they cannot actively down-regulate their body temperature or metabolic rate, ectothermic animals (including fish, reptiles, and amphibians) cannot engage in obligate or facultative hibernation. They can experience decreased metabolic rates associated with colder environments or low oxygen availability ( hypoxia ) and exhibit dormancy (known as brumation). It

1428-425: Is thought to have originally evolved in three stages. The first is development of neuroendocrine control over bodily functions, the second is pairing of that to environmental changes—in this case metabolic rates decreasing in response to colder temperatures—and the third is the pairing of these controls with reliable seasonal indicators within the arthropod, like biological timers. From these steps, arthropods developed

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1496-648: The Bering land bridge may have been possible during a major sea level low stand as early as the late Eocene (about 37 Mya) and continuing into the early Oligocene. European genera morphologically very similar to Allocyon , and to the much younger American Kolponomos (about 18 Mya), are known from the Oligocene, including Amphicticeps and Amphicynodon . There has been various morphological evidence linking amphicynodontines with pinnipeds , as both groups were semi-aquatic, otter-like mammals. In addition to

1564-646: The Isthmus of Panama . Their earliest fossil representative is Plionarctos in North America (c. 10–2 Ma). This genus is probably the direct ancestor to the North American short-faced bears (genus Arctodus ), the South American short-faced bears ( Arctotherium ), and the spectacled bears, Tremarctos , represented by both an extinct North American species ( T. floridanus ), and

1632-611: The cunner , do not. Instead, they do not actively depress their base metabolic rate, but instead they simply reduce their activity level. Fish that undergo winter dormancy in oxygenated water survive via inactivity paired with the colder temperature, which decreases energy consumption, but not the base metabolic rate that their bodies consume. But for the Antarctic yellowbelly rockcod ( Notothenia coriiceps ) and for fish that undergo winter dormancy in hypoxic conditions, they do suppress their metabolism like other animals that are dormant in

1700-412: The metabolic water that is produced in sufficient quantities to satisfy the water needs of the bear. They also do not eat or drink while hibernating, but live off their stored fat. Despite long-term inactivity and lack of food intake, hibernating bears are believed to maintain their bone mass and do not suffer from osteoporosis . They also increase the availability of certain essential amino acids in

1768-399: The spectacled bear ), and Ursinae (containing six species divided into one to three genera, depending on the authority). Nuclear chromosome analysis show that the karyotype of the six ursine bears is nearly identical, each having 74  chromosomes ( see Ursid hybrid ), whereas the giant panda has 42 chromosomes and the spectacled bear 52. These smaller numbers can be explained by

1836-470: The Asian bile bear market. The IUCN lists six bear species as vulnerable or endangered , and even least concern species, such as the brown bear , are at risk of extirpation in certain countries. The poaching and international trade of these most threatened populations are prohibited, but still ongoing. The English word "bear" comes from Old English bera and belongs to a family of names for

1904-838: The Midwest League Daytona Cubs, the former name of the Daytona Tortugas , a minor league baseball team of the Florida State League Arizona Complex League Cubs , a minor league baseball team of the Arizona League Cub Scouts , a junior age group of the Scouting movement Acronyms [ edit ] Chinese University Basketball Super League (CUBS), former Chinese basketball league Coventry University Business School in

1972-555: The Northern Hemisphere and partially in the Southern Hemisphere. Bears are found on the continents of North America , South America , and Eurasia . Common characteristics of modern bears include large bodies with stocky legs, long snouts, small rounded ears, shaggy hair, plantigrade paws with five nonretractile claws, and short tails. While the polar bear is mostly carnivorous , and the giant panda

2040-559: The QT interval changed for both typical hibernators and the bears from summer to winter. This 1977 study was one of the first evidences used to show that bears are hibernators. In a 2016 study, wildlife veterinarian and associate professor at Inland Norway University of Applied Sciences , Alina L. Evans, researched 14 brown bears over three winters. Their movement, heart rate , heart rate variability , body temperature, physical activity, ambient temperature, and snow depth were measured to identify

2108-576: The United Kingdom See also [ edit ] Cub (disambiguation) Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title Cubs . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Cubs&oldid=1182589667 " Category : Disambiguation pages Hidden categories: Short description

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2176-561: The ancestor of birds and mammals onto land introduced them to seasonal pressures that would eventually become hibernation. This is true for all clades of animals that undergo winter dormancy; the more prominent the seasons are, the longer the dormant period tends to be on average. Hibernation of endothermic animals has likely evolved multiple times, at least once in mammals—though it is debated whether or not it evolved more than once in mammals—and at least once in birds. In both cases, hibernation likely evolved simultaneously with endothermy, with

2244-507: The ancient Greek ἄρκτος ( arktos ), meaning bear, as do the names " arctic " and " antarctic ", via the name of the constellation Ursa Major , the "Great Bear", prominent in the northern sky. Bear taxon names such as Ursidae and Ursus come from Latin Ursus/Ursa , he-bear/she-bear. The female first name " Ursula ", originally derived from a Christian saint 's name, means "little she-bear" (diminutive of Latin ursa ). In Switzerland,

2312-567: The animal to restore its available energy sources or to initiate an immune response. Hibernating Arctic ground squirrels may exhibit abdominal temperatures as low as −2.9 °C (26.8 °F), maintaining sub-zero abdominal temperatures for more than three weeks at a time, although the temperatures at the head and neck remain at 0 °C (32 °F) or above. Facultative hibernators enter hibernation only when either cold-stressed, food-deprived, or both, unlike obligate hibernators, who enter hibernation based on seasonal timing cues rather than as

2380-481: The animal to study key hibernation proteins (HP). Researchers have studied how to induce hibernation in humans. The ability to hibernate would be useful for a number of reasons, such as saving the lives of seriously ill or injured people by temporarily putting them in a state of hibernation until treatment can be given. For space travel, human hibernation is also under consideration, such as for missions to Mars . Anthropologists are also studying whether hibernation

2448-760: The bear family with other carnivorans is shown in the following phylogenetic tree , which is based on the molecular phylogenetic analysis of six genes in Flynn (2005) with the musteloids updated following the multigene analysis of Law et al. (2018). Feliformia [REDACTED] Canidae [REDACTED] Ursidae [REDACTED] Pinnipedia [REDACTED] Mephitidae [REDACTED] Ailuridae [REDACTED] Procyonidae [REDACTED] Mustelidae [REDACTED] Note that although they are called "bears" in some languages, red pandas and raccoons and their close relatives are not bears, but rather musteloids . There are two phylogenetic hypotheses on

2516-468: The bear in Germanic languages , such as Swedish björn , also used as a first name. This form is conventionally said to be related to a Proto-Indo-European word for "brown", so that "bear" would mean "the brown one". However, Ringe notes that while this etymology is semantically plausible, a word meaning "brown" of this form cannot be found in Proto-Indo-European. He suggests instead that "bear"

2584-554: The bears' heart rate variability dropped dramatically, indirectly suggesting metabolic suppression is related to their hibernation. Two months before the end of hibernation, the bears' body temperature starts to rise, unrelated to heart rate variability but rather driven by the ambient temperature. The heart rate variability only increases around three weeks before arousal and the bears only leave their den once outside temperatures are at their lower critical temperature. These findings suggest that bears are thermoconforming and bear hibernation

2652-521: The brown bears (which includes the polar bear ). Modern brown bears evolved from U. minimus via Ursus etruscus , which itself is ancestral to the extinct Pleistocene cave bear . Species of Ursinae have migrated repeatedly into North America from Eurasia as early as 4 Mya during the early Pliocene. The polar bear is the most recently evolved species and descended from a population of brown bears that became isolated in northern latitudes by glaciation 400,000 years ago. The relationship of

2720-455: The drivers of the start and end of hibernation for bears. This study built the first chronology of both ecological and physiological events from before the start to the end of hibernation in the field. This research found that bears would enter their den when snow arrived and ambient temperature dropped to 0 °C. However, physical activity, heart rate, and body temperature started to drop slowly even several weeks before this. Once in their dens,

2788-634: The earliest suggested instance of hibernation being in Thrinaxodon , an ancestor of mammals that lived roughly 252 million years ago. The evolution of endothermy allowed animals to have greater levels of activity and better incubation of embryos, among other benefits for animals in the Permian and Triassic periods. In order to conserve energy, the ancestors of birds and mammals would likely have experienced an early form of torpor or hibernation when they were not using their thermoregulatory abilities during

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2856-526: The early Pleistocene. By 3–4 Mya, the species Ursus minimus appears in the fossil record of Europe; apart from its size, it was nearly identical to today's Asian black bear . It is likely ancestral to all bears within Ursinae, perhaps aside from the sloth bear. Two lineages evolved from U. minimus : the black bears (including the sun bear , the Asian black bear, and the American black bear ); and

2924-998: The extinct bear dogs of the family Amphicyonidae . Below is the cladogram based on McKenna and Bell (1997) classification: † Amphicyonidae [REDACTED] † Amphicynodontidae [REDACTED] Pinnipedia [REDACTED] † Hemicyoninae † Agriotheriinae † Ursavinae Ailuropodinae [REDACTED] Tremarctinae [REDACTED] Ursinae [REDACTED] Giant panda ( Ailuropoda melanoleuca ) [REDACTED] Spectacled bear ( Tremarctos ornatus ) [REDACTED] Sloth bear ( Melursus ursinus ) [REDACTED] Sun bear ( Helarctos malayanus ) [REDACTED] Asian black bear ( Ursus thibetanus ) [REDACTED] American black bear ( Ursus americanus ) [REDACTED] Polar bear ( Ursus maritimus ) [REDACTED] Brown bear ( Ursus arctos ) [REDACTED] Giant panda ( Ailuropoda melanoleuca ) [REDACTED] Hibernation Although traditionally reserved for "deep" hibernators such as rodents ,

2992-571: The fusing of some chromosomes, and the banding patterns on these match those of the ursine species, but differ from those of procyonids, which supports the inclusion of these two species in Ursidae rather than in Procyonidae , where they had been placed by some earlier authorities. The earliest members of Ursidae belong to the extinct subfamily Amphicynodontinae, including Parictis (late Eocene to early middle Miocene , 38–18  Mya ) and

3060-458: The genus Ursavus during the early Oligocene (30–28 Mya); this genus proliferated into many species in Asia and is ancestral to all living bears. Species of Ursavus subsequently entered North America, together with Amphicynodon and Cephalogale , during the early Miocene (21–18 Mya). Members of the living lineages of bears diverged from Ursavus between 15 and 20 Mya, likely via

3128-449: The hole is poorly insulated, the lemur's body temperature fluctuates widely, passively following the ambient temperature; if well insulated, the body temperature stays fairly constant and the animal undergoes regular spells of arousal. Dausmann found that hypometabolism in hibernating animals is not necessarily coupled with low body temperature. Historically it was unclear whether or not bears truly hibernate, since they experience only

3196-459: The late 20th century, since it is dissimilar from hibernation seen in rodents. Obligate hibernators are animals that spontaneously, and annually, enter hibernation regardless of ambient temperature and access to food. Obligate hibernators include many species of ground squirrels , other rodents , European hedgehogs and other insectivores , monotremes , and marsupials . These species undergo what has been traditionally called "hibernation":

3264-659: The lone surviving representative of the Tremarctinae, the South American spectacled bear ( T. ornatus ). The subfamily Ursinae experienced a dramatic proliferation of taxa about 5.3–4.5 Mya, coincident with major environmental changes; the first members of the genus Ursus appeared around this time. The sloth bear is a modern survivor of one of the earliest lineages to diverge during this radiation event (5.3 Mya); it took on its peculiar morphology, related to its diet of termites and ants, no later than by

3332-418: The male first name "Urs" is especially popular, while the name of the canton and city of Bern is by legend derived from Bär , German for bear. The Germanic name Bernard (including Bernhardt and similar forms) means "bear-brave", "bear-hardy", or "bold bear". The Old English name Beowulf is a kenning , "bee-wolf", for bear, in turn meaning a brave warrior. The family Ursidae is one of nine families in

3400-400: The muscle, as well as regulate the transcription of a suite of genes that limit muscle wasting. A study by G. Edgar Folk, Jill M. Hunt and Mary A. Folk compared EKG of typical hibernators to three different bear species with respect to season, activity and dormancy, and found that the reduced relaxation (QT) interval of small hibernators was the same for the three bear species. They also found

3468-419: The public use the term brumate to describe winter dormancy of reptiles, but the more general term hibernation is believed adequate to refer to any winter dormancy. Many insects, such as the wasp Polistes exclamans and the beetle Bolitotherus , exhibit periods of dormancy which have often been referred to as hibernation, despite their ectothermy. Botanists may use the term "seed hibernation" to refer to

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3536-560: The question of why hibernators may return periodically to normal body temperatures has plagued researchers for decades, and while there is still no clear-cut explanation, there are multiple hypotheses on the topic. One favored hypothesis is that hibernators build a " sleep debt " during hibernation, and so must occasionally warm up to sleep. This has been supported by evidence in the Arctic ground squirrel . Other theories postulate that brief periods of high body temperature during hibernation allow

3604-628: The relationships among extant and fossil bear species. One is all species of bears are classified in seven subfamilies as adopted here and related articles: Amphicynodontinae , Hemicyoninae , Ursavinae , Agriotheriinae , Ailuropodinae , Tremarctinae , and Ursinae . Below is a cladogram of the subfamilies of bears after McLellan and Reiner (1992) and Qiu et al. . (2014): † Amphicynodontinae [REDACTED] † Hemicyoninae † Ursavinae † Agriotheriinae Ailuropodinae [REDACTED] Tremarctinae [REDACTED] Ursinae [REDACTED] The second alternative phylogenetic hypothesis

3672-540: The slightly younger Allocyon (early Oligocene , 34–30 Mya), both from North America. These animals looked very different from today's bears, being small and raccoon -like in overall appearance, with diets perhaps more similar to that of a badger . Parictis does not appear in Eurasia and Africa until the Miocene. It is unclear whether late-Eocene ursids were also present in Eurasia, although faunal exchange across

3740-547: The species Ursavus elmensis . Based on genetic and morphological data, the Ailuropodinae (pandas) were the first to diverge from other living bears about 19 Mya, although no fossils of this group have been found before about 11 Mya. The New World short-faced bears (Tremarctinae) differentiated from Ursinae following a dispersal event into North America during the mid-Miocene (about 13 Mya). They invaded South America (≈2.5 or 1.2 Ma) following formation of

3808-434: The spring. These species have evolved freeze tolerance mechanism such as antifreeze proteins . Hibernation induction trigger (HIT) proteins isolated from mammals have been used in the study of organ recovery rates. One study in 1997 found that delta 2 opioid and hibernation induction trigger (HIT) proteins were not able to increase the recovery rate of heart tissue during ischemia. While unable to increase recovery rates at

3876-434: The suborder Caniformia , or "doglike" carnivorans, within the order Carnivora . Bears' closest living relatives are the pinnipeds , canids , and musteloids (some scholars formerly argued that bears are directly derived from canids and should not be classified as a separate family). Modern bears comprise eight species in three subfamilies: Ailuropodinae (monotypic with the giant panda ), Tremarctinae (monotypic with

3944-509: The support of the pinniped–amphicynodontine clade, other morphological and some molecular evidence supports bears being the closest living relatives to pinnipeds. The raccoon-sized, dog-like Cephalogale is the oldest-known member of the subfamily Hemicyoninae , which first appeared during the middle Oligocene in Eurasia about 30 Mya. The subfamily includes the younger genera Phoberocyon (20–15 Mya), and Plithocyon (15–7 Mya). A Cephalogale -like species gave rise to

4012-423: The term has been redefined to include animals such as bears and is now applied based on active metabolic suppression rather than any absolute decline in body temperature. Many experts believe that the processes of daily torpor and hibernation form a continuum and utilise similar mechanisms. The equivalent during the summer months is aestivation . Hibernation functions to conserve energy when sufficient food

4080-801: The time of ischemia, the protein precursors were identified to play a role in the preservation of veterinary organ function. Recent advances in recombinant protein technology make it possible for scientists to manufacture hibernation induction trigger (HIT) proteins in the laboratory without the need for animal euthanasia. Bioengineering of proteins can aid in the protection of vulnerable populations of bears and other mammals that produce valuable proteins. Protein sequencing of HIT proteins, such as α 1-glycoprotein-like 88 kDa hibernation-related protein HRP, contributes to this research pool. A study in 2014 utilizes recombinant technology to construct, express, purify, and isolate animal proteins (HP-20, HP-25, and HP-27) outside of

4148-444: The timing and extent of the seasonal diapause seem particularly variable, currently evolving as a response to climate change . As typical with hibernation, it evolved after the increased influence of seasonality as arthropods colonized terrestrial environments as a mechanism to keep energy costs low, particularly in harsher than normal environments, as well as being a good way to time the active or reproductive periods in arthropods. It

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4216-440: The transition from ectothermy to endothermy. This is opposed to the previously dominant hypothesis that hibernation evolved after endothermy in response to the emergence of colder habitats. Body size also had an effect on the evolution of hibernation, as endotherms which grow large enough tend to lose their ability to be selectively heterothermic, with bears being one of very few exceptions. After torpor and hibernation diverged from

4284-527: The winter for a long period of hibernation , up to 100 days. Bears have been hunted since prehistoric times for their meat and fur; they have also been used for bear-baiting and other forms of entertainment, such as being made to dance . With their powerful physical presence, they play a prominent role in the arts , mythology , and other cultural aspects of various human societies. In modern times, bears have come under pressure through encroachment on their habitats and illegal trade in bear parts, including

4352-403: The winter tend to have higher survival rates and slower aging. Reptiles evolved to exploit their ectothermy to deliberately cool their internal body temperatures. As opposed to mammals or birds, which will prepare for their hibernation but not directly cause it through their behavior, reptiles will trigger their own hibernation through their behavior. Reptiles seek out colder temperatures based on

4420-496: Was implemented by McKenna et al. (1997) to classify all the bear species into the superfamily Ursoidea , with Hemicyoninae and Agriotheriinae being classified in the family "Hemicyonidae". Amphicynodontinae under this classification were classified as stem- pinnipeds in the superfamily Phocoidea . In the McKenna and Bell classification both bears and pinnipeds are in a parvorder of carnivoran mammals known as Ursida , along with

4488-422: Was known to hibernate until the discovery of hibernation in the fat-tailed dwarf lemur of Madagascar, which hibernates in tree holes for seven months of the year. Malagasy winter temperatures sometimes rise to over 30 °C (86 °F), so hibernation is not exclusively an adaptation to low ambient temperatures. The hibernation of this lemur is strongly dependent on the thermal behaviour of its tree hole: If

4556-499: Was once thought that basking sharks settled to the floor of the North Sea and became dormant, but research by David Sims in 2003 dispelled this hypothesis, showing that the sharks traveled long distances throughout the seasons, tracking the areas with the highest quantity of plankton . Epaulette sharks have been documented to be able to survive for three hours without oxygen and at temperatures of up to 26 °C (79 °F) as

4624-414: Was possible in early hominid species. As the ancestors of birds and mammals colonized land, leaving the relatively stable marine environments, more intense terrestrial seasons began playing a larger role in animals' lives. Some marine animals do go through periods of dormancy, but the effect is stronger and more widespread in terrestrial environments. As hibernation is a seasonal response, the movement of

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