Hibernation is a state of inactivity and metabolic depression in endotherms. Hibernation refers to a season of heterothermy characterized by low body-temperature, slow breathing and heart-rate, low metabolic rate, it most occurs during winter months. Although traditionally reserved for "deep" hibernators such as rodents, 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 utilize similar mechanisms; the equivalent during the summer months is aestivation. Hibernation functions to conserve energy. 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, the individual's body-condition. Before entering hibernation, animals need to store enough energy to last through the duration of their dormant period as long as an entire winter.

Larger species become hyperphagic, eating a large amount of food and storing the energy in fat deposits. In many small species, food caching replaces becoming fat; some species of mammals hibernate while gestating young, which are born either while the mother hibernates or shortly afterwards. For example, female polar-bears go into hibernation during the cold winter months in order to give birth to their offspring; the pregnant mothers increase their body mass prior to hibernation, this increase 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. True hibernation is restricted to endotherms. Still, many ectothermic animals undergo periods of dormancy which are sometimes confused with hibernation; some reptile species are said to brumate, but possible similarities between brumation and hibernation are not established.

Many insects, such as the wasp Polistes exclamans, exhibit periods of dormancy which have been referred to as hibernation, despite their ectothermy. Botanists can use the term "seed hibernation". There is a variety of definitions for terms that describe hibernation in mammals, different mammal clades hibernate differently; the following subsections discuss the terms facultative hibernation. The last two sections point out in particular primates, none of whom were thought to hibernate until and bears, whose winter topor had been contested as not being "true hibernation" during the late 20th century, since it is dissimilar from hibernation seen in rodents. Obligate hibernators are animals that spontaneously, annually, enter hibernation regardless of ambient temperature and access to food. Obligate hibernators include many species of ground squirrels, other rodents, mouse lemurs, European hedgehogs and other insectivores and marsupials; these species undergo what has been traditionally called "hibernation": a physiological state wherein the body temperature drops to near ambient temperature, 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 is still not clear. One favored hypothesis is that hibernators build a "sleep debt" during hibernation, so must 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 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, 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 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 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. The related black-tailed prairie dog is a facultative hibernator. While hibernation has long been studied in rodents no primate or tropical mammal 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, so hibernation is not an adaptation to low ambient temperatures; the hibernation of this lemur is dependent on the thermal behaviour of its tree hole: If the hole is poorly insulated, the lemur's body temperature fluctuates passively following the ambient temperature.


Roseworth is a large housing estate in Stockton-on-Tees within the borough of Stockton-on-Tees and the ceremonial county of County Durham, England. It was built in the 1950s as part of the social housing expansion for northern Stockton, it is situated to the north west of the centre of the town. Every street in Roseworth begins with an R, such as Ryde Road and Reepham Road. Roseworth is bordered in the north by Junction Road, in the east by the railway, in the south by Darlington Lane and in the west by Durham Road; the population of Roseworth is diverse with the arrival of Polish and Filipino people in the past decade. At the 2011 Census, 96.1% of the population described themselves as White British, above the average for the borough, the region, England as a whole

ML 4.2-inch mortar

The Ordnance ML 4.2-inch mortar was a heavy mortar used by the British Army during and after World War II. The 4.2-inch mortar was a smooth-bore weapon of the Stokes pattern and was designed by the Armaments Research and Development Establishment and produced by the Royal Ordnance Factories. It entered widespread British service in 1942, equipping chemical warfare companies of the Royal Engineers; the Mark 3 became the standard model. The first combat use was at Second Battle of El Alamein, when the 66th Mortar Company was attached to the Australian 24th Infantry Brigade. During the battle, 66 Mortar Coy provided intense, effective supporting fire on 24 Bde's exposed right flank, as the infantry advanced, expending all of the 4.2-inch HE mortar ammunition in the theatre. Around mid-1943, the Royal Engineer chemical warfare companies were disbanded as an emergency expedient and one heavy mortar company of each infantry division machine-gun battalion was equipped with the mortar; this company was organized in four platoons of four mortars each.

In early 1944, divisions in Italy held a pool of mortars for issue to other units as required troops in the divisional anti-tank regiment, some regiments converted one or more batteries to mortars. Ordnance ML 4.2-inch mortars were slower to reach Commonwealth forces in the Asia. Australian Army units in the South West Pacific theatre were the first to receive them, before forces in Burma. After World War II, the mortars were handed over to the Royal Artillery, the 170th Mortar Battery used them at the Battle of Imjin River in Korea, they were used during the 1950s by airborne artillery, deployed to Kuwait in 1961 and manned by soldiers from air defence batteries during the Confrontation in Borneo in 1965. The 4.2-inch mortar tripod. The normal detachment was six men and it was transported with ammunition in a 10 cwt trailer towed behind a Loyd Carrier. There was an auxiliary baseplate that fitted around it, to increase its area for use on softer ground. An integrated trailer/baseplate was developed, called the Mk 1 Mobile Baseplate.

The wheels, which were on suspension arms, were raised for firing. The mobile baseplate trailer mounting could be brought into action by 2 men. Regarding rate of fire, one source reports a crew putting 23 bombs in the air before the first impacted. Both HE and smoke ammunition was used. Smoke include WP and Base Ejection, in World War II other types for practice. Two charges were available. In World War II, both streamlined and cylindrical bombs were available. Chemical munitions included the MK I chemical mortar bomb with Mustard gas. World War II Australia United KingdomPostwar Australia Canada Ethiopia Greece India Laos Malaysia New Zealand Nepal Turkey United Kingdom M2 4.2 inch mortar – US equivalent 107mm M1938 mortar – Soviet equivalent Pugh, Stevenson. Fighting Vehicles and Weapons of the Modern British Army. London: Macdonald. Bidwell, Shelford. Artillery of the World. London: Brassey's. ISBN 0-904609-04-9. Horner, David; the Gunners – A History of Australian Artillery. St Leonards: Allen & Unwin.

ISBN 1-86373-917-3. Maintenance Manual for ML 2-inch, ML 3-inch and SB 4.2-inch mortars Bishop, Chris. The Encyclopedia of Weapons of WWII. Fendick, Rex F. Diary of a CANLOAN Officer. Saint John, NB. "British mortars of the Second World War". WWIIEquipment