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A hibernaculum (plural form: hibernacula) (Latin, "tent for winter quarters") is a place in which an animal seeks refuge, such as a bear using a cave to overwinter. The word can be used to describe a variety of shelters used by many kinds of animals, including insects, toads, lizards, snakes, bats, rodents, and primates of various species.
Insects range in their size, structure, and general appearance but most use hibernacula. All insects are primarily exothermic. [1] For this reason, extremely cold temperatures, such as those experienced in the winter, outside of tropical locations, cause their metabolic systems to shut down; long exposure may lead to death. Insects survive colder winters through the process of overwintering, which occurs at all stages of development and may include migration or hibernation for different insects, the latter of which must be done in hibernacula. Insects that do not migrate must halt their growth to avoid freezing to death, in a process called diapause. [2] Insects prepare to overwinter through a variety of mechanisms, such as using anti-freeze proteins or cryoprotectants in freeze-avoidant insects, like soybean aphids. Cryoprotectants are toxic, with high concentrations only tolerated at low temperatures. Thus, hibernacula are used to avoid sporadic warming and the risk of death due high concentrations of cryoprotectants at warmer temperatures. [3] Freeze-tolerant insects, like second-generation corn-borers, can survive being frozen and therefore, undergo inoculative freezing. [4] Hibernacula range in size and structure depending on the insects using them. [5]
However, insect hibernacula are generally required to be:
Some insects, like convergent lady bugs, reuse the same hibernacula, year after year. They converge with other lady beetles and migrate to hibernacula used by prior generations. They are able to find old hibernacula due to hydrocarbons released by lady beetle feet which create a lasting path. This allows lady beetles to retrace their footsteps to previously used hibernacula. [7] Their tendency to aggregate and overwinter in groups is likely due to their attraction to similar environments and conspecifics. Beetles use rock crevices as hibernacula, often clumping in them, in groups. These rock crevices are found in rock fields the beetle are attracted to for high levels of vegetation and greenery. [8]
Other types of insect hibernacula include self-spun silk hibernacula, such as those made and used by spruce budworms as they moult and overwinter in their second instars. [9] An example is the eastern spruce budworm which creates hibernacula after dispersing during its first instar then overwinter before emerging from the hibernacula in early May. [10] Woolly bear caterpillars overwinter as caterpillars and grow to be isabella tiger moths. They use plant debris as makeshift hibernacula, to protect themselves from extreme elements. [6] Some butterflies, like the white admiral butterfly also only mature halfway as a caterpillar before hibernating for the winter. [11] For freeze-avoidant insects, ideal hibernacula are dry, as freeze-avoidant insects are less likely to dampen and freeze in them, however moist hibernacula promote inoculative freezing for freeze-tolerant insects. [12]
Amphibians that hibernate include several species of frogs and salamanders from the northern continental climates of North America and Eurasia and also from extreme Southern Hemisphere climates. [13] These amphibians slow their metabolism during winter to avoid unsuitable conditions, such as freezing. Most freeze avoidance strategies include overwintering in aquatic situations or burrowing in the soil to depths below the frostline. [14] A hibernaculum for amphibians should provide the following: [13]
Species from cool continental climates hibernate at temperatures from 0 to 4 °C. Some species will not survive hibernation at temperatures that exceed 4 °C. [13]
Generally, for amphibians that hibernate under ice, it is necessary for the animal to be submerged in water that is 10 to 15 cm deep and to maintain the temperature between 2 and 3 °C and not above 4 °C. Water should be well aerated, with maintained low-intensity light levels and minimal disturbance of the amphibians.
Like other amphibians, frogs show minimal capacities for freezing tolerance and survive winter by using terrestrial hibernacula where they avoid freezing. However, frogs may exhibit greater freeze-tolerance capacity at high latitude range limits, where winter climate is more severe. For example, data suggests that while cricket frogs in South Dakota survive winter by locating hibernacula that prevent freezing, their toleration of short freezing bouts may expand the range of suitable hibernacula. [14] However, overwinter mortality may be high at the northern range boundary due to colder temperatures and might limit cricket frogs from expanding their range northward. [14]
The microclimate refers to the climate of a very small or restricted area, like the hibernaculum, especially when this differs from the climate of the surrounding area. Overwinter survival in these cricket frogs among other frogs is dependent on using hibernacula with appropriate physical microclimate characteristics, such as moist soil, that buffer frogs from temperatures that drop below the freezing point of the body fluids for extended periods. [14] Although, determining if frogs can identify sites with appropriate microclimates to support overwinter survival and what factors might inform such choices are still unknown and will require further study. Therefore, it is still not known to what extent various types of prospective hibernacula for frogs might be suitable in the years to come, especially factoring in climate change.[ citation needed ]
As part the Highways Agency Biodiversity Action Plan (HABAP) in the UK, the Species Action Plan (SAP) for great crested newts aims to maintain and enhance existing newt populations through appropriate management of suitable habitat. As part of steps to implement the HABAP, newt hibernacula (e.g. log piles) have been constructed to improve the quality of the terrestrial habitat through increasing the number of potential overwintering sites. [15] It was also determined that habitat surrounding breeding ponds with plenty of cover and suitable overwintering sites may have less need for provision of artificial hibernacula than landscapes with less woodland, hedgerows, scrub etc. [15] Because great crested newts show high loyalty to over-wintering locations, returning to such established areas year after year, artificial hibernacula could be important in future years to conserve newts and other amphibians. [15] Although, monitoring in the vicinity of these hibernacula in autumn using felt roofing tiles did not reveal the presence of any great crested newts even though they are known to breed in nearby ponds. [15] Common toads and frogs did surround the area however. Therefore, further studies need to be conducted in order to create species-appropriate artificial hibernacula.[ citation needed ]
Many reptiles undergo hibernation or a process called brumation, which is similar to hibernation; both processes require usage of a hibernaculum. Staying inside an insulated hibernaculum is a strategy to avoid the harsh winter months when the frigid outside temperatures may kill an ectothermic reptile. They depress their metabolism and heart rates to reduce energy consumption so they don't need to exit their hibernacula. Hibernating reptiles are also safer from predation inside of their concealed and protected hibernacula. Various species of turtles, snakes, and lizards all use hibernacula, the forms of which can vary greatly. [16] [17]
Hibernacula are typically:
Common snapping turtles generally hibernate for about six months from early October to mid-April. They live in lakes during their active months, then travel to small offshoot streams to hibernate. Hibernacula are about 100–150 meters away from the main body of the home lake. Most snapping turtles hibernate by burrowing into the banks of alder streams or vegetated streams, but some use other structures such as abandoned beaver dens. These streams are typically less than 0.3 m deep and 0.7 m wide, covered by sunken alder roots or fallen trees, and not covered by ice in the winter. Many animals return to the same stream to hibernate in subsequent years. [16]
Unlike more solitary snapping turtles, snakes may either hibernate alone or in large aggregations of up to several thousand individuals of the same or different species. They use a wide variety of hibernacula, including: rock piles, debris-filled wells, caves, crevices, unused burrows made by other animals, and ant mounds. The common European viper has actually been observed using all of the hibernacula listed above. Most species seem to prefer finding an already-present suitable site rather than constructing one of their own, but they do expand upon present structures and may make their own burrows if there aren't any quality sites available. [17] Pine snakes and the closely related Louisiana pine snakes are two of the most well-studied hibernating snake species, and share similar hibernacula characteristics. These species sometimes construct their own burrows, or use tunnels formed from the decay of tree roots or by gophers. The tunnels form complex networks, and have side chambers which each house one snake. [17] [19]
Mesquite lizards in Mexico and the southern United States have been found hibernating in groups of 2 to 8 in cracks or under slabs of bark in mesquite trees. [21] Common collared lizards spend about 6 months hibernating, almost always solitarily, though pairs of juvenile females have been observed within the same hibernaculum. They use the undersides of rock slabs as hibernacula, digging a small chamber in the dirt just large enough for their bodies with a small tunnel for outside access. Adults use larger rock slabs, dig deeper chambers, and have longer tunnels than juveniles. [20] Perhaps the most extreme example is seen in the viviparous lizard, the most northern of all lizards. They can burrow into the soil, go under leaf litter, or use shelters like rocks as hibernacula. Although the air temperature in West Siberia can drop to −10 °C, the soil temperature at the depths where these lizards hibernate remains higher than −10 °C. This enables them to survive the harshest temperatures of any lizard. [18]
Like other animals, mammals hibernate during seasons of harsh environmental conditions and resource scarcity. As it requires less energy to maintain homeostasis and survive when an individual is hibernating, this is a cost-effective strategy to increase survival rates. [22] [23] Hibernation is usually perceived as taking place during winter, as in the most well-known hibernators bears and bats, [24] [23] but can also occur during the dry season when there is little food or water, as in the mouse lemurs of Madagascar. [22] Given that mammals can spend anywhere from 1 to 9 months hibernating, their choice in hibernaculum is essential in determining their survival. [23]
Hibernacula vary greatly, but are typically:
Many bears occupy similar hibernacula to smaller mammals, but theirs are, of course, much larger and can vary greatly across and within species. Most black bears excavate dens into a hillside or at the base of a tree, stump, or shrub, but some make dens at the bases of hollow trees, in hollow logs, or in rock caves or cavities. Den reuse is observed in this species, but very rarely. There were no significant den size differences between age or sex classes, except adult males creating larger entrances. [28] Grizzly bears likewise don't show age or sex class differences in den dimensions. Grizzlies prefer hibernacula sites with abundant ground and canopy cover, and abundant sweet-vetch. [23] Polar bears differ from black bears, grizzlies, and other bear species where both sexes hibernate in that only females use hibernacula. Like other female bears, polar bears use hibernacula as maternity dens. Also like other species, they tend to dig dens into the earth, although their Arctic hibernacula are usually covered with snow by the time they emerge. [30]
Bats favor larger hibernacula where large groups may roost together, including natural caves, mines, cellars, and other kinds of underground sites and man-made structures, like ice-houses. [27] Within these hibernacula, the bats are still highly tuned to environmental factors. Little brown bats in northern latitudes hibernate for up to eight months during the winter, and leave their roosts in the warm spring weather when insect prey is plentiful again. Bats gauge the outside temperature by being attuned to the airflow at the hibernacula entrance, which is driven by temperature differences between inside and outside the hibernacula, allowing bats to leave when the temperature begins to warm. [24] Some hibernacula are shared between multiple species, such as common pipistrelles roosting with soprano pipistrelles. Behavior other than hibernating can also occur at hibernacula; common pipistrelles produce most of their mating calls and mate with each other in and near their hibernacula. [29]
Many hibernating, small-bodied mammals hibernate in simple holes in the ground, though some use complex systems of tunnels and burrows. Mountain pygmy possums in New South Wales, Australia, dig holes in the ground to form hibernacula, with the preferred location being in boulder fields under a layer of snow. During the first few months of hibernation, possums awaken occasionally and leave one hibernaculum in favor of another, seemingly in an effort to find the hibernaculum with the most suitable microclimate. [25] The reddish-gray mouse lemur also wakes and leaves the hibernaculum spontaneously and for brief periods of time. Their hibernacula are located in holes in large trees with varying levels of insulation. However, the range of insulation levels is relatively narrow, as there are often small numbers of suitably large trees. [22] There can be hibernacula differences even within a species. In Columbian ground squirrels, hibernacula size is proportional to the weight of the individual occupying it, with adults having deeper hibernacula than juveniles, unlike black bears. Most juveniles choose to hibernate within 20 meters of their mother's burrow; those that don't have higher mortality rates. [26]
Hibernation is a state of minimal activity and metabolic depression undergone by some animal species. Hibernation is a seasonal heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic rate. It most commonly occurs during winter months.
The smooth newt, European newt, northern smooth newt or common newt is a species of newt. It is widespread in Europe and parts of Asia, and has been introduced into Australia. Individuals are brown with a spotted underside that ranges in colour from orange to white. They reach an average length of 8–11 cm (3.1–4.3 in); males are larger than females. The newts' skins are dry and velvety when they are living on land, but become smooth when they migrate into the water to breed. Males develop a more vivid colour pattern and a conspicuous skin seam (crest) on their back when breeding.
The slender glass lizard is a legless lizard in the glass lizard subfamily (Anguinae). The species is endemic to the United States. Two subspecies are recognized. The lizard was originally believed to be a subspecies of the eastern glass lizard. Their name comes from their easily broken tail which they can break off themselves without ever being touched. It is difficult to find a specimen with an undamaged tail. The lizard eats a variety of insects and small animals, including smaller lizards. Snakes and other animals are known to prey on the species. Humans have a part in destroying their environment and killing their food supply with insecticides. The lizard is considered to be a least-concern species according to the International Union for Conservation of Nature (IUCN), though it is vulnerable in Iowa and endangered in Wisconsin. It is important to note that the streamlined, legless species is often confused with snakes. Glass Lizards, however, differ from snakes as they possess a moveable eyelid, which is absent in snakes. Another way to distinguish glass lizards from snakes is the presence of an external ear opening, which are absent in snakes.
Garter snake is the common name for small to medium-sized snakes belonging to the genus Thamnophis in the family Colubridae. Native to North and Central America, species in the genus Thamnophis can be found in all of the lower 48 United States, and nearly all of the Canadian provinces south of the Northwest Territories and Nunavut—with the exception of Newfoundland and Labrador. They are found from the subarctic plains of west-central Canada east through Ontario and Quebec; from the Maritime Provinces and south to Florida, across the southern and central U.S. into the arid regions of the southwest and Mexico, Guatemala and south to the neotropics and Costa Rica.
The common garter snake is a species of snake in the subfamily Natricinae of the family Colubridae. The species is indigenous to North America and found widely across the continent. There are several recognized subspecies. Most common garter snakes have a pattern of yellow stripes on a black, brown or green background, and their average total length is about 55 cm (22 in), with a maximum total length of about 137 cm (54 in). The average body mass is 150 g (5.3 oz). The common garter snake is the state reptile of Massachusetts.
The gray bat is a species of microbat endemic to North America. It once flourished in caves all over the southeastern United States, but due to human disturbance, gray bat populations declined severely during the early and mid portion of the 20th century. 95% of gray bats now hibernate in only 15 caves. M. grisescens has been listed as federally endangered by the U.S. Fish and Wildlife Service since 1976, and is protected under the Endangered Species Act. Gray bat populations were estimated at approximately 2 million bats around the time they were placed on the Endangered Species list. By the early 1980s populations of gray bats dropped to 1.6 million. With conservation efforts in place, in 2004, gray bat populations were estimated to have reached 3.4 million.
Cold hardening is the physiological and biochemical process by which an organism prepares for cold weather.
Lithobates sylvaticus or Rana sylvatica, commonly known as the wood frog, is a frog species that has a broad distribution over North America, extending from the boreal forest of the north to the southern Appalachians, with several notable disjunct populations including lowland eastern North Carolina. The wood frog has garnered attention from biologists because of its freeze tolerance, relatively great degree of terrestrialism, interesting habitat associations, and relatively long-range movements.
Elaphe is a genus of snakes in the family Colubridae. Elaphe is one of the main genera of the rat snakes, which are found in many regions of the northern hemisphere. Elaphe species are medium to large constrictors by nature.
The Arctic ground squirrel is a species of ground squirrel native to the Arctic and Subarctic of North America and Asia. People in Alaska, particularly around the Aleutians, refer to them as "parka" squirrels, most likely because their pelt is good for the ruff on parkas and for clothing.
The Indiana bat is a medium-sized mouse-eared bat native to North America. It lives primarily in Southern and Midwestern U.S. states and is listed as an endangered species. The Indiana bat is grey, black, or chestnut in color and is 1.2–2.0 in long and weighs 4.5–9.5 g (0.16–0.34 oz). It is similar in appearance to the more common little brown bat, but is distinguished by its feet size, toe hair length, pink lips, and a keel on the calcar.
The moor frog is a slim, reddish-brown, semiaquatic amphibian native to Europe and Asia. Moor frogs are known for their ability to freeze solid and survive thawing. The frog makes use of various cryoprotectants i.e. antifreeze that decrease its internal freezing temperature. The species is distributed over a large range, covering a significant portion of Eurasia. Male moor frogs are known to turn blue temporarily during the height of mating season. This coloration is assumed to signal a mate's fitness. Moor frogs typically mate through multimale amplexus a form of polyandry.
Overwintering is the process by which some organisms pass through or wait out the winter season, or pass through that period of the year when "winter" conditions make normal activity or even survival difficult or near impossible. In some cases "winter" is characterized not necessarily by cold but by dry conditions; passing through such periods could likewise be called overwintering.
Insect winter ecology describes the overwinter survival strategies of insects, which are in many respects more similar to those of plants than to many other animals, such as mammals and birds. Unlike those animals, which can generate their own heat internally (endothermic), insects must rely on external sources to provide their heat (ectothermic). Thus, insects persisting in winter weather must tolerate freezing or rely on other mechanisms to avoid freezing. Loss of enzymatic function and eventual freezing due to low temperatures daily threatens the livelihood of these organisms during winter. Not surprisingly, insects have evolved a number of strategies to deal with the rigors of winter temperatures in places where they would otherwise not survive.
The Alaska marmot, also known as the Brooks Range marmot or the Brower's marmot, is a species of rodent in the family Sciuridae. Once considered to be the same species as the hoary marmot, it is now known to be unique. Alaska marmots are found in the scree slopes of the Brooks Range, Alaska. Specifically, they prefer to dwell on rocky, mountainous terrain, generally near lakes. They eat vegetation found on mountainsides, such as grasses, seeds, and lichen. Their relatively thick bodies are covered in dense, grey fur. They live in large colonies that consist of multiple families. During the winter, they hibernate for long periods of time in burrows. While not well researched, they are not believed to be particularly threatened, by human activity or otherwise. The Alaskan government has designated February 2 as "Marmot Day," a holiday intended to recognize the prevalence of marmots in the state, similar to the more widely celebrated American holiday of Groundhog Day.
The little brown bat or little brown myotis is an endangered species of mouse-eared microbat found in North America. It has a small body size and glossy brown fur. It is similar in appearance to several other mouse-eared bats, including the Indiana bat, northern long-eared bat, and Arizona myotis, to which it is closely related. Despite its name, the little brown bat is not closely related to the big brown bat, which belongs to a different genus.
Cryopreservation or cryoconservation is a process where biological material - cells, tissues, or organs - are frozen to preserve the material for an extended period of time. At low temperatures any cell metabolism which might cause damage to the biological material in question is effectively stopped. Cryopreservation is an effective way to transport biological samples over long distances, store samples for prolonged periods of time, and create a bank of samples for users. Molecules, referred to as cryoprotective agents (CPAs), are added to reduce the osmotic shock and physical stresses cells undergo in the freezing process. Some cryoprotective agents used in research are inspired by plants and animals in nature that have unique cold tolerance to survive harsh winters, including: trees, wood frogs, and tardigrades.
Gynaephora groenlandica, the Arctic woolly bear moth, is an erebid moth native to the High Arctic in the Canadian archipelago, Greenland and Wrangel Island in Russia. It is known for its slow rate of development, as its full caterpillar life cycle may extend up to 7 years, with moulting occurring each spring. This species remains in a larval state for the vast majority of its life. Rare among Lepidoptera, it undergoes an annual period of diapause that lasts for much of the calendar year, as G. groenlandica is subject to some of the longest, most extreme winters on Earth. In this dormant state, it can withstand temperatures as low as −70 °C. The Arctic woolly bear moth also exhibits basking behavior, which aids in temperature regulation and digestion and affects both metabolism and oxygen consumption. Females generally do not fly, while males usually do.
The wildlife of Norway includes the diverse flora and fauna of Norway. The habitats include high mountains, tundras, rivers, lakes, wetlands, sea coast and some lower cultivated land in the south. Mainland Norway has a long coastline, protected by skerries and much dissected by fjords, and the mostly-icebound archipelago of Svalbard lies further north. The flora is very varied and a large range of mammals, birds, fish and invertebrate species live here, as well as a few species of reptiles and amphibians.
The Alameda whipsnake, also known as the Alameda striped racer, is a federally threatened subspecies of California whipsnake. It is a colubrid snake distinguishable by its broad head, large eyes, black and orange coloring with a yellow stripe down each side, and slender neck. The California whipsnake is found in California's northern and coastal chaparral. The Alameda whipsnake is a wary creature known for its speed and climbing abilities utilized when escaping predators or hunting prey. In winter months, the Alameda whipsnake hibernates in rock crevices and rodent burrows.
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