So rather than squander energy and resources in the current era, Sandberg and company believe it makes more sense for an advanced, computer-based civilization to aestivate and wait until the Universe is much colder than it is today.
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Insecta: Lady beetles (Coccinellidae) have been reported to aestivate. Mosquitoes also are reported to undergo aestivation. False honey ants are well known for being winter active and aestivate in temperate climates. Bogong moths will aestivate over the summer to avoid the heat and lack of food sources.
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During the dry season, these frogs bury themselves and aestivate.
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Velesunio wilsonii is able to aestivate for up to 5 years.
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Those few species that dwell in arid environments typically hibernate or aestivate during dry periods to preserve moisture.
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In other words, animals which aestivate appear to go through nearly the same physiological processes as animals that hibernate.
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Instead, adult bogong moths migrate in a southerly direction during the summer and aestivate (remain dormant), until conditions are favourable again.
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Aestivation has been put forward as the most likely explanation why this therapsid cynodont Thrinaxodon liorhinus shared its burrow with a temnospondyl amphibian, Broomistega putterilli. Non-mammalian animals that aestivate include North American desert tortoises, crocodiles, and salamanders. Some amphibians (e.g. the cane toad and greater siren) aestivate during the hot dry season by moving underground where it is cooler and more humid.
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1998: 19(2) : 91-93 PDF They aestivate in summer.McCann, C. 1946. Aestivation of the frog Ramanella montana (Jerdon). J. Bombay. Nat. Hist. Soc. :404-406.
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Under extreme conditions, some are able to aestivate in chambers under ground. Pocket mice normally run around on four limbs but can also move with leaps.
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During the dry season the juveniles become white as they aestivate the skin in the inside of their limbs becomes red due to the underlying capillary network.
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Although relatively uncommon, a small number of mammals aestivate. Animal physiologist Kathrin Dausmann of Philipps University of Marburg, Germany, and coworkers presented evidence in a 2004 edition of Nature that the Malagasy fat-tailed dwarf lemur hibernates or aestivates in a small tree hole for seven months of the year. According to the Oakland Zoo in California, East African hedgehogs are thought to aestivate during the dry season.
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Due to the ephemeral nature of many of Bayardella's habitats, Bayardella are able to aestivate on the underside of hard surfaces such as rocks and large pieces of wood.
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Gastropoda: some air-breathing land snails, including species in the genera Helix, Cernuella, Theba, Helicella, Achatina and Otala, commonly aestivate during periods of heat. Some species move into shaded vegetation or rubble. Others climb up tall plants, including crop species as well as bushes and trees, and will also climb man-made structures such as posts, fences, etc. Their habit of climbing vegetation to aestivate has caused more than one introduced snail species to be declared an agricultural nuisance.
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During dry spells, P. axanthus is known to aestivate in muddy burrows, and adults have been kept for periods longer than two months in dry soil with no ill effects in the laboratory.
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This toad breeds opportunistically at any time of year in stationary or slow-moving water, depositing strings of black eggs in the water. Under adverse conditions, this toad can bury itself in the ground and aestivate, remaining dormant until rain falls or conditions improve. It has been known to aestivate for as long as three years at a time. Stimulated by changing conditions, all the toads may emerge at once and congregate in great numbers in suitable places to breed.
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N. cleaveri can aestivate if water in its location dries up in summer or in times of drought, burying horizontally in the mud or by seeking out moist areas of substrate under rocks and logs.
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Over most of their range, they hibernate in winter, using mainly subterranean hiding places, where many individuals will often congregate. In their southern range, they may instead sometimes aestivate during the dry months of summer.
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CABI Publishing, Oxon, UK, 2001, . 1-146, cited pages: 455. (see also Yom-Tov 1971). These snails dig themselves into the soil to depths from 1 to 5 cm while they aestivate during summer in the Negev Desert.
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For example, the internal temperatures of hibernating arctic ground squirrels can drop to , however the head and neck always stay above . A few mammals in hot environments aestivate in times of drought or extreme heat, namely the fat-tailed dwarf lemur (Cheirogaleus medius).
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Generally occurs on fine sediment and/or on and under rocks and logs. Members of Notopala are thought to be grazers of periphyton and occur in slow moving or still waters. Some species are able to aestivate in mud during dry periods.
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Hoplobatrachus crassus is a terrestrial frog that lives in seasonally flooded dry grasslands, open plains and arid areas, also in cultivated areas and near human settlements. Adult frogs are often found in burrows. They may aestivate during dry periods. Breeding takes place in water.
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The red-footed tortoise's climate in the northern part of the range changes little day to day and rarely gets too hot for them, so the tortoises do not need to practice any form of dormancy and can often forage all day long. The tortoises in Moskovitz's study area were most active after 3:00pm while many species from warmer climes would be most active in the morning and evening. Tortoises from the southern parts of the range experience much hotter, colder, and drier conditions than most of the range and aestivate when food becomes scarce. They may aestivate or brumate when the temperatures are low enough. p. 82.
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It is common near beaches. In dunes it can live on nearly bare sand that is poorly fixed in place by grasses. In colder regions the snails do not aestivate, but they do climb on plants in dry weather. This snail does not survive serious winter frosts.
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If the water temperature becomes too high, some species of sea cucumber from temperate seas can aestivate. While they are in this state of dormancy they stop feeding, their gut atrophies, their metabolism slows down and they lose weight. The body returns to its normal state when conditions improve.
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They are largely nocturnal but sometimes move about by day in wet weather. The adults may aestivate from May till September though the juveniles remain active for at least part of this time. In the winter they probably hibernate and the females probably only breed every alternate year.
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Adult alfalfa weevils (Hypera postica) aestivate during the summer in the southeastern United States, during which their metabolism, respiration, and nervous systems show a dampening of activity. Crustacea: An example of a crustacean undergoing aestivation is with the Australian crab Austrothelphusa transversa , which undergoes aestivation underground during the dry season.
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During the dry season, Florida gars burrow into the sediments of the marshes they inhabit and aestivate through the dry season. Aestivation, similar to hibernation in other species, lowers the animal's metabolic rate. This allows the Florida gar to withstand the high temperatures and dry conditions of their habitats during the summer.
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During the intermittent dry seasons, the snails, young and adults alike, aestivate ("the warm weather equivalent of hibernation"Gould, S.J., 1985. The Flamingo's Smile; Reflections in Natural History. Norton, New York) on the rocks or in crevices inside the rocks. For aestivation, aggregates are often formed, sometimes reaching sizes of many hundreds of individuals.
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Theba pisana snails aestivate on fennel Foeniculum vulgare in Montbazin, France. Drawing of love dart of Theba pisana. Theba pisana usually lives in coastlands, in or near sandy habitats. In hot climates it aestivates often directly exposed to the sun, attached to grasses, shrubs or succulent plants, fence posts, tall weeds, and so on.
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The Fourche Mountain salamander hides in undergrowth and under rocks and logs. It mainly feeds at night on small invertebrates such as insects, spiders, and worms. Between May and September when the weather is hot and dry, it may aestivate underground, emerging to forage during any wet periods that may occur. It probably hibernates between November and March.
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Regardless of the lack of evidence confirming the bowfin's ability to aestivate, it has been noted that bowfin can survive prolonged conditions of exposure to air because they have the ability to breathe air. Their gill filaments and lamellae are rigid in structure which helps prevent the lamellae from collapsing and aids gas exchange even during air exposure.
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Here it is cooler and more humid which conserves moisture and the animals may temporarily block the entrances to augment this. They are able to concentrate their urine to a viscous consistency which further reduces water loss. Under extreme conditions, some are able to aestivate in chambers under ground. Kangaroo rats have large hind feet with long metatarsals and no first digits.
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D. p. arnyi will aestivate in the summer if the temperature is too hot and brumate in the winter when the weather is too cold. This is because the snake is an ectotherm (that is, cold-blooded) and needs to stay warm enough or cool enough to survive. For this reason it can be seen sunbathing when the temperature is cool.
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There are several native Aboriginal (Ngarigo) names associated with Mount Townsend, where J. Macarthur recorded in 1840 some campings of the natives. There is some confusion as to the exact sounds. These are Jagungal, Jar-gan-gil, Tar-gan-gil, Tackingal; however, all of them mean Bogong Moth, which aestivate on the mountain. See the cited letter by A.E.J Andrews.
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They are able to aestivate for multiple years if necessary, burrowing into mud and exuding a cocoon of dead skin cells. Known predators include the American alligator and the mud snake. Their spermatozoa possess a pair of flagella, and their courtship behavior is unknown. Mating occurs in February and March, with mothers guarding clutches of eggs that hatch about two months later.
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The subdesert toad lives in arid regions and may aestivate for long periods. In northwestern Africa it is active between September and March with breeding taking place in September and October, clutches of eggs being laid in temporary ponds and pools in river beds. it is mainly nocturnal and feeds on small invertebrates such as spiders, beetles and other insects.
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Froglets hide in cracks and shade and live off stored tissue in their tails until they can start feeding as adults. Frogs can only live where the ground is suitable for burrowing, and reproduce within 1 km of where they aestivate. Like all frogs, they are immobilized by low temperatures. This species prefers to burrow near large objects such as logs or rocks.
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The slender lungfish has an anguilliform body, much like an eel. The body of the slender lungfish is generally brown; young of the species oftentimes have black spots throughout the body, however adults generally lose these spots as they age. Like all African lungfish the slender lungfish is an obligate air-breather and is capable of aestivation; however, it generally does not aestivate.
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For this reason it must keep moist at all times. In California it may aestivate in summer and be active in winter while in Vancouver Island it may be active in summer and hibernate in winter. Breeding takes place in spring and early summer. The female lays a clutch of six to nine eggs in some concealed location such as under bark.
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If a predator bites off a tentacle, the slug can grow a new one. Banana slugs have a single lung (on the right side) which opens externally via a pneumostome. The pneumostome lung cavity is heavily vascularized to allow gas exchange. Dehydration is a major problem for the mollusk; to combat this, banana slugs excrete a thick coating of mucus around their bodies and can also aestivate.
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During wet weather P. subrufa will often leave water bodies and embark on long overland journeys. During exceptionally dry weather when water bodies dry up, it will typically dig into the ground and bury itself until rains return; it has been known to spend months or even years in such a state. It will also hibernate during very cold weather, and aestivate during unusually hot, dry weather.
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Like other African lungfish, the West African lungfish is an obligate air breather and a freshwater-dwelling fish. It is demersal, meaning that it lives primarily buried within riverbeds. Due to the dry season frequently drying the rivers and floodplains in which it lives, the West African lungfish can aestivate for up to a year; however the West African lungfish generally only aestivates between wet seasons.
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Also, when dealing with the univoltine or bivoltine species, the infestation is brief, just a few weeks, before the beetle population moves off to aestivate. However, in a region where the biology is well understood, it may be worth spraying the inactive masses of beetles, always bearing in mind that if biologically naive practitioners spray the wrong species of aestivating beetles, the results could be expensive.
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The species inhabits mostly open forests, glades, rocky clearings, embankments and meadows in the elevation range from 1500 to 2300 metres above sea level. The larval host-plants are various grasses, including Poa annua. The eggs are not stuck to the host plant but fall among the foliage. The first instar caterpillar may aestivate until the autumn, at which time it feeds to some extent before overwintering.
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The Caspian turtle may occur in large populations in certain areas, especially in permanent water bodies. In temporary waters, it is forced to aestivate in the mud in summer, and the more northern populations hibernate during winter. It often basks, but disappears at the least disturbance. Many are killed each year by humans who obtain their eggs to use in treating ubiquitous eye ailments.
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This terrestrial species is known for its defense strategy that involves coiling into a tight ball when threatened, with its head and neck tucked away in the middle. In this state, it can literally be rolled around. Favored retreats include mammal burrows and other underground hiding places, where they also aestivate. In captivity, they are considered good pets, with their relatively small size and placid nature making them easy to handle.
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Common vampire bat (Desmodus rotundus) New World leaf-nosed bats are usually brown, grey, or black, although five species are white. They range in size from in head-body length, and can weigh from . Most roost in fairly small groups within caves, animal burrows, or hollow trees, although some species aggregate in colonies of several hundred individuals. They do not hibernate, although some species have been reported to aestivate.
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Barbegazi are mythical creatures from Swiss and French mythology. A variety of dwarf or gnome, a barbegazi resembles a small white-furred man with a long beard and enormous feet. They travel in the mountains that are their home by skiing with their massive feet, or using them as snowshoes. In the summer they aestivate in caves and tunnels and do not come out until the first snowfall.
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Active Novisuccinea chittenangoensis are generally found at temperatures from 12 to 20 °C. During warmer periods, snails retreat to cool areas provided by the moist rock and moss, or aestivate in the vegetation. During cold winter temperatures, it is believed that the snails at the Falls retreat into cracks or fissures in the rocks and remain inactive. Various temperature readings were gathered during the summers of 1980-1982.
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The most common sounds made by four-toed hedgehogs are snorts, hisses, and a quiet twittering sound. When attacked, the animal can scream loudly, and males also produce a birdlike call during courtship. Although four-toed hedgehogs do aestivate through the summer, this is not thought to be connected to a rise in temperature, but rather to a lack of available food. Aestivation rarely lasts for more than six weeks.
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During the hottest months of summer they may aestivate, depending on location, and individuals at higher elevations hibernate during the winter. They show great fidelity to their hiding and breeding places. It used to be thought that they were resident within small home ranges but it has now been shown that this is not the case. Migrations of populations sometimes take place and individuals sometimes wander far from their normal bases.
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They are said to aestivate in the months of June through September, or when their natural environment is not normal, or when in captivity. Little is known about their reproductive behaviour. When the female is ready to lay eggs, she digs a hole in the ground and covers it with grass or other vegetation. The geometric tortoise tends to feed during cooler parts of the morning and afternoon.
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Members of the Australian genus Cyclorana bury themselves underground where they create a water-impervious cocoon in which to aestivate during dry periods. Once it rains, they emerge, find a temporary pool, and breed. Egg and tadpole development is very fast in comparison to those of most other frogs, so breeding can be completed before the pond dries up. Some frog species are adapted to a cold environment.
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About 20% of the snails in a population survive to lay eggs in the 3rd year, 5% of the snails lay eggs again in the 4th year. The mortality rates decrease with age. The animals hibernate (in northern Greece) or aestivate (in Crete), but juveniles and adults show differences in their behaviour. Adults dig into the soil and build an epiphragm, while juveniles search protected places under stones or leaves of low plants.
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They inhabit the coastal plain from Washington, D.C., to Florida and Alabama. A population of sirens in the Rio Grande has been tentatively determined to be S. lacertina. Greater sirens live in wetlands, preferring those with a slow or nonexistent current and a thick layer of organic material. They are capable of inhabiting seasonal and permanent wetlands given their ability to aestivate, and will burrow into mud if their wetland dries up.
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In the northern parts of its range, the western whiptail usually emerges from hibernation in May, and most adults aestivate during the midsummer months, but in the south it is active from April through late August. The seasonal period of activity is therefore considerably shorter in the north. Daily periods of activity are of similar duration from north to south, although the time of emergence tends to be later in northern areas.
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Video clip Their natural habitat ranges from savannah to forest edges around the Amazon Basin. They are omnivorous with a diet based on a wide assortment of plants, mostly fruit when available, but also including grasses, flowers, fungi, carrion, and invertebrates. They do not brumate, but may aestivate in hot, dry weather. Eggs, hatchlings, and juvenile tortoises are food for many predators, but the main threats for adults are jaguars and humans.
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It inhabits shallow swamp-forest wetlands. If the water dries out over summer, it is able to aestivate in damp areas, such as under logs and in root holes, until the water returns. In 2014, the New Zealand Department of Conservation classified the brown mudfish as "At Risk: Declining" with qualifier "C(1/1) >100,000 mature individuals, predicted decline 10–70%". Also in 2014 the IUCN rated the brown mudfish as "Endangered".
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Sphincterochila boissieri is active for a few days only after rainfall during the winter season, from November to March. At this time of the year they feed, mate, and lay eggs. Thus these snails are active for only 5-7% of the year (nearly 18 to 26 days), and aestivate during all the rest of the time. Dormant snails are known to have survived in museum collections for up to 6 years.
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The Sardinian brook salamander is largely aquatic, though it does hibernate and sometimes aestivate on land near the water's edge. Mating takes place in the water, the male having first carried the passive female in his jaws to a suitable location. He clasps her body with his jaws and bends his body around, wrapping his tail around hers. He transfers spermatophores to her cloaca from his cloaca, sometimes with the aid of his spurs.
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The California red-legged frog may aestivate to conserve energy when its food and water supply is low. The water-holding frog has an aestivation cycle. It buries itself in sandy ground in a secreted, water-tight mucus cocoon during periods of hot, dry weather. Australian Aborigines discovered a means to take advantage of this by digging up one of these frogs and squeezing it, causing the frog to empty its bladder.
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Night snakes are known to be both crepuscular (most active at dawn and dusk), and nocturnal. They are usually seen at night while crossing roads, but can be found under rocks, boards, dead branches and other surface litter during the day. Night snakes hibernate during the winter months, and are known to aestivate during periods of the summer. They are generally most active from April to October, with peaks of activity usually occurring in June.
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Rocks and tiles are placed on the bottom to provide settlement for larvae and protection from predators. Breeding programs are under way to improve growth rates and disease resistance and the genome is being sequenced. Hatchery techniques are being developed in Japan and China as are the preparation of suitable culture feeds and the investigation of the best methods of ranching. Albino forms and a thermally resistant strain that is less prone to aestivate are being developed in China.
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The lower slopes of Mount Bogong are covered with tall forests of Alpine Ash (Eucalyptus delegatensis) to an altitude of about . From to , woodland and open woodland of Snow Gum (Eucalyptus pauciflora) dominate, and above , the vegetation consists of alpine shrubland, grassland and herbfield. Animals that live on Mount Bogong have all found some way to adapt to the environment which is very harsh. For example, bogong moths gregariously aestivate in caves throughout the mountain to avoid desiccation.
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Food is mostly gathered in the morning between the hours of 9.00 and 11.00, stuffed into the cheek pouches and carried back to the burrow for later consumption. If food is scarce in the hottest part of the year, this ground squirrel may aestivate for a short time. It may breed throughout the year in farmland but in deciduous woodland it probably breeds between May and June before the start of the wet season. The population size varies widely from year to year.
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The new weevils apparently aestivate during the summer and become active as the weather cools down in the fall when they infest stressed trees, feed and mate. Deodar weevils usually don't infest trees younger than age 5 (hey need stems large enough to support larval galleries). Deodar weevils tend to infest the bottom 10 feet of the main stem. These weevil grubs feed beneath the bark and sometimes girdle the stem causing it to die from the damaged portion outward.
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As this fish grows the spots get smaller. Like most plecs this species is primarily herbivorous though will eat dead animals. In the wild these fish are found in shoals in sluggish rivers of the Amazon and Orinoco river systems, they also occupy flooded land during the wet season. During the dry season P. gibbiceps will aestivate in burrows around 1 metre long dug into mud banks along the length of a river, egg rearing is also presumed to take place in burrow.
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Wild and captive specimens often bask and, although they do not appear to hibernate, there are reports that they may aestivate beneath flat rocks during the hottest months. Most activity occurs during the morning hours or in the late afternoon and early evening. The diet primarily consists of dry grasses and vegetation. The pancake tortoise is a fast and agile climber, and is rarely found far from its rocky home so that, if disturbed, it can make a dash for the nearest rock crevice.
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The bronze caco or bronze dainty frog (Cacosternum nanum) is a species of frog in the family Pyxicephalidae, found in South Africa and Swaziland, and possibly Lesotho and Mozambique. Cacosternum nanum is one of the most common frogs in its range. It occurs in a wide range of habitats, including fynbos heathland, savanna, shrubland, grassland, farmland, plantations, rural grassland, degraded forest, and urban areas. They aestivate below the surface or under logs and stones during dry periods, and may emerge in large numbers after heavy rain.
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Mudfish have the ability to aestivate during droughts, seeking out moist areas under logs and vegetation so they do not dry out. While emersed (out of the water), they respire through cutaneous respiration, either through their skin, or by taking mouthfuls of air. Emersed mudfish frequently lie on their backs, possibly improving cutaneous respiration through the thinner abdominal skin, improving oxygenation of vital organs, or rehydrating skin on their upper surfaces. As wetland habitats dry out, the standing water may become stagnant and hypoxic.
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Small groups of these animals are often found in unusual roosting sites such as in the suspended nests of weaver finches and sunbirds, banana tree leaves, or under the eaves of huts. Painted bats have been known to roost in pairs. They apparently aestivate during the day, as they are relatively sluggish when disturbed. The bright and broken coloration of these bats may be a form of camouflage to protect them, as they have been reported to blend in with dried leaves and flowers when they roost.
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Spotted turtles do become active very early in the spring, and are often active at relatively cold water temperatures during that season. Activity appears to peak during April and May in the northern part of the range. In the warmest part of the summer (when water temperatures exceed 30 °C), they may aestivate terrestrially or aquatically for long periods of time. During summer dormancy, the turtles may burrow into leaf litter in woodlands or marsh edges or open fields; others remain in muskrat burrows or other aquatic refuges.
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Despite the fact that butterflies, particularly the mourning cloak butterflies, have an affinity for perches on high objects, they are not known to display any hilltopping behavior, where male butterflies fly up to perch on hill summits. Spring marks the beginning of their mating season, when female mourning cloaks will find a host plant and begin to lay their eggs. Adult mourning cloak butterflies can first be seen in late spring through early summer. They then aestivate for the summer, where they will enter into a "dormant" state similar to that of hibernation.
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This species is, with the possible exception of a single specimen found north of Kyogle, as of yet unidentified and most probably belonging to a distinct species, unique amongst known Australian hydrobiids in being able to aestivate and withstand drying. The type series were found in dry soil in a small, dry creek bed on the landward side of a small hill, in a small coastal rainforest remnant in Burleigh Head National Park, Queensland. Several days after collection they were placed in water, after which they soon emerged and crawled about actively.
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The salamanderfish (Lepidogalaxias salamandroides) is the sole species in the endemic family Lepidogalaxiidae. Salamanderfish can aestivate during the summer months, an adaptation to the region's dry summers. Other endemic species are the nightfish (Bostockia porosa), western mud minnow (Galaxiella munda), black-stripe minnow (Galaxiella nigrostriata), Balston’s pygmy perch (Nannatherina balstoni), western pygmy perch (Nannoperca vittata), and western galaxias (Galaxias occidentalis). Southwest Australian varieties of the diadromous common galaxias (Galaxias maculatus) and spotted galaxias (Galaxias truttaceus) have adapted so they can live their life-cycle and reproduce in fresh water.
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Generally, these salamanders only come above ground during the night when the temperature is above 45 °F. Coeur d'Alene salamanders are known to eat aquatic insects and other invertebrates, which are also active at night. In northern Idaho, P. idahoensis emerges from winter hibernation in late March and is active near the surface through April and May; this surface activity is negatively correlated with both high daytime temperatures and the number of days since last rain. From June until mid-September, Coeur d'Alene salamanders retreat underground to aestivate.
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This caiman sometimes uses a burrow as shelter during the day and in the Pantanal may aestivate in the burrow to stay cool in the dry season. The female buries her eggs on a mounded nest and these take about 3 months to hatch. She helps the hatchlings to escape from the nest and provides some parental care for the first few weeks of their lives. This caiman has a wide range and large total population and the IUCN lists its conservation status as being of least concern.
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Most species tend to live in arid to fairly arid habitats, often in places with sandy soils, but there are also species in moist habitats. When the weather is warm and dry, they regularly visit places with water or retreat to damp, hidden locations. In the most arid regions, they are usually restricted to areas near water sources like oases and river valleys, and they may aestivate during the driest periods (in contrast to northern populations that hibernate in winter). They are quite tolerant of high temperatures and only die when they have lost about half their body fluids.
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In the vicinity of the Dead Sea, they usually either burrow to depths of up to 10 cm, or aestivate hidden under stones. All dormant snails of this species can resist ambient temperatures up to 50 °C, but temperatures of 55 °C and above are usually lethal. The soft parts of the animal's body shelter inside the second and the third whorl of its shell, where the temperature can reach up to 50.3 °C. Temperatures of up to 56.2 °C were measured and are known to occur inside the shell's body whorl, which is mostly filled with air during aestivation.
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The bogong moth (Agrotis infusa) is a temperate species of night-flying moth, notable for its biannual long-distance seasonal migrations towards and from the Australian Alps, similar to the diurnal monarch butterfly. During the autumn and winter it is found in southern Queensland, western New South Wales, western Victoria, and also in South and Western Australia. Adult bogong moths breed and larvae hatch during this period, consuming winter pasture plants during their growth. During the spring, the moths migrate south or east and reside in mountains such as Mount Bogong, where they gregariously aestivate over the summer until their return towards breeding grounds again in the autumn.
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As typical ground squirrels, Spermophilus live in open habitats like grasslands, meadows, steppe and semideserts, feed on the low plants, and use burrows as nests and refuge. They are diurnal and mostly live in colonies, although some species also can occur singly. They are found in both lowlands to highlands, hibernate during the colder months (up to 8 months each year in some species) and in arid regions they may also aestivate during the summer or fall. The distributions of the various species are mostly separated, often by large rivers, although there are regions inhabited by as many as three species and rarely two species may even form mixed colonies.
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The permanent burrows are often complex systems with multiple entrances and exits, consisting of storage chambers, hibernation chambers and a nesting chamber at the very bottom. The burrows are well-hidden and sealed with a plug of sand in late spring and summer to keep the heat out and moisture in, providing an ideal place for the animal to rest, evade predators and escape from the heat of the day. This species has also been observed sheltering under desert truffles. During particularly hot or dry spells the jerboa will aestivate in the burrow and in winter it is thought to hibernate, but this has only been reported in a few individuals.
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Except for Antarctica, leeches are found throughout the world but are at their most abundant in temperate lakes and ponds in the northern hemisphere. The majority of freshwater leeches are found in the shallow, vegetated areas on the edges of ponds, lakes and slow- moving streams; very few species tolerate fast-flowing water. In their preferred habitats, they may occur in very high densities; in a favourable environment with water high in organic pollutants, over 10,000 individuals were recorded per square metre (over 930 per square foot) under rocks in Illinois. Some species aestivate during droughts, burying themselves in the sediment, and can lose up to 90% of their bodyweight and still survive.
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Organisms that aestivate appear to be in a fairly "light" state of dormancy, as their physiological state can be rapidly reversed, and the organism can quickly return to a normal state. A study done on Otala lactea, a snail native to parts of Europe and Northern Africa, shows that they can wake from their dormant state within ten minutes of being introduced to a wetter environment. The primary physiological and biochemical concerns for an aestivating animal are to conserve energy, retain water in the body, ration the use of stored energy, handle the nitrogenous end products, and stabilize bodily organs, cells, and macromolecules. This can be quite a task as hot temperatures and arid conditions may last for months.
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Frogspawn (eggs) of the eastern spadefoot, Rehovot Vernal pool, Israel Close up of a several days old frogspawn (eggs) of the eastern spadefoot Rehovot Vernal pool, Israel The eastern spadefoot is nocturnal and returns to the same lair each night when it has finished foraging for molluscs, spiders, insects and other small arthropods. As well as digging its own burrow, it sometimes makes use of a rodent hole or a crevice under a rock. At times when the air temperature is very hot it retires to the deepest part of its burrow and may aestivate in mid-summer. At these times the toads that live in the moist soil of riverbanks may fare better than those elsewhere and in times of drought, there may be a high mortality rate among toads.
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The frogs change their body colors in response to temperature differences in order to maintain a good body temperature and minimize evaporative water loss. When they are dark, their body temperature follows air temperature more closely, it is common for them to do this when the air is below 36 °C. The white coloration helps them to maintain a temperature below the ambient temperature by reflecting heat away. Their skin has an integumentary resistance to evaporation that rivals that of terrestrial reptiles, earning them the nickname of "waterproof frogs", but this resistance isn't present in their ventral skin, so when met with a dry period, these frogs tuck their water losing ventral areas under them so that only their resistant skin is exposed and the secrete a water-resistant mucus to seal any small gaps and they aestivate.
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