The only argument in favour of hibernation is that it is a habit resorted to by other vertebrates to escape the consequence of exposure to severe temperatures.
As Seebohm puts it--"The hibernation of birds is a theory, the evidence in support of which has completely broken down.
Other details of the many stories of swallow hibernation are due to exaggeration or to misconception.
The arguments against it are that not a single instance of avian hibernation will stand the light of reason and investigation, and that birds are provided with the means of escaping from the cold zone and certainly use these means.
Science can only say that the known cases of hibernationamong warm-blooded animals show that the vital forces may be reduced much lower without destroying life, than but for them we should have deemed conceivable.
In the first place, it must be noticed that in the phenomena of hibernation we have what at a first view seems closely to resemble the results of Signor Rotura's apocryphal experiments.
It has been justly said, that if hibernation had only been noticed among cold-blooded animals, its possibility in the case of mammals would have seemed inconceivable.
He states, however, that inhibernation the complete state of passive efficiency is not produced.
He does not accept the opinion of those who consider that in true hibernation breathing ceases as above described.
Physical conditions of the environment (overcrowding of nest sites, inadequate hibernation sites) and probably some kinds of parasitism contribute to mortality.
There are numerous published statements to the effect that the period of hibernation is passed under a shallow covering of mud in deep water.
Hibernation of blue racers and bull snakes in western Illinois.
However, a small percentage of the population probably emerged even earlier each year than my records indicate, and retired into hibernation later than my records indicate.
In racers recently emerged from hibernation he found the seminiferous tubules filled with Sertoli syncytium, but containing few germ cells.
Hibernation of amphibians and reptiles in Richmond County, Georgia.
The spring records in nearly all instances pertain to snakes found in the open or beneath flat rocks warmed by sunshine, usually at or near the rock ledges where hibernation occurs.
Many racers, especially the larger and older ones, have parts of the tail missing, as a result of such escapes, and perhaps also from freezing in hibernation or from certain injuries and infections.
I have been unable to detect differences in types of hibernationsites preferred between the racer and the copperhead, which is somewhat more numerous on the same area.
Several authors have contributed to knowledge of hibernationin the racer.
Actual field work at the Reservation consisted of studies of hibernation and long-term observations on movements of a few box turtles.
Emergence from hibernation usually occurs in April but in some years a few turtles may emerge as early as the first week of March.
It may therefore be understood that growth-rings are compound in origin; each ring is formed in part at the beginning of hibernation and in part at the beginning of the following growing season.
Increase in size following emergence from hibernation may be due in part to proliferation of the sustentacular cytoplasm.
Turtles burrow upward at the end of hibernation and remain just below the surface for a week or two before emerging.
Few individuals retained the caruncle when they entered hibernation late in November, and none retained it upon emergence from hibernation.
Observations on hibernation and nests of the collared lizard, Crotaphytus collaris.
Hibernation habits of amphibians and reptiles in Richmond County, Georgia.
Possibly some spermiogenesis takes place in the early phases of hibernationor in the period in late autumn when turtles are intermittently active.
They remain large from early September until hibernation is begun, becoming only slightly smaller in late September and October.
The caterpillars hatch out in August, and while still very small go into hibernation in a common nest.
The caterpillars hatch out in July, feed for a few weeks, and go into hibernation while still small.
The question of hibernation need not be entertained, but there may be doubt as to whether the specimens are British born or aliens.
It hatches from the egg in the autumn and goes into hibernation while still very small; reappearing in the spring and feeding on until July, when it spins a flimsy silken web-like cocoon well down among moss and litter.
When hibernation was observed, it was found, that, whilst some animals become torpid in winter, others were torpid in summer: hibernationthen was a false name.
The newly hatched caterpillars go into hibernation and live through the winter without feeding, finding shelter at the surface of the ground, especially beneath the leaves of violets which form their chosen food plants.
The result is that these butterflies lay eggs so late that the cold nights come on apace and the little caterpillars apparently take no food at all but go into hibernation immediately.
The Compton Tortoise butterflies which are thus abroad in early spring have been in hibernation since October.
Farther south there are probably three broods a year and hibernation may take place in various stages.
The full-grown caterpillars change to chrysalids beneath the shelter of the small stones in practically the same sorts of situation which they have chosen for hiding at night or for hibernation through the winter.
As one would expect, the conditions of hibernation vary greatly with the latitude.
This habit is doubtless of value, especially during hibernation or possibly during the summer lethargy or aestivation, the latter a habit which may be more general among these butterflies than is now supposed.
Notwithstanding all the attention which has been paid to butterfly life-histories there is still some uncertainty in regard to the hibernation of many of our species.
These examples are all cases of truehibernation in a lethargic condition.
The conditions as to hibernationby the larvae of butterflies are very different from those of the egg.
Hibernation proves thus to be a trait acquired by the organism in consequence of climatic conditions.
Such curious hibernation was early hinted to the keenness of Schiaparelli, and most incomprehensible as well as difficult of verification at that stage the phenomenon was.
Then the pole passed into its star-strewn arctic night, a polar night of twice the duration of our own and the circumpolar regions entered upon their long hibernation of ten of our months.
This it did by living during its brief summer and then going into hibernation the balance of the time.
On his return he and his band seem to have passed the winter at Cap Rouge more comfortably than the firsthibernation six years before, for the French had now learned the winter hygiene of the northern regions.
During this hibernationthe fates were far more kind.
They were just coming out of hibernation and had not yet started to feed.
They consider that in bear killed as soon as they come out ofhibernation the intestines are useless, for they believe the bear retire to their winter quarters in the fall gorged with fish.
He thrust the thought away angrily and ordered the Moruan physicians to bring in ice packs to cool the patient's huge hulk down to hibernation temperatures.
In the year of their hatching they attain but half their proper size, but after hibernation they eat voraciously and grow rapidly, so as to attain full size in a little more than a year.
In such a case hibernation in the pupal state would certainly give rise to seasonal dimorphism.
This follows from the fact that hibernation takes place in the caterpillar stage in many species of the sub-family Satyridæ which are now digoneutic, as well as in the remaining monogoneutic species of the same sub-family.
Its hibernationis passed by preference in a cave, whence it emerges for a flight whenever the weather is fine.
The process of development is more prolonged than in the Frogs and Toads, but it is mostly complete at the end of summer before the hibernation begins.
In early spring, when the sallows are in bloom and attracting swarms of insects, the Long-eared Bat is there also: fresh from hibernation and with a keen appetite.
Recent progress in the biochemistry and physiology of hibernation and hypothermia have shown that the oxygen requirements of individual mammals, organs, and tissues can be reduced.
Hibernation is a nonstressful state and results in a great decrease in metabolism.
Experimental evidence is being accumulated to show that hibernation and hypothermia somewhat protect animals against radiation.
Animal metabolism may be depressed by reducing body temperature, as inhibernation and hypothermia.
Studies on the physiology of hibernation in mammals are important to understand temperature regulation and the mechanism of survival at low body temperatures.
However, human beings are not hibernators, and much research is needed before the mechanism of hibernation is understood, and the possibility of inducing it in humans evaluated.
Soviet work comparing various depressed metabolic states and resistances to acceleration shows deep winter hibernation to be most effective, followed by deep hypothermia, and drug narcosis as the least effective.
Hibernation appears to be helpful and not harmful, and it may therefore continue for ages even though not required.
I quote as follows:-- "The period of hibernation in any mammal not only varies in a given species, but is largely influenced by the available supply of food to which it is accustomed or that is necessary for its requirements.
Hence we find the marmot, a much larger animal, making no provision, although his habitat is confined to the higher altitudes and his period of hibernation is extended over a greater length of time than many other species.
He is sometimes driven forth during hibernation by landslides as well as by snow-slides and floods.
The rest which hibernation gives to mind and stomach, with the entire organism relaxed, may both increase efficiency and lengthen life.
Figgins has written one of the best comments on hibernationthat I have read.
In the mean time there has been a gradual reduction in food as the period of hibernation approaches and a consequent lessened activity of the bowels.
These cases of protracted sleep present many analogies with the condition of hibernation which certain of the lower animals enter into at stated periods.
It retires for hibernation when quite small, and recommences to feed in March.
Feeds in July and after hibernation on various grasses, among which Poa annua, Festuca ovina, Aira praecox, and A.
The young caterpillar, before hibernation in October, is greenish, with darker green and yellow lines.
Although this butterfly is often common in the caterpillar state, the perfect insect, which emerges in July and August, is more frequently seen in the spring afterhibernation than before that event.
After hibernation they recommence feeding, and are full grown in May and June, when they pupate, and the butterflies appear at the end of June and in July.
The temperature of animals in a profound state of hibernation is approximately the same as that of the surrounding medium or at most a degree or two higher.
Amongst the terrestrial carnivora hibernation appears to be practised, with one possible exception, only by species belonging to the group Arctoidea.
This interrupted hibernation takes place at least in England and even in Scandinavia; but in countries where frost is continuous throughout the winter it is probable that the badger's sleep is unbroken.
There is much diversity of opinion on the subject of the hibernation of Polar bears.
In other words, all the phenomena characteristic of hibernation are exhibited in these animals during the periods of sleep interrupting their periods of wakeful activity.
Merriam believes that the hibernation of this animal is determined by cold, and not by failure of food-supply, for he observes that skunks may frequently be seen in numbers on snow lying 5 ft.
These and other facts justify Marshall Hall's conclusion that cold is merely a predisposing cause of hibernation in the sense that it is a predisposing cause of ordinary sleep.
It is evident, therefore, that during hibernation the irritability of the heart is augmented in a marked degree, and that the irritability of the left side of the organ is scarcely less pronounced than that of the right side.
When the bats are clustering for hibernation one of the number hangs itself up by its hooks, head downward, and the others cling to it.
The male bear is frequently roused from his sleep and is found by the woodsman roaming about in mid-winter, but they have never known, they say, a female bear to be killed after the season for hibernation has set in.
When the marmot is in its peculiar state of hibernation the electric spark will not rouse it.
In the latter the phenomenon of hibernation is especially remarkable.
After emergence from their first hibernation the young continue their rapid growth.
The best indication of the time necessary to attain breeding condition was provided by an adult male whose hibernation was interrupted on December 15 by bringing him into a warm room where he was kept at 80 deg.
In the period of weeks between the emergence from hibernation and the onset of the breeding season, these skinks tend to be less secretive than at other times, and secondary sexual and age differences in behavior are minimized.
Growing seasons that average long enough and warm enough to permit attainment of maturity by onset of the second hibernation period may be essential to the species.
On January 3, nineteen days after hibernation terminated, the suffusion was near its maximum.
Hibernation site of the lizards Eumeces and Anolis in Louisiana.
Remarkably little is known of the hibernation habits of this species or of reptiles in general for that matter.
Even if it made rapid growth subsequently, this yearling could scarcely have attained by midsummer the pre-hibernation length of the most accelerated individuals.
Individuals living on north slopes in thick woods, and receiving the minimum amount of sunlight may have their emergence from hibernation and attainment of breeding condition delayed.
Skinks that are dormant in hibernationsurvive for periods of months without drinking, with but little loss of weight.
At the time of emergence from hibernation the males rarely have even a trace of reddish coloration on their heads, and more than a month normally elapses before attainment of breeding coloration.
Their incubation is evidently somewhat protracted, although later emergence from hibernation and later breeding of adults in these situations might also contribute to the delay.
He had supposed that the grizzlies were all in hibernation now; he hadn't conceived of the possibilities whereby the great creature had been called from his sleep.
It feeds on stinging nettle, probably on other plants, and after hibernation attains full growth about May.
It may be found after hibernation in the spring, and a second generation occurs in the summer.
There are certainly two broods in the south, one feeding up in the summer, and the other hatching in September, and after hibernation attaining full growth in May or June.
The caterpillar adorns itself with particles of its food as soon as it leaves the egg in July; after hibernation it uses the scales or husks of the oak buds for the same purpose.
After hibernation it reappears as early as February, and visits the sallows as soon as the catkins open.
After hibernation it becomes full grown about June, and is then brown with a downy appearance; there are three faintly darker lines along the back, and the usual dots are dusky.
It feeds at night on the tufted vetch (Vicia cracca), and after hibernation attains full growth about May, when it pupates in a cocoon among leaves on the plant, or on the ground.
The moth flies in September and October, and then visits ivy bloom and sugar at night; after hibernation it comes to sallow bloom.
After hibernation it may be found without much difficulty in May and June on its food plants, either in the daytime, or by the aid of a lamp at night.
The caterpillar hatches from the egg in August, and after hibernation is to be found in May and June on Traveller's Joy or Old Man's Beard (Clematis vitalba).
The moth is out in August and September, and after hibernation reappears in the spring, and may be met with until June.
The effects of progressive diminution of the temperature of the air are well illustrated by the hibernation of animals.
And this leads us on to consider what in reality hibernation is.
