The embankment being completed, the animals construct their lodges. Fragments of wood, deprived of the bark, are arranged and united by clay or mud which the Beavers take from the riverside, transport, mix, and work with their fore-paws. During a single night they can collect as much mud at their houses as amounts to some thousands of their small handfuls. They thus plaster their houses with mud every autumn; in the winter this freezes as hard as a stone and protects them from enemies. These cabins form domes from three to four metres in diameter at the base, and from two to two and a half metres in height. The floor is on a level with the surface of the artificial pond. A passage sinks in the earth and opens about one and a half metres below the level of the water, so that it cannot be closed up by ice during the severe winters of these regions.
Within, near the entry, the beavers form, with the aid of a partition, a special compartment to serve as a storehouse, and they there pile up enormous heaps of nenuphar roots as provisions for the days when ice and snow will prevent them from barking the young trunks.
A dwelling of this kind may last for three or four years, and the animal here tranquilly enjoys the fruits of its industry, as long as man fails to discover the retreat; for the beaver can escape by swimming from all carnivorous animals excepting, perhaps, the Otter. During floods the level of the water nearly reaches the hut; if the inundation is prolonged and the animal runs the risk of being asphyxiated beneath his dome, it breaks through the upper part with its teeth and escapes. When the water returns to its bed the beaver comes back, makes the necessary repairs, and resumes the usual peaceful course of its life.[109]
We have thus seen, from a shapeless hole to these complex dwellings, every possible stage; we have found among animals the rudiments of the different human habitations, certain animals, indeed, having arrived at a degree of civilisation which Man himself in some countries has not yet surpassed, or even indeed yet attained.
CHAPTER VII.
THE DEFENCE AND SANITATION OF DWELLINGS.
GENERAL PRECAUTIONS AGAINST POSSIBLE DANGER — SEPARATION OF FEMALES WHILE BROODING — HYGIENIC MEASURES OF BEES — PRUDENCE OF BEES — FORTIFICATIONS OF BEES — PRECAUTIONS AGAINST INQUISITIVENESS — LIGHTING UP THE NESTS.
The building of comfortable dwellings is not the last stage reached by the industry of animals. There are among them some who show genuine skill in rendering them healthy and defending them against invasions from without.
General precautions against possible danger. — Some animals show, even during the construction of the nest, extreme prudence in preventing its site from being discovered. Several authors refer to the stratagem of the Magpie, who begins several nests at the same time; but only one is intended to receive the brood, and that only is completed. The aim of the others is merely to distract attention. It is around these latter that the bird shows ostentatious activity, while it works at the real nest only for a few hours during the day, in the morning and evening.
The Crane takes equally ingenious precautions in order that its constant presence at the same spot may not arouse suspicion. It never comes or goes flying, but always on foot, concealing itself along tufts of reeds. De Homeyer even reports that the female at the time of laying covers her wings and back with mud. When dried this gives the animal a red tone, which causes it to be confused with neighbouring objects; this is intentional mimicry.