Nesting instinct
Nesting behaviour refers to an instinct or urge in pregnant animals caused by the increase of estradiol (E2) to prepare a home for the upcoming newborn(s). It is found in a variety of animals such as birds, fish, squirrels, mice and pigs as well as humans.
In rodents and lagomorphs, the nesting instinct is typically characterized by the urge to seek the lowest sheltered spot available; this is where these mammals give birth. Female dogs may show signs of nesting behaviour about one week before they’re due that include pacing and building a nest with items from around the house such as blankets, clothing, and stuffed animals. Things which are able to be laundered or are disposable should be made available to the dam. Items which can be ingested by the dam should be placed out of reach. (They also sometimes do this in cases of false pregnancy, or pseudocyesis). Domestic cats often make nests by bringing straw, cloth scraps, and other soft materials to a selected nook or box; they particularly are attracted to haylofts as nest sites. Commercial Whelping and queening boxes are available however, children's wading pools (dogs) and plastic dishpans (cats) work just as well. In birds it is known as "going broody", and is characterized by the insistence to stay on the nest as much as possible, and by cessation of laying new eggs. Marsupials do not exhibit a nesting instinct per se, because the mother's pouch fulfills the function of housing the newborns. Nest building is performed in order to provide sufficient shelter and comfort to the arriving offspring.
Under natural conditions, sows will leave the herd and travel up to 6.5 km a day prior to parturition in order to find the appropriate spot for a nest. The sows will use their forelimbs and snouts in order to create excavated depressions within the ground and to gather/transport nesting materials. Although the nests vary in radius dependent on the age of the sow, the nests are generally a round to oval shape and are usually located near trees, uprooted stumps or logs. The shelter provided by the nest built in sows is of utmost importance to thermoregulation. For the first two weeks of the piglets life their physiological thermoregulation is still developing, and due to a lack of amount of brown fat tissue, piglets require an increased surrounding temperature. Without the protection of the nest, the piglets will be subjected to climatic influences causing their internal temperature to drop to life-threatening levels.
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