Pigs, as individuals and as a species, have an enormous number of people and cultures who detest them or adore them. While most pigs are observed from a distance and there is a common slanted social tenet that they relish being in muck and mud such as being as happy as a pig in mud – these highly social and intelligent animals are clearly misunderstood. Few other creatures can match pigs for their combination of being simple, yet complex. They have been domesticated for forty thousand years, about twenty-eight thousand years longer than dogs!
When behaviourists study these creatures that have lived in close association with humans for forty-thousand years and compare them to dogs that have been man’s best friend for only twelve-thousand years, one should set aside religious prejudices, superstitions and urban legends purely from an educational, scientific and ethological point of view to understand and realize how much humans, pigs and dogs have in common.
Pigs can be incredibly fastidious and clean animals – in every sense of the word.
Their eyesight is almost as good as humans. Pigs’ eyes are the same size as humans and have similar colour vision and acuity. The pupils and lenses are similar. Their binocular field is twelve degrees compared with the human value of just below two degrees and compared with cattle of one hundred and thirty degrees. Pigs have a wide peripheral vision of three-hundred-and-ten degrees – almost a panoramic view of surroundings. Visual communication is important to pigs. It is important for humans who deal with pigs to realize the value of eye expression and contact. Pigs are past masters in the art of staring and they can hold their ground in this aspect with anyone – when they glare, everything they are doing comes to a standstill – all the foraging, grunting, blowing, every game and suddenly you are being stared at while their snouts sniff the air to determine your identity, value, safety factor etc.
Pigs have excellent hearing with a frequency range double that of a human which is about forty-thousand cycles per second. They have a sound localization threshold of only four degrees which places them up with the most accurate detectors of the origin of sound, in the animal kingdom – closest to cats.
Newborn piglets learn to identify and respond to their mother’s voices within a few minutes of birth!
All pigs have an acute sense of smell whereby the snout is ingenuously designed as the arm, hand, spade and nose of the pig. It is a probe that allows the pig to move, drink, feed and interact with others even in the dark. The anatomical design of the large nasal cavity and the advancement of the olfactory bulb in the brain render these creatures to be highly proficient in the sense of smell.
Pigs do not sweat. They do not have sweat glands. Hence another urban legend about pigs is settled. Sweating like a pig can never happen! Pigs rely on evaporation and insulation for thermoregulation. Special behaviour patterns assist in body heat control, which include huddling, panting and wallowing. The ideal environmental temperature for most pigs is around thirty degrees Celsius. There is a process where moisture passes through the skin against a vapour pressure gradient. Pigs, thus, experience a net water gain under humid conditions. As an adaptation of nature, pigs living in arid conditions, such as warthogs and peccaries, have thicker and larger kidney medullae increasing their capacity to concentrate urine and conserve body water.
The facial muscles of pig species are designed mostly for opening and closing the mouth with frightening speed and strength. They are as a species, domesticated or wild, such as peccaries, bushpigs, river hogs or warthogs, limited with facial expressions – in general they are poker-faced and “talk” with their eyes and snout.
Pigs, humans and dogs are anatomically and physiologically designed to be omnivorous. The physical similarities have placed them in certain scientific categories for experiments of pharmaceuticals and organ transplants. The complex aspect is that their Order in nature is the Artiodactyls which include camels, hippopotami, deer, sheep and cattle.
The prototype pigs of forty million years ago were scavengers in Asia. It had an enormous head of about one metre in length with a tiny brain. They were tall and slim living off carcasses with a tendency towards eating on a wide range of foods, including plants – a versatile diet was emerging which has carried through to today. One of the proto-pig species was the size of a buffalo with a ridge of shaggy erectile hair running down its neck, it boasted large muscles across its shoulders and a set of long, sharp teeth – this was an extreme form of pig in size and preference for a meat diet. Most of those features still exist in a more minuscule form in the wild amongst bush-pigs, peccaries, warthogs and hogs. The evolved pigs of today have six bones less in their legs than their evolutionary ancestors.
Pigs are capable of holding something down with their front feet while they examine, shred or eat it which other species in their Order cannot do.
Pigs are gregarious by nature, only equaled by the herd behaviour of elephants, where they form friendly tolerant societies amongst themselves. This instinct renders them rewarding company for humans and certain dog breeds as well. The advantages of gregariousness, that is living in a sounder of pigs, is that there are more observers to detect dangers of predators, learning behaviour regarding diet, safety, defense or counter-attack in numbers and in wild breeds there is a confusion effect caused by the sudden flight of all the pigs fleeing in different directions before they re-group.
Pigs are mostly active during the day, diurnal, but prefer to concentrate their activities at dawn and dusk, crepuscular, when environmental odours are at a maximum and temperatures the most tolerable
There is no real clarity as to what the differences are between pigs and hogs and although these terms are used it is not definitively related to size, species, domesticity or behaviour. People use the terms of porky, hog, pig and swine for a multitude of purposes, meanings and reasons in all the various forms of literature. A fat person may be deemed porky, an inconsiderate motorist may be a road hog, a pig can be a greedy person and a swine can be a nasty criticism of human attitude. There is an enormous amount of well-document literature in the use of this animal’s various names construed for human expression, habit, culture, religion or superstition.
Pigs are highly sociable with close family ties. They are intensely aware of each other at all times and maintain contact with a concert of agreeable vocalizations, always replying to each other, helping to maintain their bond and commitment to their group formation. This is continued when they are out of sight of each other but in hearing range. Hence, these closely-knit pig societies are collectively known as sounders.
The nucleus of each sounder is the matriarchal family. This is a basic social unit comprising of a sow and her litter that stay bonded until sometimes even after the next litter is farrowed. Farrowing is the term for giving birth to piglets. Often one family can band together with other mother families to form a harem for a single boar. He qualifies by fighting to defend the extended family. The matriarchal sow often determines where the sounder may forage for food and when they should move on to other areas.
Young sows are known as gilts and they remain with their mothers until they reach puberty in their second year and farrow litters of their own. Young male pigs are known as shoats and they may the leave the group voluntarily or may be chased out when they attain sexual maturity. It is unlikely for them to mate until their fourth year or until they have attained dominant status to be accepted by unrelated sows. While they wait their turn to challenge the protector of the harem they will join a loose satellite group of sub-adults.
Old sows remain within the group whereas old boars remain either in close contact or they may drift out on their own – becoming a redundant old pig. A castrated boar is known as a barrow.
Newborn piglets sometimes start suckling while still attached to the umbilical cord, within seconds of birth they try to reach a teat preferably a more anterior one which produces more milk. Once a special teat is selected the piglet does not drink from any other nipple and defends its own teat against all competitors, slashing and biting with eight already well-developed canines and incisors that are curved outwards. A teat order for the entire litter is established within an hour. Struggle for survival commences in the uterus. Piglets born first get the best teats. The latest born have twice as much chance of dying. Piglets die if they have not taken ownership of a teat within twenty-four hours. Piglets also die from being sat on by the sow. Mothers usually eat their dead infants.
Rooting is an integral part of a pig’s foraging activity where they plough through the soil with their muzzles. They can physically do this abrasive process due to the possession of a cartilaginous disc at the end of the nostril further supported behind and above by a rostral bone.
Rooting behaviour may appear destructive but it loosens and aerates the soil and exposes insects for birds, reptiles, monkeys, mongoose and other insectivorous animals. Rooting encourages natural mulching of the soil, helps with the pollination of seeds, either by becoming attached to pig’s fur and transferred to another area or is ingested and deposited in the pigs droppings in other areas. The only negative function is the uprooting of fruits and vegetables, upsetting farmers and creating havoc.
When pigs are stressed or fearful of a strange situation the pig opens its jaws wide to show its dagger-sharp lower canines, foams at the mouth followed by rapid chomping of the teeth – as if tapping loudly, then spraying saliva in every direction while all the hair on its neck and back stand stiffly erect. The entire body is puffed up to appear larger and more daunting. The entire display is intended to be defiant and defensive.
Although pigs are not territorial in the true sense of the classification but they do enjoy a home range which must accommodate a certain number and type of guaranteed venues, all connected by a path network.
A resting area is essential as pigs can spend at least twelve hours per day sleeping in a comfortable, inactive posture. Half of the sleep is deep and slow-wave with occasional snoring, interrupted by short periods of absurd rapid eye movements that resemble dreaming. Piglets do this more than the adults. The other half of the awesome sleep behaviour is spent in an unusual half-sober, drowsy state that most likely includes sufficient cognizance to be semi-alert.
Some pigs sleep or rest together in amiable clumps of bodies in close contact with one another. Their spines are too rigid to permit them to curl up like dogs do. They lie close because of their instinctive gregarious nature and the tactile effect of huddling together is a natural temperature control mechanism, especially in cold climates.
Before pigs can derive their pleasure from being bone-idle which they certainly enjoy, they need to seek out or create a suitably secure shelter. Some pigs build nests which may vary from temporary hollows in the grass to well-built hides in which each piece of vegetation is meticulously placed to provide both security and comfort. These elaborate structures are usually constructed for farrowing.
Pigs need scratching posts of any kind which offers the desired relief. It may be a rough rock or the base of a tree. Because of their short muscular necks pigs find it almost impossible to implement any form of self-grooming. They can reach certain parts of their hind feet but for the rest of the body they depend on being able to rub themselves against a scratching post especially after wallowing. If these structures are unavailable they will have to depend being rubbed down and combed by the snouts and incisor teeth of their sounder mates. These preening activities depend on reciprocity and goodwill. They have to do this in a standing position alongside each other facing in opposite directions. They simultaneously scent mark each other as a means of bonding, accurate identification and positive group interaction.
An essential venue in any pigs’ home range is a communal middening area, also known as a dunging site or toilet facility. This is where all members of the sounder deposit their excreta. This is a hygienic attitude of pigs and is set far away from sleeping or foraging areas. In the wild these midden areas may be used as indicators of territorial boundaries. Although pigs are not territorial t the point that they will fight over it, it is for the general information of others in the vicinity.