November 22, 2008

Animal behaviour and welfare: Pigs Part 1


Senses: Social behaviour: Learning: Abnormal behaviour: Moving pigs

By Dr Clive Dalton

Man and pig
  • The pig is farmed in a wide range of farming conditions around the world, except in Moslem countries. It evolved mainly in China and Asia, and our New Zealand Kunikuni pig shows all the traits of these early Chinese ancestors.
  • The many types of wild ancestor of the modern pig were domesticated to provide meat and they took well to confinement and being omnivorous and were useful to clean up human waste and garbage.
  • If was the first animal apart from the hen, to be subjected to very intensive housing and management.
  • Pigs have now become fashionable pets in some modern cultures.
Pig senses

Pet pig - house trained and sits on command
  • Pigs are forest dwellers and nocturnal feeders in the wild.
  • Their eyes are highly developed and they can see colour like other higher mammals.
  • Their sight can be greatly reduced by their floppy ears which act as protection when rooting in scrub.
  • The pig's other well-developed senses compensate for any limitations in vision.
  • Sight is important in reproduction as the boar uses visual clues as to the oestrous state of the sow.
  • The pig has an acute sense of smell, exploited by man in hunting truffles.
  • It has a well-developed olfactory lobe in the brain.
  • The design of the pig's nose and strong neck give it very powerful rooting abilities.
  • Feral pigs use scent to follow trails and can smell feed and carrion from a considerable distance.
  • They can locate each other in the wild by smell when spaced out foraging.
  • Smell and taste are thought to be important in recognition, as at first meeting pigs sniff each other in the face, along the line of the jaw and around the eyes and ears.
  • Smell is very important in piglets to find their own chosen teat for sucking.
  • Pigs have extremely good hearing and clearly recognise a wide range of sounds used in communication between them.
  • They can be easily panicked by unfamiliar sounds - which can cause major problems in intensive housing e.g. when jet planes fly over or thunder.
  • They must be able to sense very low pitched sound by reports of their early reactions to earthquakes.
  • Pigs have clear taste preferences.
  • Creep feed for piglets is sweetened with sugar to encourage intake.
  • Mature pigs love apples - they're a great means of getting a pig to follow you.
  • Pigs use a wide range of sound to communicate - probably developed because they evolved as forest dwellers.
  • Young piglets squeak, grunt, bark and squeal.
  • Older pigs use various grunts and squeals to indicate hunger, thirst, alarm, fear, terror, affection, calling a litter to suckle, courtship, and many others.
  • Pigs respond very well to human communication, and soon seem to learn what human sounds mean. One researcher suggested that "uff uff" uttered with the lips and your face level and close to the pig was very successful in establishing friendship. To move pigs forward "choo choo" achieved interesting results.
  • Pigs squeal can reach 112 decibels which can damage human hearing and stress the animals. Wearing ear muffs, especially at feeding time is essential in large intensive operations. A level of 85 decibels should be the limit aimed for in housing.
  • The terror squeal of pigs when held by a nose strop is also damaging to hearing.
Social behaviour
  • Pigs are very social animals but do not show tight herding behaviour. You soon learn this when trying to drive pigs!
  • Wild pigs that are hunted are very nocturnal; otherwise they can be active at any time. Pigs farmed intensively are diurnal and active during the day because of the husbandry system.
  • As they are den-living animals, social contact developed at birth is very important for the rest of the pig's life. Pigs enjoy the close company of mates.
  • They develop a social rank very early within their litter by vicious blows with their needle teeth while fighting for teats. Farmers clip these teeth off to prevent damage to other piglets and to the sow.
  • Pigs have many ways of communicating with each other - sound is the most important because of the bush environment in which they evolved.
  • Twenty different calls have been identified - 6 of which can be identified by man such as the grunt, bark and squeal.
  • Body language is also important at close quarters, especially in courtship.
  • Feral pigs are usually found in groups of about 8 made up of 3 sows and their offspring. Males tend to be solitary.
  • Groups of wild pigs have their own home range, and these can overlap with other bands of pigs.
  • Pigs don't have sweat glands over their body so wallowing is a common behaviour in feral pigs in warm conditions. However, they'll also wallow and enjoy mud in cold climates.
  • If water is deep enough outdoor pigs will swim.
  • There is little social grooming in pigs as we know it in other animals. This is surprising as they enjoy rubbing and scratching so much. But they do nuzzle each other along the flank and back - areas they can't reach on their own.
  • Lone pigs scratch these parts against objects in their territory.
  • Pigs yawn like other farm animals, and this is often combined with stretching the back leg and closing the eyes.
  • Pigs also shake themselves after a period of rest, especially if they've been lying in a group.
  • Pigs regularly "tuck in" with their mates and by wriggling settle right down into the bedding.
  • When growing pigs have selected their own temperatures, they chose warm afternoon temperatures and quite cool conditions at nights when they lie huddled with their mates for warmth.
  • Pigs show a lot of play behaviour, and it's very common in young pigs when they leave the nest or lying area.
  • They show great play behaviour especially when they go into a new environment as part of their exploration.
  • Social play usually consists of fighting with selected littermates. Often one animal runs away eliciting a chase by mates.
  • A piglet playing by itself will whirl round trying to scratch itself and may jump up and down on the spot.
  • Pigs are great investigators and play by lifting and moving objects on the ground and throwing them in the air.
  • With their sensitive nose, rooting is a favourite pastime and treasured finds are carried away with other pigs in pursuit.
Pig learning ability
  • Pigs learn quickly and show great variation in their ability to learn and solve problems.
  • Teaching pigs can be done easily by using mild electric shock avoidance, audio signals and feed rewards.
  • They have been taught to control their heating and lighting regime - which saves human labour and reduce costs.
  • This learning ability is moderately inherited so you could increase this trait in a herd through selection.
  • Pigs quickly learn all the details of a new environment because of their well-developed exploratory behaviour. When tested in a maze, pigs are smarter explorers than any other farm animal. Depriving them of this natural ability can cause great stress as seen in pigs kept in barren concrete environments with no bedding to chew.
Pig-human interaction
  • There is now plenty of research to show the benefits of pigs that have a strong relationship or bond with their human minders.
  • The pigs have clearly been "tamed" and have responded to good handling.
  • Taming is best done by quiet and gentle handling of young pigs at feeding time.
  • Lay your hand on the pig's had or back, talk gently and scratch or stroke the animal. The best areas to touch are behind the ears, shoulders, along the back and down the sides.
  • Pigs soon learn to enjoy this contact and will often lie down to enjoy it. Complete taming can be done in 2-3 weeks after which they will come when called.
Dunging behaviour
  • Pigs are probably the cleanest and most orderly farm animal if their environment allows this, and if they have learned appropriate behaviours during their early rearing.
  • Pigs defaecate and urinate regularly throughout the day and night in intensive housing although they rest a lot between 7pm and 6am the following morning.
  • By 3 days old, piglets have learned not to dung where they sleep. After this age further dunging behaviour is learned from their dam - habits they maintain throughout life. A "dirty" sow that dungs and urinates on her bed will produce "dirty" piglets that do the same.
  • Good dunging habits can be encouraged by a few management practices:
  • When changing pigs from one pen to another, give them a run for a while before they enter the new pen. This will let them empty out and their first urge in the new pen will not be to defaecate and urinate.
  • After moving, dampen the dunging area of the new pen, and put some dung from the old pen on it.
  • Pigs that are scouring should have the problem fixed as they will have less control of their faeces and where it goes.
  • If there are too few pigs in the pen, use temporary barriers to reduce space in the sleeping area so they are forced to dung elsewhere. Put fresh bedding on the sleeping area.
  • A false roof maintaining warmth over the sleeping area will encourage them to rest there and they'll hopefully be less keen to foul the area.
  • Cleaning their pen at night may help if the problem exists. After cleaning the fouled area, put some bedding and feed on it.
  • Pen shape and the position of the feed and water sources can affect where pigs eliminate. Try moving troughs until the pigs modify their habits.
Abnormal pig behaviour
  • Pigs show a long list of abnormal behaviour where stress is the major underlying cause.
  • Tail biting
  • Ear biting
  • Cannibalism - killing and eating pen mates
  • Belly nibbling
  • Tongue rolling
  • Rubbing the nasal bone
  • Rubbing snout
  • Hyperactivity
  • Massaging the anus
  • Vacuum chewing
  • Biting pen bars
  • Rocking back and forward when tethered

The “runt“ pig and its problems
  • It's difficult to describe in precise terms what a runt is. It's not necessarily a small piglet, as these can be the result of poor nutrition.
  • These nutritional runts are commonly seen in large litters where pigs are not weaned until 5 or 8 weeks.
  • Piglets can be runts because of their position in the uterus, where for some reason they have been deprived of nutrients. These runts never catch up, even with extra feeding as they are physiologically under-developed.
  • As litter sizes increases and competition for milk and feed increases, the problem the runt has to survive and grow increases. Commercial pig farmers often see euthanasia as a cost-effective solution.
Moving pigs
  • Pigs are den-living, home-loving animals and do not show any flocking/herding response when moved.
  • In the wild, frightened pigs scatter and crouch in the undergrowth, or race back to their den. Domestic pigs still show this behaviour.
  • They just don't like being moved - especially from their darkened den into bright outside light.
  • Loading and unloading are the most stressful part of transport when pigs are pushed, dragged by their ears, have their tails pulled, or goaded physically or electrically. (Note that electric prodders should not be used on pigs in New Zealand).
  • Suggestions for loading and transport of pigs:
  • Select the pigs for market the night before, and hold them in an unfamiliar pen.
  • Reduce feed before transport but not water.
  • Move them in the early morning.
  • Don't attempt to rush, abuse or punish them.
  • They'll go better up a ramp or along level ground.
  • Avoid having to move them down a ramp.
  • Keep ramp sides fully covered so they can't see through.
  • Spread some bedding along their path you want them to go.
  • Spread some feed or slices of apple along the path and up the ramp.
  • Use a hand-held pig board to approach them - this also protects your legs. Use any solid barrier to bring up behind them.
  • Don't do anything like pulling ears or tails that will make them squeal. Use a canvas slapper so as not to bruise them.
  • To move an awkward individual - put a plastic bucket over its nose and eyes and reverse it along.
Transporting pigs
  • Transport can be very stressful for pigs. Here are some recommendations to reduce stress:
  • Don't transport pigs that are not familiar with each other.
  • Provide plenty of ventilation in the truck.
  • Avoid transporting when temperatures exceed 28 C.
  • Avoid long parking periods on hot sunny days. Always park in the shade.
  • Avoid physical exertion and excitement before and during transport.
  • Do not feed during the 12 hours before transport.
  • Put the pigs direct from their pen on to the truck.
  • Transport the following pigs separately:
  • Young piglets
  • Sows with piglets
  • Adult boars
  • Unfamiliar groups of pigs
  • Sows in advanced pregnancy


  1. Hi Clive

    Just reading your blog about pig aggression. Here is a short clip of our piglets from last year.

    They were either 1 or 2 days olds at the time, I was astonished they they were so feisty.

    We are now eating the ginger one - delicious.

    Bye Karen

    Editors Note: this video is posted within the body of this post. Thanks Karen!

  2. What about head butting? My daughter has a pig 3 months old and weights 30 pounds already. She worries about head butting and he kinda bites. What do you think?

  3. It's more a nose butting action - as the pigs nose is it's major sense organ and tool, as well as a weapon!
    I would either start giving it a very positive reprimand at this stage or get rid of it incase it gets more cheeky as it grows. A mature pig with this form of 'fun' in it's mind could be very dangerous, especially if it uses it's teeth which can be lethal.