Pig Behaviour

Natural behaviour of pigs

Supporters of factory farming like to claim that modern pigs are different to their ancestors and no longer have the same needs. Therefore, they don't suffer in the barren confinement of factory farms. Such statements have no basis in fact. Modern pigs still have the same instincts and the same needs as their ancestors, as shown by the ease with which they become feral.

Well-known animal behaviourist Marian Stamp Dawkins has concluded (1):
"...domestic animals are not man-made for confinement. They bring with them an evolutionary legacy from the past..."

Similarly, veterinarian Dr Michael Fox has stated (2):
"Domesticated animals can differ greatly in size and shape from their wild relatives, but they differ little in terms of their behavioural repertoires."

That modern pigs show the same behaviour as their wild relatives has been demonstrated by researchers from the Edinburgh School of Agriculture. They observed 13 groups of commercially bred pigs over a 3.5 year period. The pigs lived in groups of 1 boar, 4 sows plus their current litters, and several juveniles in two paddocks with various vegetation types (3).

One notable feature of their behaviour was a high level of activity. In 31% of observations they were grazing, in a further 21% rooting with their snouts, and in another 23% working over the enclosure (walking and nosing the ground). They used the rooting pad of their snout to level out roots and overturn tussocks of grass.

They wallowed in muddy places and near a stream when the temperature was over 18degC. They rubbed their face and body against tree trunks.

Being social animals, each member of the group carried leaves and grass to the communal nesting site. Contrary to the image of pigs as dirty, they used a dunging area well away from this sleeping area. There was very little aggression, what there was being associated with the delivery of foods. However, threatened pigs could simply move away from the aggressor.

The behaviour of these modern, commercially bred pigs was very similar to that of wild and feral pig (4)

Sows leave the group and become very restless 2 days before their piglets are due. They walk considerable distances looking for a suitable nest site - in one study they covered 2.5-6.5km in the 24 hours before giving birth (5). Once they find a protected site, they scrape a hole and line it with vegetation.

The restlessness is similar in all pigs and is due to a rise in prolactin at this time. The collection of nesting of nesting materials, on the other hand, is also influenced by environmental factors, such as temperature (6).

Even when they aren't out in paddocks, sows are still highly motivated to build a nest. In an indoor pen, they rooted and pawed with their feet to make a hollow in the sand, and carried an average of 23kg of straw to line the hollow (7).

Piglets are active little animals, and the amount of walking, scampering and trotting increases steadily during the first weeks and months of life (8). Sniffing the ground, rooting and biting objects are other important behaviours. In one study, 9 week old piglets spent 60% of their time foraging, that is sniffing, rooting and chewing (9).

To summarise:

Intensive piggeries prevent most of these natural behaviours, causing stress and frustration. For more information on this point, go to Evidence of suffering in factory farms .

References

  1. Dawkins M (1988), "Behavioural deprivation: a central problem in animal welfare", Applied Animal Behaviour Science , vol 20 (209-225)

  2. Fox M (1983), "Animal freedom and well-being: want or need?", Applied Animal Ethology , vol 11 (205-209)

  3. Stolba A & Wood-Gush D (1989), "The behaviour of pigs in a semi-natural environment", Animal Production , vol 48 (419-425)

  4. Graves H (1984), "Behavior and ecology of wild and feral swine (Sus scrofa)", Journal of Animal Science , vol 58 (482-492)

  5. Jensen P (1986), "Observations on the maternal behaviour of free-ranging domestic pigs", Applied Animal Behaviour Science , vol 16 (131-142)

  6. Jensen P, Vestergaard K & Algers B (1993), " Nestbuilding in free-ranging domestic sows", Applied Animal Behaviour Science , vol 38 (245-255)

  7. Arey D, Petchey A & Fowler V (1991), "The preparturient behaviour of sows in enriched pens and the effect of pre-formed nests", Applied Animal Behaviour Science , vol 31 (61-68)

  8. Newberry R & Wood-Gush D (1988), "Development of some behaviour patterns in piglets under semi-natural conditions", Animal Production , vol 46 (103-109)

  9. Jensen P & Stangel G (1992), "Behaviour of piglets during weaning in a semi-natural enclosure", Applied Animal Behaviour Science , vol 33 (227-238)