Behavioral Genetics in Pigs and Relations to Welfare - Genetics and the Behavior of Domestic Animals - page 394

genetic selection to increase pigs' performance, modern pigs differ from their
wild counterparts not only in production and reproduction, but also in behav-
ior. The relaxation of natural selection has reduced the degree of fear of pre-
dators and made pigs easier to handle. It is, however, important to remember
that only the frequency and the threshold at which behaviors are triggered
have changed. No new behavior has appeared and none has disappeared.
Pigs are sentient animals. They express strong behavioral needs relat-
ing back to the behavior of the wild boar in nature. Welfare problems
arise if those needs are not met. When the production system does not
permit a sow to build a nest for farrowing (because there is no building
material) it may redirect the behavior into bar-biting, which may become
a behavioral disorder ( Lawrence and Terlouw, 1993 ). The behavior is a
good indicator of welfare because it refers to strong decision-making and
motivational processes

in the pig ( Dawkins, 2004; Kittawornrat and

Zimmerman, 2011 ).
Pigs are probably the smartest animals among livestock ( Broom et al.,
2009 ). They are able to make contextual associations and to memorize them
for a long time. Following the example of wild boars that have their home
range in memory ( Spitz, 1986 ), De Jonge et al. (2008) showed that piglets
were capable of associating music to access to a playroom, and also sug-
gested that music can elicit play behavior. Pigs' hearing range is similar to
that of humans and they show aversion to loud noise. From birth, piglets rely
on olfactory cues from the dam and its udder. In adulthood, recognition
between individuals also depends on olfactory cues ( Curtis et al., 2001 ).
With its highly developed senses and its large cognitive abilities, the pig has
a very good perception of its surroundings.
Being a generalist, the pig is a forager that can eat almost anything.
Domestic pigs fed from an automatic feeder eat around seven times a day
and spend almost 1 hour feeding per day during the growing finishing phase

( von Felde et al., 1996 ). On pasture, feed-related behaviors like rooting, graz-
ing, and exploring substrate account for 75% of daily activity ( Stolba and
Wood-Gush, 1989 ). The explorative behavior is promoted by their capacity
to detect odors that they memorize for several hours ( Signoret et al., 1975 ).
In parallel, pigs show a high level of curiosity. Given the choice, they choose
to enter environments that contain new objects to investigate, and this inves-
tigation is not only related to feeding motivation ( Wood-Gush and
Vestergaard, 1991 ). The investigation of novelties is rewarding in itself.

Adaptation and Learning
The pig is a generalist that can adapt in many different environments
( Figure 11.1 ). When domestic pigs are released into the wild, they show a
large capacity for behavioral adaptation. Feral pigs have colonized many dif-
ferent types of habitats, e.g., in Australia ( Edwards et al., 2004 ) and in the