T. Tanaka’s research while affiliated with Azabu University and other places

This study examined the influence of human posture and movement on the behaviour of pigs. Thirty-six 3-week-old crossbred (Duroc × Large White) weanling pigs from five litters were used. In order to identify the main cues that pigs use when interacting with humans, several tests were conducted. Responses to a dummy and a walking human were studied in Experiment 1, and responses to a human looking over a partition and a human approaching and withdrawing were studied in Experiment 2.Latency to initiated tactile contact with a dummy lying face down (LFD) was significantly (P < 0.01) shorter than that with a dummy standing straight (SS) or a dummy stooping down (SD) at distances of 1 m and 2 m. Latency to contact in SS treatment was significantly (P < 0.01) longer than that to SD treatment at a distance of 1 m, but there was no significant difference in latency to the two postures at 2 m. A flight zone toward humans existed in the pigs. The height of a partition which screened a human did not influence the response of the pigs. The pigs showed less (P < 0.05) withdrawal to a human moving away than to a human approaching, and they spent significantly (P < 0.05) more time in close proximity of a human in a quadrupedal posture than a human in a standing posture.In conclusion, posture, distance, type of movement and direction of approach of a human affect a pig's fear response.

This study examined the effects of darkness and shadows on the behavioral responses of piglets. Twenty-six 1-week-old piglets were used for two tests. In the test of ‘response to darkness’, piglets were held in an enclosure, then allowed access to a like-sized adjacent enclosure. Treatments (original enclosure and exposed enclosure) were light to light, light to dark, dark to light, dark to dark with provision of dazzling light beam, dark to dark with provision of a light beam from the back, and dark to dark. The stimuli evaluated in the test of ‘response to shadows’ were a vertically striped shadow, horizontally striped shadows, painted black and white vertical stripes, painted black and white horizontal stripes, a moving shadow of human shape, a spot light, and no shadows as a control.The piglets significantly (P < 0.05) feared staying in darkness. Provision of the light beam significantly (P < 0.01) enhanced the piglets' movement into a dark area. The spot light and painted black and white patterns on the floor had a tendency to frighten the piglets. The results of the present study indicate that piglets have a tendency to move towards a more brightly illuminated area and that they negatively respond to sharp contrast of black and white on the floor. Shadows and darkness influence piglet behavior.

This study examined how handling of individual animals affected their responses to humans, and whether they discriminated among humans based on previous experience. Twelve 4-week-old crossbred weanling pigs from three litters were allotted at random within litters to one of two treatments: handling (n = 6) and no-handling (n = 6). The pigs in the handling treatment received individual handling from the same person for 10 min day−1, 5 days a week for 3 weeks. The pigs in the no-handling treatment had no contact with humans apart from that received during routine husbandry. A ‘human test’, a ‘catching test’ and a ‘walking human test’ were conducted to see the effect of individual handling on the responses of pigs toward humans. The Wilcoxon signed-rank test was used to compare the treatments.With the progression of the handling treatment, the mean elapsed time until pigs initiated physical contact with the handler significantly (P < 0.01) decreased and the total contact time significantly (P < 0.01) increased. The transitional patterns between physical interactions with the handler became more complex with time. Pigs in the handling treatment touched and interacted with the experimenters significantly (P < 0.01) sooner and longer than pigs in the no-handling treatment, regardless of whether this ‘human test’ was conducted by the handler or an unfamiliar person. The non-handled pigs showed avoidance behavior toward a walking or sitting human in the ‘walking human test’ and ‘human test’. When the responses of the handled pigs toward the stranger and the handler were compared in the ‘human test’ and ‘catching test’, they significantly (P < 0.01) preferred to interact with the handler. In conclusion, the handled pigs reduced their fear of humans in general, but they responded differently to familiar and unfamiliar individuals.

This study examined whether regular handling influenced the behavioral response and patterns of the pigs toward a human during the progress of the treatment. Eighteen 4-week-old crossbred weanling pigs from three litters were allotted at random within litters to one of two treatments. The pigs in the handling treatment were individually identified and received regular handling from the experimenter for 15 min, three times per week for 4 weeks. Besides this treatment, the pigs in the handling treatment received brushing for 15 min, once per week for 3 weeks. The pigs in the no-handling treatment had no contact with humans apart from that received during routine husbandry. A catching test was conducted on the pigs in the handling treatment once a week for 4 weeks, and the same test was imposed on the pigs in the no-handling treatment at the start of the experiment. At the end of the experimental period, an experimenter unknown to the pigs conducted the catching test on both treatment groups. The response of the pigs toward the experimenter was classified as either approaching or avoiding behaviors. Specific transitional patterns existed in pigs' physical interaction with a human. During the progression of the handling treatment, the proportion of avoidance behavior significantly (P < 0.05) decreased and the mean aversion score also significantly (P < 0.05) decreased. The variety of physical interactions significantly (P < 0.05) increased. As a consequence, the number of interactions observed in the handling treatment was more than that of the no-handling treatment during the catching test at the end of the experiment. The pigs receiving the regular handling repeatedly tried to make frequent physical contact with the experimenter in spite of repeated chasing and catching events. In conclusion, handling pigs regularly from 4 to 7 weeks of age increases their propensity to approach humans and the variety of their interactions with a human handler, possibly by reducing their fear of humans.

The sexual behaviors of pigs were observed at a commercial farm to study the selection of mating partners in boars and estrous sows under multi-sire mating. In Experiment 1, three sire groups and nine sow groups were used to characterize the courtship behavior between boars and sows. The flow diagram of the behaviors constructed by sequence analysis revealed that ‘nosing’ by boars played an important role to induce sows to stand still, which in turn motivated boars to mount. In Experiment 2, two sire groups and four sow groups were used. Each sire group consisted of three Duroc boars raised from the same litter. Each sow group consisted of eight crossbred sows in which estrus had been induced. Each sire group was assigned to a sow group for 48 h, and their sexual behaviors were recorded continuously with an infrared camera connected to a time lapse video recorder. The same procedure was repeated 3 months later with the same sire groups and different sow groups, which made two observations per sire group. Time spent on courtship behavior with each sow varied significantly (P<0.001) within each set of three boars. The boars spent longer times on courtship behavior and mounted and copulated more frequently with some specific sows than with others. The dendrogram constructed, based upon the time spent on courtship behavior between a sow and a boar, showed that boars and sows had a tendency to select mating partners and that some boars received more attention from sows than others. The cell by cell test on the number of mounts from boars to sows indicated that each boar had a favorite mate or mates (P<0.05). It is likely that selection of mating partners exists between boars and sows in estrus.

The mating behavior of boars toward a herd of sows in a mating pen was observed for 72 h at a commercial swine farm. Mating pens consisted of two to four purebred boars and eight crossbred sows. The observation was conducted on a total of four pens during summer 1987. Boars often mounted sows in estrus, but rarely attempted to mount anestrous sows. Total numbers of mounting events varied among boars in a pen. Mounting efficiencies (number of copulations per number of mounting events) were < 10% for most boars. There was a diurnal pattern in mounting events and the peak occurred at around 03.00 h. The observed courtship behavior of boars was broken down into seven categories: sniffing, head to head, nosing, following, chin resting, mounting and copulation. Sequence analysis was used to determine the pattern of the boars' preliminary courtship behavior before mating. The most frequently observed transition was from “head to head” to “nosing”, and “nosing” was located in the center of the courtship behavior pattern. It is likely that preferential mating exists between boars and sows in estrus.