Applied Animal Ethology最新文献

The behavior of 2 groups of 6 calves that were managed in 2 different ways were observed, and the development of their behavioral patterns, spatial patterns and social behavior in the groups were discussed, together with the effect on these processes of their social experience before grouping.

Twelve 5-month-old Holstein steers, reared alone from one week of age, were divided into 2 groups of 6 calves each; Groups A and B. Calves in Group A were penned together in a 14.4 × 28.8 m pen, and the position and behavior of individuals was observed throughout a continuous 153-h period at 15-min intervals. Aggressive behavior between calves was also recorded. The position of calves was recorded as coordinates on a grid on the pen floor. There were 8 × 16 squares in the grid, and each square measured 1.8 × 1.8 m.

Group B was further divided into 3 groups of 2 calves each, which were kept in 9.6 × 14.4 m pens. The pair-mates were changed every 3 days in order to combine all possible pairs in the group. After this treatment, calves were all housed together in a 14.4 × 28.8 m pen, and observed using the same methods and for the same duration as Group A.

The lying pattern of Group A was not diurnal until the latter half of the observation, while calves in Group B showed clear-cut diurnal variations from the initial stages. Concerning the spatial patterns; the mean distance to nearest neighbor in Group A tended to decrease and become stable. The ratio between the mean distance to nearest neighbor and the distance expected in random distribution also declined from 0.7 to a significant aggregation of 0.5 (P < 0.05). For Group B, a similar change in the mean distance to the nearest neighbor was observed, although this showed significant aggregation from the first 24-h period (P < 0.05). The mean area occupied by a group in each 24-h period, for both groups, declined for 72 h after grouping and became stable at around 18 m², for both groups, thereafter. The frequency of aggression in Group A declined from 23 times in the first 24-h period to 9 times at the end of the observation period. For Group B, the aggression frequency was 53 times in the first 24-h period, thereafter decreasing rapidly.

A stable food competition order was established in a flock of 8 hens. Each hen was then provided with a choice of competitor by allowing it to choose between 2 of its group-mates in 10 consecutive competitive trials. All hens were given a choice of every possible pairing of the remaining 7 birds in the flock. Many statistically significant social discriminations were recorded. Although there was a low correlation between the total number of choices for each bird and competitive rank, there was a significant tendency for birds to avoid higher-ranking hens when individual “dominant-subordinate” choices were analysed. Subjects could also assess relative rank rather than merely distinguishing between birds more or less dominant than themselves. Implications of these findings for the interpretation of competitive orders in domestic fowl are discussed.

It was noted that adult birds of Alectoris rufa, hatched and reared in captivity, cannot survive in nature after their release for restocking for hunting. An attempt was made to ascertain what effect various kinds of visual experiences with man during the first 2 months of life might have on the escape-response of young individuals.

It was observed that absence of visual contact with man during the 48 h after hatching causes fear of human beings in those individuals when 2 months old. Conversely, subjects which were in visual contact with man during the 48 h after hatching did not show this tendency to escape in front of him.

The possible links between this finding and the phenomenon of imprinting, together with the need for new rearing techniques, are discussed.

In a short (28-day) experiment, weanling village pigs, Sus scrofa papuensis, gained weight at the rate of 147 g daily when foraging on tethers in harvested sweet potato gardens, Impomoea batatas (L) Lam., and fed additional raw sweet potato tubers. A comparable group of pigs that had no access to soil lost weight and exhibited signs of protein malnourishment. The highly significant difference in growth rate was thought to be due to the foraging pigs consuming earthworms, Pontoscolex corethrurus, which were abundant in the soil.

Ten foraging pigs were closely observed over a period of 3 months. Daily weight gains increased to 190 g, and it was recorded that each pig ate between 414 and 1224 earthworms daily (half the daily amount being eaten in the first hour of foraging), and that this activity was predominant. As the day progressed, the pigs spent more time lying down, standing doing nothing, or eating green vegetation. These observations are discussed in the context of local pig husbandry.

Homosexual mounting (buller syndrome) was observed incidentally during approximately 3900 h of field observations of 2 populations of American bison (Bison bison) in the course of an 11-year study of social and reproductive behaviour. Buller behaviour was regularly observed in intact, free-ranging males up to the age of 4 years. This suggests that some level of this behaviour, which is an economically significant problem in cattle husbandry, may be a natural trait of feed-lot steers.

A common male homosexual vice in feedlot cattle is an activity where some steers, “bullers”, sexually attract other steers, “riders”. One theory of the cause is that bullers are excessively feminized and give off sexually stimulating pheromones. Because pheromones are detected in many mammals by the vomeronasal organ (VNO), we tested the role of this system by cauterizing duct openings which lead to the VNO. Cautery of non-bullers did statistically reduce bulling, but the magnitude of bulling was still high. Cautery of bullers revealed that they were indeed subjected to less mounting than were the non-cauterized bullers in the same herd.

Bullers commonly participated in mounting and had aggression scores about twice that of riders. We believe that aggresssion is a key element in bulling behavior because: (1) most (over 80%) of the steers withdrew from the social contesting engaged in by both riders and bullers; (2) riders were challenged by bullers, in that bullers also mounted riders, as well as other bullers; (3) bullers were more aggressive than riders in the conventional measures of aggression; and (4) the amount of bulling was much greater during the periods of greatest social stress (such as just after the herds were formed and, in one pen, just after 50 new steers were added to the pen). Thus, we are led to advance a new hypothesis about bulling; namely, that it is a ritualized “game” based on social hierarchy contesting.