Changes of Affiliative Relationships in Japanese Black Calves after Grouping in the Same Pen

Abstract

The objective of the present study was to investigate changes in the affiliative behaviour of 5 Japanese Black calves after grouping together in a pen through 5.5 months. The maintenance of these affiliative relationships was thereafter observed for one month after beginning to graze with the other group. The average frequency of rubbing and physical contact at 1 month after grouping was 0.4 times per calf per hour. In the following month, it increased to 1.1 times per calf per hour, and then leveled off. Allogrooming was rare in the first 2 months in the pen and then began to increase remarkably. The number of allogrooming pairs also increased during this time, from 2 pairs in the first month to 6 pairs in the fourth month. At 5.5 months after grouping, the 5 heifers were grazed with the other group of 27 animals on pasture. The focal heifers chose their pen mates as their nearest neighbours more frequently (P<0.05), and allogroomed with them more frequently than with the other animals (P<0.05).
The affiliative relationships among the 5 calves in this study changed through the 4 months of being reared together in the same pen. When the 5 calves grouped together with other animals, the stronger affiliative relationships among them were maintained for at least 1 month after grouping with unfamiliar animals.