Social Dominance in South African Indigenous Zulu Rams

*Mhlengani Z. Dlomo, Cyprial N. Ncobela and Nokuthula W. Kunene*

### **Abstract**

Social ranking is usually caused by limited access to resources such as feed, water as well as mating partners. In rams, social dominance is mostly related to physical traits such as body weight, horn size, body length and scrotal circumference. The objective of the study was to determine the relationship between physical traits of Zulu sheep rams and the establishment of social rankings. The social dominance rank was determined by a feed competition test using rams of the same age. Physical traits such as body weight, chest girth, horn length, scrotal circumference and withers height were measured for each ram. Sheep A was ranked first with a 100% number of wins (*P* < 0.01) followed by sheep E with an 86% number of wins (*P* < 0.05). A positive linear relationship between time spent on the feeder against the number of wins was not significant (*P* > 0.05). There was a significant positive correlation between the proportions of wins against horn length (*P* < 0.05) and chest girth length (*P* < 0.05). Time spent at the feeder was positively correlated with body weight and withers height (*P* < 0.05). Social dominance in Zulu sheep can be determined by particular physical traits such as horn length and chest girth.

**Keywords:** dominant, body weight and chest girth, feed, rank

### **1. Introduction**

The importance of reproductive success in mammals, specifically in males, has caused the notion of social dominance to be investigated [1]. Social rankings are associated with inadequate access to various resources such as water, food, territory and shade [2]. Ungerfeld and González-Pensado [3] reported that mating performance is affected by hierarchical relationships in rams. Lower-ranking rams have restricted access to on-heat ewes [4]. Social rank is achieved by provoking other members in dominance fights [5].

Social rank is determined by physical traits such as body size, horn size and body condition score [3]. However, the authors further pointed out that rams with larger testicular circumference have a higher mating rate. Kabiraj et al. [6] reported that larger rams have larger testicular sizes. Larger and dominant rams have a tendency to suppress submissive rams to mate ewes [7].

Under an extensive farming system, where animals are reared in one herd, dominance ranking is likely to occur [2]. Research to understand the relationship between social behaviour and body developments in male ungulates is limited. In general, very little is understood about determinants of the individual rank of male animals of any ungulates [2]. However, some studies were conducted on Merino and Border Leicester sheep [8], Bighorn sheep [9] and with three breed crosses, Wurttemberg, Ile De France, and Pirot Pramenka [2]. Such study has not been documented in indigenous Zulu sheep. Therefore, the objective of the study was to investigate the relationship between the physical traits of Zulu sheep rams and the establishment of the dominance hierarchy.
