The ecology of feral cattle: Phenotypic plasticity, parasite epidemiology, social strategies, and environmental adaptations in a subtropical free-ranging bovid

Abstract

The present thesis examines the ecology of a unique feral cattle (Bos taurus) population in Hong Kong Special Administrative Region (SAR) of China. These cattle are free-ranging across parts of the territory, and while no routine care is provided, some herds are fed commercial hay, fresh-cut grass, and tap water by local citizen groups (hereafter referred to as provisioned cattle). Using non-invasive methods, this thesis aims to examine the interactions between feral cattle and their environment. Chapter 2 investigates sexual dimorphism in body size and horn length, as well as seasonal coat colour changes in these cattle. This reveals a male-biased dimorphism, with males being larger than females, consistent with general phenotypes of bovids. The dimorphism is moderate compared to European and commercial breeds, confirming previous findings in South Asian domestic and wild bovids. Notably, I provide the first record of seasonal changes in coat colour in cattle, with cattle appearing paler in the wet season (May to October) compared to the dry season (December to February), supporting the theory of thermal melanism and highlighting the role of coat colour in thermoregulation. Using faecal samples from seven herds, Chapter 3 explores endoparasite infections in these feral cattle across two seasons. Our findings indicate that endoparasite infections follow seasonal patterns and are influenced by provisioning, although the direction of this interaction varies between parasite taxa. Chapter 4 investigates the interactions between endoparasite infection and social behaviours in feral cattle. Contrary to the general expectations of decreased sociality in infected mammals, I demonstrate that infected cattle engage more frequently in social grooming, aggression, and sexual behaviours. Due to the inability to determine the temporal causation of this effect, Chapter 5 analyses social behaviour across four periods related to two faecal sampling intervals. As expected, I found that inter-individual differences in competitive ability (dominance) were not impacted by changes in strongyle and Eimeria counts. I confirmed our findings from Chapter 3 and highlight that cattle do not adapt their social interactions based on the infection status (with strongyles and Eimeria) of their social partners. Chapter 6 evaluates the impact of weather and provisioning on body condition and rumen fill, adapting Body Condition Score (BCS) and Rumen Fill Score (RFS) scales to these unique cattle. I identified specific time windows and weather values that impact body condition and demonstrated that provisioning can buffer the effects of climate events. This thesis enhances our understanding of cattle ecology in natural settings and contributes to the broader knowledge of ungulates adaptations to their environment.

Date of Award	31 Jul 2025
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Kate Jade FLAY (Supervisor) & Alan G. McElligott (Co-supervisor)