Phenotypes of a unique free-roaming bovid: Impact of urbanization on the appearance of cattle

Participant(s)

Activity date	12 Nov 2023
Degree of recognition	International

Description

Purpose: Phenotypes are observable characteristics of individuals reflecting their ability to respond to environmental conditions. Anthropogenic factors produce habitats that present unique conditions and faster rates of phenotypic change occur in urban environments. Bovids display diversity in body size, coat colour dimorphism and horn shapes, reflecting their different social and behavioural contexts. The feral cattle of Hong Kong (HK) are a unique subspecies with an estimated population of 900 individuals, yet their phenotypic diversity has not been studied to date. They freely roam in a variety of environments, from urban areas to rural country parks. We investigated Hong Kong feral cattle phenotypes to: i. Develop a methodology for scoring free-ranging large cattle in urban and field environments, ii. Describe the phenotypic diversity of a unique population, and iii. Describe the relationship between phenotype and anthropogenic factors.

Methods: Coat colour was assessed using a seven colours chart on three body parts. Head pattern and coat colour around the eyes was scored in categories using charts. The presence of backline and countershading were scored as a binary variable. Categories were used to score: horn length compared to ear length; horn tip compared to the horizontal line and to the midline from a frontal view; horn tip direction from a side view and horn curve. We used side view photos of each individual to measure wither height, hip height, body length, hip width and chest depth. Our methods were approved by the Animal Research Ethics Sub-Committee of City University of Hong Kong (Reference: A-0826) and were undertaken in compliance with the ISAE ethical guidelines.

Results: We found evidence for within-sex variability and sexual dimorphism (Mann-Whitney, p<0.05); notably, males were larger, had darker coat colour colours and longer horns than females. Both male and female phenotypes were influenced by environmental factors (Linear Mixed-effect Model LMM, p<0.05). Both sexes were smaller (LMM, p<0.01) and had lighter coat colour colours (LMM, p<0.05) in highly urbanised areas compared to rural areas. Cattle roaming near roads were also more likely to have broken or downward facing horns (LMM, p<0.01). For both males and females, individuals with broken horns were less likely to be in herds with calves (LMM, p<0.05), while males with short horns were likely to be in herds that had breeding activity (LMM, p<0.0001).

Conclusions: We show that phenotypes of this unique cattle subspecies are influenced by their environment, and that anthropogenic disturbance impacted the distribution of phenotypes. Our methodology provides robust and valuable phenotype information, while being simple and requiring few financial resources. Phenotypes may give an indication of bovid behaviour and welfare in urban and rural environments, but further studies would be required to confirm these relationships. For example, HK feral cattle may use roadways to move around, increasing likelihood of traffic accidents in urban areas and in turn impacting horn phenotypes. Our findings may also reflect differences in behaviour between different phenotypes, such as individuals with darker vs lighter coat colour thriving in different environments. Overall, our work contributes to the development of non-invasive methods for studying free-ranging populations, enabling quantification of the impact of anthropogenic disturbance and providing an insight into the consequences of urbanisation.

Research Unit / Event Journal/Book Series

Link(s)

Other link(s)	Links https://twitter.com/ISAE_Oceania