Sexual dimorphism and phenotypic plasticity in a subtropical feral bovid Bos taurus(Artiodactyla: Bovidae).

ABSTRACT Phenotypes reflect how organisms adapt to their environments. Hong Kong (HK) feral cattle, a crossbreed of Bos taurus taurus and Bos taurus indicus, present an opportunity to study these adaptations in one of the very few global cattle populations not directly controlled by humans. These cattle are free-ranging since their release from farms in the 1970’s. HK has a subtropical climate, characterized by high humidity and temperatures during the wet season, and scarce precipitation during the dry season. We studied seasonal coat colour changes in HK feral cattle, and sexual dimorphism in body size and horn length. We provide the first evidence of seasonal changes in coat colour in cattle, with paler coats being more common in the wet season, while darker coats prevailed in the dry season. These seasonal changes were influenced by temperature, humidity, solar radiation, and body condition. We found that males were larger and had longer horns than females. Our results show a male-biased sex dimorphism in the HK feral cattle. Additionally, our findings suggest that thermoregulation costs drive colouration in these cattle. The phenotypic plasticity we demonstrate in these subtropical feral cattle improves our knowledge of the adaptations of ungulates to their habitat. Competing Interest Statement The authors have declared no competing interest. Footnotes The title was updated, and the order of sexual dimorphism and seasonal coat colour changes was reversed consistently throughout the manuscript. https://osf.io/5m62e/?view_only=5f11a74225994407bf92503502fa98a6