Ethology at the roof of the World: A cross-language systematic review of the behaviour and welfare of yaks (Bos mutus and Bos grunniens)

The yak serves an important role in the Himalayan ecosystems of the Qinghai-Tibet plateau. Current management practices, and the change to more intensive farming methods, are a concern for their welfare especially in terms of behavioural expression. While focus has been on yaks within the context of the ecosystem, their behaviour has not been widely documented. The aim of this review is to evaluate the status quo on yak behaviour and welfare, and to synthesise the existing information on yak behaviour (domesticated and wild) to provide an ethogram that can benefit future empirical studies. Peer-reviewed literature was retrieved from three databases while making no restriction on language. We included 39 Chinese language papers, 19 English and 1 German source (total n = 59). Studies mostly considered grazing behaviour and activity time budgets. Other topics included reproductive and social behaviour and animal welfare. The data showed that yaks graze for nearly the full daytime when on summer pasture (11 h), with variations in behavioural patterns depending on the season. Social and reproductive behaviour occur limitedly when outside the mating season. Welfare issues are, amongst others, the lack of veterinary services, painful and stressful management procedures, and heat stress due to climate change. From the overall review a clear picture emerges about the behaviour of yaks, which was summarized into a comprehensive ethogram. However, there are still many knowledge gaps regarding yak welfare as well as known welfare issues that require urgent change in practice. We aspire that this review will open up discussion on yak welfare and their possibility for behavioural adaptation, especially in the light of climate change and new management systems.