Abstract Proliferation of shrubs at the expense of native forage in pastures has been associated with large changes in biomass and spatial distribution of forage for grazing livestock, and such changes influence the grazing behavior of ruminants. However, little information is available concerning the effect of pastoral shrub coverage on grazing pattern. To better understand the grazing behavior of yaks and their response to increased shrub coverage in alpine meadows, 48 yak steers were randomly assigned to four pastures with shrub coverage of 0, 5.4%, 11.3%, and 20.1% (referred to as control, low, middle, and high, respectively) on the Qinghai-Tibetan Plateau. The primary behavioral patterns (grazing, walking, and ruminating/resting) of three focus animals per experimental group were recorded repeatedly in scan sampling every 10 minutes from 07:00 to 19:00 h in three observation periods (the first 10 days of each month) from July through September. Furthermore, the secondary behavioral patterns (bites per minute, steps per minute, and bites per step) were observed 15 times per focus yak on each observation day. Behavioral observations showed that yaks had similar diurnal behavioral patterns with two main grazing bouts—in the morning and afternoon—and a ruminating/resting peak at midday when grazing in pastures with different shrub coverage. However, yaks significantly enhanced the time allocated to walking (P = 0.029) and decreased ruminating/resting time (P = 0.045) with increasing shrub coverage, although the grazing time was not significantly different (P = 0.663). Compared with the control and low shrub-coverage groups, yaks in the middle and high groups had more bites per minute (P = 0.036) and steps per minute (P = 0.029), whereas the number of bites per step was not influenced (P = 0.877) by shrub coverage. The increased time allocated to walking at the expense of ruminating/resting as well as the high number of feeding stations may be an adaptive strategy for searching and obtaining sufficient forage resources. Increased walking time and step rate for the yaks grazing in the high shrub-coverage pasture could increase the energy expenditure and consequently reduce the energy available for growth and production. Our findings provide evidence for the influence of shrub coverage on grazing behavior of yaks grazing in alpine meadows as well as insights into the sustainable production of grazing yaks on lands with increasing shrub coverage on the Qinghai-Tibet Plateau.

中文翻译：

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青藏高原灌木草地放牧牦牛（Bos grunniens）的行为模式

摘要 以牺牲牧草原生草料为代价的灌木增殖与放牧牲畜草料生物量和空间分布的巨大变化有关，这种变化影响了反刍动物的放牧行为。然而，关于牧区灌木覆盖对放牧模式的影响的信息很少。为了更好地了解牦牛的放牧行为及其对高山草甸灌木覆盖率增加的反应，48 头牦牛被随机分配到灌木覆盖率分别为 0、5.4%、11.3% 和 20.1%（称为对照，低、中、高分别）在青藏高原。从 07 开始，每 10 分钟在扫描采样中重复记录每个实验组三只焦点动物的主要行为模式（放牧、行走和反刍/休息）：从 7 月到 9 月的三个观察期（每个月的前 10 天）的 00 到 19:00 h。此外，在每个观察日，每头焦点牦牛观察 15 次次要行为模式（每分钟咬伤、每分钟步数和每步咬伤）。行为观察表明，牦牛具有相似的昼夜行为模式，有两个主要的放牧活动——上午和下午——中午在不同灌木覆盖的牧场放牧时出现反刍/休息高峰。然而，牦牛显着增加了分配给步行的时间（P = 0.029）并随着灌木覆盖率的增加而减少了反刍/休息时间（P = 0.045），尽管放牧时间没有显着差异（P = 0.663）。与对照组和低灌木覆盖组相比，中高组牦牛的每分钟叮咬次数（P = 0.036）和每分钟步数（P = 0.029）较多，而每步的叮咬次数不受灌木覆盖率的影响（P = 0.877）。以反刍/休息为代价的增加的步行时间以及大量的喂食站可能是一种用于搜索和获得足够草料资源的自适应策略。在高灌木覆盖的牧场放牧的牦牛增加步行时间和步频可能会增加能量消耗，从而减少可用于生长和生产的能量。