Overgrazing by introduced herbivores is widely recognized as a threatening process in Australia's semi-arid rangelands. Comparatively, grazing by native herbivores is generally considered to have benign effects. Populations of introduced herbivores are controlled in conservation reserves, but populations of native kangaroos and wallabies are seldom subject to control. We investigated the impacts of rabbit and kangaroo grazing on vegetation and soils at Yathong Nature Reserve in semi-arid Australia during the dry conditions that prevailed in 2019. We conducted spotlight and dung surveys to measure the relative abundance of kangaroos and rabbits, and assessed understorey biomass, woody plant density, soil bulk density and water infiltration rates in selective herbivore exclosures that had been established in 1979, and nearby controls that all herbivores could access. Kangaroos were the dominant herbivores at the time of our study. Grazing by kangaroos decreased grass biomass, increased soil density and reduced the rate of water infiltration. Rabbits reduced woody plant density but had no detectable effect on understorey vegetation cover or soil attributes. Our findings question the existing paradigms about how grazing by kangaroos should be viewed and prompt the question: should kangaroo populations be managed within conservation reserves to reduce their impacts on ecosystems?

引入的草食动物过度放牧被广泛认为是澳大利亚半干旱牧场的威胁性过程。相比之下，通常认为以天然食草动物放牧具有良性效果。引入的草食动物种群在保护区中受到控制，但本地袋鼠和小袋鼠的种群却很少受到控制。我们调查了在2019年盛行的干旱条件下，兔和袋鼠放牧对半干旱澳大利亚Yathong自然保护区植被和土壤的影响。我们进行了聚光灯和粪便调查，以测量袋鼠和兔的相对丰度，并评估了地下蓄积量1979年确定的选择性草食动物排泄物中的生物量，木本植物密度，土壤容重和水的渗透率，以及所有草食动物都可以使用的附近控件。在我们研究时，袋鼠是主要的食草动物。袋鼠放牧减少了草的生物量，增加了土壤密度并降低了水的渗透率。兔子降低了木本植物的密度，但对下层植被覆盖或土壤属性没有可检测的影响。我们的发现质疑关于应如何看待袋鼠放牧的现有范例，并提出了一个问题：应该在保护区范围内管理袋鼠种群以减少其对生态系统的影响吗？兔子降低了木本植物的密度，但对下层植被覆盖或土壤属性没有可检测的影响。我们的发现质疑关于应如何看待袋鼠放牧的现有范例，并提出了一个问题：应该在保护区范围内管理袋鼠种群以减少其对生态系统的影响吗？兔子降低了木本植物的密度，但对下层植被覆盖或土壤属性没有可检测的影响。我们的发现质疑关于应如何看待袋鼠放牧的现有范例，并提出了一个问题：应该在保护区范围内管理袋鼠种群以减少其对生态系统的影响吗？