Megafauna play important roles in the biosphere, yet little is known about how they shape dryland ecosystems. We report on an overlooked form of ecosystem engineering by donkeys and horses. In the deserts of North America, digging of ≤2-meter wells to groundwater by feral equids increased the density of water features, reduced distances between waters, and, at times, provided the only water present. Vertebrate richness and activity were higher at equid wells than at adjacent dry sites, and, by mimicking flood disturbance, equid wells became nurseries for riparian trees. Our results suggest that equids, even those that are introduced or feral, are able to buffer water availability, which may increase resilience to ongoing human-caused aridification.

巨型动物在生物圈中发挥着重要作用，但人们对它们如何塑造旱地生态系统知之甚少。我们报告了一种被驴和马忽视的生态系统工程形式。在北美的沙漠中，野生马科动物挖 2 米以内的地下水井增加了水景的密度，缩短了水之间的距离，有时还能提供唯一的水源。马科动物井的脊椎动物丰富度和活动高于邻近的旱地，并且通过模拟洪水干扰，马科动物井成为河岸树木的苗圃。我们的研究结果表明，马科动物，即使是引进的或野生的马科动物，也能够缓冲可用水量，这可能会增加对持续的人为干旱化的恢复能力。