This paper considers how prehistoric rock art can illuminate the environmental conditions of a vast but poorly known region in the distant past and in the process shed light on issues of environment, faunal survival, and cultural change. The rock art being considered here is located in the Baga Oigor valley of Bayan Ölgiy aimag, northwestern Mongolia; together with the petroglyphic complexes of Tsagaan Gol and Aral Tolgoi, it is part of the largest, most ancient, and best–preserved body of rock art in this mountainous region dividing North and Central Asia. The Baga Oigor complex itself includes materials dating from the late Paleolithic (12,000 yrs BP) through the Turkic Period (mid-first millennium CE). Within the thousands of compositions included in the complex, one of the least noticed images is that of the moose (Alces alces). Yet as much as any other animal representation within the petroglyphs of Baga Oigor, this image reveals the radical transformation of the environment of the Altai Mountains over several thousand years and its cultural implications. The examination of Alces alces and of its pictorial contexts sheds light on a world inhabited by ancient hunters and herders and sharpens our understanding of the dynamics of cultural change.