How similar are high latitude and high altitude habitats? A review and a preliminary study of the adrenocortical response to stress in birds of the Qinghai-Tibetan Plateau
Matthew I. RICHARDSON ①** Ignacio T. MOORE① Kiran K. SOMA② LEI Fu-Min③ John C. WINGFIELD① (① Department of Zoology, University of Washington, Seattle, WA 98195, USA) (② Department of Physiological Sciences, UCLA, Los Angeles, CA 90403, USA) (③ Institute of Zoology, Chinese Academy of Sciences, Beijing 100080, China)
Arctic and alpine biomes are frequently considered the same in introductory textbooks, conservation planning and even in the primary literature. Both alpine and arctic biomes are treeless expanses with low amounts of grass- and forb-based primary productivity, and simplified food webs. Furthermore, with the possible exception of tropical alpine habitats, both environments are highly seasonal. Few studies, however, have made a critical comparison of these superficially similar environments. They have some significant differences, including energy regimes, proximity to refugia and scale of the habitat. If the environments are the same, our hypothesis is that birds inhabiting them will exhibit similar responses to unpredictable stressors. Conversely, if these habitats are sufficiently different, then responses to acute stress should be attuned to the local environment and not be the same. A preliminary study was conducted to compare the adrenocortical responses of selected avian species breeding on the Tibetan Plateau of Central China with published data of birds inhabiting the arctic tundra ecosystem. Two species of snowfinch, Onychostruthus taczanowskii and Pyrgilauda ruficollis, are regarded as high altitude specialists and show typical increases in plasma levels of corticosterone following a standardized stress of capture, handling and restraint. However, neither showed any seasonal variation in adrenocortical response to stress, unlike many arctic specialists. This study suggests that avian species living in alpine and arctic environments may have hormonal responses tailored to the ecological challenges presented by their environment[Acta Zoologica Sinica 49(1):1-19,2003].