The role of den quality in giant panda conservation

Abstract

Small features in ecological systems are often underrepresented in conservation monitoring, management and policy. Tree cavities and other forms of refuge play disproportionately large ecological roles due to their importance for shelter and rearing vulnerable offspring. Giant panda (Ailuropoda melanoleuca) cubs are highly altricial, and dependent on dens. In Fengtongzai—a reserve with cavity-containing old growth forest—we measured 19 structural and microhabitat variables in potential tree dens. We also established data loggers in rock cavities in Foping Nature Reserve (which due to logging does not contain old growth) and tree cavities in Fengtongzai to monitor temperature and humidity inside and outside dens to evaluate microclimatic buffering. Fengtongzai pandas selected tree dens that were better concealed, with large interiors and entrances but smaller entrance to interior ratios. Microclimate inside dens differed dramatically from ambient conditions outside: in cold weather dens were warmer, in hot weather dens were cooler, dens were less humid and dens had more stable microclimates. Dens used by maternal pandas were warmer, drier and less variable than tree and rock cavities that were not used. Tree dens showed better capacity to buffer against extremes of temperature and humidity than did cave dens. Our findings have important conservation implications, including the value of den sites and the need for better monitoring and management. Specifically, management practices that preserve large old trees may increase carrying capacity and any experimentation with artificial dens as a conservation intervention should reference our findings on structural and microclimatic characteristics of preferred den sites.