| Understanding the effects that wildlife researchers have on their study animals is crucial to interpreting the results of the studies and implementing conservation actions based on those results. The increased use of global positioning system (GPS) tracking devices on greater sage-grouse (Centrocercus urophasianus) in recent years has contributed to our understanding of fine-scale movements and habitat use compared with the traditionally-used very high frequency (VHF) transmitters. However, GPS units differ from VHF units in ways that may negatively affect grouse behavior and survival and therefore yield biased results. We evaluated differences in seasonal survival in >1000 sage-grouse marked with VHF and GPS tracking devices throughout their distribution in California and Nevada. We observed decreased survival for GPS-marked birds compared to VHF-marked birds for both sexes, all age classes, and all seasons. This difference was likely related to features of the GPS units that include greater weight, a rump-mount harness attachment, and a reflective solar panel, all of which may increase an animal's susceptibility to predation. While GPS units produce useful movement data, we recommend that grouse marked with currently available GPS packages not be used in demographic analyses. Future research should assess new designs that reduce negative impacts on sage-grouse and limit biased results. |