Global positioning system tracking devices can decrease Greater Sage-Grouse survival

Abstract

Reliable demographic estimates hinge on the assumption that marking animals does not alter their behavior, reproduction, or survival. Violations can bias inference and are especially egregious for species of high conservation concern. Global positioning system (GPS) devices represent a recent technological advancement that has contributed greatly to avian ecological studies compared with traditionally used very high frequency (VHF) radio transmitters, but may affect demographic rates differently than VHF transmitters. We compared survival between VHF (necklace attachment) and GPS (rump-mounted attachment) devices from >1,100 Greater Sage-Grouse (Centrocercus urophasianus), a species of high conservation concern, across multiple populations within California and Nevada. We found lower survival for GPS-marked compared to VHF-marked sage-grouse across most sex, age, and seasonal comparisons. Estimates of annual survival for GPS-marked sage-grouse were 0.55–0.86 times that of VHF-marked birds with considerable variation among sex and age classes. Differences in survival could be attributed to features associated with GPS devices, including greater weight, position of attachment (e.g., rump-mount harness), and a semi-reflective solar panel. In a post hoc analysis, we evaluated additive and interactive effects between device type (GPS vs. VHF) and transmitter mass as a proportion of body mass (PBM). While the device type effect alone was the best model, the PBM interaction also had support. For GPS devices, survival decreased with increasing PBM, whereas PBM effects were not found for VHF. We attributed differences in PBM effect to placement of transmitters on sage-grouse, as weight of GPS devices was positioned rearward. This information can help managers and researchers weigh costs and benefits of GPS-based monitoring. Our results indicate demographic data collected from GPS devices should be interpreted with caution, and use of these devices should be tailored to specific ecological questions. Future research aimed at investigating behavioral impacts and GPS designs that reduce adverse impacts on survival would be beneficial.

A Rump‐mount Harness Design Improvement for Greater Sage‐grouse

“…Thus, we suggest researchers and managers currently deploying this design, recapture fitted birds and report findings. The negative effects we observed from rump‐mount transmitter design and attachment could be especially pronounced in small populations of greater sage‐grouse or threatened Gunnison sage‐grouse (Barron et al 2010, Ouren et al 2018, Severson et al 2019). Our modified harness design and detailed protocols will help alleviate potential injuries especially to male greater sage‐grouse, and we encourage developing protocols to mitigate these potential effects.…”

“…Rappole and Tipton (1991) also cautioned against using leg-loop harness materials that are (or become) too narrow and result in irritation. If the mark influences behavior or survival, it could result in misleading inferences related to demographic rates, habitat use, and movement (Foster et al 2018, Severson et al 2019. We suggest additional research into this topic and recommend that investigators planning to use a rump-mount harness on male or female greater sage-grouse consider adopting our harness design or develop a new or improved design.…”

“…Rappole and Tipton (1991) also cautioned against using leg‐loop harness materials that are (or become) too narrow and result in irritation. If the mark influences behavior or survival, it could result in misleading inferences related to demographic rates, habitat use, and movement (Foster et al 2018, Severson et al 2019).…”

Low-cost DIY GPS trackers improve upland game bird monitoring

“…The trackers were built at the maximum weight capacity for pheasants to maximize data accruement. However, concerns regarding the influence of GPS receiver weight on survival and behavior may limit application for smaller species (Foster et al 2018, Severson et al 2019. Therefore, researchers should be weary of weight thresholds for specific species.…”

Gps Telemetry and Home Range of the White-Backed Woodpecker Dendrocopos leucotos: Results of the First Experience

“…obs.). Some studies have shown that carrying of GPS-tags can increase predation risk for birds by making them more visible and reducing their ability to escape predators (Severson et al 2019). However, it is unclear whether this happened to juveniles of the WBW.…”