Factors affecting the quantity and quality of Argos telemetry locations for wolverines in the northern Cascade Range in Washington

Abstract

Satellite telemetry systems provide wildlife researchers with a valuable tool for tracking species that range over large distances or inhabit remote or inaccessible terrain, such as wolverines (<italic>Gulo gulo<italic>) in the northern Cascade Range in Washington. The Argos system is 1 of 2 satellite telemetry systems that are currently available, and is being used by the USDA Forest Service's Pacific Northwest Research Station's North Cascades Wolverine Study (NCWS) to track study animals. In order to use Argos location data, an understanding of how environmental characteristics and animal behavior may affect location quality and quantity is necessary. However, the only quantitative evaluations of system performance in North America pre-date one or both major upgrades made to the system in 2005 and 2011. Moreover, there have been no published tests of the potential effects of animal behavior on Argos system performance. I conducted a series of static and dynamic tests, the latter using a collared dog, to evaluate the potential effects of environmental factors and animal behavior on the quantity and quality of Argos telemetry locations in the NCWS study area. My static test results indicated that Argos location data is largely robust to the effects of the vegetative and topographic variables included in the analyses, suggesting that extensive static tests may not be necessary in similar study areas. I report a much higher proportion of high quality locations as well as much smaller location errors for one class of locations (A) than reported from previous tests. However, the dynamic tests I conducted revealed a large decline in both location quality and quantity compared to concurrent static tests. This effect was observed both when the dog wearing the dynamic collar was moving and at rest, so I could not attribute the decrease in location quality to animal movement alone. Test results indicate that researchers should not expect the results of static tests to be representative of location quality in a study area, and that recent upgrades to the Argos system have resulted in improved performance that may allow researchers to use location data at a finer spatial scale than previous tests indicated.