Evaluation of GPS telemetry collar performance for habitat studies in the boreal forest

Telemetry collars using Global Positioning System (GPS) technology may prov ide biased locations, and their capability under field conditions should be evaluated before the units are used in habitat studies. We assessed influe nce of vegetation features, terrain slope, and weather conditions on perfor mance of GPS collars. We used a GPS collar that attempted 5 fixes, separate d by 5-minute intervals, in 45 sample sites equally distributed among 3 for est types (deciduous, mixed, and coniferous stands) and 3 age classes (10, 30-50, and greater than or equal to 70 years old). We visited all sites dur ing late September and mid-December. Mean location success was significantl y less in fall (69.3+/-5.3%) than in winter (89.8+/-3.0%, P<0.05). Mean num ber of satellites tracked by the CPS antenna was related negatively to tree height. Location success within tree-height classes (<10 m, 10-13 m, great er than or equal to 13 m) did not differ among habitat types by season. Res ults from free-ranging moose (Alces alces) fitted with GPS collars indicate d that location success varied significantly among months, being least from June to September and greatest during March and April. Location success di ffered between day and night during summer, which could be explained by cha nges in habitat use. These results indicated that CPS collars may underesti mate use of mature stands relative to other habitat types. This potential b ias must be addressed when analyzing frequency distributions of habitats us ed at location points.