What determines global positioning system fix success when monitoring free-ranging mouflon?

We have assessed behavioural and environmental factors influencing the success of global positioning system (GPS) fixes recorded from 15 collared free-ranging female Mediterranean mouflon (Ovis gmelini musimon x Ovis sp.). We have demonstrated that fix success was 8% lower in resting animals (0.81, 95% CI = 0.79-0.84) than in active animals (0.89, 95% CI = 0.86-0.91) at an average temperature (13.8A degrees C), but was similar and relatively constant at lower temperatures. When temperatures increased above the average temperature, fix success strongly decreased in resting animals (0.44, 95% CI = 0.36-0.52 at 30A degrees C) as compared to active animals (0.76, 95% CI = 0.65-0.85). These results probably involved behavioural changes in habitat use of mouflon, as temperature and activity strongly influence the use of cover in ungulates. We also found that the success of GPS fixes was influenced by habitat types, increasing from 0.76 to 0.93 (under average sky openness of 33%) along a continuum going from forested to open areas. After controlling for differences in vegetation, sky openness had a positive effect on fix success (from 0.76 to 0.97 in evergreen oak forest). Our approach based on free-ranging animals and using a robust interpolation procedure should provide biologists with a more reliable method to account for bias in GPS studies.