New GPS technology improves fix success for large mammal collars in dense tropical forests

There have been few telemetry studies on large and medium-sized mammals from Neotropical lowland forests. This can partly be explained by the difficulty of tracking animals with radio-telemetry in these forests, often in remote areas with poor access due to limited transportation infrastructure. Researchers have been forced to follow their collared animals by aeroplane (Crawshaw 1995, Fragoso 1998, Rabinowitz & Nottingham 1986), but aerial telemetry is dangerous and involves difficult logistics and high costs. GPS (Global Positioning System) collars that allow the collection of data automatically at long intervals would be a good alternative. The effect of canopy cover on GPS fix success and location accuracy was of concern from the beginning and has been widely investigated in temperate forests (D’Eon 2003, Di Orio et al. 2003, Dussault et al. 1999, Moen et al. 1996, Rempel et al. 1995). All studies found a significant decrease in fix success and a large increase in location errors under forest canopy. Tropical lowland rain forests have a much denser canopy than temperate forests, and up to now the performance of GPS collars in tropical forest has been very poor. Rumiz & Venegas (2006) showed that while GPS collars worked in the dry forest of the Bolivian Chaco, they only obtained a successful fix in 1–3% of all attempts in the lowland forest of the Madidi National Park, Bolivia. A study on the ecology of lowland tapirs (Tapirus terrestris Link, 1795) in the Peruvian Amazon required a system that would work in the dense forest and acquire data with a high temporal resolution. The present study evaluates a new system called TrackTag (NAVSYS Limited, Springwood House, Linburn Rd, Kirknewton, West Lothian EH27 8DY, UK). The TrackTag differs from