Effects of camera trap placement on photo rates of jaguars, their prey, and competitors in northwestern Costa Rica

Abstract

AbstractThe use of camera‐trap methods, though important, has pitfalls and inconsistencies such as factors and interactions that may influence species photo rates. Jaguar (Panthera onca) camera‐trap studies place cameras at sites where jaguar detections are likely greater (e.g., sites with previous evidence such tracks, feces, and other presence signs), but do not account for potential placement biases. Our study evaluated methodological implications of a paired camera‐trap design at trail and off‐trail locations, and climate seasonality, on photo rates of jaguars, their prey, and competitors. From June 2016 to June 2017, camera traps were deployed at 58 different sites in a hexagon grid array of 3 km2 each in the Sector Santa Rosa (SSR) of Área de Conservación Guancaste in Costa Rica. Half of the cameras were located at a trail location that jaguars were likely to use, and the other half at an off‐trail location closest to each hexagon centroid. We estimated a photographic relative abundance index (RAI; no. of independent photos/100 trap nights) and used Generalized Linear Models (GLMs) to assess statistical evidence of trail location and climate seasonality. With a total effort of 19,408 trap nights, we recorded 12,678 independent photo events of 64 species of amphibians, reptiles, birds, and mammals. For the 3 bird species and 14 mammal species we focused on, most species‐specific RAIs were greater at trail locations (n = 8 species, including jaguars and pumas [Puma concolor]), some were greater at off‐trail locations (n = 2 species, including collared peccaries [Pecari tajacu]), and there was no discernable location effect for others (n = 7 species, including tapirs [Tapirus bairdii] and white‐tailed deer [Odocoileus virginianus]). For jaguars, sex ratio data showed a smaller proportion of males at off‐trail locations. Analysis of competitor and prey interaction data indicated temporal segregation at trail locations. Further jaguar camera‐trap studies should highlight camera placement as important source of bias that might influence results; hence, conservationists must be aware of this to avoid erroneous decisions.