Four years of vertebrate monitoring on an upper Amazonian river
Long-term monitoring of tropical forest animals lags far behind long-term monitoring of tropical forest plants, compromising ecologists’ ability to identify parallel trends. On 257 occasions over 4 years, park guards in a newly protected lowland Amazonian forest in southeastern Peru tallied individuals of 31 reptile, bird, and mammal species sighted along a 47-km stretch of river. Each survey entailed ~3 h of observation from a motorized boat; total survey effort was 892 h and ~12,048 km. Our primary goals were descriptive: to establish baseline sighting rates for these species and to document trends over time and the influence of environmental and sampling factors on sightings. Our secondary goals were to identify the advantages and disadvantages of river-based monitoring and to assess how useful these data are for ecologists and protected areas managers. Over the 4 years of monitoring we observed 1.8 animals/km. More than 90% of recorded individuals belonged to seven common taxa: two reptiles, four birds, and one mammal. Season was the most frequent correlate of sighting frequency; sightings increased in dry season. For the majority of taxa common enough to analyze, sightings increased over the 4 years of monitoring; this is possibly a result of reduced hunting since the establishment of the protected area. Compared to forest-based surveys, river-based surveys were inefficient at recording most mammals. Results to date suggest that river-based surveys can be a valuable, inexpensive tool for monitoring some ecologically important Amazonian animals, and especially those in protected areas.