Occupancy modeling of medium and large mammal diversity in a Central American biological corridor
Cove, Michael V.
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Noninvasive camera traps are commonly used to detect mammals in the Neotropics, but few studies have evaluated the effectiveness of this technique for species inventories. This study used passive infrared camera traps to survey medium and large mammal diversity at the San Juan – La Selva Biological Corridor, Costa Rica. The connectivity of the corridor is highly affected by the spread of large scale agriculture, cattle ranching, and a growing human presence which influenced the selection of sixteen forested sites during surveys in 2009 and 2010. An occupancy modeling approach was used to estimate corridor species richness and species-specific detection probabilities. Rarity had a highly negative effect on the ability to detect species presence, while hunting/poaching and diet also had negative but weaker effects on detection. Large carnivores had the lowest detection probabilities whereas medium-sized rodents and generalist mesopredators had the highest detection probabilities. Corridor richness was high and encouraging but site-level richness estimates were highly variable and might be poor reflections of true richness. Occupancy modeling has only recently been applied to camera trap data and these results suggest that this approach provides robust richness and detection probability estimates at the landscape-level and should be further explored. Further occupancy analysis was performed to examine habitat influences on the occurrence and detection probability of the Baird’s tapir (Tapirus bairdii) and four common mesopredators. The tapir was selected for further analysis because this endangered species is considered rare and locally extirpated from most of its historic range within Costa Rica, while the mesopredators were selected because as common nest predators they pose a serious threat to migratory songbirds. Tapir occurrence was positively influenced by forest cover and the proposed Maquenque National Park, and negatively affected by large-scale pineapple production and habitat heterogeneity. Habitat variables affecting mesopredator occurrence varied among species but overall mesopredator occurrence was negatively affected by forest cover and positively influenced by large-scale pineapple production. These results suggest that the San Juan – La Selva Biological Corridor still maintains a diverse mammal community, but there will be important complications as human disturbance within the corridor increases in the future.