Dynamics of a low-density tiger populationin Southeast Asia in the context of improved law enforcement
Abstract: Recovering small populations of threatened species is an important global conservation strategy.Monitoring the anticipated recovery, however, often relies on uncertain abundance indices rather than onrigorous demographic estimates. To counter the severe threat from poaching of wild tigers (Panthera tigris),the Government of Thailand established an intensive patrolling system in 2005 to protect and recover itslargest source population in Huai Kha Khaeng Wildlife Sanctuary. Concurrently, we assessed the dynamicsof this tiger population over the next 8 years with rigorous photographic capture-recapture methods. From2006 to 2012, we sampled across 624–1026 km2with 137–200 camera traps. Cameras deployed for 21,359trap days yielded photographic records of 90 distinct individuals. We used closed model Bayesian spatialcapture-recapture methods to estimate tiger abundances annually. Abundance estimates were integrated withlikelihood-based open model analyses to estimate rates of annual and overall rates of survival, recruitment,and changes in abundance. Estimates of demographic parameters fluctuated widely: annual density rangedfrom 1.25 to 2.01 tigers/100 km2, abundance from 35 to 58 tigers, survival from 79.6% to 95.5%, and annualrecruitment from 0 to 25 tigers. The number of distinct individuals photographed demonstrates the value ofphotographic capture–recapture methods for assessments of population dynamics in rare and elusive speciesthat are identifiable from natural markings. Possibly because of poaching pressure, overall tiger densities atHuai Kha Khaeng were 82–90% lower than in ecologically comparable sites in India. However, intensifiedpatrolling after 2006 appeared to reduce poaching and was correlated with marginal improvement in tigersurvival and recruitment. Our results suggest that population recovery of low-density tiger populations maybe slower than anticipated by current global strategies aimed at doubling the number of wild tigers in adecade