- The government of Thailand adopted an intensive patrolling system in 2005 in order to protect the country’s largest source population of wild tigers, in Huai Kha Khaeng Wildlife Sanctuary.
- Over the next 8 years, researchers with Thailand’s Department of National Parks, Wildlife and Plant Conservation and the Wildlife Conservation Society (WCS) monitored the tiger population closely using a method called “photographic capture-recapture.”
- The researchers believe that because it takes longer for prey populations to recover, and because targeted poaching of breeding animals inside the reserves continues to be a problem, populations may not recover as quickly as conservationists expect.
In 2005, the government of Thailand stepped up patrolling and law enforcement efforts to protect the country’s largest source population of wild tigers, in Huai Kha Khaeng Wildlife Sanctuary, which were under severe threat from poaching.
Over the next eight years, researchers with Thailand’s Department of National Parks, Wildlife and Plant Conservation and the Wildlife Conservation Society (WCS) closely monitored the population of wild tigers (Panthera tigris) in the reserve.
The researchers, who published their findings in the journal Conservation Biology this month, say that the Thailand government’s increased protection efforts are starting to pay off, though their results also suggest that “population recovery of low-density tiger populations may be slower than anticipated” by current global conservation strategies.
Tigers have high reproduction rates and had been anticipated to recover more rapidly, Ullas Karanth of WCS India, one of the authors of the study, told Mongabay.
“However, we now believe that because it takes longer for prey populations to recover, and because targeted poaching of breeding animals inside the reserves continues to be a problem in much of Southeast Asia, ‘doubling tiger numbers in 10 years,’ as many conservationists wish to do, may be an over-optimistic goal,” he said.
“But, our paper shows not only in India but even in Southeast Asia, recoveries at a slower rate are possible, if we pay attention to strict protection,” Karanth said.
Based on historical evidence from tiger reserves in India and Nepal, Karanth and co-authors write, 10–15 years of intensive protection might be required before prey populations recover to ecologically optimal densities.
Due in large part to poaching pressure, the tiger population densities in Huai Kha Khaeng prior to 2006 were 82–90 percent lower than in ecologically comparable sites in India, the researchers note.
Intensified patrolling after 2006 not only appeared to reduce the amount of poaching but correlated with marginal improvement in tiger survival and recruitment, as well.
From 2006 to 2012, the researchers sampled across a large area of the sanctuary using as many as 200 camera traps that were deployed for 21,359 days and recorded 90 different individual tigers.
They performed the study using a rigorous capture-recapture method Karanth and others first started developing in the 1990s in India. Initially, the methodology simply provided estimates of numbers and population densities at a single point in time, but starting in 2006 Karanth and his team began developing an “open” capture-recapture method, which uses annual surveys to estimate change in population numbers over time.
Estimates for Huai Kha Khaeng Wildlife Sanctuary (HKK) over the period of the study are wide-ranging: annual tiger population density ranged from 1.25 to 2.01 tigers per 100 square kilometers, and abundance from 35 to 58 individuals. Tiger survival rate in the sanctuary was between 79.6 and 95.5 percent, while anywhere from 0 to 25 tigers were added every year.
While Karanth and co-authors write that, overall, these results do not constitute unambiguous evidence that the tiger population in HKK increased between 2006 and 2012, they do show that “rigorous assessment and longterm monitoring of tiger population response is critical as demonstrated by our results.”
Given the slow recovery of HKK’s tiger population, the researchers add that the goal of doubling wild tiger populations in the next decade set by the Global Tiger Initiative in 2013 might be unrealistic.
“Targeted management and increased protection have enabled rapid recovery of populations in some felid species after negative impacts were controlled. In contrast, our results indicate that population recoveries of tigers in the face of prevailing levels of poaching pressures in Southeast Asia are likely to be much slower and uncertain, as seen in HKK.”
Duangchantrasiri, S., Umponjan, M., Simcharoen, S., Pattanavibool, A., Chaiwattana, S., Maneerat, S., Kumar, N. S., Jathanna, D., Srivathsa, A., & Karanth, K. U. (2016). Dynamics of a low-density tiger population in Southeast Asia in the context of improved law enforcement. Conservation Biology. doi: 10.1111/cobi.12655