A landmark study by the Wildlife Conservation Society (WCS) and U.S. Geological Survey (USGS) says tigers living in one of India's best-run national parks lose nearly a quarter of their population each year from poaching and natural mortality, yet their numbers remain stable due to a combination of high reproductive rates and abundant prey. The study, which appears in the journal Ecology, underscores the need of maintaining protected areas with high prey densities in an overall tiger conservation strategy, along with anti-poaching efforts and eliminating trade in tiger body parts.
The nine-year study in India's Nagarahole National Park found that an average of 23 percent of the park's tigers either move away or die each year from either naturally or from poaching outside of the park, yet total numbers remained high.
"This study shows that even well-protected wild tiger populations have naturally high rates of annual losses, and yet do fine because of their high reproductive rates," said WCS researcher Dr. Ullas Karanth, lead author of the study. "The conservation implications of this study show that effectively protecting reserves to maintain high prey densities is a key pillar in an overall strategy for the conservation of tigers."
The research team, which included Dr. Karanth and Dr. Jim Nichols from USGS, used remote cameras to identify individual tigers and then accurately estimate population trends in the park. Tigers can produce between 3-4 cubs per litter every 2-3 years.
Unfortunately, in other parts of the tiger's range, relentless poaching of the big cats and their prey has caused numbers to plummet. Another WCS study that appeared in a recent issue of the journal Animal Conservation revealed that tiger numbers in a protected area along the Laos-Vietnam border are severely depressed from commercial poaching, and prey depletion which may increase competition between large carnivores.
"The good news is that given the chance, tigers can replenish their numbers; the bad news is that they are not being given that chance in many parts of their range," said WCS's noted big-cat researcher Dr. Alan Rabinowitz.
Earlier this year, WCS launched a new program called "Tigers Forever" that pledges a 50 percent increase in tiger numbers in key areas over the next decade.
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