Reintroduction of Tigers in Sariska Tiger Reserve, Rajasthan

Abstract

This chapter provides firsthand information on the reintroduction of tigers in Sariska Tiger Reserve. The first author was actively involved in the planning and operation of the revival of tigers at Sariska conducted by the Wildlife Institute of India (WII), Dehradun, India, in collaboration with the Department of Forests and Environment, Government of Rajasthan. After the extermination of tigers in Sariska Tiger Reserve (STR) in 2004, WII’s report entitled “Status of tiger in STR” strongly suggested reintroduction of tigers in Sariska with a simulation of the population growth pattern of the proposed reintroduced stock to establish self-sustaining population with high reproductive fitness in the wild environment and ample genetic diversity. A suggestion to translocate an initial population of a total of five tigers (two males and three females) from Ranthambhore National Park (RNP) was made, with a supplementation of three tigers (one male and three females) in every three years for a period of six years. Accordingly, in December 2005, a “Species Recovery Plan for Tigers” in STR was prepared. An adult tiger and tigress were chemically immobilized, fitted with radio collars (VHF–satellite) and translocated from RNP to STR on 28th June and 4th of July 2008 respectively, and were kept in 1-ha enclosure. The tiger was released into the wild after eight days of observation on 6th July 2008, while the tigress was released on 8th July 2008 after three days of observation. On 26th February 2009, a female tigress was released. All these big cats are being monitored continuously for home ranges, feeding behavior, and reproduction through ground tracking using “homing in technique” and also through satellite tracking.

Annexure A

Simulation of population growth pattern of reintroduced tiger population [4]: To reestablish tiger population in Sariska, it is important to remove disturbance factors affecting habitat condition and prey availability to tigers. Reintroduction should establish self-sustaining populations with high reproductive fitness in the wild environment and ample genetic diversity [6]. We suggest that a tigress from (two females and two males) Ranthambhore National Park may be brought to establish the population in Sariska Tiger Reserve. We visualized following scenarios.

Five tigers only: Reintroduction of two males and three females with no supplementation in future. Mean final population for successful cases was 11.91 (0.17 SE, 3.32 SD). The deterministic population growth rate, based on females, with assumptions of no limitation of mates, no density dependence, and no inbreeding depression, was r = 0.128, lambda = 1.137, and R ₀ = 2.401. The observed growth rate was 0.0589 (0.0022 SE, 0.2285 SD). In 500 simulations of population for 25 years, 126 went extinct and 374 survived. This gives a probability of extinction of 0.2520 (0.0194 SE) or a probability of survival of 0.7480 (0.0194 SE). The mean time to first extinction was 10.73 years (0.62 SE, 6.99 SD). The final observed heterozygosity was 0.7535 (0.0083 SE, 0.1605 SD) (Fig. 7.10a–c).

Fig. 7.10

The mean population growth (a), survival probability (b) and inbreeding coefficient of reintroduction scenarios, Intro5NS—reintroduction of two males and three females with no supplementation, (c) Intro5S2/3y—reintroduction of two tigers and three tigresses with supplementation of two tigers every 3 years and Intro3S2/2y—reintroduction of one male and two females and supplementation by two tigers every two years

Initial population of five tigers, which is supplemented by two tigers every 3 years: Reintroduction of two tigers and three tigresses with supplementation of two tigers (male and female each) every three years in three subsequent batches, i.e., supplementation from third to ninth year. Mean final population for successful cases was 12.89 (0.13 SE, 2.89 SD). The deterministic population growth was r = 0.128, lambda = 1.137, and R ₀ = 2.401. The mean observed growth rate without supplementation was 0.0784 (0.0021 SE, 0.2145 SD) and with supplementation 0.2954 (0.0058 SE, 0.2214 SD). In 500 simulations of population one for 25 years, 19 went extinct and 481 survived. This gives a probability of extinction of 0.0380 (0.0086 SE) or a probability of survivorship of 0.9620 (0.0086 SE). Mean time to first extinction was 9.70 years (1.40 SE, 8.88 SD). The observed heterozygosity was 0.8518 (0.0056 SE, 0.1237 SD) (Fig. 7.10a–c).

Initial population of five tigers which is supplemented by three tigers every two years: Reintroduction of one male and two females which is supplemented by two tigers every two years for three subsequent batches. The deterministic growth rate was r = 0.128, lambda = 1.137, and R ₀ = 2.401. Mean final population for successful cases was 12.80 (0.14 SE, 3.05 SD). Without supplementation, the mean observed growth rate was 0.0664 (0.0021 SE, 0.2178 SD), and during years of supplementation mean growth rate (r) was 0.4441 (0.0074 SE, 0.2803 SD). In 500 simulations of population one for 25 years, 31 went extinct and 469 survived. This gives a probability of extinction of 0.0620 (0.0108 SE) or a probability of survivorship of 0.9380 (0.0108 SE). The mean time to first extinction was 5.77 years (0.79 SE, 8.10 SD). Observed heterozygosity was 0.8369 (0.0062 SE, 0.1334 SD) (Fig. 7.10a–c).

We modeled the more realistic scenario of three or five tigers being introduced in initial phase and supplemented with tigers at varying interval. The survivorship and inbreeding coefficient (Fig. 7.10a–c) of initial population of five and three tigers which is supplemented with two tigers every two or three years is good, and both have extinction probability <6%. The supplementation is most important to maintain the genetic vigor and can reduce the risk of extinction. The tiger population of five without supplementation has shown high rate of extinction (25%). This reintroduction scenario operates in a situation of very low or no poaching and no prey depletion and thus highlights the importance of either supplementing the introduced population or establishing dispersal coridors with Sariska. Given the insular nature of Sariska Tiger Reserve, the second option is far more formidable and the only option for a viable tiger population in a highly managed tiger population.

Epilogue by the editors: As per the above study, in the year 2009, one male and two female tigers were relocated to Sariska Tiger Reserve. By November 2010, the number rose to two males and three females and subsequently the very first relocated male tiger ST-1 was found dead due to feeding on a poisoned buffalo kill. Interestingly, a male tiger (now called ST-6 or T-07) rambling the forests near Keoladeo National Park, Bharatpur, was caught by author’s team on 24 February, 2011 and released in STR. As of february, 2013, two male, five female tigers and two cubs are freely wandering at STR.