Recently, wildlife enthusiasts rejoiced in the birth of half a dozen tiger cubs in Sariska Tiger Reserve (STR). It took more than a decade for the tiger population to show a rise, after a long-stagnant phase following their reintroduction in Sariska from the Ranthambhore Tiger Reserve (RTR). The breeding rate has steadily increased in the last five years, indicating that the environment is becoming conducive for big cats to raise their young ones. But the question of recuperation of the whole ecosystem still looms over this success. Can the increasing population be a yardstick of successful re-establishment of reintroduced tigers? While the increase in tiger numbers can be considered as a parameter to measure the success of the reintroduction program, it cannot alone be conclusive to decide the sustainability of the program. A new study on the kill pattern of Sariska’s reintroduced tigers shows that a long road lies ahead in order to re-establish the natural self-sustaining ecosystem of STR.
Sariska at a Glance
Situated in the semi-arid parts of Rajasthan, amongst the Aravalli hill range, STR sprawls over an area of 1213sq.km., and marks the westernmost distribution limit of tigers in the region. The reserve had lost all its tigers to poaching in the year 2004-05. In 2008, the world’s first tiger reintroduction program was launched to reinstate the population in STR. Tigers were brought from RTR, a similar habitat in the state of Rajasthan. A total of nine tigers (four males and five females) were translocated to STR in the last 12 years. During the initial years no breeding was reported among tigers. A study by Bhattacharjee et al. 2015 had suggested high stress in the tigers owing to high anthropogenic pressure in a new habitat as the reason for no breeding activities. In 2012, after four years of reintroduction, the first tiger cub was born in the reserve. Gradually, with improved protection and management interventions, the breeding rate improved significantly. Currently, STR hosts a population of 22 tigers (11 adults, 5 sub-adults and 6 cubs).
Although the recorded area of STR is 1213sq.km., a study by Bhardwaj et al. 2020 suggests that due to the immense anthropogenic pressure in the region the actual inviolate area available for tigers is only 548sq.km. About 175 villages are situated in and around STR. Out of these, 26 villages are situated in critical tiger habitat. The human population is over 1700 in the villages inside the reserve along with a livestock population of 10,000, mainly buffalos and goats. In addition to this, the large human and cattle population in villages surrounding the reserve intensifies the pressure on the natural forest. Livestock rearing is the prime occupation of the local communities in STR. The commercialisation of milk products, especially the ‘milk-cake’ of Alwar, which is famous across the country, is one of the primary reasons behind rampant livestock grazing in STR. With one of the most robust protocols for 24x7 monitoring of tigers in the country, individual tigers in STR are monitored using advanced and conventional monitoring methods such as GPS/VHF-based radio telemetry, mobile-based tracking, e-surveillance and camera traps. This level of intensive monitoring enables a meticulous collection of information that is then utilised for scientific management.
Changing Ecology of Big Cats
The study by Bhardwaj et al. 2020 demonstrates the extent of anthropogenic pressure in terms of livestock presence in the tiger reserve. Drastic changes in dietary preferences of tigers and leopards were observed when analysing the data collected around the kill recovery of these big cats. A total of 737 kills were reported from June 2016 to November 2018; 67.84 per cent were made by tigers, 30.80 per cent by leopards, and 1.36 per cent kills were by unknown predators.
Tiger kills were reported mainly from comparatively undisturbed forests. Out of the total reported 500 kills, 77 per cent were livestock (especially buffalos (Bubalus bubalis)), followed by Sambar (Rusa unicolor) (13.6 per cent), Chital (Axis axis) (3.6 per cent), Blue Bull (Boselaphus tragocamelus) (2.4 per cent) and Wild Boar (Sus scrofa) (0.95 per cent). Such a high livestock to natural prey ratio, 3.34:1, indicates an abundance of livestock population inside the reserve. The substantial increase of prey preference for livestock from 10.4 per cent (Shankar et al. 2010) to 19.4 per cent (Mondal et al. 2012) and now 77 per cent is alarming (Fig. 1) This was corroborated with the number of cases of ex gratia relief (compensation afforded to the aggrieved) for cattle-killing by tigers, which has increased by almost six times in 2017 in comparison to 2011 (although the tiger numbers have also doubled in said period). At the same time, the observed livestock to natural prey base ratio for two tigresses (ST-7 and ST-8) was found to be 1:1.1, which can be attributed to the high density of natural prey base in their respective home ranges which are situated in comparatively less disturbed forest areas.
Leopards, on the contrary, are very flexible and opportunistic in their feeding habits and their diet ranges across a wide range of taxa. Since leopards are smaller in size compared to tigers, they prefer small to medium-sized prey species. Chital is their preferred prey in natural undisturbed forests. When tigers were exterminated from the STR, leopards became dominant and occupied the prime habitat of the reserve. During this time STR recorded one of the highest densities of leopards in the country. But as the tigers came back and regained their territory, the leopards were pushed out to the peripheral areas of reserve. As per Bhardwaj et al. 2020, a high percent of livestock prey (84.2 per cent) was observed for leopards as compared to that reported in earlier studies (7.1 per cent) by Mondal et al. 2012, which reported wild ungulates, especially Chital as the dominant prey species of the leopard. This can be attributed to the fact that leopards occupied prime habitat with a high predominance of wild ungulates. Also, preying on full-grown livestock is difficult for leopards, but was easier to prey upon wild ungulates which were in fair abundance.
In the study, most leopard kills were reported in open and degraded forests, on the periphery of human settlements in highly disturbed habitats. Among 227 cases of leopard kills analysed, a stark difference in the size of the livestock preyed upon was observed. This indicated that leopards preferred smaller to medium-sized individuals, mainly goats and fawns of buffalos.
Big cats like tigers are free-ranging and territorial in behaviour. Factors such as habitat quality, natural cover, availability of water and most importantly density and biomass of prey; determine the effective size of the territory of these large felids. Nevertheless, in human-dominated landscapes where livestock availability is higher than the natural prey base, the extent of human disturbance also becomes pivotal in area preferences for tigers. Even for large predators like tigers, hunting in the wild is not a cakewalk and they generally succeed once for every ten attempts made. Tigers are crepuscular in habit and spend the majority of their time during the day resting and actively hunting at night. They prefer big body prey to balance their energy dynamics during hunting expeditions.
In undisturbed natural forests, Sambar is one of the most preferred prey species due to its body size and solitary nature. But in human-dominated landscapes like STR where cattle population is abundant, tigers prefer cattle over wild prey owing to the ease in hunting and their larger body mass.
A comparison with other tiger reserves in the country shows that despite having a fair density of wild prey, and a high density of Sambar, the tiger density is quite poor in STR (Table 1). Jim Corbett Tiger Reserve, situated in the Himalayan region, has the highest density of tigers on the planet – 14 tigers/100sq.km. In comparison, STR has a very low tiger density of 0.9 compared to 9.6 in RTR, which has a similar habitat, and 1.41 in Panna, which is also built up on a re-introduced tiger population. Such poor tiger density in STR is attributed to factors like very high anthropogenic disturbance, habitat fragmentation and a lack of inviolate pockets as compared to other reserves. Also, the distribution of prey density is not evenly distributed, and varies throughout the reserve. Thus, tigers relying on cattle as prey indicates that there is a high abundance of cattle in the reserve which are far easier to kill than other prey.
The Brewing Storm
Large carnivores occupy an important position in the ecological niche, and their food habits play an important role in maintaining the community structure. As mentioned in the beginning, the increasing number of tigers cannot be a conclusive performance indicator of wildlife management. The audit-minded governance only focuses on increasing tiger population without making efforts to remove anthropogenic disturbances through relocation of villages from core areas. This will lead to increasing human-tiger interactions, in turn paving the way for possible conflict. This will further erode the conservation support from the communities as human-wildlife conflict can not only aggravate the law and order situation but also the conservation prospects of magnificent mammals like the tiger.
Attacks from tigers and other wild animals are often responded to with violent retaliation from the public. A study by one of the authors in 2018 revealed that the extremely low strength (in numbers) and lack of motivation in frontline staff in wildlife law enforcement is evident from the observed declining trend in registration of forest offences during the last decade. It has resulted in high anthropogenic disturbances and has further led to rampant grazing inside the reserve, including core areas.
Generally, big cats rely on one large-sized prey per week. But certain tigers, on occasion, were observed killing multiple livestock, probably due to more availability. This has caused serious outrage in the local community and such behaviour patterns can lead to victimisation through retaliatory action. The increasing predation of livestock by large carnivores can be seen as increasing human-carnivore interface, which may further escalate intolerance among the local communities towards the presence of carnivores. This is evident from past incidents, when the first reintroduced tiger ST-1 was poisoned with a buffalo carcass. In 2018, a tigress ST-5 went missing and one young male ST-11 got strangled in a wire snare, indicating that threats of poaching and retaliatory killings are still prevalent in the reserve. During the winter season in 2017-18, seven people were killed by leopards in the villages situated on the periphery of the reserve, following which there was a huge public outrage. An angry mob not only manhandled the staffers and damaged the reserve’s property but also burnt a leopard while it was alive and had been tranquilised for relocation by the staffers. Although the process of voluntary relocation of villagers from this critical tiger habitat is in progress, the observed slow pace of the same for the last decade has brought the landscape to a further stage of degradation. Speeding up of the village relocation process along with strict law enforcement in STR is the need of the hour.
Note: The views expressed by the authors are personal.
Reference: Gobind Sagar Bhardwaj, Gogul Selvi, Saket Agasti, Balaji Kari, Hemant Singh, Anand Kumar, GV Reddy, Study on kill pattern of re-introduced tigers, demonstrating increased livestock preference in human dominated Sariska tiger reserve, India, SCIREA Journal of Biology. Vol. 5 , No. 2 , 2020 , pp. 20-39.