Endangered Bengal tiger: the trilemma of a tigress            

Although Bengal tigers are at the top of the food chain in the Bandhavgarh Tiger Reserve, located at the heart of India, they still face a number of serious difficulties, especially for the tigresses who have cubs to raise. In the episode 5 of Dynasties (Season 1), David Attenborough describes the lives of a Bengal tigress called Raj Bera and her four young cubs. At 14:51 of this episode, Attenborough summarizes the trilemma Raj Bera faces: her time was divided between hunting, scent marking her territories, and nursing the cubs. All of these three activities are vital for this tiger family, and each requires a considerable amount of time and energy.

Hunting ensures the survival of the cubs but is never an easy job for a tiger. The documentary depicts several scenes in which Raj Bera ambushes the prey, but most of the times she fails to secure any food. Studies have shown that hunting success of a tiger is closely related to special characteristics of hunting site, such as denser, patchier, and more complex vegetation with lower visibility [1]. These special characteristics are important for a tiger to capture prey, since he/she needs to hide in the bush and strike with surprise. Thus, sometimes without bushes to hide, Raj Bera often goes home empty-handed. Although the primary challenge for Raj Bera is the successful capture of prey, for other tigers across the world, the abundance of prey is a more pressing concern. Studies have shown that nature preserves in northern China only include 20% of the core habitat of tigers [2]. Due to the small and damaged habitats, many tiger preserves around the world have prey densities that are below the level necessary to support a viable tiger population [3].

Tigers who have territory intensively patrol the boundaries and mark them with scent [4]. Intense intraspecific competition makes scent marking and patrolling important activities, since they prevent the trespassing of other tigers. Raj Bera has to devote a decent amount of time to patrolling the boundaries, not only to make sure the food in her territory is only accessible to her family, but also to protect her cubs from other tigers who may relentlessly kill cubs that are not their own. Besides hunting and patrolling, Raj Bera devotes a lot of effort in nursing her children, including feeding them with milk, guarding them against sloth bears, and teaching them how to survive in the wilderness alone.

Since most tigresses do not have time to thoroughly perform these three activities that are essential to the survival of offspring, there is only a 50% chance that a baby tiger develops into adulthood. Luckily, Raj Bera’s four cubs all managed to grow into adulthood. While the burden on the mother is ameliorated, the young tigers now have to survive on their own, and great challenges await them in the near future.

by Tiankai Han

Dynasties, Season 1, Episode 5 Tiger, from 14:51

  1. [1] Miller JR, Jhala YV, Jena J & OJ Schmitz. 2015. Landscape-scale accessibility of livestock to tigers: implications of spatial grain for modeling predation risk to mitigate human-carnivore conflict. Ecology and evolution 5(6): 1354–1367. 
  2. [2] Luan X, Qu Y, Li D, Liu S, Wang X, Wu B, Zhu C. 2011. Habitat evaluation of wild Amur tiger (Panthera tigris altaica) and conservation priority setting in north-eastern China. Journal of Environmental Management 92(1): 31-42.
  3. [3] O’Kelly HJ, Evans TD, Stokes EJ, Clements TJ, Dara A, Gately M, Menghor N, Pollard EHB, Soriyun M & J Walston. 2012. Identifying conservation successes, failures and future opportunities; assessing recovery potential of wild ungulates and tigers in Eastern Cambodia. PloS One 7(10), e40482.
  4. [4] Naha D, Jhala YV, Qureshi Q, Roy M, Sankar K & R Gopal. 2016. Ranging, Activity and Habitat Use by Tigers in the Mangrove Forests of the Sundarban. PloS One 11(4), e0152119.

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