Code Orange for the Bengal Tiger!

Genetic study highlights challenging conservation of the Bengal Tiger in India.

India not only houses a significant proportion of the human population, it is also home to roughly 70% of the global tiger population. The most numerous subspecies, the Bengal Tiger (Panthera tigris tigris), roams in six areas across India. A study in the scientific journal PLoS ONE assessed the genetic architecture of a population in one of these areas, the Terai Arc Landscape (TAL), a stretch of habitat along the foothills of the Himalayas. The results, based on 13 microsatellites,  are not very reassuring for this endangered cat…

Bengal_Tigress
Bengal Tiger (by Kaksbhatt, from Commons Wikimedia)

First, the genetic diversity of Bengal tigers in TAL is lower compared to previous studies. Small populations often exhibit low levels of genetic diversity and are expected to lose more diversity due to genetic drift. This continuous reduction in genetic diversity might make it impossible for these populations to adapt to rapidly changing circumstances.

In addition, the level of inbreeding among these tigers is relatively high (mean inbreeding coefficient = 0.23, for the formula fetishist among the readers). Inbreeding, the mating between close relatives, can have devastating health effects (just look at the royal families in Europe) and often leads to a further degradation in genetic diversity.

Finally, the genetic analysis uncovered two distinct populations connected by moderate gene flow. These two populations, referred to as Corbett Tiger Reserve (CTR) and Rajaji Tiger Reserve( RTR), are connected by a corridor (very originally dubbed the Corbett-Rajaji corridor). The genetic differentiation between CTR and RTR suggests that this corridor is under severe pressure by human disturbance. The loss of another corridor has previously led to the extinction of a western tiger population in RTR. The Corbett-Rajaji corridor needs to be preserved, certainly a challenge in this area of India, which has a higher population density (over 500 people per km2) compared to the Indian average (300 people per km2).

One solution is the relocation of human settlements. For example, the Gujjars, a pastoralist community in TAL, were relocated to the east, creating more room for the tigers. But can the Indian government convince people to leave their homes for a striped cat? The locals certainly wouldn’t move for an insignificant songbird, meaningless moth, or trivial termite. In this respect, tigers can function as so-called ‘umbrella species’, which is a species selected for making conservation-decisions, because protecting these species will indirectly protect other species in their ecological community.

umbrella species

References

Singh, S., Aspi, J., Kvist, L., Sharma, R., Pandey, P., Mishra, S., Singh, R., Agrawal, M., & Goyal, S. (2017). Fine-scale population genetic structure of the Bengal tiger (Panthera tigris tigris) in a human-dominated western Terai Arc Landscape, India PLOS ONE, 12 (4) DOI: 10.1371/journal.pone.0174371

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