TIGER CONSERVATION

Source- TheHindu

Introduction:

The ominous word extinction has one meaning- the death of a species.
July 29^th is Global Tiger Day, the world and India can celebrate the recovery of at least one endangered species.
According to IUCN reports, tiger numbers have increased by 40% since 2005.

Genetics & connectivity:

Populations that are smaller than 100 breeding individuals have a high probability of extinction.
For a population to persist, they should be part of larger landscapes with other populations that are connected.
Small & isolated populations face a high probability of extinction. This is because small populations are subjected to chance / random events.

These chance events may cause them to lose advantageous genetic variants, while other, detrimental genetic variants might increase in frequency. This process is called genetic drift.
Individuals in small populations are likely to be related, leading to inbreeding.
This exposes many slightly disadvantaged genetic variants that are present in all genomes.
When expressed together, these detrimental genetic variants cause inbreeding depression and reduced survival, and reproduction of inbred individuals.
Most tiger populations are smaller than 100. On their own, most tiger populations do not have a high chance of survival.
Most tiger reserves in India are small & embedded in human-dominated landscapes.

Researches:

Tigers can be genetically sampled using their scat or excreta, hair, and other biological samples from different tiger reserves & analyzed in a laboratory.
Genetic variants in tiger DNA can be identified, analyzed, and compared across tiger reserves.
Sets of tiger reserves that show shared genetic variation are well connected.
On the other side, sets of tiger reserves that share less genetic variation must have barriers or landscapes that impede movement & connectivity.
Researches were made among tiger genetic samples in the central Indian tiger landscape & investigated genetic sharing between populations.
Surprising results were found that most land-use types were not too bad for tiger connectivity.
Presence of high-traffic roads, and built-up areas greatly impeded tiger movement.
Extinction of tigers could be avoided if corridors were safeguarded.
Fencing tiger reserves and isolating them resulted in high extinction.
As long as, we manage landscapes outside tiger reserves to allow tiger movement and protect prey and tigers inside tiger reserves, tigers are sure to survive in landscapes like central India.

Similipal tiger reserve:

It's always been wondered that the existence of black tigers is only in Similipal tiger reserve, Odisha.
The reason behind this is the genetic effects of isolation.
Genome sequences of a litter of zoo tigers that included pseudo-melanistic/black tiger cubs revealed that a single mutation in the specific gene causes these tigers to look this way.
The excreta/scat of Similipal tigers was studied showing that the tigers in Similipal form a small & isolated population.
It shows the genetic drift or random events that lead to this genetic variant of pseudo-melanistic coat colour.
In Rajasthan, genome sequences from wild tigers reveal that individuals in the Ranthambore tiger reserve show inbreeding.

Through this inbreeding, individuals are related & carry potentially disadvantageous genetic variants, which might affect the survival and the reproduction of tigers.

Strategies for the future:

Special attention is needed for populations that are becoming isolated and facing the genetic consequences of isolation.
The future of such populations may depend on genetic rescue or even the introduction of novel genetic variants.
It is fortunate that novel genome sequencing technology provides an opportunity to understand tigers much better in the context of their conservation.
The future of tigers will require a dialogue between such data and management strategies to ensure their survival.

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