A team of scientists has resolved the genetic mystery of Simlipal’s so-called black tigers.

What are Black Tigers?

• Tigers have a distinctive dark stripe pattern on a light background of white or golden.
• A rare pattern variant, distinguished by stripes that are broadened and fused together, is also observed in both wild and captive populations.
• This is known as pseudo-melanism, which is different from true melanism, a condition characterized by unusually high deposition of melanin, a dark pigment.
• This pseudo-melanism is linked to a single mutation in Transmembrane Aminopeptidase Q (Taqpep), a gene responsible for similar traits in other cat species.

Where are they mostly found?

• While truly melanistic tigers are yet to be recorded, pseudo-melanistic ones have been camera-trapped repeatedly, and only, in Simlipal, a 2,750-km tiger reserve in Odisha, since 2007.
• Launched in 2017, the study was the first attempt to investigate the genetic basis for this unusual phenotype (appearance).

Why they are rare?

• Mutants are genetic variations which may occur spontaneously, but not frequently, in nature.
• A cub gets two copies of each gene from both parents, and a recessive gene can show up only in the absence of the dominant one.
• So, two normal-pattern tigers carrying the recessive pseudo-melanism gene will have to breed together for a one-in-four probability of giving birth to a black cub.
• But recessive genes are rare and it is unlikely that two unrelated tigers will carry the same one and pass it on together to a cub.

Connection with Simlipal TR

• In an ideal tiger world, where far-ranging individuals are never short of choices for partners, that makes succession of black tigers a rarity.
• Under exceptional circumstances, a black tiger may succeed as part of a very small population that is forced to inbreed in isolation for generations.
• As it turned out, that is what happened at Simlipal.
• Pseudo-melanistic tigers are also present in three zoos in India — Nandankanan (Bhubaneswar), Arignar Anna Zoological Park (Chennai) and Bhagwan Birsa Biological Park (Ranchi) — where they were born in captivity.
• All of them have ancestral links to one individual from Simlipal.

What about natural selection?

• Natural selection eliminates the weakest from a gene pool, and the traits of the more successful get passed on.
• Niche modelling, the study said, shows higher frequency of melanistic leopards in darker tropical and subtropical forests than in drier open habitats.
• Likewise, darker coats may confer a selective advantage in both hunting and avoiding hunters in Simlipal’s tropical moist deciduous and semi-evergreen closed-canopy forest, with a relatively darker understory.

Try this PYQ:

Two important rivers – one with its source in Jharkhand (and known by a different name in Odisha), and another, with its source in Odisha – merge at a place only a short distance from the coast of Bay of Bengal before flowing into the sea. This is an important site of wildlife and biodiversity and a protected area.

 

Which one of the following could be this?
(a) Bhitarkanika
(b) Chandipur-on-sea
(c) Gopalpur-on-sea
(d) Simlipal

 

Post your answers here.

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Back2Basics: Project Tiger

• Project Tiger is a tiger conservation program launched in April 1973 during PM Indira Gandhi’s tenure.
• In 1970 India had only 1800 tigers and Project Tiger was launched in Jim Corbett National Park.
• The project is administrated by the National Tiger Conservation Authority (NTCA).
• It aims at ensuring a viable population of Bengal tigers in their natural habitats, protecting them from extinction etc.
• Under this project the govt. has set up a Tiger Protection Force to combat poachers and funded relocation of villagers to minimize human-tiger conflicts.

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