Use of genetics in captive breeding:

No matter which category an animal falls into biologists must know they're breeding for stability and health.

Studbooks are kept for each tiger subspecies and the history of each animal carefully tracked.

Genetic testing can show how closely related each animal is to another, whether or not they are suitable breeding partners and what, if any, undesired outcomes there are likely to be.

It can also detect genetic pollution, a situation which arises through hybridisation and makes a tiger unsuitable for use in a captive breeding programme -- plus it can be used to establish where  a tiger skin may have been misidentified. The mounted tiger on this page was originally identified in a Natural History Museum as a Caspian/Amur cross. In the normal scheme of things a living specimen of this animal would not be able to be listed in either the Caspian or the Amur studbook, since it is neither one nor the other. The skin is now identified as a Manchurian(Amur)/Bengal cross, a much more likely combination.

Inbreeding becomes a problem once a group shrinks to 50 individuals or less. It results in serious problems including blindness, cleft palate, sway backs and crossed eyes. Ultimately, inbreeding leads to weakened immune systems and lowered rates of cub survival. The ability of a small inbred group of wild tigers to fight off a sudden virus can reduce to such an extent that catastrophic loss of the population occurs in the event of illness.

In captivity, biologists can use genetics to ensure the risk of inbreeding is significantly lowered, so giving the tiger a greater chance of developing healthy long-lived stock from which to breed in the future. For instance, the pair shown on this page were not permitted to mate as they are father and daughter. When she was not yet sexually mature he engaged in sex play such as that shown here. She was then transferred to another zoo to continue the bloodlines.

Testing wild tigers:

A recent discovery which came about after genetic sampling was that the Bengal tigers located in Dudhwa Tiger Reserve are not of pure stock. India spends about US$75 million a year to protect its tigers and maintain genetic purity, yet hair sample testing on two tigers in this area revealed Amur genes.

It is now considered extremely important further genetic testing is carried out in Dudhwa Tiger Reserve so as to establish how widespread this genetic pollution is.

Testing privately owned tigers:

Recent efforts have been made to encourage private owners to have their tigers genetically tested. This is not a practice that hurts the animal and DNA tests can be run from gathering up naturally shed hair, stool samples, or blood obtained during routine examinations.

From the testing that has been carried out to date a reasonable number of purebred tigers have been discovered. It was previously thought that few privately-owned tigers were of breedable stock, but this may not necessarily be correct.

Newly discovered purebred cats can assist in the conservation of the tiger as a whole as some can be used for breeding; this then extends the gene pool. The more cats involved in a breeding programme, the less the issues caused by inbreeding.

The South Chinese tiger:

The South Chinese tiger subspecies is extremely inbred, both in the wild and in captivity. The population numbers no longer exist to breed without high probability of some undesirable side effects.

Well before such inbreeding occurs it would be usual to seek out new 'founder' tigers. An animal is termed a founder if it has no relatives already in the local captive population, and so is an entirely new genetic line. Founders may be wild caught or imported from a breeding program in another region. With the South Chinese tiger neither of these things is possible.

Suggested reading:

Tiger Missing Link Foundation

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Photography With Thanks To S. Hartwell (Photo 1)
Ralf Schmode (Photo 2)
Aditya Singh (Photo 3)

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