Tiger Genes

Published: August 9, 2010 - 14:01 Updated: August 10, 2010 - 18:48

Is the tourism lobby of Ranthambore Tiger Reserve, which sees profits slipping if tigers are moved out, really behind the controversy surrounding tiger inbreeding? Or does declining genetic diversity seriously endanger India's national animal?

Akash Bisht Sariska/Jaipur

The Rajasthan forest department was in a celebratory mood recently when they shifted a new tiger from Ranthambore Tiger Reserve (RTR) to Sariska Tiger Reserve (STR) in the state. The endeavour - part of the relocation drive to repopulate the reserve that went tiger-bare after poachers wiped out the entire population in 2005 - is, however, now in jeopardy. 

Wildlife experts have raised doubts on the selection of the newly relocated tiger that has taken the count of tigers in STR to four. Experts believe it is difficult to ascertain whether the tiger sent to STR is actually the one that had been selected after DNA tests. The tests were conducted on eight tigers to ascertain their genetic compatibility with the Sariska tigresses; only two were considered fit for relocation.    
Dharmendra Kandhal, a biologist working in Ranthambore, informed Hardnews that the tiger might not be the one that had been selected after DNA tests. He revealed, "Scat (excreta) samples of tigers were sent to Bangalore for DNA tests to avoid genetic incompatibility. The area from where this tiger was selected was regularly frequented by more than eight tigers - so how did the forest department determine which scat sample belonged to whom?"

SP Yadav, DIG, National Tiger Conservation Authority (NTCA), didn't rule out the possibility and mentioned that "if it has happened, it is just another case of human error". "You can't expect a person to follow the tiger with a bucket in his hand to ensure that the scat samples are genuine," he said. 

To avoid this confusion, Kandhal suggests that a DNA dart could be used - the dart extracts the tissue sample and falls to the ground. "This is a much safer and accurate technology and avoids the uncertainty caused by the obsolete technology of collecting scats," informed Kandhal.   

The whole debate surrounding DNA testing surfaced after reports suggested that the three animals - one tiger and two tigresses - shifted to STR in the first phase of translocation between 2008 and 2009 are siblings. Wildlife authorities later confirmed the allegation. 

Wildlife experts, scientists and NGOs demanded that the new tigers should be brought in only if DNA tests confirmed that they are not closely related to the tigresses already in STR. Thereafter, the Bangalore-based National Centre of Biological Sciences conducted the tests and zeroed down on two tigers for relocation. 

Scientists believe that siblings find it difficult to breed and could trigger 'inbreeding depression' that could amplify the feline mortality rate. "Inbreeding is a condition where genetically similar individuals in a population breed with each other and over time individuals of the population become even more similar to each other. The population suffers from a loss of genetic diversity. This can lead to adverse conditions that result from inbreeding (inbreeding depression) such as muscle degeneration (observed in humans), low sperm count and quality, inability to fight some infections (lowered immunity) etc," apprised Dr Shomita Mukherjee, Principal Scientist, Salim Ali Centre for Ornithology and Natural History. 

However, officials in Rajasthan and Delhi call inbreeding a common phenomenon in the wild and believe that most animals in RTR are closely (or distantly) related to each other.

"The present tiger count in RTR is 40 while it was only 14 a few years ago. So, possibly, siblings mated with each other to take the population to its current numbers. There is an unnecessary issue that is being created by the media and so-called experts. Animals choose the best compatible partner to mate with, even if they are siblings. Weak genes are eliminated either by predation or by infighting and these are the rules of the forest," said RN Mehrotra, Chief Wildlife Warden, Rajasthan.

Mukherjee doesn't rule out this possibility and claims, "It need not always be the case that if related individuals breed, their offspring will always be at risk. But the probability that it will, increases with inbreeding." It is perceived that the genes of the RTR population could be severely damaged because of extensive inbreeding. 

To ensure genetic variation, tigers could be brought in from other geographical locations, especially the central zone comprising Madhya Pradesh and Maharashtra. Media reports had earlier highlighted that the central government tried to persuade Madhya Pradesh and Maharashtra to donate a few tigers so that the gene pool of STR could be diversified. However, MP's forest minister made it clear that they had no surplus tigers to donate and refuted claims of receiving any such request from the ministry. 

Even the NTCA denies knowledge of any such request. "I am not aware of any such request made by the ministry. We are also reviewing the study done by SP Goyal, a Wildlife Institute of India (WII) scientist, wherein he has mentioned that gene pools of different geographical regions should not be mixed," Yadav said.

Hardnews spoke to Goyal and has a copy of the study in which concerns have been raised about mixing tiger populations of different geographical areas - northern, north-eastern, southern, western and central - that have distinct genetics.

Refuting these claims, Mukherjee said, "I have no clue why and on what basis Goyal says tiger populations cannot be mixed. The barriers and fragmentation of habitat that we see today are all due to human-made changes. In fact, tigers should be brought from other places. On the one hand, we rant about fragmented landscapes and talk of connecting these with corridors for greater genetic exchange, and then when we have a chance, we bring in related individuals from a very similar population."
Kandhal agrees with Mukherjee that instead of donating tigers, the two states could work on an exchange programme wherein certain tigers from Ranthambore could be sent to MP and vice versa: "This would help in maintaining a wide pool of genes of tigers and both the states could benefit."

To the forest department's embarrassment, the first tiger relocated to STR failed to impregnate the two tigresses despite mating. Experts believe that since the tigers are closely related, it could have aggravated the problem. "It is foolish to say that the tiger has been unable to impregnate females because of their being closely related. There could be a host of other issues that could lead to this situation," said Yadav.

A WII scientist who has been monitoring the tigers in Sariska told Hardnews that tigers have been mating frequently and one of the tigresses has even shown signs of pregnancy. "We could not confirm it as the tigress gets very secretive when pregnant and any disturbance could lead her to stray to the periphery, which could be very dangerous for the animal," he said.

However, KK Garg, Field Director, STR, denied pregnancy of any of the tigresses and maintained that the tigers are too young to produce litter and would only show results in a year's time. "Come after a year and these tigers would produce a healthy litter," said Garg. This fact is refuted by Yadav who said that the tigers are of the right age and healthy enough to mate successfully. He believes that the male tiger could be sterile, but wants to wait before passing the final judgment.  

Additionally, this relocation of unrelated tigers from RTR also violates the International Union for Conservation of Nature (IUCN) guideline that strongly suggests that taking away genetically unrelated animals from a bottlenecked population, as in the case of RTR, would lead to serious inbreeding. 

Even NTCA guidelines that have been adapted from IUCN mention that breeding individuals from host populations should not be translocated, but the guideline has been flouted. "The recently relocated tiger (T-12) belongs to the breeding population and has recently mated with a tigress that is carrying his litter," a source said. 

Kandhal also claims that the Rajasthan forest department flouted an NTCA guideline which states that male tigers between two to four years and females between two to three years, who are independent of the mother but are yet to establish their territory, should be chosen for translocation. 

Kandhal said that T-12 is between the age group of six to seven years and has a territory of his own in the core area. He reveals that instead of choosing a sub-adult who is yet to establish his territory, the forest department went ahead with T-12. "Why has the Rajasthan forest department shifted a tiger that could threaten the host population? They are compromising with the social structure of RTR and it will have an adverse implication on the tiger population of the park," he said.

Responding to this, Yadav mentions that NTCA guidelines have been followed and T-12 was a 'floater' that occupied the peripheral forests. This, Yadav believes, would not compromise with the 'social structure' of the RTR. "We were given a report by the Rajasthan forest department and acted accordingly," said Yadav.

"We have surplus tigers in RTR and they are finding it difficult to find a territory and hence roam around in peripheral forests. This makes them very vulnerable to increasing human-animal conflict that could lead to poaching," said Mehrotra. He added that saturation of tiger numbers in the park is also leading to increasing infighting among the animals and leading to higher mortalities. Two tigresses recently succumbed to injuries after infighting, while villagers poisoned  two young tigers to death. 

Interestingly, RTR's geographical area equals that of Jim Corbett Tiger Reserve, which boasts four times the number of tigers in RTR. The reason: out of the total 1,300 sq km of RTR, only 300 sq kms is inhabited by tigers while the rest has a shortage of prey base, suffers from massive anthropogenic pressure, and is considered unsafe for animals. The Rajasthan forest department has been unable to manage the remaining 1,000 sq km that includes the Sawai Man Singh sanctuary, the Kela Devi sanctuary and reserve forests.

"The surplus tigers are those that stray out of the 300 sq km and occupy the rest of the park. But since these parks are not well managed, the best bet is to shift these tigers to Sariska rather than let them be poached," said a WII expert. 

"We are trying to relocate villages from this area, but it cannot be done in a fortnight as we live in a democratic country where everybody's rights have to be taken into consideration. Also, the enactment of Forest Rights Act has made relocation of villages a little more difficult," said Mehrotra. 

However, he believes that the entire controversy surrounding genes, inbreeding, floaters et al is being created at the behest of the strong tourism lobby of RTR that believes moving tigers out from the reserve could mean lesser tiger sightings and eventually a sharp drop in profits. He feels that STR would soon boast a healthy tiger population, laying all speculation to rest. "Is restricting inbreeding at the cost of losing a species a viable solution?" he asked.

Meanwhile, the villagers in the heart of STR, unaware of the controversy, believe that the real tigers of STR have been lost forever. "The tiger that the forest babus got from RTR behaves more like a dog. It follows vehicles as if he is waiting for people to drop food and growls like a domestic cat. The tigers that once ruled our forests were ferocious and roamed like kings. No wonder this tiger has not been able to mate successfully," said a grinning Nanakram Gujjar of Haripura, a village within the STR core.

Is the tourism lobby of Ranthambore Tiger Reserve, which sees profits slipping if tigers are moved out, really behind the controversy surrounding tiger inbreeding? Or does declining genetic diversity seriously endanger India’s national animal?
Akash Bisht Sariska/Jaipur

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This story is from print issue of HardNews