Diverse gene pool critical for tigers' survival, say experts

New research by Stanford scholars shows that increasing genetic diversity among the 3,000 or so tigers left on the planet is the key to their survival as a species.

Iconic symbols of power and beauty, wild tigers may roam only in stories someday soon. Their historical range has been reduced by more than 90 percent. But conservation plans that focus only on increasing numbers and preserving distinct subspecies ignore genetic diversity, according to the study. In fact, under that approach, the tiger could vanish entirely.

"Numbers don't tell the entire story," said study co-author Elizabeth Hadly, the Paul S. and Billie Achilles Professor in Environmental Biology at Stanford and senior fellow at the Stanford Woods Institute for the Environment. She is a co-author of the study, which was published April 17 in the Journal of Heredity.

That research shows that the more gene flow there is among tiger populations, the more genetic diversity is maintained and the higher the chances of species survival become. In fact, it might be possible to maintain tiger populations that preserve about 90 percent of genetic diversity.

Rachael Bay, a graduate student in biology at Stanford's Hopkins Marine Station and the lead author of the study, said, "Genetic diversity is the basis for adaptation."

Loss of diversity

The research focused on the Indian subcontinent, home to about 65 percent of the world's wild tigers. The scientists found that as populations become more fragmented and the pools of each tiger subspecies shrink, so does genetic diversity. This loss of diversity can lead to lower reproduction rates, faster spread of disease and more cardiac defects, among other problems.

The researchers used a novel framework, based on a method previously employed to analyze ancient DNA samples, to predict what population size would be necessary to maintain current genetic diversity of tigers into the future. The authors believe this new approach could help in managing populations of other threatened species.

The results showed that for tiger populations to maintain their current genetic diversity 150 years from now, the tiger population would have to expand to about 98,000 individuals if gene flow across species were delayed 25 years. By comparison, the population would need to grow to about 60,000 if gene flow were achieved immediately.

Neither of these numbers is realistic, considering the limited size of protected tiger habitat and availability of prey, among other factors, according to the researchers.

Limited habitat

"Since genetic variability is the raw material for future evolution, our results suggest that without interbreeding subpopulations of tigers, the genetic future for tigers is not viable," said co-author Uma Ramakrishnan, a former Stanford postdoctoral scholar in biology and current researcher at the National Centre for Biological Sciences in Bangalore, India.

Because migration and interbreeding among subspecies appear to be "much more important" for maintaining genetic diversity than increasing population numbers, the researchers recommend focusing conservation efforts on creating ways for tigers to travel longer distances, such as wildlife corridors, and potentially crossbreeding wild and captive tiger subspecies.

"This is very much counter to the ideas that many managers and countries have now - that tigers in zoos are almost useless and that interbreeding tigers from multiple countries is akin to genetic pollution," said Hadly. "In this case, survival of the species matters more than does survival of the exclusive traits of individual populations."

Understanding these factors can help decision-makers better address how development affects populations of tigers and other animals, the study noted.

Conservation efforts for other top predators have shown the importance of considering genetic diversity and connectivity among populations, according to the report. One example is Florida panthers: since individuals from a closely related panther subspecies were introduced to the population, Florida panthers have seen a modest rise in numbers and fewer cases of genetic disorders and poor fitness.

The Eurasian lynx as a key to the conservation and future viability of the endangered Iberian lynx

Understanding the mechanisms which control reproduction in lynx is essential for their continued viability and effective conservation.

A team of international scientists from Europe discovered that the Corpus luteum of the Eurasian lynx (Lynx lynx) has the longest lifespan among mammals known to date. This hormone producing tissue is responsible for restricting this lynx species (and presumably the other lynx species as well) to only having one estrous cycle per year (mono-estrous) and therefore only one opportunity per year to become pregnant. The findings were published in the scientific journal PLOS ONE.

The Eurasian lynx recovered in many parts of its European range.

The scientists from the Leibniz Institute for Zoo and Wildlife Research in Berlin (IZW) took the Eurasian lynx as a "model" species to investigate the reproductive cycle of lynxes in order to assist in the conservation of the highly endangered Iberian lynx (Lynx pardinus), the most threatened cat species worldwide, restricted to a few locations in southern Spain. A key component in the conservation strategy for the Iberian lynx are the captive breeding centers in Spain and Portugal where Iberian lynx are bred in order to be re-introduced back into the wild. Improving reproductive performance in captivity entails a thorough understanding of the mechanisms that facilitate reproduction in these felids.

The team's key discovery is that lynxes have corpora lutea (CLs, the gland producing the pregnancy hormone progesterone) which are maintained in their ovaries over many years -- the longest lifespan known in mammals, and therefore indicative of a reproductive strategy unique for felids -- and probably for mammals in general. In other species, the CLs disappear before, or shortly after, the female gives birth. Surprisingly, the female lynx can switch off its CL's progesterone production when entering a new cycle during spring or before giving birth without destroying the CL. Later on, progesterone is produced continuously, suppressing the follicular development in the ovary and therefore preventing the onset of a second oestrus cycle within the same year. If a female cannot mate during its 5 -- 7 estrous days per year, an entire reproductive period will therefore be lost, reducing fertility and effective lifetime reproductive output, a substantial problem for a small population such as the Iberian lynx.

"To obtain these results, our international team followed the reproductive cycles of captive Eurasian lynx in German zoological gardens and of free-ranging Eurasian lynx in Norway with the help of a Norwegian wildlife research project, Scandlynx, over a period of almost three years. We used advanced three-dimensional ultrasound techniques and in-house hormone analyses to uncover the mysterious development of the oestrus cycle," says veterinarian scientist Johanna Painer from the IZW.

Europe is home to two Lynx species, the Eurasian lynx and the Iberian lynx. Both species experienced drastic declines in population size during the last century. Whereas the Eurasian lynx recovered in many parts of its European range with the help of re-introduction projects, the population of the Iberian lynx crashed completely and was declared to be the most critically endangered felid species worldwide, today.

It is unknown to what extent lynxes will have the flexibility to adapt their reproduction to anthropogenic environmental changes. This study provides essential information for the assisted reproduction techniques in Iberian lynx which continue to be refined and improved, such as artificial insemination or embryo-transfer. Future research will focus on the manipulation of reproductive cycles to increase the reproductive output for breeding centers and to discover the molecular mechanism underlying this unique phenomenon.

TIGER FOUND DEAD

  A tiger was found dead in suspicious circumstance with its limbs missing in the Nllamala Forest in Mabhubhnagar district. Though the big cat reportedly died two days ago, the incident came into light on Thursday when the Shepherds alerted the local officials. It is suspected that the smugglers kills the tiger and cut off its limbs for nails due to the high demands of then\m in the international market. The carcass of the tiger was found at Rushula Cheruvu in the Munnanoor forest range. Rushula Cheruvu is major source of water for the wild animals. That's why the smugglers always keep an eye on this.
              Though the officials also suspected that the tiger was old enough, so it can be possible that the tiger was dead because of its age, and after the death of that big cats, the smugglers came and took away its limbs. The Post-mortem report will ensure the real cause of the death of this tiger.

FUTURE OF THE SIBERIAN TIGER

INTRODUCTION

          Siberian tiger (Panthera tigris altiaca), also known as the Amur tiger is the largest living big cat and also ranked among the biggest felids that ever exists in the world. Amur tiger once found throughout the Russian Far East, north China and the Korean peninsular. By the 1940s, hunting has driven the Amur tiger to the brink of extinction- with no more than 40 individuals remaining in the wild. The subspecies was saved when Russia become the first country to grant the tigers full protection. By 1980s, the population increases around 500. Although poaching increases in these days, the number of the Amur tiger in the wild is now stable (400-500).

THREAT FOR THE SIBERIAN TIGER

         The main threats for these tigers today are the habitat loss, very low density of prey and poaching. 

FUTURE OF SIBERIAN TIGER

         The future of these tiger completely depends on the human. If we do not care, then these tiger will extinct in future. At present these Amur tigers are Endangered species according to IUCN 3.1 Red List. 

WHAT TO DO

       To save these creature the best we can do is to do nothing i.e. leave them in the wild, do not interface their life. But all of us know that is impossible today. So we have to do a lot to save them. 

MY THOUGHT TO SAVE AMUR TIGER

       Here is my thoughts to save them. 

1. We use camera traps to watch whole movement of the Amur tigers.

2. Use radio- collars for their exact locations.

3. Capture some of the pregnant tigress and transfer them to a safe location or area where we can monitor them 24 hours. But those tigress must not feel caged.

4. When the tiger cubs are old enough we transfer them to the wild.

5. To deal with the poachers, the government must enforce new laws and strict punishment for the poachers.

PROBLEMS AND HOPE

       Still there is no solution for the habitat loss and the low prey density though we knew the cats are the best in adaptation and evolution. So we hope the life will find its way and these Amur tiger find there way of life and will not extinct in future.

LAND VANISHES IN EAST SUNDARBANS

           The upper Bidya and Raimangal regions in the Sunderbans, key human and wildlife habitat in the eastern  parts of the mangroves, are under severe threat of inundation due to the sea-level rise.

           A recent study by the World Bank and the Institute of Environmental Studies and Wetland Management (IESWM) has suggested to de-populate parts of some islands along the fringe areas on this parts so that the existing embankments can be moved back to allow a wider tidal channel to develop. This will, in turn, lead to deposition of sediments which can raise the land faster than the sea level rise.

            The study has also alerted  if the sedimentation can’t keep pace with the sea level rise- believed to happening at 3 millimetres annually- the Sunderbans may see a huge loss of mangroves which will put the survival of the endangered Royal Bengal tiger at risk. A recent camera trap report has captured presence of at least 55 tigers on this part of the mangroves.

            Agreeing to the report WWF-INDIA’s Sunderbans chapter head Anurag Danda said there is a need to De-populate some islands, as once these erode the man groves will get new sediments which will help it flourish in the future.

            But for now, the fate of 3.5 million people living within 20 km of the mangroves’ northern and eastern boundaries and more than 50 tigers believed to be ruling the forests of its eastern region hang in the balance.

             However, the IESWM senior scientist Somenath Bhattacharyya is of firm opinion that with proper modelling a d consequent management, it is possible to save the Sunderbans even with 1 metre sea level rise.

              The West Bengal Govt. has to handle this matter very sincerely as this is very important issue of the ecosystem. It’s already proved that the Sunderbans is the only habitat where the tigers have maintained their own regions. Why this endangered species do not have the attention of the WB Govt. is a very interesting question. May be they have no voting power, that is why they are neglected so far.