Putting Together the Pieces to Prevent Tiger Extinction
Two hundred years ago, over 60,000 tigers lived in India. This figure has since decreased by 90 percent. Today, fewer than 3,500 tigers remain in the wild, and only seven percent of the historic tiger habitat remains. These habitats, mostly scattered across India, are becoming increasingly isolated as the country continues to urbanize. Dr. Uma Ramakrishnan, a population geneticist and biodiversity ecologist at India's National Centre for Biological Sciences, uses genetic information from tigers and landscape modeling of India to help curtail this disturbing trend.
Dr. Ramakrishnan examines past and present tiger genes to compare the differences in genetic variants. In order to extract DNA from the past, she took small pieces of tissue from 200-year-old tiger pelts, borrowed from the London Museum of Natural History. Country of origin records accompanied each of the tiger skins, so she was able to map out historic tiger habitats.
Some of these skins came from Afghanistan, where tigers don’t exist today. “DNA is like having a time machine; each string has a unique identity and story, and all of this information is recorded in its sequence. DNA is stable enough where we can piece together information even from these old skins to understand variation in the past that we would otherwise have no possibility of understanding,” said Ramakrishnan.
To get current DNA, Ramakrishnan and her team tracked down tiger feces from forests in several states across India. Since the specimens come from tigers indirectly, the DNA is fragmented and much harder to read. “It’s like detective work trying to figure the story this particular tiger tells us about the tiger species as a whole; all of this is without actually having seen the tiger,” said Ramakrishnan. She then used the excrement information to determine whether the tigers were natives or immigrants to the area, and mapped these current patterns on top of the historic information collected from the tiger pelts.
Recently in her work, Ramakrishnan uses SNP genotyping, which enables her to map each tiger’s individual DNA using thousands of bits of information from the genome. “Imagine a puzzle and you just have small, random pieces. It’s very difficult to determine the whole picture. But imagine that you have 300 pieces, and the puzzle starts to take a better picture form. That’s what we’re trying to do with SNPs,” said Ramakrishnan. “We’re looking at minuscule parts of the genome, and we need to sequence them to understand the whole picture.” Sequencing genomes has become faster and more precise since she initially started her work. It is now possible to determine much more information from a single strand of degraded DNA. This helps Ramakrishnan to be more conclusive in her findings and make better recommendations for the future of wild tigers.
Ramakrishnan’s findings show that the disconnected tiger populations have high levels of relatedness, and certain populations are completely inbred. Since tigers are forced into small areas, there are fewer genetic variants within isolated populations, but more differences between the populations. Tigers across India are not able to share genes as easily because there is a loss of connectivity. They seem to avoid areas of high traffic and human population density. Due to increasing urbanization in India, it is becoming more difficult for tigers to travel long distances. This lack of tiger movement and, therefore, high level of inbreeding, means tigers are potentially headed toward extinction.
“We have the responsibility to safeguard the future because human intervention is the reason that tigers run the risk of becoming extinct. We are the reason they live in fragmented, small reserves today, and we need to find solutions to cohabitate,” said Ramakrishnan.
As conservation becomes much more data-driven, easy fixes like conserving plots of land are not the answer. India is in the intermediate stages of development, so it is not feasible for tigers to freely roam across the country anymore. “We’re not going to be able to veto development plans and set aside huge tracts of land. It’s not practical, and we must think differently,” said Ramakrishnan.
Other options for conservation include assisted migration, where scientists would physically move the animals across India. Ramakrishnan thinks this should be used as a last-case scenario because it further interferes with the natural system. Therefore, it runs the risk of reaping unintended consequences that speed up the process of extinction.
The preferred solution is collaboration with the Indian government so that inevitable city planning does not completely disrupt biodiversity. Without scientific knowledge, policymakers may not understand that there are major implications on where they decide to build. “If we come in with our data and say ‘You can build a highway here and this is the impact it will have on tigers versus building a highway there,’ they can be informed and make better developmental decisions,” said Ramakrishnan.
Her work is not only relevant for India and the tiger population, but for conservation on a global basis. The process of genetic mapping can be used to look at other animals’ interactions with increasingly urban populations. Tigers are not the only population that is disrupted by encroaching land development, and scientists need to understand how populations will respond as the urban population expands and wildlands shrink.
The Field Museum will honor Ramakrishnan with the Parker/Gentry Award at the Conservation Celebration on Monday, April 18. This award honors an outstanding individual, team or organization in the conservation biology field whose efforts have made a significant impact on biodiversity and whose process and approach can serve as a model to others.
By Becca Conley, Public Relations Intern
