This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Editor’s Note: “Along the Tiger’s Trail” is a series about the efforts to monitor tigers and their prey in the Malenad landscape in southwestern India that harbors one of the world’s largest population of wild tigers. The series tracks on-going annual activities of the world’s longest running research project on tiger and their prey, implemented under the leadership of Dr. K. Ullas Karanth of the Wildlife Conservation Society. These tales from the Indian jungles will take you through a virtual journey into the lives and work of people dedicated to the cause of India’s wild. For more posts in the series click here.
Hunched over a forest trail in Malenadu, WCS field scientists intently investigate animal signs amidst dust and leaf litter. They discover “carnivore researcher’s gold”: nothing more than scat, left behind by a tiger or leopard. They pick up a spoonful, store it in an ethanol vial, and note the GPS location and other observations.
In the nearby metropolitan Bangalore, these vials are re-opened in a sanitized laboratory. Extracting and analyzing the DNA from these scats–which are actually the poorest sources of DNA–geneticists in white coats open up a new world of information and opportunities for conservation.
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A century ago, long before Watson and Crick described DNA, India boasted of more than 60,000 tigers. Today, we are left with a population of around 2,000. Globally, tigers are found in less than 7 percent of their historic range. Many populations are confined to increasingly fragmented protected areas, making it imperative to understand the genetic consequences of such a drastic decline.
Is there enough genetic variability to maintain healthy populations? Are existing populations genetically isolated and doomed to extinction? The WCS India Program and its partners in the National Centre for Biological Sciences and Wildlife Institute of India have been using conservation genetics to answer these crucial questions and more. This has unveiled many fascinating aspects of tiger genetics, at a global to a local scale.
To begin with, our collaborative research has established that Indian tigers still retain more than 60 percent of the global genetic diversity. This highlights the importance of the tiger population in India to the survival of the species worldwide.
Combined with ecological and demographic knowledge, genetic studies have helped identify priority tiger conservation landscapes in India: Malenadu, central India and the Himalayan foothills. Studying the genetic make-up of individual tigers in a landscape, we can identify if they belong to a distinct population or to a meta-population with regular gene-flow warranting landscape conservation efforts. Further, understanding of genetic dispersal–where do tigers move and what factors define or hinder these movements–aids in devising appropriate landscape conservation strategies.
For instance, research in central India established connectivity between different tiger populations from six protected areas. The results also showed evidence of genetic dispersal over 400 miles! It additionally revealed dispersal over highly human-influenced landscapes, an indication of the animals’ situation as well as their survival instincts.
Genetics is now being used to study tigers at a much finer scale. Devising improved methods, our researchers have enhanced the accuracy of identifying not just species, but also individual tigers and their gender, based on fecal DNA. In a pilot study, we demonstrated how one can effectively estimate the population size of tigers living in smaller areas based on encounter histories of genetically identified individual tigers within the classical capture-recapture methodological framework.
In areas where you cannot assess tiger population density using the standard camera trapping method, one can do so by simply collecting scats! This technique has now become a boon to survey difficult-to-access areas that are a logistic nightmare for such surveys. Reliable individual identification also facilitates swift actions while dealing with ‘conflict’ tigers or seized tiger pelages. Using these genetic tools, our ongoing research is trying to understand tiger population dynamics in the entire Malenadu region for their continuing survival.
These genetic advances are also being used to assess the conservation status of species that do not have natural patterns on their skin unlike tigers and leopards.
Furthermore, our collaborators are now exploring the use of noninvasive genetic and endocrine measures to assess how physiological and reproductive health of tiger and leopard populations in Malenadu varies across a geographic gradient of human disturbances.
Conservation genetics is today an invaluable tool for wildlife management and science. As technology advances, we will be able to delve deeper and more accurately into the subject animal’s present and its past, and work more effectively towards securing its future.