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.
Every fall, our field biologists in India begin their eight-month long tenure in the spectacular forests of the Western Ghats. Multiple teams embark on an arduous march, scanning nearly every inch of the dirt roads in these Malenad forests in southwestern India. Much like detective work, this can be an exciting and endearing experience – tracking wild animals based solely on indirect evidence of their presence.
First, a pungent smell on the trunk of a Terminalia tree by the path teases the senses, alerts us to a big cat’s scent mark. A little distance away, there is a series of unmistakable saucer-sized pugmarks along the dirt road. A couple of steps ahead and we find what can aptly be described as a carnivore biologist’s gold. Two deep scrape marks with loose grass torn off the path and at the other end, a mass of black, wet tiger scat teeming with flies.
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Wild animals in tropical forests are generally elusive and often hard to spot or observe directly. However, many animals, including tigers, leave telltale signs of their presence, which can provide incredible information about their secretive lives. Among the many indirect pieces of evidence of animals’ presence is their “poop” or fecal matter. We call this “dung” for large herbivores like elephants, “pellets” for animals like deer, and “scat” for large carnivores such as tigers, leopards and dholes. These bits of animal excreta can provide useful insights about individuals, populations and communities.
We analyze carnivore scats in our research to generate data on multiple species. Research by the WCS in India has relied on scat, dung and pellet surveys to obtain information on tigers, leopards, dholes, their prey, and other large mammals across 12,000 square miles (30,000 square kilometers) of Malenad. Our field teams walk hundreds of miles along forest roads and trails, recording evidence of animal signs and in rare instances, some fortuitous sightings of charismatic carnivores.
Different types of fecal matter, with their distinctive physical appearance, size, content and even smell, provide insights about the species that produced them. Sighting of tiger scat therefore can inform us of the cat’s presence in the area. By meticulously examining the undigested hair of prey remains in scat, we can identify what a tiger has eaten. Our scientific work has applied this to compare the prey preferences of tigers and those of leopards and dholes. The three species, sympatric through much of the Malenad landscape, prey on the same suite of herbivores such as chital, sambar, gaur, wild pig and barking deer. However, by studying their scats, our research showed nuanced differences in prey preferences among the three carnivores, a mechanism to avoid intense competition and facilitate co-existence.
Advances in the field of genetics allow us to use these scats for identifying species without even having to see the animals themselves. Furthermore, with certain reliability, it is possible to also identify individual tigers based on DNA extracted from their scat. In collaborative efforts with scientists at the National Centre for Biological Sciences, we developed novel genetic methods to extend the classic capture-recapture models (earlier tested using camera-trap photographs) to reliably estimate tiger populations based completely on genetic data from their scats. With recent developments in this field, we can now distinguish species, ascertain gender and also associate individual tigers and leopards with the sub-population from which they originate. These developments open up a whole new window of possibilities where we can estimate population sizes, understand genetic connectivity and track crucial dispersal events that ensure long-term viability of wildlife species.
The past few decades have seen wildlife biologists increasingly appreciate the utility of non-invasive “sign surveys” to understand elusive animals like the tiger. Such surveys, besides being cost-effective, provide insights into carnivore ecology using a method that is simpler than camera trapping or fitting animals with expensive radio-collars. Surveys relying on indirect signs have helped us determine the distribution patterns of tigers across space, and can even reveal changes in their distribution over time. In doing so, these approaches have enhanced our ecological understanding of a suite of large mammals in the Malenad landscape.