Researchers at National Centre for Biological Sciences (NCBS) in Bengaluru have developed, a first of its kind, non-invasive method for identifying the age, sex, and reproductive status of tigers and leopards from the chemical signatures left behind in their urine and scat, offering conservationists a powerful tool for tracking two most elusive big cats in the wild.
Supported by a grant from the National Geographic Society, the study was recently published in the Journal of Chemical Ecology, in collaboration with Ahmedabad University, with samples collected from zoos in Bengaluru, Ahmedabad and Vadodara, and Ranthambore Tiger Reserve in Rajasthan.
“This study presents the first chemical characterization of tiger and leopard scats and the first sampling of tiger odours from the wild. Our simple and cost-effective method of sampling tiger and leopard odours offers a novel method of chemical fingerprinting to monitor populations in situ,” claimed the paper titled “Non-Invasive Sampling of Odours from Tiger (Panthera tigris) and Leopard (Panthera pardus) for Wildlife Conservation”.
Clues from urine and scat
“Tigers and leopards are elusive, solitary, and endangered, making them notoriously difficult to monitor in the wild. Big cats, however, leave a scent when they roam the forests. They mark territory with urine and scat, both laced with volatile organic compounds (VOCs) that carry information to other animals,” explains the report.
“Current monitoring methods, like camera traps and genetic sampling, can estimate how many big cats are out there, but they fall short on the demographic and physiological details that matter for better monitoring- age, sex, reproductive status. Volatile organic compounds are known to carry this kind of information in other species, which makes our approach promising,” says the first author BV Aditi Prasad.
According to the report, the research team collected urine and scat from nine captive tigers and 15 captive leopards across three zoos, as well as urine from 28 individually identified wild tigers in Ranthambore Tiger Reserve. This is the first time tiger odours have been sampled directly from wild individuals.
Tell-tale chemicals
Volatiles were captured on small silicone sorbent tubes and analysed using thermal desorption gas chromatography-mass spectrometry to identify which compounds reliably predicted species, sex, age, and reproductive status.
They found that these samples could reliably identify species using both urine and scat volatiles, with compounds like γ-dodecalactone and 2-decanone distinguishing tiger from leopard urine, and δ-valerolactam, p-cresol, and 2-ethylhexanol doing the same in scat.
The team could also predict sex and age from specific volatile combinations, though accuracy was lower for males and older individuals, a pattern the researchers link to greater individual variation in these groups.
Aditi and team were also able to pinpoint signals of reproductive status in wild cats. They found that another compound, 2-nonanol was markedly elevated in the urine of pregnant and lactating wild tigresses compared to non-reproductive females.
They could also examine health in captive tigers. During their study, they came across a captive tiger being treated for epilepsy. The scat of the individual showed elevated levels of dimethyl tetrasulphide. Although this finding is based on a single animal, it hints at the potential for VOCs to flag health complications.
Health trackers
“Detecting chemicals in urine and faecal matter has been widely used in nutrition, medicine, and forensics. Applying such techniques to conservation offers researchers and managers the opportunity to directly monitor individual statuses for population health and safety,” says Shannon B. Olsson, supervising author. “Because collecting fresh samples from wild animals is difficult, our technique offers a simple strategy to detect some of these chemicals after the animal has left the area,” said the scientist adding that further studies can improve the accuracy of this technique and offer more insights on monitoring a variety of wild animals beyond big cats.
“The novel chemical ecology tools showcased here when integrated with other approaches are sure to help us understand, and conserve, these amazing animals better,” says Uma Ramakrishnan, NCBS.