The forests are ruled by the cat families. They are feral, ferocious and far too similar, so spotting them is never an easy task. For researchers studying big cats, this means looking into the traces they leave behind. If you have ever been on a safari and your guide has pointed towards their paw prints, scratch marks or droppings, you know that they are onto something and so are the researchers. While these signs have long helped researchers understand which animal might have passed through an area, it can leave behind traces of its presence without ever appearing in front of a camera or a person. But did you know that even the odour of a tiger's urine or scat could offer clues about the animal, including the species it belongs to and possibly aspects of its age, sex and reproductive health? A study published in the Journal of Chemical Ecology on May 29, 2026, explored chemical compounds released by tiger and leopard urine and feces, leading researchers to distinguish between the two species and question the veracity with which they can be differentiated. The study, titled Non-Invasive Sampling of Odours from Tiger (Panthera tigris) and Leopard (Panthera pardus) for Wildlife Conservation, was conducted by researchers from the National Centre for Biological Sciences (NCBS), Ahmedabad University and the Danish Academy of Technical Sciences. The researchers were at first interested in volatile organic compounds (VOCs), which are chemical compounds that evaporate and are released into the air. These compounds can carry information about an animal's physiological appearance and can play a role in how anials communicate amongst themselves. By examining the chemical composition of urine and faeces, researchers had hoped to identify patterns that could help distinguish one species from another, whilst also seeing what other information could be gathered about the individual species. To investigate this, the team collected urine and scat samples from captive Bengal tigers and Indian leopards whose ages and sexes were known. They also collected urine samples from identified wild Bengal tigers, for which information about age, sex and reproductive status was available. This allowed them to examine whether the chemical signatures found in the samples corresponded with characteristics that were already known about the animals.
Collecting the samples was only one part of the process. The researchers used a technique called headspace solid-phase field sampling to capture the volatile compounds released by the urine and faeces. These compounds were then analysed using thermal desorption-gas chromatography-mass spectrometry. The team then used a machine-learning technique, called Random Forest, to monitor the chemical patterns and identify compounds that could serve as possible indicators of species, age, sex and reproductive state. Researchers were able to classify tigers and leopards with an accuracy of approximately 79% using urine samples and 75% using scat samples. The study also revealed that these chemical markers could offer clues about age and sex, although the veracity varied depending on the group being examined. Urine samples provided stronger classification results for females and younger individuals, while older animals and males were more difficult to distinguish. Scat samples, meanwhile, performed better across different groups.
Perhaps one of the more interesting aspects of the research is the possibility that animal odours could reveal information beyond species identification. The researchers also identified potential chemical markers associated with reproductive status in tigers. One of the findings concerned nonanol, a compound found in higher abundance in urine samples from pregnant and lactating female tigers than in non-reproductive females. The team also observed elevated levels of another compound, dimethyl tetrasulphide, in the scat of a captive tiger being treated for epilepsy. However, this finding came from an individual animal and would require further investigation before the compound could be considered a reliable indicator of the condition. While these findings are only in their preliminary phase, they do open up an interesting possibility for wildlife monitoring. Details about an animal's reproductive state for instance could help understand the population and breeding patterns without actually having to physically examine the animal.
Monitoring big cats in their natural habitats often involves techniques such as camera trapping and genetic sampling. While these methods can help researchers estimate population numbers, density and, in some cases, identify individual animals, they may not always provide information about their physiological condition. Analysing chemical signatures could potentially add another layer to this understanding.
