Why lemon grass and snow leopards are aroma twins
doi:10.1038/nindia.2019.57 Published online 15 May 2019
Biologist Mousumi Poddar Sarkar has been researching aroma chemicals or pheromones in big cats for over 30 years. A protégé of pheromone studies pioneer Ratan Lal Brahmachary, her investigations on snow leopards are among the first on this vulnerable species called the beautiful ghost of the Himalayas.
Nature India: How did you get into pheromone research?
Mousumi Poddar Sarkar: I started my journey with pheromones in 1988 as a research scholar at the embryology unit of Indian Statistical Institute, Kolkata. The legendary Prof. Ratan Lal Brahmachary asked me a question during my first visit to the institute: "Do you have any idea about the word ‘pheromone’?" I was acquainted with the word hormone, but not pheromone. He explained quite simply: hormones work to evoke your ‘self-system’ but pheromones work for ‘non-self systems’, meaning inter-individual communication. So it’s chemicals through which animals such as tigers, leopards or snow leopards and others respond to signals coming from other members of their own community in a shared natural environment. That was the first time I started thinking about this unknown world of smells. At the core of my heart I had selected my mentor, friend, philosopher and guide that very day.
NI: What led you to research snow leopards?
MPS: While working on different tropical species of big cats – tiger, Indian leopard, African cheetah, African lion and Asian Lion – in different zoos of India, we got curious about comparing them with an animal of temperate climate. With this in mind, around 2015, we began studying the snow leopards at the Darjeeling Zoo with the permission of the Principal Chief Conservator of Forests, West Bengal. We reported the first scientific evidence on snow leopard pheromones during the 14thMeeting on Chemical Signals in Vertebrates at Cardiff University, UK in 2017.
Pheromones have enormous significance in various stages of an animal’s life cycle. Big cats use it mainly to maintain ‘territory’. Pheromone smells convey messages to secure an animal’s access to a mating partner and also inform eligible opposite-sex partners about their reproductive will.
Just like tigers and lions, snow leopards spray urine to mark their territory. They have two different modes for urination. We coined the term ‘marking fluid’ (MF) and used it in several scientific articles to avoid contradiction with ordinary urination, which drips downward. Snow leopards raise their tail up and spray urine, though the jet is not as strong as that of tigers.
NI: What methods did you use to analyse snow leopard pheromones in the laboratory?
MPS: After collection, we transported the samples on ice to the laboratory. We analysed the molecules in vapour phase with fiber technology, a new method currently being used by the perfume industry in India. It’s a green, solvent free technique that works at micro level concentrations for isolation of very elusive aroma molecules.
NI: What are the significant findings of your studies on snow leopards?
MPS: A cardinal find in the research on tiger pheromones was that the molecule 2 Acetyl 1 Pyrroline (2AP) present in tiger marking fluid was also found to be present in basmati rice. Similarly, the molecule 6 methyl-5 heptane-2-one in snow leopard marking fluid is also present in lemon grass oil. We have seen in many cases that the same molecule with identical chemical structure is present both in animal and plant systems. Co-evolution of the molecules is a very common biological phenomenon because in most cases these molecules are the breakdown product of either the primary precursor molecules or synthesised product, or a by-product of vital physiological systems.
Apart from pheromones, we also studied the hair of snow leopards and found that the structure is just like other mammalian hairs. Since body rolling and rubbing on grass or other surfaces are a very common behavioural means of transferring information for sexual status in these animals, we have tried to explore whether there are any specialised modifications to facilitate the transmission of signalling molecules. Hairs, with their network of channels, might be evolved to create a specialised mode for connection with the outer environment.
NI: What is the significance of the 6 methyl-5 heptane-2-one molecule in snow leopards or in lemon grass?
MPS: The molecule is a ‘chemical messenger’ and has important physiological significance in the organisms. If we trace the evolutionary history of origin of life, there is only one system which can manufacture food utilising solar energy – chlorophyllous plants – and the whole living world is dependent on it. Hence, in both plant and animal systems, common molecules may be coming through similar biochemical pathways and developed species-specific biological significance through time.
NI: What is the significance of this research in conservation of the vulnerable snow leopards? How will this research help the animals in the wild?
MPS: Broadly, pheromones play a significant role in mate choice, which is the basis for successful breeding. Therefore, background knowledge about these molecules may help in strategic formulation of breeding programmes in zoos or in ex situ conservation of this ‘high risk’ animal. This research was performed in a zoo, with restricted movement of the animal. In captivity, there are some changes in their behavioural pattern but the major biochemical pathways remain same. Wild animals are not different in physiology. Therefore, these findings are equally valid for wild snow leopards.
[Shubhobroto Ghosh is a Wildlife Project Manager at the World Animal Protection in India and author of the Indian Zoo Inquiry and the book, ‘Dreaming in Calcutta and Channel Islands’.]
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