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2019-06-24

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Endangered : The wild yak is restricted to higher Himalayas of Asia, the Tibetan plateau and parts of North Russia..  

A pile of dung may irk many, but not these researchers who spend days analysing yak dung to understand the vegetation and climate of the past and the connections they have to extinct mega herbivores such as the woolly rhino and mammoth.

The wild yak is an endangered species restricted to the higher Himalayas of Asia, the Tibetan plateau and parts of North Russia. It can tolerate temperatures as low as -40 degrees Celsius and is associated with the Himalayan tahr and White-bellied musk deer. The most non-invasive way to study its diet and the local vegetation is by examining its dung.

During the summer of 2017, researchers from Birbal Sahni institute of Palaeosciences, Lucknow set out to the hilly terrain which is about 25 km from the Dronagiri village in Chamoli district of Uttarakhand and collected the dung samples. This exercise was repeated in the winter season too.

Once back in the laboratory, they carried out the macro- and micro-botanical analyses to decode its diet. A good diversity of pollen, spores and phytoliths (silica bodies found in plants) were seen. This meant that the yak preferred a variety of food — simple grass to leaves and fruits of woody trees. This diversity was high during summer and the yak could walk up to 50 km in search of food.

This also indicated that the yak was able to modify its diet according to the climatic change of the past. “The end of the Pleistocene epoch (11,700 years ago) and the start of Holocene brought about a change in vegetation and also introduced humans,” explains Swati Tripathi, one of the authors of the paper published in PLOS ONE. “Giant mammoth and woolly rhino which used to live with the yak about 18,000-20,000 years ago were not able to adapt to these changes and thus went extinct. This is a classic example of ‘survival of the fittest’. Our humble yak proved to be the fittest one.”

The yak dung analysis also helped to map out the different plants and trees in that area, thus, generating modern botanical analogue for palaeo environmental studies in higher Himalayas.

“Across the globe, many researchers are working on coprolite or fossilized dung of extinct animals. A comparison of the present results with the extinct ones can help understand more about ancestor climatic factors and other adaptation strategies of mega herbivores.

“These animals mostly depend on the regional flora and studies can throw light on the past vegetation of an area,” adds Dr. Sadhan Kumar Basumatary, corresponding author of the paper.

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