Nutritional profiles of some preferred food grasses of the greater one-horned rhinoceros before and after grassland burning in Manas National Park, India

Abstract

The nutritional variations of food plants play a significant role in the health and population dynamics of wildlife. The body conditions of vulnerable greater one-horned (GOH) rhinoceros (Rhinoceros unicornis) in Manas National Park, Assam, India deteriorate noticeably during the late monsoon to winter, and improve after routine grassland burning, when rhinos feed on the newly emerged leaves and young shoots of grasses. To investigate this, we analysed the nutritional parameters of the leaves of five grass species preferred by rhinos, including three tall (Saccharum spontaneum, S.narenga and Imperata cylindrica) and two short grasses (Cynodon dactylon and Axonopus compressus), before and after grassland burning. Leaf samples were collected in triplicate from five different sites in MNP before (September) and after (March) grassland burning. Biochemical analyses showed the highest crude protein content in S. narenga before and after grassland burning. S. spontaneum and S. narenga had the highest and second highest fat contents, respectively, after grassland burning. Crude fibre content in S. narenga increased significantly (p < 0.05) after grassland burning, but not in the other two tall grasses. The total ash content and the acid-insoluble ash content increased significantly (p < 0.05) in post-burning samples of all five grasses. The short grasses A. compressus and C. dactylon showed the highest calcium and phosphorus contents, respectively, after grassland burning, highlighting their significance in the diets of GOH rhinos along with tall grasses with higher proximate nutrient contents, and their contribution to the improved health status of rhinos after grassland burning. This study will be helpful for improved management of rhino health and their habitats,  essential to maintaining the progress made in MNP since the 2008 to 2012 GOH rhino reintroductions under the Rhino Vision 2020 initiative.