Seasonal effects on the nutritional ecology of blackbuck Antilope cervicapra.
Seasonal food habits of the endangered blackbuck antelope Antilope cervicapra were studied by observing wild and captive blackbuck feeding in different habitats within Velavadar National Park, Gujarat, India. Proportional use of different habitats was estimated in each season for 2 years. Seasonal forage consumption and digestibility were estimated using captive blackbuck subsisting on natural forage. Blackbuck primarily used grassland habitat for grazing. Dichanthium annulatum and pods of the exotic shrub Prosopis juliflora contributed 35% and 9.5% to the annual dry matter intake, respectively. Forage consumption and nutrient digestibility were high in the monsoon and winter seasons, but low in summer. Both were positively correlated with crude protein content of the forage. In summer, the crude protein content of forage (3.6%) was below the critical requirements of ungulates. Apparent digestibility of crude protein was negative during summers. Faecal nitrogen content and faecal ether extract were correlated with forage quality and in vivo digestibility. These were used to develop relationships for estimating forage quality. Seasonal lows in forage quality, which became even more pronounced during droughts, together with limited grazing area were considered to be important limiting factors for blackbuck. Pods of P. juliflora were considered a significant food resource, especially when grazing deteriorated. Therefore, total eradication of this exotic shrub from the park would not be desirable. Instead, managing P. juliflora to produce more available pods is recommended. Increasing the grazing area of the park and/or managing the habitat to produce high quality forage, especially during summer, would benefit the blackbuck population.