Publications

The reproductive phenology of blackbuck : influence of seasonal nutritional resources and flexible lactation as an adaptive strategy

Priyadarshini, K.V.R.; Gort, G.; Rice, C.G.; Yoganand, K.

Summary

Seasonality poses significant nutritional constraints for ungulates. Consequently, most ungulates time their energy-demanding events like calving and lactation to the availability of abundant and high-quality nutritional resources. We investigated the reproductive phenology of blackbuck, Antilope cervicapra, in relation to resource seasonality, in a semi-arid grassland in western India. We examined whether the body condition of females, forage abundance and forage quality influenced the timing of blackbuck reproduction. We also used a conceptual model to explore whether blackbuck use behavioural adaptations in maternal care as an adaptive strategy to buffer the high nutritional demands of lactation. Blackbuck showed biannual calving, which occurred before (pre-monsoon) and after the rains (post-monsoon). We found statistically significant relationships, albeit small effect sizes, of body condition, forage abundance (biomass) and moisture content of grasses on the proportion of lactating females. The biannual reproductive phenology seems more complex than a simple relationship of reproduction with body condition and optimal nutrition supply. In the conceptual model based on our data, we propose that blackbuck females shortened their lactation time and weaned their calves sooner during the pre-monsoon calving to coincide with a period of optimal food quality, thus, ensuring sufficient nutrition for both weanlings and allowing the females to regain body reserves, whereas, resource availability during the post-monsoon calving likely allowed females to invest in longer lactation, weaning the calves later, as compared to the pre-monsoon calving season. Thereby, blackbuck may be maintaining biannual calving and thus increase their lifetime reproductive output.