Hiss and tell: What influences venom yields of India's big four snakes?

Snake venoms have evolved over millions of years to subdue prey and deter predators rapidly. The potency and amount of venom differ both within and across species, and are primarily influenced by their ecology and environment. Understanding venom yields in clinically relevant species is essential for refining treatment approaches for snakebite. Despite this, venom yields have seldom been documented, especially in snakes of the Indian subcontinent. To address this knowledge gap, we analysed venom yields from 338 specimens of the clinically most important "big four" Indian snakes-Naja naja, Daboia russelii, Bungarus caeruleus, and Echis carinatus-collected across diverse biogeographic and agroclimatic zones. We systematically compared yields across different genders, regions, and life stages to uncover patterns in venom production and explored the relationship between venom yield and dry weight. Our findings reveal substantial inter- and intraspecific variation, with N. naja and D. russelii exhibiting the highest average yields, while B. caeruleus and E. carinatus produced much lower quantities. Geographic variation was significant for B. caeruleus, but not for the other species. No sex-based differences were observed; however, life stage was an important determinant, with adults producing more venom than juveniles or subadults. Comparative analysis with captive populations indicated that captivity may not substantially alter venom yields. By integrating venom yield and toxicity data, we highlight the distinct envenomation strategies among the big four snakes and their implications for snakebites. These insights are crucial for improving antivenom production, clinical management, and understanding the ecological and evolutionary dynamics of Indian snake venoms.