Indian Forest Service (IFS) officer Himanshu Tyagi explained why the incident of an elephant giving birth to twin calves in Jim Corbett is "rare and accounts for < 1% of births". "A single...calf weighs...70-120 kg at birth. Carrying two...is metabolically enormous for the mother," he said. He also cited long gestation period of "22-24 months" as one of the reasons.