New Delhi, March 3 -- Surveying elephants is hard, risky work. Dedicated biologists have been doing this challenging task across Africa for decades.

Systematic surveying started in the late 1960s but has been sporadic, as access to remote areas takes logistical planning, funding and well-trained teams. Surveys can easily be derailed by civil unrest or lack of available survey teams. Consequently, the information on the numbers of elephants across Africa is spotty. Even for a single population, survey effort and coverage can change over the years.

Still, the efforts of governments and conservation organisations to count elephants have amassed a remarkable dataset, held by the International Union for the Conservation of Nature and its Afr...