Gus Mills is a smiling man who speaks with an English accent peppered with what sounds like hints of Dutch—perhaps from all the time he’s spent interacting with speakers of Afrikaans in the South African area of Kalahari Transfrontier Park. For the past five years, Mills and his wife have been studying the approximately 350 cheetahs that live in the region, a highly arid environment consisting primarily of vegetated sand dunes. In often scorching conditions, Mills tracks cheetah lifestyle patterns through a variety of data collection methods. Among these methods is photographic recognition: The park’s nearly 20,000 annual visitors are encouraged to submit photos of any cheetahs they encounter so that the animals’ spot patterns might be identified, much like an iris scan or fingerprint on humans. Another method is radio collaring, which has so far enabled Mills to map the migratory patterns of 19 cheetahs. Mills also conducts DNA sampling from hair specimens from cubs, biopsy darting, and fecal collection, and works with native Bushmen to track spoors and analyze sand patterns.

Through all of these approaches, his overarching goals are to better understand the demographics of the cheetah population, as well as their feeding ecology, land tenure system, mating system, and mortality and limiting factors. Ultimately, Mills aims to compare his results with another famous cheetah study that was implemented in the Serengeti, a far more temperate region.

Why do this? Funded by a grant from the Big Cats Initiative, Mills works toward conservation through knowledge. “The more we understand about the species we are trying to conserve,” Mills explains, “the more we can do to help them.” He firmly believes that protected areas like Kalahari Transfrontier Park (which spans parts of South Africa and Botswana, transcending political boundaries) are absolutely crucial, and perhaps, in the near future, the only remaining option for animals, because “intervention [in a species’ life] is quite unfortunate.” And intervention is unnecessary in parks like this because animals are protected from human harm. Mills hopes that by better comprehending how cheetahs adapt their life patterns to such an arid ecosystem, conservation programs can be rolled out in non-protected areas like Iran, where the only known Asiatic cheetahs naturally occur and are currently endangered.

Humans can become attached to animals, anthropomorphizing them in some ways. Mills has christened many of the female cheetahs that he’s tracked: quaint, nostalgic names like Eleanor, Lisette, and Gertie. He even seems wistful when describing a mother cheetah that starved to death to provide her four cubs with enough steenbok (a type of small antelope) meat to survive past the crucial age of six months. This, he points out, is a big difference between the Kalahari and Serengeti cheetahs. The survival rate of Kalahari cubs is 22 percent higher than Serengeti cubs, yet Serengeti mothers can rebreed much faster than their Kalahari counterparts due to the more accessible nature of food there.

Despite what seems like a lifetime of work on cheetahs—a half-decade traverse of dusty desert, up into trees and down into dens—Mills views the approaching end of his field work this summer as only preliminary. “This was all data collection,” he says. “Now comes … the real number crunching.” He expects to compile all his results into a definitive study, revealing for the first time what could be paradigm-shifting conclusions about cheetahs as a whole and how they relate to the ecosystems around them. Mills has worked for the majority of his life with African carnivores, advocating for their conservation and further analysis, and is now an author of four books and over 120 scientific papers, a professor at Pretoria University, a senior member of several specialist groups, a board member of scientific journals and conservation organizations, a research fellow, and the founder of an advisory group on the preservation of endangered species.