His nephew recalled that the children were taught to chant, “Hyenas are beautiful!” as often as possible. On visits to Kruger National Park, he got them out of bed at midnight to look for bushbabies and again at five in the morning to search for big cats. Wildlife was often most active at inconvenient hours, and he expected anyone accompanying him to adjust.

Michael “Gus” Mills, who died on July 13th, spent more than 40 years studying Africa’s large carnivores, especially hyenas, wild dogs, and cheetahs. He published more than 150 scientific papers, chapters, and reports, advised conservation bodies, and trained younger researchers. Much of his working life was spent in a vehicle on a sandy track, waiting beside an animal that might sleep for most of the day.

At school he had seemed an unlikely future scientist. He described himself as a “very bad student,” failed South Africa’s high-school leaving examination, and was told that science was beyond him. After passing the examination on a second attempt, he joked that he had earned an MA: “Matric Again.” Three years of psychology persuaded him that he did not want to be a psychologist. Zoology held his attention. A visit to Kruger in 1954, when he was eight, had already pointed him toward field biology. “It did something to me,” he said. From then on he wanted to work in the bush.

After studying at the University of Cape Town and completing honors in wildlife management at the University of Pretoria, he heard about a project on brown hyenas in the Kalahari. In 1972 he went there with Margie, his wife. Their first home was a caravan. They remained for 12 years, studying brown and spotted hyenas in a landscape where distances were large, equipment was basic, and results took years to establish.

Hyenas suited him. They were complicated animals burdened by simple reputations. Spotted hyenas, he argued, were skilled hunters with intricate social lives. He objected when familiar descriptions persisted after research had disproved them. When the BBC called them “ferocious scavengers,” he began a correspondence. The wording was eventually changed to “formidable hunters.” When people complained that hyenas smelled, he replied that he knew humans who smelled worse.

Hans Kruuk, the pioneering hyena researcher, became his mentor and co-supervisor. Through Kruuk, Mills encountered the methods of Niko Tinbergen, one of the founders of ethology. He learned to begin with a precise question and to spend enough time with the animals to answer it. New instruments helped him record movements and behavior, though he continued to value direct observation. He warned young scientists that equipment was of limited use when the researcher knew little about the animal carrying it.

His years in Kruger broadened his work. He studied lions, cheetahs, and the relationships among predators and prey. His research on African wild dogs continued for 15 years. He also asked visitors to submit photographs, allowing individual animals to be identified from their markings. These public censuses helped establish the size and composition of Kruger’s wild-dog and cheetah populations. Tourists with cameras became a useful source of field records.

Administration occupied more of his time as he became a senior scientist and helped shape park policy. He questioned the emphasis placed on animal counts. Numbers alone, he argued, said little about whether a population could persist or whether an ecosystem was functioning well. He wanted managers to consider the larger systems in which predators moved, hunted, and reproduced. Fences and reserve boundaries often divided the ranges they needed. He also challenged conservation projects when he thought their ecological assumptions were weak.

In 2006, after retiring from SANParks, he returned with Margie to the Kalahari for a six-year cheetah study. They identified 176 animals, aided by photographs from visitors, and spent around 7,000 hours watching them. About 5,000 of those hours were spent watching cheetahs rest, he said. The rest yielded a detailed account of hunting, reproduction, movement, mortality, and survival in an arid environment.

The fieldwork involved many repetitive and awkward tasks. Gus and Margie crouched in the sand with tweezers to collect hairs from cheetah resting places for DNA analysis. They waited near animals for data loggers programmed to fall from radio collars. Their vehicle once suffered eight punctures in a day. Lisette, the first cheetah they collared, was followed for more than six years. Their records showed that steenbok, rather than springbok, made up the largest share of 539 recorded kills. They also found that males living in coalitions were not always brothers.

Margie described her husband as a “cheerful pessimist.” He was sociable, readily amused, and deeply concerned about environmental decline. His concern kept him engaged in research and conservation after formal retirement. He supervised graduate students, worked with San trackers, and continued taking on physically demanding journeys. In 2021, in his mid-70s, he became the oldest man to reach the 5,100-meter summit of Margherita Peak in Uganda’s Rwenzori Mountains.

The Kalahari remained what he called the “home of his heart.” It offered the conditions in which he had learned his craft: long distances, few distractions, and animals that revealed themselves slowly. A cheetah might spend hours under a tree before rising to hunt. A hyena’s tracks might continue over several dunes. Mills was prepared to stay with either for as long as the work required.

Cite this article

Rhett Ayers Butler (2026). Gus Mills, hyena expert and ‘the cheerful pessimist of the Kalahari’, has died. Mongabay Conservation news. DOI: https://doi.org/10.66709/news-323402

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Rhett Butler Editor

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AnimalsBiodiversityCarnivoresCatsCheetahsMammalsObituaryWildlifeAfricaSouth AfricaSouthern Africa

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