Research in Namibia

If you want to study cheetahs, you have to be quick. Few people know this better than Bettina Wachter. The night's cold is still in the bones of man and beast as the evolutionary biologist drives her 4x4 through the Namibian bush one May morning. Shortly before, a cheetah had fallen into the trap, the second male in as many days. Wachter and her colleagues from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) in Berlin don't want to keep the big cats waiting. They want to examine the two cheetah brothers, fit them with GPS collars and then release them back into the wild by the time the sun sets.

Wachter and her team have been studying the behaviour, ecology, health and reproduction of the cheetah, Africa's rarest big cat, for almost twenty years. The species is on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. There are only just under 7100 left on the entire continent. About a fifth of them live in Namibia.

The cheetah is a highly specialised hunter. Everything about it is designed for speed: its claws are permanently extended, like spikes on an athlete's shoe, to help it increase its speed. Its physique is similar to that of a greyhound; it is lightweight, weighing no more than 60 kilograms. All this makes it the fastest mammal in the world. However, the cheetah pays a price for this record-breaking physique. It is ruthlessly physically inferior to other predators such as lions, leopards and hyenas. "It's like a 100-metre sprinter against a heavyweight boxer," says Wachter's colleague Jörg Melzheimer, "no chance". When a cheetah meets a leopard, the encounter is often fatal for the former.

So cheetahs have sought out their niches. They are now rarely found in protected areas, where their burly competitors reign supreme. Instead, most of the remaining cheetahs have moved to farmland - often to the displeasure of the owners.

The fact that the population has been declining for decades is also due to the age-old conflict between humans and predators. On one side are the cheetahs, who continue to kill calves in search of prey. On the other side are the farmers, who are no longer willing to accept these losses. According to some farmers, they have lost up to 30 per cent of their calves to predators every year in the past. As a result, the hunter has become the hunted and farmers have been catching and shooting cheetahs. Wachter cannot say exactly how many animals have been killed in this way. The shootings on private farmland were not illegal.

At first, the farmers were suspicious of the cheetah researchers. "It was tricky," says Wachter, "because once a cheetah was dead, the next one would just come along and take over the territory. The number of calves continued to dwindle, as did the number of endangered cheetahs. The researchers wanted to break this vicious cycle. But they needed the farmers' help. "Of course, the farmers knew best where the cheetahs were and how to catch them, for their benefit," says Wachter. The problem is that cheetahs cannot be baited with meat. Unlike lions or leopards, they only eat freshly killed prey. But farmers have known for generations that the big cats will always return to the so-called game trees, where they can find scent marks, droppings and faeces. If you set traps there, sooner or later the big cats will fall into them.

Traditional knowledge of the farmers, says Heiko Freyer. The German-Namibian breeds cattle on 16,000 hectares near the capital Windhoek. He keeps an average of 800 bulls and cows on his farm, more in good rainy seasons and fewer in dry periods. In some years, he has lost as many as 35 of his calves to predators. "When a calf is torn to pieces, there's not much left - if anything at all. It was only when he rounded up the herd that he noticed the animals were missing. He could only assume they were cheetahs. After all, the shy animals are rarely seen, and only by chance, even near their play trees. "We didn't have any scientific data to rely on," says Freyer. So Wachter and her team made a deal with farmers like Freyer: if you show us the trees, we'll give you our data later.

The researchers have also caught the cheetah brothers, who are due to be tagged this morning. They are waiting in traps under a camel thorn tree. It is just before nine when vet Rebekka Müller anaesthetises the first cheetah through the bars. Soon after, she is lying on a treatment table in the middle of the bush. The researchers have about an hour before the anaesthetic wears off and the big cat wakes up. Wachter and the vet take samples: a few tubes of blood, some fur, semen and faeces. Meanwhile, the technician puts a GPS collar on the cheetah and injects a chip into its back. This will allow scientists to answer several questions at once: How resilient is the cheetah's immune system? Where do they stay? And how do they communicate?

The Leibniz-IZW researchers have fitted around 300 cheetahs with sensors and tracked them for two years. When the animal moves, the GPS collar records its position every 15 minutes. When the cheetah is at rest, the device also switches to low-power mode. To retrieve the data, the researchers need to get within a few hundred metres of the cheetah. The best way to do this is in a small plane. The effort is great, the costs are high.

The Leibniz-IZW researchers published their results in December 2020 in the scientific journal PNAS. They show how sophisticated the communication and territorial behaviour of the big cats is. They do not choose their playgrounds at random. "The distance between these hotspots or communication centres is always 23 kilometres," says Wachter. These hubs are scattered across the Namibian farmland like a uniform network. Wachter's colleague Melzheimer compares these hubs to trendy bars. It's all about showing off, finding potential partners - and clarifying the hierarchy. Dominant males occupying the territory regularly leave scent marks.

A second communication channel is used by the sexes to communicate with each other. If they are ready to mate, the females leave a scent mark on the marking tree. Then they have to be patient. They stay at the hotspot for up to several days, waiting for a male to respond to their signal. This can be by calling or by leaving a scent mark on the tree. "Without these opportunities for exchange, it would be very unlikely that males and females would meet," says Melzheimer.

In the 1990s, biologist Tim Caro discovered during research in Tanzania's Serengeti National Park that not all male cheetahs have their territory. He distinguished between dominant territory holders and so-called floaters - weaker male cheetahs that travel long distances in search of vacant territories. The average territory of a territorial male in Namibia, for example, is about 380 square kilometres. On the other hand, the non-territorial males roam areas of up to 1,595 square kilometres, from hotspot to hotspot. The term "floating" - English for hovering, gliding, drifting - is therefore misleading, says Melzheimer. "Our data show that the non-territorial males do not move randomly from one communication centre to the next, but in a very targeted way. The areas between the hotspots, on the other hand, are of no interest to either territorial or non-territorial males.

With this knowledge, the solution to the human-predator conflict was within reach. If farmers grazed their calves away from cheetah hotspots, the researchers hypothesised, they could reduce their losses. But before they could prove it, they were met with scepticism. "If we move the calves, the cheetahs will just follow their prey," some farmers argued. But they had nothing to lose.

Subsequent experiments showed that cheetahs do indeed remain loyal to their communication centres. The calves were quickly forgotten and the cheetahs simply moved on to other prey: hartebeest, springbok, oryx, warthog. Farmers were able to reduce their losses by up to 86 per cent. Melzheimer says there is only one parameter that cheetahs consider when choosing a hotspot, and that is the distance to neighbouring hotspots. "We now know that there are no problem animals," says Melzheimer, "but there are problem areas.

The team is now in dialogue with several hundred Namibian farmers. Heiko Freyer also appreciates the new knowledge. What he ultimately wants to achieve, says the cattle farmer, is peaceful coexistence with all species - not a "sterile agricultural factory" that only provides space for livestock. "The predators have always been here and part of life in Namibia - long before we started farming here.

Has this solved the human-animal conflict and saved the cheetah? It will probably never be 100 per cent successful, says Melzheimer: "There will always be losses that can't be avoided. But two or three calves a year is acceptable to most farmers. The next step for Melzheimer and his colleagues is to apply and disseminate their knowledge to farms in other African countries. The cheetahs' communication strategy is the same everywhere, from southern to eastern Africa.

But some developments continue to worry Melzheimer. For example, there are foreign investors who - unlike traditional farmers like Freyer - are erecting high-game fences around their land. "Such barriers naturally destroy the cheetah network very quickly," says Melzheimer. The researchers are also concerned about the return of an old competitor. For some years now, Namibian farmers have been seeing more and more leopards on their land. The big question is why they are returning. "The farmers have now stopped shooting the cheetahs," says Wachter, "but it is still difficult to predict how the livestock population will develop because of the new threat from the leopards.

The heat has already settled over the farmland as the second cheetah awakens from its tranquilliser and calls to its ally. It's a sound that doesn't quite belong to a predator: delicate and fragile, barely distinguishable from the twittering of a bird. "They will find each other again at night," says Wachter. Together with the vet, she dismantles the improvised surgery in the bush. Meanwhile, technician Röder prepares the traps on the cheetah tree for the next capture.

The researchers will soon be analysing the cheetah brothers' movement data. Although they are still young and slender, the area around the play tree could now be theirs. One of the previous owners, also part of a coalition, has been off the researchers' radar for weeks. Now the remaining one has to defend his territory alone. "He's already old, so he won't stand much of a chance against the younger ones in a fight." For the brothers, it would be a rapid ascent in the cheetah hierarchy, from herdsman to territory owner. For the Leibniz-IZW researchers and the Namibian farmers, it is another piece of the puzzle that is beginning to fit together. "You just have to ask the right questions," says Wachter, "and it will all make sense in the end.”