The 4x4 shudders through the bush in Gorongosa National Park, Mozambique, where uneven terrain tests the sturdiest of suspensions. Baboons survey the vehicle curiously as field guide Samuel Mitha Caringuene pulls up alongside a severed warthog leg lying in the dry grass. He is on the right track: at 4am, the cries of the unfortunate hog had broken the silence over Chitengo Camp and startled Caringuene from his sleep: a lioness with two cubs in tow had snatched the warthog from right beneath his bedroom. Lions rarely enter the staff area at the camp, but these ambush predators must have had an instinct that their next meal was snoozing within easy reach, laid out like a buffet under the house.
The time is 6.45am, but Caringuene is convinced the lions are still in the area. Once lions have subdued their prey, the matriarch will open the abdomen and start her meal with the internal organs – the most nutritious part. She will then work her way up from the fleshy hindquarters towards the head, in a process that can take several hours.
From a nearby tree, a baboon lets out a guttural howl to warn others of nearby predators, triggering a hornbill to follow suit. All at once, the trees are alive with sound. “Here!” whisper Caringuene excitedly. He plunges the vehicle down a slope, dodging branches before bringing the vehicle to a halt. Barely ten metres ahead, a collared lioness called Rosa lies in the tall grass, gnawing at the bones of her breakfast and lazily rolling bloody sinew and gristle around in her huge jaws. The male cubs keep a respectful distance, patiently waiting their turn.
Carnivores are finally making a comeback in Gorongosa, more than two decades after a 16-year civil war brutally decimated their numbers. As rebel groups took refuge in the park, hundreds of lions, leopards and wild dogs fled, starved or died in snares used to catch bushmeat. By 1996, the park was barren. Since then, the Mozambican government has teamed up with a US tech entrepreneur and an international team of scientists to restore the park’s ecosystem, from the bottom of the food chain to the top. In a watershed experiment, they are taking a hands-on approach to rebuilding the park’s fauna, first by reintroducing herbivores such as elephant, zebra and wildebeest; and, more recently, working to re-establish healthy populations of carnivores such as lions and wild dogs.
Because carnivores cover large areas in search of food and mates (and easilywander into areas inhabited by humans), only a few reintroductions had previously been attempted anywhere. As a result, Gorongosa has attracted the attention of naturalists around the world, eager to track the recovery of a complex ecosystem in what is in effect a living laboratory at the southern end of Africa’s Great Rift Valley.
One issue scientists are exploring is the “landscape of fear”: the theory is that the presence or absence of predators changes animal behaviour. For small forest antelopes such as bushbuck, a landscape devoid of predators means they can browse freely in open areas where they would normally be at risk of attack. As Gorongosa’s carnivores return, scientists hope to find out what happens when apex predators are unleashed in an environment that has adapted to life without them.
Named after a mountain bordering the national park, Gorongosa means “Place of Danger” in the indigenous Mwani language. In the 1960s and 70s, it was the jewel in Mozambique’s wildlife crown and a popular safari destination for Hollywood stars including John Wayne and Joan Crawford – but that was before the end of Portuguese colonial rule in 1975, and the ensuing civil war in which at least a million people died and the park became a battlefield. Fighters from the anti-communist Renamo militant group, supported by neighbouring Rhodesia (now Zimbabwe) and apartheid-era South Africa, made Mount Gorongosa their base. Government troops arrived to challenge them, and there was bloody fighting across the savanna and floodplains.
Throughout the conflict, thousands of elephants were slaughtered for their ivory to buy weapons, while eland (a large antelope) and zebra were hunted as bushmeat to feed fighters. Lions, leopards and hyenas were killed simply for being in the way. A ceasefire halted the civil war in 1992, but the 200,000 people living in the buffer zone on the edge of the park, along with professional hunters, picked off what little game remained.
While the populations of small- and mid-size antelope began to bounce back in post-conflict Gorongosa, the large grazers and predators struggled. In 2008, the Greg Carr Foundation – a nonprofit set up by a tech entrepreneur-turned-philanthropist from Idaho – reached an agreement with the Mozambique government, pledging $40 million (£31 million) over 30 years to revive the park and rebuild it as a source of income for the local population through employment opportunities and tourism. The team started by restocking the larger herbivores: six bull elephants and five hippos were brought in from South Africa that year, with 99 buffalo, 35 eland and 15 zebra following later.
“The reintroductions have been very important, but, for most of the species, that’s not what drove the recovery,” Marc Stalmans, Gorongosa’s director of scientific services, says. Of the 100,000 large animals that roam the park today, fewer than 500 individuals were brought in from other reserves. The biggest plant-eating species such as elephant, hippo, buffalo and zebra – dominant in the past – are now easily outnumbered by waterbuck and other smaller antelope, whose populations exploded in the absence of competitors and predators.
In their most recent aerial survey by helicopter, Stalmans and his colleagues estimated there could be more than 55,000 waterbuck roaming the floodplains. “For all the [smaller] species, it has been a natural recovery from the viable nuclei that were still in the park,” he says. “In this very productive system, once you apply good protection, they start coming back very quickly.”
The park has seen a 95 per cent recovery of herbivores since the war, but that is not true for carnivores. When South African ecologist Paola Bouley arrived in 2012, she found a struggling population of lions; despite an ample food supply, fewer than 50 of the pre-war population of 200 were left. In southern Mozambique lions are hunted for their teeth and claws, but Gorongosa’s lions were being killed or injured by snares and traps placed to catch bushmeat. Putting her ecological research on the back burner, Bouley started working more closely with the park rangers, most of whom grew up in communities around the park, to launch an anti-poaching patrol and a veterinary unit in 2013. “In the early days, all we did was respond to snares,” she says. “We were like a medical unit. It was traumatising to say the least.”
Since August 2019, the team has been using EarthRanger, a tech platform developed by Microsoft co-founder Paul Allen’s company Vulcan, which pulls together data from GPS collars, trackers on radios and vehicles, and camera-trap photos to give rangers a bird’s-eye view of the lions’ movements and identify poaching hotspots.
In a park that has no fences, the anti-poaching efforts had a strong impact. There are now at least 146 lions. But other apex predators that used to exist in the park – wild dogs (also known as painted wolves), leopards and hyena – were still missing. To bring these carnivores back, Bouley’s team is taking a more direct approach.
On 16 April 2018, a group of sedated wild dogs were transported in a single-engine turboprop plane from South Africa to Gorongosa – a two-hour flight instead of a two-day drive along difficult roads. The eight males and six females stemmed from two separate reserves managed by the Endangered Wildlife Trust, so the team at Gorongosa had to construct a boma, a Swahili term for an open-air enclosure where the new arrivals would be kept together for eight weeks, to grow familiar with each other and establish a hierarchy, before being released into the wild. Upon arrival, the EWT and Gorongosa teams rubbed the sleeping dogs against each other to aid the acclimatisation process. Wild dogs have scent glands located around the anus and genitals, which they use to communicate and form tight-knit bonds within the pack; much like their domesticated cousins, they sniff the scent left by other known individuals from which they can recognise their gender, age and status.
“Before you open those gates, you want to be sure that the pack stays together,” Bouley says. The newly formed pack, led by alpha female Beira, stayed together for nearly a year, when three males and one female split off to form a separate pack.
Bouley knew that Beira was pregnant when the pack was released from the boma, but her pups didn’t make it. The only explanation she could find in Beira’s abandoned den was a giant African rock python – the continent’s largest species of snake. Wild dogs only breed once a year, so the scientists had to wait until the alpha female was ready again in April 2019. To their surprise, the pack's beta female, Nhamagaia, was also pregnant. She gave birth nine weeks after Beira, and the mothers now share the parenting duties of their 18 pups.
“It’s a pile of puppies,” says Bouley, laughing, as her team returns from a daily visit to the dens. In a few weeks, when the pups are around three months old, they will start running with their pack and learn to hunt. But until then, one of the adult dogs will have to stay on guard in the underground den while the rest of the pack sets off in the early mornings and late afternoons to hunt – co-operatively and ferociously. Bushbuck, impala and waterbuck are all on the menu.
Locating the dens would be difficult if it weren’t for the GPS collars attached to the adult dogs. On their field trips, wildlife veterinarians Mércia Ângela and António Paulo study the pups to understand their diet and development. “In the early stage of their lives, we generally don’t intervene, because if we touch them, the mother might reject the pups,” Ângela says. To avoid getting too close, camera traps pick up what the team might miss.
While the survival rates are generally quite high for lion cubs, only a few pups in a wild dog litter will make it to adulthood. Even if their dens are kept safe, they are vulnerable to infectious diseases such as canine distemper and rabies, as well as attacks from larger predators. Human persecution has been a major factor in reducing the entire African population to 6,600 wild dogs, with just 1,400 adults. This iconic species is one of the continent’s most at-risk carnivores, and is listed as “critically endangered” by the International Union for Conservation of Nature, which keeps the “red lists” of Earth's threatened animals, plants and fungi.
But Gorongosa’s wild dog comeback hasn’t ended there. After witnessing the raising of pups, some of the lower-ranking female dogs are also starting to look for a mate. “We already have a female dispersing. She’s looking for a pack, but there’s no one to mate with,” Bouley says. Since only alpha and (sometimes) beta pairs mate in wild dog communities, lone females have to find their own pack. To this end, another cargo of 15 wild dogs was translocated from the Kalahari desert in South Africa in November 2019, bringing the total count to 52. “The genetic mixing is important, because we are trying to jump-start a population and want to get the ecology going,” Bouley says.
The landscape of fear model theorizes that, when apex predators disappear from an ecosystem, plant eaters become less fearful and start to occupy new habitats where they can graze in peace. But verifying this hypothesis is no simple task.
Perhaps the best known example of restoring a carnivore population is the reintroduction of grey wolves into Yellowstone National Park in the US in 1995. By the end of the 1920s, almost all of America’s native wolves had been killed off, primarily by ranchers protecting their livestock. In Yellowstone, the subsequent loss of aspen trees was attributed to a soaring number of elk and other ungulates, which were increasingly grazing on small shoots with little fear of wolf attack. In an ecological phenomenon called the trophic cascade, the loss of trees and shrubs then caused a ripple effect of stream erosion, decline in beaver dams and collapsing food webs affecting birds, insects, fish and other plant and animal species.
When grey wolves were reintroduced to the park in the mid-1990s, some scientists hypothesised that the predator re-established a landscape of fear that caused elk to avoid places where they could be easily attacked. This introduced the idea that predators could not only affect prey populations and ecosystems by eating them, but by scaring them into changing their behaviour.
The concept that prey species move and shift their feeding grounds to avoid predators has been studied extensively. However, the opportunity to observe the opposite – a “landscape of fearlessness” following a dramatic decline in predator populations – is what makes Gorongosa a unique case study.
Robert Pringle, an associate professor of ecology and evolutionary biology at Princeton University, has been visiting Gorongosa since 2012 to study how food availability influences the movement patterns of antelope. Warthogs and antelope such as impala, bushbuck and kudu now make up 98 per cent of the park’s largest omnivores and herbivores. Vegetation flourishes in the open, treeless floodplains, and herds of grazers can fatten there.
Pringle noticed quickly that the animals here behaved differently to those he had observed in places like the Serengeti in Tanzania. Even the usually shy, forest-dwelling bushbuck had brazenly expanded into this habitat, where they started grazing on a type of waterwort plant called Bergia mossambicensis and an invasive shrub, Mimosa pigra. At the time, lions were the only predator in the park, but they don’t tend to hunt in open terrain, so the ecologist suspected the bushbuck's unusual behaviour could be explained by a lack of fear of their main predators, leopards and wild dogs.
To test this idea, Pringle and PhD student Justine Atkins fitted seven floodplain bushbuck, and five less conspicuous individuals roaming the woodlands, with GPS satellite tags that pinged the animals’ location to a tracking system every 15 minutes. They then played recorded leopard calls over a speaker and placed artificial carnivore urine and scat – commercially available pellets soaked in real lion dung that gardeners use to deter domestic cats – to mimic the presence of predators. Bushbuck in the open plains retreated to the relative safety of the dense woodland within 48 hours after the cues were placed. The five individuals that were tracked in the woodlands avoided the cues but didn’t change their behaviour.
“It gets really difficult to simulate the presence of predators on a longer timescale, because if you play the sounds long enough, the animals will eventually figure out what’s going on and become habituated,” says Pringle, acknowledging the limitations of the experimental study, which was published in the journal Science in 2019. Still, the researchers concluded that the fear of predation may have an effect on bushbuck behaviour – and reintroducing predators to the park could have a similar effect.
Further work is needed to test the hypothesis, not least because any scientific experiment in a living laboratory is influenced by compounding factors. “If something changes from year one to year two, you don't know if it's because predators were introduced, because there was a cyclone, or because it was hot,” says Pringle. “You can say that something happened, but you don’t know why.” Mozambique was hit by cyclone Idai in March 2019. It passed through Gorongosa, felling trees and forcing many animals to migrate to higher, drier grounds.
Now that the real predators – the wild dogs – are back, the bushbuck will need to become more vigilant. For their size, wild dogs consume more meat per day than any other carnivore, and they are prodigious killers: a pack might make three kills a day and will tend towards hunting slower prey (young, old, pregnant or injured animals), which means that they have the potential to impact the structure of antelope populations at Gorongosa over time. Antelope have steadily colonised the floodplain in the past decades, so the most dramatic confirmation of a returning “landscape of fear” would be if they moved to another habitat within the next few years.
Those movements can now be tracked in near real-time: combining GPS data from bushbuck, nyala and kudu with that from wild dogs may give researchers a clearer picture. While Gorongosa’s wildlife vets continue to monitor the wild dogs’ hunting and breeding and behaviour, Pringle’s team is using dietary analysis and DNA barcoding in the hope of gleaning a greater insight into the predator-prey relationship.
Not all scientists are convinced of the effect of the landscape of fear. Dan MacNulty, an ecologist at Utah State University, believes it is not as powerful as often thought. MacNulty has studied wolf-elk interactions in Yellowstone since the apex predator's reintroduction. By tracking elk and wolves across four winters between 2012 and 2016, he and his colleagues found that, although elks encountered wolves once every seven to 11 days, they generally didn’t avoid sites where wolves roamed or where elks had previously been killed.
“One of the main predators in Yellowstone and the surrounding area that is often neglected in discussions about wolves and reintroductions is the human being,” MacNulty says. In autumn and winter, elk herds migrate out of the park where they are still hunted by people. “We can't talk about the ecological consequences of wolf reintroduction without putting it in the context of the entire predator community, which includes human beings and other large predators such as grizzly bears, black bears and mountain lions.” MacNulty thinks this human angle may also affect Gorongosa. Anti-poaching efforts and community outreach have drastically reduced the amount of hunting of all animals. “What I wonder is how much of this response that we’re seeing in Gorongosa is to the fact that they’re not being hunted as much as they were during and after the civil war,” he says.
With three thriving wild dog packs, the first carnivore reintroduction in Gorongosa has been a success, but the dogs and lions alone cannot handle the swelling numbers of prey. The park will need a more diverse troop of predators if it is to return to how it was before the war.
The conservation team hopes to bring in spotted hyenas, common in many parts of sub-Saharan Africa, in the next couple of years. Leopards were thought to have been wiped out completely during the war, but in March 2018, a Mozambican guide driving with tourists at night spied a male leopard. The territory of this solitary and primarily nocturnal feline can vary from ten to hundreds of square kilometres, meaning that the male may have been a visitor from an outlying area – possibly the corridor between Gorongosa and Coutada 12, a former hunting area 200km to the northeast of Chitengo Camp.
Bouley thinks that translocating a few female leopards to the park might lure males in pursuit of a mate. “The idea is if we bring in females and they stick around, they are going to bring [male] leopards from that corridor and the exterior area in,” she says. “It will be an incentive for them to stick around.”
The team hopes to bring in leopards from fenced reserves in South Africa where they are no longer wanted, although their efforts to import the spotted carnivore from across the border have so far proved legislatively challenging. The international trade in this threatened species has been banned, and South Africa has shut down exports, even for restoration purposes. “We were ready and had a plane. Leopards were ready to fly but we just couldn’t get the permits,” Bouley says. If they succeed, the leopards will be kept in a boma at both sides of the border for a few weeks to be screened for diseases and collared, and to break the homing instinct of the highly mobile species. Bouley remains hopeful that leopards would quickly set up a territory within the park. “Our rationale is that they don’t really have to go far,” she says. “There’s very little competition and a tonne of food. This is a good place for them.”
Pending the arrival of the big cats, Gorongosa’s baboons – a popular item on the leopard menu – continue to breed and devour everything they can get their opportunistic fingers on. Not even the fake rubber snakes that lie curled on top of rubbish bins and around the reception area of the park’s guest lodge are able to prevent an uninhibited baboon from rifling through waste in search of a morsel.
Indeed, Gorongosa may have the largest population of baboons on the continent, with more than 200 troops of between 30 and 80 individuals. The primates have caught the attention of University of Oxford researchers because they appear to be more active after dusk, when there is normally a high level of predation. In July 2019, an interdisciplinary team led by primatologist and palaeoanthropologist Susana Carvalho fitted four females from two different troops with GPS collars and accelerometers in order to track if their movements and sleeping sites differed from baboons in areas outside the park where leopards are present. “These [Gorongosa] baboons are displaying a number of behaviours, such as potentially sleeping on the ground, that baboons normally don’t do, and we think they can partially be explained by the lack of these threats,” Carvalho says.
By following the Gorongosa baboons on foot from morning to night, the researchers hope the primates will accept their human observers and allow them to get much closer in future field seasons. “Collaring these individuals is going to give us the first data on what happens during the wet season, which is something that has been impossible for us to gather,” Carvalho says.
It may never be possible to restore Gorongosa to its pre-war state, but the changing nature of its habitats will continue to offer scientists a unique opportunity to study how different species shape an ecosystem, and how the presence and absence of predators affects the behaviour of their prey.
“The massive advantage of Gorongosa as an experimental system is that the scale of it is enormous,” Pringle says. Field ecologists typically rely on small plots. “This is a 4,000 square kilometre ecosystem that has been effectively manipulated in the process of being restored, so we have the opportunity to scale up what we know from small-scale experiments and theoretical models to see how well they actually predict what happens in a real ecosystem with big animals.”
Beyond Gorongosa, information from experiments in the park could help to inform the restoration of ecosystems elsewhere. “We have stripped the Earth of the big mammals that used to exist basically everywhere,” Pringle says. Where these large mammals still exist, they remain under threat. “For a lot of us, the big motivating idea is that by better understanding how this works in Gorongosa, we'll be in a better position to apply the Gorongosa model in other places that have lost all their wildlife.”
This article was originally published by WIRED UK
