Text: Tim Jackson. Photography: Various. Article from the July 2013 issue of Africa Geographic Magazine.

‘I would be quite happy to walk down one of my local alleyways in broad daylight,’ says science editor Tim Jackson. ‘But would I make the same decision in the early hours of the morning?’ The dilemma posed by that question is, in essence, part of what is known as the ‘ecology of fear’.

However, the phrase is applied to the study of wildlife and not of people. It investigates how animals experience their environment in terms of the risks that it may pose and the decisions they take to reduce those risks.

The ecology of fear, the science, one may call it, of how animals respond to conditions in their environment they may regard as threatening, applies to the hunted and not the hunters, though predators such as lions and even large beasts like elephants also operate within this so-called ‘landscape of fear’. When moving through this landscape, animals have to consider, for example, the safety of the destination, the time of day and whether to travel alone or in a group.

Much as I view walking that alleyway at night, wild animals can show marked differences in the areas they use at different times of the day or in the periods during which they are most active. Take jackals – they will readily forage throughout both day and night, at least when left to their own devices. But are you likely to see a jackal during daylight hours on farmland? Probably not, as it runs the risk of being shot. So it alters its activity period and prowls at night, a time when it’s harder to see and farmers are less likely to be active.

The same principle is true of antelopes in areas where they are hunted for sport. In Zimbabwe’s Hwange National Park, antelopes such as impala, kudu and sable generally drink at waterholes during the day, when predation is less of a threat. However, in hunting areas that lie close to the park, the animals are more likely to be killed by bullets, so in those enclaves the antelopes, particularly sable, tend to drink under cover of darkness when the chances of being shot are reduced. It seems that, to the animals, the risks posed by hunters are higher than those posed by nocturnal predators.

These examples show that animals will readily assess the predation threat – immediate or perceived – and adjust their behaviour accordingly. (Read about how lions adjust their hunting habits to take advantage of the movements of herbivores at Hwange’s waterholes in ‘Where there’s water, there are … lions?’ on page 56.)

Is it safe here?

The time of day isn’t the only consideration when contemplating one’s safety. Like humans, animals view certain areas as safer than others and avoid the places they regard as high risk. The lions in Botswana’s Makgadikgadi area, for instance, like to feed on antelopes, but their favoured prey is an ephemeral food present only during the annual wildebeest and zebra migration. For the rest of the year the lions, which are resident in the area, turn their attention to the abundant supply of livestock, as well as the relatively scarce wild herbivores that live there. To reduce persecution by the livestock owners, the lions tend to avoid areas close to cattle posts, but when they do venture into these danger zones they usually do so at night. They also move more quickly when they are within six kilometres or so of the settlements in order to minimise the time they spend in the vicinity of humans.

The actions of the Makgadikgadi lions are similar to those of elephants in much of Kenya. Here, the satellite tracking of individuals fitted with GPS devices has revealed substantial differences in how they move across the land in protected reserves and in adjacent unprotected areas, which are often inhabited by people. Elephants tend to shun unprotected areas, but will use them as corridors to move from one relatively safe haven to another. Like the lions, they travel through the peopled landscape under cover of darkness, and also move quickly – around three times faster than they do in protected areas – a behaviour described affectionately as ‘streaking’. While elephants obviously have no idea of the location of officially designated protected areas – after all, the pachyderms can’t read signboards – their behaviour strongly suggests that they see reserves as islands of relative sanctuary in a sea of dangerous land.

Primates too live in fear. In South Africa’s Waterberg mountains, researchers have built up a complex picture of the ways in which vervet monkeys respond to predators in their landscape. Their results produced some interesting findings. The monkeys tended to avoid areas favoured by leopards and baboons – both predators of vervets in the Waterberg. But they treated eagles, also a potential threat, differently, and the way they ranged across the land showed their scant regard for their aerial enemy. The difference, it seems, is that it’s less easy to predict where eagles may attack than where leopards and baboons pose a danger. As predators of the sky, eagles are much more mobile and can easily traverse large areas, and their use of space is relatively unpredictable.

Of course monkeys live in a far more complex environment than most land animals do. For them, their ability to climb trees makes their world three-dimensional, and that additional element also affects their perception of fear.

Monkeys live in a far more complex environment than most land animals do. For them, their ability to climb trees makes their world three-dimensional, and that also affects their perception of fear

When it comes to their willingness to take risks when foraging, Sykes’ monkeys (they used to be known as samango monkeys) in the Soutpansberg mountains of northern South Africa are more sensitive to the vertical dimension of their space than they are to the horizontal one. So they prefer to forage higher up in trees than closer to the ground, despite the presence of both crowned and Verreaux’s eagles, which are quite capable of feeding on them. Like the vervets, the Sykes’ monkeys’ idea of fear suggests that attacks by terrestrial predators like leopards may be a more important consideration when foraging than an onslaught from above.

Are we safer in a group?

Avoiding predators is one reason that many animals, and even birds, stick together in a herd or a flock. One of the obvious advantages of being part of a group is safety in numbers – the so-called ‘dilution effect’. Individuals are less likely to be predated when surrounded by others of their kind. And with more pairs of eyes scanning for predators, individuals can spend less time on lookout duty and more on activities such as feeding.

In baboons there is clear support for the influence of predation pressure on troop size, so in areas where the risk of predation is high, the size of the troop tends to be larger than it is in places where there is little danger. With more individuals on the alert, the troop’s chances of timeously spotting danger improves.

Chimpanzees react similarly when faced with a risky situation. In Uganda’s Kibale National Park, for example, groups moving from the safety of the park to feed on farmers’ crops tend to bunch together into larger bands than they usually do. They are much quieter too, reducing the number of their ‘pant-hoot’ calls when raiding the fields, presumably to draw less attention to themselves.

Nocturnal primates, of which half the species live in Madagascar, also offer some interesting insights into the influence of predation on group living. Typically, the primates there, mainly lemurs, are relatively small nocturnal creatures. They use the cover of night to hide from predators. However, several species have evolved from being active at night to daytime living. These include the ring-tailed lemur and some bamboo lemurs, whose ancestors were nocturnal. It’s thought that their revised group-living habit may have helped them adapt to the pressures of diurnal predation.

The difference between daytime and night-time threats is very real. In fact, it’s amazing how few nocturnal primates actually fall victim to the likes of leopards, though that’s not the case for their diurnal cousins. Consider the Ituri Forest in the Democratic Republic of Congo, where diurnal primate species make up a quarter of the diet of leopards, yet only one scat from these forests has turned up the remains of a nocturnal potto. In fact it’s the only published record worldwide of a cat taking a nocturnal primate and one of only three records from across the African continent of nocturnal primates being predated – the other two by a bonobo and an African crowned eagle.

So what happens to prey species like antelopes when the threat of predation increases? It’s a question that biologists looked at in South Africa’s Phinda Private Game Reserve. After the reintroduction of cheetahs and lions to the area, the local antelope populations soon took action. Both wildebeest and impalas spent more time scanning for predators and did so more often as their chances of being eaten increased dramatically.

The Stress Effect

Imagine an existence where being killed by a predator is almost inevitable. It must be a stressful way to live – at least if you think about it like humans do. And perhaps wild animals think that way too. Recent research suggests the mere fact that there may be predators around can have a profoundly stressful effect on prey animals. While this hasn’t received much attention in Africa, there are studies that point to the indirect negative impacts of having predators in your back yard.

The ecology of fear, the science of how animals respond to conditions in their environment they may regard as threatening, applies to the hunted and not the hunters

For instance, song sparrows in Canada will reduce the number of chicks they produce each year by 40 per cent in response to an increase in predation.

Researchers subsequently discovered the ‘predator’ that had this effect was simply a predator call, so the threats were only perceived to exist. It seems the mere thought of being in a risky situation can have a powerful outcome for wildlife. Recent studies in the UK show that introducing models of domestic cats to areas used by nesting birds persuades the adults to reduce the amount of food they bring to their chicks by about a third – conditions consistent with the smaller clutch sizes and poorer condition of chicks in urban environments where domestic cats pose a real threat. These effects result not from direct predation, but from the overbearing threat of it, and they can be attributed, in part at least, to stress.

The presence of domestic dogs around pregnant rabbits has been shown to reduce both the number and size of their young; it’s also associated with an increase in stress-related hormones in the mother. There seems to be a clear relationship between canid-induced stress and the rabbits’ breeding success.

There is little evidence to date of these types of stresses in African mammals. However, work on elephants in southern Kenya has shown high levels of stress hormones in males that typically leave the sanctuary of protected areas such as Amboseli National Reserve to raid crops in farmers’ fields. These so-called ‘rogue’ elephants clearly feel the heat when they come into this sort of conflict situation with humans.

So, when investigating how and why animals move around their landscape, there’s a lot more to consider than simply food, water and mates. The ecology of fear may play a far more important role than is currently understood.