The comparative behavioural ecology of the brown hyaena Hyaena brunnea and the spotted hyaena Crocuta crocuta in the southern Kalahari

1. What they did

Brown hyaenas and spotted hyaenas are close relatives that share the southern Kalahari. The author asked how the two manage to live side by side, how their different food habits have shaped their social lives and behaviour, and how each species affects the other.

He drew on his own intensive study of brown hyaenas in the region (1972 to 1980) and on an ongoing study of spotted hyaenas begun in 1979, most of it not yet published. Much of the information came from following individual hyaenas in a vehicle at night and recording what they ate, how far they travelled and how they behaved. He compared the two species on:

• Diet, and whether food was killed or scavenged.
• Foraging: activity, distances travelled, group size and hunting.
• Social organisation: group size, who leaves the group, mating and territory size.
• Denning and how cubs are fed.
• Communication: calls, visual displays and scent marking.
• Relations between the two species.

2. What they found

Numbers and size

• Brown hyaenas are the most common of the larger carnivores in the southern Kalahari: an estimated 172 in the Kalahari Gemsbok National Park, at 1.8 per 100 km². There were about 85 spotted hyaenas, at 0.9 per 100 km².
• Spotted hyaenas are much larger. Adult females averaged 70.9 kg (7 animals) and adult males 57.2 kg (12 animals); adult brown hyaenas averaged 39.1 kg (20 animals), with no real difference between the sexes.

Diet

• Brown hyaenas eat many small items: small mammals, hide and bone, wild fruits, insects and other small food. They are mainly scavengers; only 5.8% of the food (by mass) they were seen eating had been killed by them.
• Spotted hyaenas mainly eat large and medium-sized mammals and kill much of it themselves: 49.2% of the large mammals and 77.5% of the medium-sized mammals they were seen feeding on.
• The two overlap mainly when scavenging large and medium-sized carcasses, a rich food source.

Foraging

• Both are mainly active at night. Brown hyaenas were active for 80.2% of the night (18h00 to 06h00) and spotted hyaenas for 55.3%, a significant difference.
• Both covered similar distances per night: on average 31.1 km for brown hyaenas and 26.5 km for spotted hyaenas. But brown hyaenas found a relatively large meal every 9.2 km on average, while spotted hyaenas travelled 32.7 km.
• Brown hyaenas forage almost always alone, walking erratically at about 4 km/h and finding much of their food by smell, often from downwind with repeated upwind sniffs. They hunt small animals opportunistically, in short chases usually under 100 m; only 10 of 104 hunting attempts (9.6%) succeeded. Extra food is stored nearby in tall grass, under a bush or, rarely, down a hole, or carried to the den.
• Spotted hyaenas often forage in groups (mean 3.0, up to 12), move faster, and lope at about 10 km/h for about half the distance. They run prey down at up to 50 km/h, usually over 500 m to 2.5 km. Young gemsbok under a year old were the most common kills (31.7% of 104 kills). Carcasses are eaten quickly by several hyaenas together, and food storing is rare.

Social life and territories

• Brown hyaenas live in small groups (mean 3.7 adults and subadults, range 1 to 9) that share and defend a territory, with no obvious dominance order. About 8% of the population (a third of adult males) are nomadic males, and they do the mating; group-living males were never seen to mate.
• Spotted hyaenas live in clans (mean 8.0, range 3 to 12), where the larger females dominate the males. All nine males born into one closely studied clan left at adulthood; females were more likely to stay.
• Brown hyaena territories averaged 330 km². Spotted hyaena territories appear to be about 1000 to 2000 km² or more. In both species, territory size seemed to depend on how food was spread out rather than on group size.

Dens and cubs

• Both keep cubs in holes with tunnels about 40 cm wide, and cubs stay at a den for a year or more.
• Brown hyaena dens usually hold one litter (modal litter size 3, range 1 to 4). Females sometimes suckle each other’s cubs, and adults carry food, mostly meat, to the den, so cubs eat meat from about 12 weeks old.
• Spotted hyaena dens are usually shared by several females, no female was seen with more than two cubs, females never suckle others’ cubs, and cubs get little meat until they can follow adults at nine to 12 months. Both species are weaned at 12 to 15 months.

Communication

• Brown hyaenas have eight short-range calls; spotted hyaenas have 12, including the long-distance whoop, and are far noisier.
• Spotted hyaenas have more visual signals (contrasting tail, head movements) and an elaborate greeting ceremony. Brown hyaenas greet by presenting the anal pouch. Their most striking display is raising the long hair on the back and neck.
• Both species use latrines, pasting (leaving a scent paste on grass stalks) and scratching the ground with the forefeet. Brown hyaenas paste far more often (2.6 pastings per km against 0.1 for spotted hyaenas), leave two kinds of paste at once, and mark throughout their territory. Spotted hyaenas mark almost only at latrines, often away from the most used parts of their territory.

Between the two species

• Spotted hyaenas easily drive brown hyaenas off carcasses and dominate them even when no food is present, sometimes grabbing and shaking them by the neck. Four spotted hyaenas once killed a large brown hyaena cub. Brown hyaenas sometimes feed on the remains of spotted hyaena kills.
• The two are often drawn to each other, sometimes use the same latrines and may even paste on the same grass stalk.
• Along the Nossob riverbed, brown hyaenas were seen significantly less often where spotted hyaenas were more common, and lost a substantial amount of food to them there.

3. What they concluded

• The two species largely use different foods. The spotted hyaena is a specialist hunter and scavenger of large and medium-sized mammals; the brown hyaena is an opportunist scavenger that adds wild fruits, insects and other small items.
• These different diets have led to large differences in foraging, social organisation, denning and communication. Brown hyaenas forage alone because most food items feed only one animal; spotted hyaenas forage and live in larger groups because their food can feed several at once and cooperation helps them hunt.
• The ratio of territory size to distance travelled per large meal is similar for both (about 1:36 and 1:38), suggesting that the way food is spread out mainly sets territory size.
• Brown hyaenas can carry food to cubs because they usually feed alone; spotted hyaenas feed in competition and eat as much as they can quickly. The author suggests the spotted hyaena’s smaller litters may have evolved because their cubs depend so heavily on milk.
• Long-range calls help spotted hyaenas gather for hunting and to face lions. Frequent pasting may tell brown hyaenas where group mates have recently foraged and reinforce their presence in the territory.
• The brown hyaena is the best adapted large carnivore in the southern Kalahari. Because spotted hyaenas are scarce there, their competition limits brown hyaena numbers only in a few local areas.

7. Implications for conservation (from the paper)

• These questions matter for managing both carnivores.
• Management that increases the number of resident hoofed animals would probably increase spotted hyaena numbers, which would almost certainly reduce the brown hyaena population through competition for food and direct aggression.