Striped Hyaena: Diet and Foraging
The diet of the striped hyaena remains a matter of some debate. However, these animals have been reported to consume a wide variety of vertebrates, invertebrates, vegetables, fruit, and human originated organic wastes (Flower 1932, Novikov 1962, Harrison 1968, Ilani 1975, Kruuk 1976, Macdonald 1978, Leakey 1999, Wagner 2006). It is known to scavenge off lion and spotted hyaena kills (Kruuk 1976, Wagner 2006) as well as discarded livestock carcasses (Leakey 1999, Wagner 2006). The overall reputation, therefore, of the species is that of an omnivorous scavenger. However, in central Kenya analysis of bone fragments and hairs from faecal samples indicate that hyaenas regularly consume smaller mammals and birds that are unlikely to be scavenged (Wagner 2006). This is in line with Kruuk’s (1976) observations, but previous interpretations of the limited data available on striped hyaena diet often under-emphasized the evidence for active hunting.
The striped hyaena scavenges carrion and the remains of kills of other predators (wolf, spotted hyaena, cheetah, leopard, lion, tiger). It also consumes a wide variety of vertebrates, invertebrates, vegetables and fruits, including the fruits of Balanites trees, and human-associated organic matter (Kruuk 1976, Rieger 1979a, Heptner and Sludskij 1980, Osborn and Helmy 1980, Kerbis-Peterhans and Horwitz 1992). The massive cheek teeth and supporting musculature easily permit the gnawing and breaking of bones and carapaces. The striped hyaena may also kill smaller vertebrates including livestock.
The proportion of scavenged and killed prey items is still a matter of debate as there are no detailed studies on the diet of the striped hyaena. Rieger (1979a) suggests that only individuals from the three larger subspecies H. h. barbara, H. h. syriaca and H. h. hyaena (Middle East, Asia minor, central Asia and the Indian subcontinent, and North Africa) kill larger prey animals including livestock, as there is no evidence that the smaller subspecies H. h. dubbah and H. h. sultana (east Africa and Arabian peninsula) attack larger herbivores. In Turkmenistan it has been recorded to feed on wild boar, kulan, porcupine, and particularly tortoises. In Uzbekhistan and Tadzhikistan, seasonal abundance of oil willow fruits (Eleagnus angustifolia) is an important contribution to their diet, while in the Caucasus region it is grasshoppers (Heptner and Sludskij 1980). In Israel it feeds on garbage, carrion, and fruits, particularly dates and melons (Macdonald 1978, Mendelssohn 1985, Mendelssohn and Yora-Tov 1988). In eastern Jordan near the Azraq oasis, the main sources of food are carcasses of feral horses and water buffalo, and refuse from local villages (Al Younis 1993). The striped hyaena is able to drink water of very variable quality, from freshwater to soda and salt water, but it may also fulfil its water requirements with melons (Heptner and Sludskij 1980).
Less is known about the sensory capacities, prey location and hunting behaviour of the striped hyaena than of either the spotted or brown hyaena. Seasonal influxes of striped hyaenas accompanying migrations of large herds of domestic and wild ungulates in Turkmenistan suggest that it may cover long distances on foraging trips, or at least part of the time live a nomadic existence in this region (Heptner and Sludskij 1980). In Egypt it is known to move along ancient caravan roads where the chance of locating a dead camel is high (Osborn and Helmy 1980). In the Serengeti, the greater part of its nocturnal activity is spent searching for food or moving between established foraging sites. It covers a total of 7-27km (mean 19km) per night, either following established animal tracks or zig-zagging cross-country (Kruuk 1976). While walking at a speed of two to four km/h (Kruuk 1976), it stops to investigate the bases of tree trunks, dense shrubs, clumps of grass, old holes, etc. It is apparently able to memorise the location of fruiting trees, garbage dumps and other established feeding sites. It is able to locate tortoises in their hiding places during periods of aestivation and hibernation (Kullman 1965, Gaisler et al. 1968); one hyaena was observed locating and digging out three tortoises in two and a half hours in one night (Heptner and Sludskij 1980). Observed hunts were a simple chase and grab procedure (Kruuk 1976). Food storage is practised commonly; the relevant food item may be stored in tall bushy or marshy clumps or at the base of dense shrubby vegetation (Kruuk 1976).
Bone collections are common at den sites for the species, although the degree to which these collections represent scavenged vs. killed prey and the nutritional role of the bones collected is unclear. Several studies have inferred diet by combining data from bone collections and faecal samples (Kerbis-Peterhans 1992, Leakey 1999). In central Kenya, however, the bone collections represented a much broader range of prey than did scat analysis and significant portions of bone assemblages were very old bones unlikely to represent scavenging from fresh kills (Wagner pers. obs.). From faecal analysis alone, Kruuk (1976), Macdonald (1978), Bouskila (1984), Leakey (1999), and Wagner (2006) all found remains of prey items that are more likely to be scavenged. In addition, larger mammals were represented far less often in the analysis of hairs by Wagner (2006) than would have been expected based on den bone collections alone.
Although sometimes found in small groups of up to four individuals while resting, striped hyaenas appear to be strictly solitary foragers in Africa (Kruuk 1976, Wagner pers. obs.). In Israel, however, groups of hyaenas do converge at feeding sites (Kruuk 1976, Macdonald 1978, Bouskila 1984), but there is no clear indication of cooperative foraging and relatedness of observed groups has not been investigated. Foraging activity in Kenya and Tanzania was restricted entirely to nighttime except during rain and/or unusually dark and cloudy weather (Kruuk 1976, Wagner pers. obs.). Under those circumstances, striped hyaenas may return to previously visited kills or carcasses, but do not embark on full foraging forays (Wagner pers. obs.). Crude food storage under bushes was observed by Kruuk (1976) in the Serengeti. In many areas, striped hyaenas have also been described as raiding human grave sites and carrying away bones (Horwitz 1988, Leakey 1999), and fruit and vegetable crop raiding is considered a serious problem in Israel (Kruuk 1976).
Kruuk (1976) described foraging behaviour in which striped hyaenas zigzagged across the landscape and did not follow set routes, even when returning to the same food source on multiple nights. Striped hyaenas spent long periods of time sniffing at the base of trees and bushes, but the head is generally held vertically while travelling. Minimum mean distance travelled per night was 19 km at speeds of 2-4 km/h, occasionally trotting at speeds of up to 8 km/h, or running at a maximum of 50 km/h.
Overall, the evidence indicates striped hyaenas in Africa are solitary foragers for which fruit and vegetable matter, where available, may play a significant part. Striped hyaenas also regularly consume insects, invertebrates, small vertebrates, and actively hunt small mammals and ground-nesting and/or ground-feeding birds. In addition, they scavenge off carcasses of larger mammals and this activity appears to account for a significant portion of the bones collected at den sites.