Catfolk Species Accounts: African lion (Panthera leo)

Description and Behavior
Smuts (1976) reports the following weight series for lions in South Africa's Kruger National Park: adult males (>4 years) 181 kg (n=14) and females 126 kg (n=25); sub-adult males (2-4 years) 146 kg (n=25) and females 103 kg (n=11); large male cubs (1-2 years) 77 kg and females 60 kg. The largest adult male weighed 225 kg, and the largest female 152 kg (Smuts 1982). A male shot near Mount Kenya in 1993 weighed 272 kg (R. Kock in litt. 1993). The record total lengths (including the tail) for male lions are around 3.3 meters (Guggisberg 1961). Lions have uniformly tawny coats. While the color may vary locally from pale to dark, leucism (unusual white pelage but with pigmented eyes and skin, as opposed to true albinism which is a complete lack of pigmentation) has been reported only from the vicinity of Kruger National Park and the Umfolozi Game Reserve in South Africa (McBride 1977, Smuts 1982), and a black form has never been observed (Guggisberg 1975). Lions are the only cats with tufted tails and manes (males only). The mane appears to serve several functions: increased protection during intraspecific fighting; a signpost of gender distinguishable at distance (possibly linked to the lion’s historic colonization of open plains); and an indicator of individual fitness (Schaller 1972, Kingdon 1977). The males of many polygynous species tend to develop conspicuous display features. The fact that only the lion, out of all cats, has done so suggests that the mane is closely linked to the lion’s distinctive social system. Mane development is strongly influenced by testosterone (Schaller 1972).
The core unit of the lion’s matrilocal society is the pride, which consists of a group of related females (none dominant) and their cubs (Schaller 1972, Bertram 1975a, Packer et al. 1991a). There are only two recorded cases of unrelated females forming a pride, and both cases involved prides giving up their original natal ranges: the first when prolonged severe drought in Botswana’s Central Kalahari Game Reserve rendered the females' original ranges uninhabitable (Owens and Owens 1984), and the second when extensive culling of lions in the Kruger National Park opened up large vacancies for immigration (Smuts 1978a). Pride sizes (measured by the number of adult females) are smallest in very arid environments (mean 2.2 in South Africa’s Kalahari Gemsbok National Park: Eloff 1973a) and otherwise average between four and six (Schaller 1972, Smuts 1976, Hanby and Bygott 1979, Ruggiero 1991, Stander 1991). Pride size is positively correlated with lean season prey abundance, and in the Ngorongoro Crater, where prey is abundant year-round, groups of up to 20 adult females have been observed (van Orsdol et al. 1985).
Prides are “fission-fusion” social units: membership is stable (for example, three prides in the Serengeti have occupied the same ranges for more than 20 years), but the pride members are often scattered in small sub-groups throughout the pride range, and each individual spends a considerable amount of time alone (Schaller 1972, Bertram 1978, Pusey and Packer 1987). Females demonstrate several cooperative behaviors unique among the felids. Pride members often give birth in synchrony, and the young are reared communally, with cubs suckling freely from lactating females (Schaller 1972, Rudnai 1974, Bertram 1975b). Groups of females do most of the hunting, and males, for the short time that they are living together with females, concentrate their energy on defending their tenure (see below). Stander (1992a) found that males in Namibia's Etosha National Park failed to participate in hunts in 96% of 461 opportunities.
In general, prides often divide into smaller sub-groups when foraging (range 1-7: Stander 1992a, Scheel 1993). Stander (1992b) found a complex division of labor among hunting lionesses, with individuals repeatedly playing the same role of either "centre" or "wing". Centres, which tended to be larger and heavier lionesses, generally ambushed and captured prey chased by the wings. However, lionesses were flexible and would switch roles, depending on group composition and positioning. D. Joubert (in litt. 1993) suggests that lionesses also switch roles according to prey type: in Botswana’s Savuti National Park, he has observed, “with some consistency,” the same lioness take the lead in warthog hunts, while playing a passive role in buffalo hunts.
A single male or coalition of males (up to seven) holds tenure over one or more prides, and effectively excludes strange males from siring cubs with pride females (Packer et al. 1991a). Competition among males for pride tenure is intense, and average tenure is only two (Packer et al. 1988) to three years (Stander 1991). Males will only seek tenure over or breed with related pride females under unusual circumstances (e.g., when the population is small and there are barriers to dispersal: Pusey and Packer 1987, Packer et al. 1991a,b). Males are also highly social: coalitions in the pre- and post-tenure periods hunt and scavenge cooperatively, and larger coalitions of 4-6 males can maintain tenure more than twice as long as 1-2 males (> 47 months) (Bygott et al. 1979).
Despite maternal defense, infanticide is common when males take over a new pride: most females with dependent offspring lose their cubs within a month of a takeover, and those that are pregnant lose their cubs shortly after giving birth. In this way, males assure paternity during their short reproductive lifetime, which is generally only as long as their period of pride tenure. In response, females show a burst of heightened sexual activity for about three months following a takeover, attracting other males and encouraging competition that ensures that the fittest (often largest) coalition is able to gain tenure. They remain infertile (anovulatory: Smuts et al. 1978) during this "testing" period, and only afterwards, when tenure has stabilized, tend to breed in synchrony (Packer and Pusey 1983). Litters born synchronously have a higher survival rate (probably due to maximal maternal care [Bertram 1975b]), and tend to show a sex ratio biased toward males. This may be because groups of related males reproduce more successfully (Pusey and Packer 1987).

Coalitions of >4 males are always related (being born in the same pride, but not necessarily of the same mother), while pairs frequently consist of unrelated males (and less frequently, a related pair teams with an unrelated male to form a trio) (Packer et al. 1991a). Reproductive success increases with coalition size (Bygott et al. 1979, Packer et al. 1988). Although at least one member of male coalitions larger than two fails to breed successfully (Packer et al. 1991a), through kin selection (Bertram 1976) non-breeding helpers which are related still ensure that some portion of their genes are passed down.
The question of why sociality evolved to such a high degree in lions has been the subject of considerable debate. There were probably several contributory causes, which occurred many generations ago. Data from present-day studies cannot refute any of them, but can shed some light on how and in what circumstances they might work (B. Bertram in litt. 1993). Evidence suggests that coordinated group hunts are more successful at capturing (Packer and Ruttan 1988, Stander 1992a,b) and killing (Packer 1986) very large prey (see below for discussion of major prey species). Stander and Albon (1992) found that hunting success, even for smaller antelope prey, increased linearly with foraging group size in the semi-arid open plains of Etosha National Park. However, what would seem to be the most obvious explanation -- increased hunting success yields more food -- becomes less so on closer examination. Even on large carcasses, it appears that the presence of numerous non-hunting "cheaters" (Packer and Ruttan 1988) within the pride can reduce per capita food intake to the point where cooperative hunting does not appear to be economic for the hunters. The highest rate of food intake per hunt appears to be gained by solitary females (Packer 1986). Packer (1986), based on the theory of kin selection, argued that lions became social because it is evolutionarily more advantageous to share kills with scavenging relatives than to yield to strange lions or other large predators. Other benefits of sociality have also been pointed out: defense of young, maintenance of long term territories (Packer et al. [1990]), insurance against individual injury or incapacity, and minimization of chances of getting no food at all (B. Bertram in litt. 1993).
Major large ungulate prey species recorded in East, Central and Southern Africa include buffalo, zebra, wildebeest, roan, sable, springbok, gemsbok, kob, impala, warthog, waterbuck and hartebeest (Mitchell et al. 1965, Makacha and Schaller 1969, de Pienaar 1969, Schaller 1972, Eloff 1973a, Rodgers 1974, Rudnai 1974, Bertram 1978, Berry 1981, van Orsdol 1982, 1984, Smuts 1982, McBride 1984, Mills 1984, Fagotto 1985, Prins and Iason 1989, Ruggiero 1991, Stander 1992a, Scheel 1993, Viljoen 1993). While medium to large-sized ungulates make up the bulk of their diet, lions, like leopards, are generalist hunters, and will take a wide range of prey, from small rodents (Eloff 1973a) to young rhinos, hippos and elephants (McBride 1990, Ruggiero 1991, Viljoen 1993; H. Dublin, H. Jachmann in litt. 1993). Individual differences in prey selection and killing techniques are often discernible for different prides in the same area (Rudnai 1973, van Orsdol 1984, McBride 1990, Mills and Biggs 1993), indicating a strong role for learning in the lion’s hunting behavior. For example, a pride of lions which occasionally foraged along Namibia’s Skeleton Coast desert learned how to prey and scavenge upon Cape fur seals (Bridgeford 1985, Berry 1991a). (The entire pride was eliminated in 1991 by cattle herdsmen [Berry 1991b., L. Scheepers pers. comm. 1993]). Lions (especially males) frequently scavenge (>40% of food items in the Serengeti: Packer et al. 1990), although this behavior is less common in arid environments, where prey occurs at lower density (4.6 [Mills 1990] - 6% [Stander 1992a] of food items).
Lions usually (but not always) hunt at night (Schaller 1972, van Orsdol 1982, Mills and Shenk 1992, Stander 1992a). In Botswana’s Savuti National Park, D. Joubert (in litt. 1993) reported a higher success rate when lions hunted on moonless nights. Their distinctive roar, which in optimal conditions can be heard up to five km away (Guggisberg 1975), appears to serve to demarcate territories (Schaller 1972), much as scat deposits do for the other large cats. Stander and Stander (1987) found it possible to distinguish between not only the roars of males and females, but also of individual males.
Outside protected areas, where lions are heavily persecuted and the wild ungulate prey base is reduced, group sizes are reported to be much smaller (1-2: Thomas 1990, F. Hurst in litt. 1991), and they are seldom heard to roar (Thomas 1990, C. Stuart in litt. 1991). It is not clear whether the lion’s social system "breaks down" under such conditions of low prey and low lion density. Small foraging group size may be more efficent for stock-raiding - larger groups would be more conspicuous and vulnerable to rancher retaliation (H. Dublin, C. Packer in litt. 1993).