Panthera leolion

Geographic Range

African lions (Panthera leo) live in most of sub-Saharan Africa except in desert and rainforest habitats. Lions were once exterminated from South Africa, where they remain in Kruger and Kalahari Gemsbok National Parks and possibly some other protected areas. Lions once ranged throughout southwest Asia and north Africa. Asiatic lions (P. l. persica) belong to the single remaining subspecies in this region. Once roaming from Greece to central India, Asiatic lions persist in the Gir forest of northwest India. ("Asiatic Lion Information Center", 2001; Alden, et al., 1998; Estes, 1993)

In addition to the asiatic subspecies, many taxonomists contend that there are five extant African subspecies. Each subspecies is identified by geographic region. Panthera leo senegalensis (west African or Senegalese lions), P. l. azandica (north east Congo lions), P. l. bleyenberghi (Katanga, Angolan, or south Congo lions), and P. l. krugeri (south African or Transvaal lions). Panthera leo krugeri includes Kalahari lions (sometimes denoted as P. l. verneyi). Lastly, there are East African lions (P. l. nubica). These animals have been categorized as Somali lions (P. l. somaliensis), Masai lions (P. l. massaicus), Serengeti lions (P. l. massaicus), Congo lions (P. l. hollisteri), and Abyssinian lions (P. l. roosevelti). It should be noted, however, that there is some debate as to the validity of the African subspecies classifications, leaving only the Asiatic subspecies, P. l. persica, uncontested. (O'Brien, et al., 1987; Urban and West, 2002)

Habitat

African lions live in plains or savanna habitat with a large prey base (mostly ungulates) and sufficient cover available. In these optimal habitats, lions are the second most abundant large predator, after spotted hyenas Crocuta crocuta. Lions can also live, with wider ranges, in most habitats except in tropical rainforests and in deserts. Lions can live in forested, shrubby, mountainous, and semi-desert habitats. They are capable of living at high altitudes. There is a lion population in the Bale Mountains of Ethiopia at 4,240 m.

Asiatic lions live in scrubland and teak forest in the small Gir Forest preserve of India. ("Asiatic Lion Information Center", 2001; Alden, et al., 1998; Cat Specialist Group, 1996; Estes, 1993)

  • Range elevation
    4240 (high) m
    13910.76 (high) ft

Physical Description

Lions are large cats with short, tawny coats, white underparts, and long tails with a black tuft at the end. They are sexually dimorphic and male lions are the only cats with manes. Three year-old male lions grow manes that vary in color from black to blond. Manes tend to be fuller in open habitats. Adult males typically weigh 189 kg; the heaviest male on record weighed 272 kg (Mount Kenya). Females weigh 126 kg on average. The average male height is 1.2 m and the average female height is 1.1 m. Length ranges from 2.4 to 3.3 m and tail length ranges from 0.6 to 1.0 m; the longest male lion recorded was 3.3 m.

Cubs have brown spots on a grayish coat until the age of three months; spots may remain on stomach, especially in east Africa. Albinism does occur in some populations, but there are no published records of melanism (black fur) in lions. Adult lions have 30 total teeth and adult females have four mammae. (Alden, et al., 1998; Cat Specialist Group, 1996; Estes, 1993; Urban and West, 2002)

Asiatic lions (P. l. persica) are slightly smaller than African lions and have shorter manes, thicker elbow and tail tufts, and longitudinal skin folds on their stomachs. Although Asiatic lions are genetically distinct from African lions, the genetic difference between the two species is smaller than that between human races. ("Asiatic Lion Information Center", 2001)

  • Range mass
    126 to 272 kg
    277.53 to 599.12 lb
  • Range length
    2.4 to 3.3 m
    7.87 to 10.83 ft
  • Average basal metabolic rate
    94.58 W
    AnAge

Reproduction

Lions breed year-round and are usually polygynous. It is estimated that lions copulate 3,000 times for every cub that survives over one year. One estrus out of every 5 results in a litter and lions mate approximately 2.2 times per hour for the 4 day estrus period. The first male member of a pride that reaches a female in heat has the mating priority over her. Fighting between pride members over females does not normally occur. (Estes, 1993)

Male lions are conspicuously large and showy because they have the opportunity to control the reproduction of many females when they rule over a pride. Males form coalitions with each other to increase their chances of pride takeover. The fierce competition among males and the social structure of a pride have led to infanticide by both males and females. Successful males that takeover a pride have about 2 years before another younger, stronger coalition will replace them. Pride takeover battles are often violent leading to severe injury or death of the losing lions.

It is to the successful male’s reproductive advantage to kill the suckling cubs of the defeated males. A nursing lioness that loses her cubs will come back into estrous within 2 to 3 weeks. The normal time between births is 2 years, which is the typical time for a male to rule a pride. Therfore, by killing all unweaned cubs at the time of pride takeover, males can ensure that they have some opportunity to father offspring of females who would otherwise not be available to them during their tenure as pride leaders. Females vigorously defend their cubs during a takeover and are sometimes killed also. (Estes, 1993; Packer and Pusey, 2001)

Female lions are polyestrous, breeding throughout the year and peaking in the rainy season. Female lions tend to have cubs every 2 years. However, if a female's cubs are killed (usually by an intruding male lion), then the female comes into estrus early and has more cubs. Females are able to breed at 4 years of age and males at 5 years. (Alden, et al., 1998; Estes, 1993; Schaller, 1972)

One to six cubs are born after a 3.5 month gestation period. There is an interbirth interval of approximately twenty to thirty months. Newborn cubs weigh 1 to 2 kg. Eyes typically open by 11 days, cubs can walk by 15 days and are able to run by 1 month of age. Mother lions keep their cubs in hiding until they reach about 8 weeks of age. The cubs are weaned between 7 and 10 months, however they are dependent upon adults in the pride until they are at least 16 months old. (Estes, 1993; Schaller, 1972)

  • Breeding interval
    Female lions tend to have cubs every 2 years. However, if a female's cubs are killed (usually by an intruding male lion), then she will come into estrus early and have more cubs.
  • Breeding season
    Breeding peaks during the rainy season, but is year-round.
  • Range number of offspring
    1 to 6
  • Average number of offspring
    3
  • Average number of offspring
    3
    AnAge
  • Average gestation period
    3.5 months
  • Average gestation period
    109 days
    AnAge
  • Range weaning age
    7 to 10 months
  • Range time to independence
    16 (low) months
  • Average age at sexual or reproductive maturity (female)
    4 years
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    1095 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    5 years
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    1095 days
    AnAge

Females are mainly responsible for care of the young. Females nurse their young, but will also nurse the young of their female relatives in the pride if litters are born close together. Cub mortality is lowest when related females in the same pride synchronously reproduce and cross-suckle. Since synchronous reproduction is common in prides, cubs are often raised in crèches where the entire pride helps to raise several litters. (Estes, 1993; Urban and West, 2002)

Cubs are often left alone for more than one full day by the time they are 5 to 7 months old. This is a particularly vulnerable time for the cubs to be attacked by predators (often hyenas). Hungry mothers occasionally abandon weak cubs that can not keep up with the pride. (Estes, 1993)

Although males do not directly provide care for the young in a pride, they are important in the protection of the cubs from rival males. So long as a male maintains control over a pride, preventing another male from taking over, the cubs he has sired are at lower risk of infanticide. (Packer and Pusey, 2001)

  • Parental Investment
  • no parental involvement
  • altricial
  • male parental care
  • female parental care
  • pre-fertilization
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • post-independence association with parents
  • inherits maternal/paternal territory

Lifespan/Longevity

Female lions typically live longer than males. Males reach their prime between five and nine years but few males survive past ten years of age. Some males have survived until 16 in the wild. Females normally live until 15 or 16 years. In the Serengeti, females live up to 18 years. In captivity, lions live approximately 13 years. The oldest known lion was 30 years old. (Cat Specialist Group, 1996; Estes, 1993; Urban and West, 2002)

Adult lions have no predators, but are vulnerable to humans, starvation, and attacks from other lions. Infanticide is an important contributor to cub mortality and cub mortality increases when prey is scarce. (Schaller, 1972)

Female Asiatic lions live an average of 17 to 18 years, with a maximum of 21 years. Male Asiatic lions generally live for 16 years. Adult Asiatic lions have a less than 10% mortality rate. In the Gir forest, 33% of cubs die during their first year of life. ("Asiatic Lion Information Center", 2001)

Behavior

Lion prides are fission-fusion societies; pride members come and go and are rarely all together at once. There can be anywhere from 2 to 40 lions in a pride. In Kruger and Serengeti National Parks, pride size was on average 13 lions. The average composition of these prides was 1.7 adult males, 4.5 adult females, 3.8 subadults, and 2.8 juveniles. (Estes, 1993; Packer and Pusey, 2001)

The resident males of a pride are immigrants that have forcefully gained control of the pride from the previous male members. In order to successfully take over a pride, males form coalitions, usually consisting of brothers. Adolescent males leave their natal pride when their fathers (or the new male leaders of the pride) begin to view them as competition at about 2.5 years. These males lead nomadic lives for two to three years, then form a coalition and seek a pride to take over. Male coalitions of 2 tend to rule a pride for no more than two and a half years, long enough for one set of cubs to be reared. Coalitions of three and four tend to rule a pride for longer than 3 years. Coalitions of more than four are rare, most likely because large coalitions are difficult to keep together. (Estes, 1993; Packer, et al., 1990)

Prides are comprised of related females. Females are lifelong residents in their mother’s territory. Female pridemates do not compete or fight with each other and do not display the kinds of dominance behavior that are observed in many matriarchal social systems. Related females in the same pride tend to have synchronous reproduction, and they cross-suckle their cubs. This cooperative behavior discourages dominance behavior. In contrast, males are very aggressive with other pride members, especially when feeding. The lack of dominance among females may have made it easier for communal cub-raising, since females are unable to influence the reproduction of other female pride members. Alternatively, the mutualistic benefits of communal cub-raising may have reduced the tendency to form pride hierarchies.

Lions have the great ability to critically injure or kill other lions when engaged in a fight. Fighting with a pridemate of similar age and sex not only threatens the survival of the individual but also risks injuring a valuable team-member that could later help to defend the pride against intruders. It would seem, therefore, that intrapride aggression would be selected against. (Estes, 1993; Packer and Pusey, 2001)

The lions of the Serengeti National Park in Tanzania have been studied continuously since 1966. Research has shown that lions form groups for many reasons besides greater hunting efficiency. Because lions live at higher population densities than other large cats, there is a great need for pride members to collectively defend their territory against takeovers by other lions. Also, lionesses reproduce synchronously and form highly stable groups that defend their cubs against infanticide. Finally, smaller prides tend to be more gregarious than larger prides in order to defend their territory as a group. (Packer, et al., 1990)

Areas that have the greatest variety and total biomass of hoofed mammals (prey) in open habitats can support up to 12 lions per 100 km^2. In an area with bountiful prey, lions spend approximately twenty hours per day sleeping. They become most active in the late afternoon, mainly socializing with the pride. Hunting typically takes place at night and into the hours of the early morning.

Lastly, lions have a common greeting ritual of rubbing heads together with tails looped in the air, while moaning. (Estes, 1993)

  • Range territory size
    20 to 400 km^2

Home Range

Home range sizes of African lions depend on the prey density. Home ranges can be from 20 to 400 km^2. (Estes, 1993)

Communication and Perception

Lions have the cognitive ability to recognize individuals and to interact with other lions to benefit their own survival. They use visual cues in this communication. For example, the mane is thought to signal to other lions the sex of a male from a distance and to indicate individual fitness. (The rate of mane development is mostly controlled by testosterone.)

Resident male lions regularly mark their territory by spraying vegetation with urine and by scuff-marking. Females spray occasionally. This behavior starts at the age of 2 years. This type of marking uses both chemical and visual communication signals.

Male lions start to roar at 1 year of age and females start shortly after this. The male’s roar is both louder and deeper than the female's. Lions can roar at any time, but they typically stand or crouch while roaring. Roaring serves to advertise territories, to communicate with other pride members, and to demonstrate aggressions toward enemy lions. Lions also roar in chorus; this may be a form of social bonding. This is accoustic communication.

Finally, lions use tactile communication. Males engage in physical aggression during pride take over. There is touching during greetings between pride members. Physical communication passes between lactating females and the cubs they are nursing. (Estes, 1993; Grinnel, et al., 1995; Schaller, 1972; Urban and West, 2002)

Food Habits

Lions are predatory carnivores. They usually hunt in groups, but the actual killing is done by an individual lion. They frequently bring down prey much bigger than they are themselves. Showy males have more difficulty hunting than females because of their conspicuousness, therefore females in a pride do the majority of hunting. Males are still more aggressive during feeding than are females, even though they are less likely to have killed the prey. (Estes, 1993)

African lions eat the most common large ungulates in the area (Thompson's gazelles Eudorcas thomsonii, zebras Equus burchellii, impalas Aepyceros melampus, and wildebeests Connochaetes taurinus). Individual prides tend to have their own eating preferences. Some prides tend to target large prey such as cape buffalo Syncerus caffer and giraffe Giraffa camelopardalis. Lions that are not able to capture large prey will eat birds, rodents, fish, ostrich eggs, amphibians and reptiles. Lions also actively scavenge, taking cues from hyenas and vultures. (Alden, et al., 1998; Estes, 1993)

In Tanzania's Serengeti National Park, local lions subsist on a diet comprized mainly of 7 species: zebras Equus burchellii, wildebeests Connochaetes taurinus, Thompson's gazelles Eudorcas thomsonii, buffalos Syncerus caffer, warthogs Phacochoerus aethiopicus, hartebeests Alcelaphus buselaphus, and topis Damaliscus lunatus provide 90% of their diet.

Hunting effectiveness is increased by hunting in groups. Serengeti research has shown that individual lions succeed in their hunting 17% of the time, whereas group hunts succeed 30% of the time. (Urban and West, 2002)

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates
  • Animal Foods
  • birds
  • mammals
  • amphibians
  • reptiles
  • fish
  • eggs
  • carrion

Predation

Adult lions have no natural predators, excepting persecution by humans. Lions often kill and/or compete with other predators (leopards Panthera pardus and cheetahs Acinonyx jubatus). Spotted hyenas Crocuta crocuta defend kills or scavenged food from immature and female lions, but typically leave the food to a big male lion. Hyenas are known to kill lion cubs, juveniles, or weak and sick adult lions. (Estes, 1993; Schaller, 1972)

Lion cubs, if left alone, can be vulnerable to other large predators. However, infanticide is the primary threat to cubs. (Estes, 1993; Schaller, 1972)

Human poaching is a problem for lions. These animals are poached with wire snares, rifles, and arrows. Since lions are scavengers, they are particularly vulnerable to intentionally poisoned carcasses. There are still poachers that operate within some national parks in Africa. It has been estimated that in the 1960's, poachers were responsible for approximately 20,000 lion deaths per year in Serengeti National Park. Trophy hunting is allowed in 6 African countries. (Cat Specialist Group, 1996; Estes, 1993; Schaller, 1972)

Ecosystem Roles

Lions are the top predators in their range. It is not clear to what extent lions regulate their prey population; some studies have shown that food availability plays a larger role in regulating prey populations than consumption by lions. (Eltringham, 1979)

Economic Importance for Humans: Positive

Lions are a glamorous species, well-known throughout the world. They are a cultural icon in England and are one of the highest valued eco-tourism species in Africa. They are also the subject of many documentaries and research efforts. (Dudley, 2002)

  • Positive Impacts
  • ecotourism
  • research and education

Economic Importance for Humans: Negative

Humans are fearful of being attacked by lions and of their livestock being killed by lions. In most cases, this has not been a large problem. Lions have historically coexisted with the Masai and their cows in east Africa. When the prey base is plentiful, lions do not typically attack cattle. Also, if a lion sees a human on foot, it will typically run in the opposite direction. (Eltringham, 1979; Packer and Pusey, 2001)

There have been well-publicized attacks on humans by lions, such as the man-eating lions of Tsavo (killed 135 construction workers) portrayed in the 1996 movie The Ghost and the Darkness. As lions lose habitat, they are more frequently entering human inhabited areas, thus creating more conflict and potential for "problem lions" that attack humans. (Dudley, 2002; Pickrell, 2004)

Lions are frequently infected with FIV (Feline Immunodeficiency Virus) which is similar to HIV. In Tanzania’s Serengeti National Park, Ngorongoro Crater, and Kruger National Park of South Africa, 92% of lions tested had FIV. FIV does not seem to adversely affect lions but it will kill domestic cats. (Packer and Pusey, 2001; Urban and West, 2002)

Conservation Status

Panthera leo leo (Barbary lions) and P. l. melanochaita (Cape lions) are two extinct subspecies of African lion.

African lion populations have greatly declined in West Africa and in many African countries they are restricted to protected areas. If there are no connecting corridors between wildlife reserves genetic viability will likely become a problem. (Cat Specialist Group, 1996; Hanby, et al., 1995; Urban and West, 2002)

Asiatic lions, P. l. persica, are confined to one population in the Gir Forest reserve of India, consisting of less than 200 mature individuals. This subspecies is listed as critically endangered on the IUCN red list and is on Appendix I of CITES. Another population of Asiatic lions is desperately needed in order to safeguard the survival of this subspecies. The Palpur-Kuno Wildlife Sanctuary in northern Madhya Pradesh had been identified as a potential reintroduction site in India. Threats to the Gir Forest population include the close proximity of humans and their cattle and habitat degradation. ("Asiatic Lion Information Center", 2001; Cat Specialist Group 2001, 2003; O'Brien, et al., 1987)

Some very small lion populations require genetic management in order to survive and maintain genetic diversity. Hluhluwe-Umfolozi Park (HUP) in Natal, for example, has a population of 120 lions produced from only three lions that were introduced into the park in the 1960s. In 2001, researchers tried artificial insemination techniques to rejuvenate the genetic pool of these South African lions. This process is very difficult and energy intensive. Inbred populations could also potentially be rejuvenated by introducing adult females and whole prides into an area (minimizing conflict between existing lions and introduced lions). (Trivedi, 2004)

Other Comments

Fortunately, individual lions can be dependably identified in an unobtrusive manner. Lion whisker spots are similar to our finger prints. Every individual lion has a unique whisker spot pattern. More specifically, the number and relative position of whisker spots on the top row are used to identify individuals.

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

Erin Harrington (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

carrion

flesh of dead animals.

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal

chemical

uses smells or other chemicals to communicate

choruses

to jointly display, usually with sounds, at the same time as two or more other individuals of the same or different species

cooperative breeder

helpers provide assistance in raising young that are not their own

crepuscular

active at dawn and dusk

ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

nomadic

generally wanders from place to place, usually within a well-defined range.

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

polygynous

having more than one female as a mate at one time

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

scrub forest

scrub forests develop in areas that experience dry seasons.

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

sexual ornamentation

one of the sexes (usually males) has special physical structures used in courting the other sex or fighting the same sex. For example: antlers, elongated tails, special spurs.

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5? N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

year-round breeding

breeding takes place throughout the year

References

2001. "Asiatic Lion Information Center" (On-line). Accessed February 09, 2004 at http://www.asiatic-lion.org.

Alden, P., R. Estes, D. Schlitter, B. McBride. 1998. National Audubon Society Field Guide to African Wildlife. New York, United States of America: Alfred A. Knopf, Inc..

Cat Specialist Group 2001, 2003. "Panthera leo" (On-line). 2003 IUCN Red List of Threatened Species. Accessed February 09, 2004 at http://www.redlist.org/search/details.php?species=15951.

Cat Specialist Group, 1996. "African Lion Panthera leo (Linnaeus 1758)" (On-line). Accessed February 09, 2004 at http://lynx.uio.no/catfolk/afrleo01.htm.

Dudley, J. 2002. Issues and Priorities for Mammal Conservation. Conservation Biology, 16/4: 1169.

Eltringham, S. 1979. The Ecology and Conservation of Large African Mammals. London, Great Britain: The MacMillan Press Ltd..

Estes, R. 1993. The Safari Companion: A Guide to Watching African Mammals. Vermont, United States of America: Chelsea Green Publishing Company.

Grinnel, J., C. Packer, A. Pusey. 1995. Cooperation in male lions: kinship, reciprocity, or mutualism?. Animal Behavior, 49/1: 95-105. Accessed February 10, 2004 at http://www.sciencedirect.com/science.

Hanby, J., J. Bygott, C. Packer. 1995. Ecology, Demography, and Behavior of Lions in Two Contrasting Habitats: Ngorongoro Crater and the Serengeti Plains. Pp. 315-331 in A Sinclair, P Arcese, eds. Serengeti II. Chicago, United States of America: The University of Chicago Press.

O'Brien, S., J. Martenson, C. Packer, L. Herbst, V. de Voss, P. Jocelyn, J. Ott-Jocelyn, D. Wildt, M. Bush. 1987. Biochemical genetic variation in geographically isolated populations of African and Asiatic lions. National Geographic Research, 3/1: 114-124.

Packer, C., A. Pusey. 2001. Egalitarianism in Female African Lions. Science, 293/5530: 690-693. Accessed February 09, 2004 at http://www.sciencemag.org/cgi/content/full/.

Packer, C., D. Scheel, A. Pusey. 1990. Why Lions Form Groups: Food is Not Enough. American Naturalist, 136/1: 1-19.

Pickrell, J. 2004. "Man-Eating Lions Not Aberrant, Experts Say" (On-line). National Geographic News. Accessed February 12, 2004 at http://news.nationalgeographic.com/news/2003/02/0211_030211_tsavolions.html.

Schaller, G. 1972. The Serengeti Lion. Chicago, United States of America: The University of Chicago Press.

Trivedi, B. 2004. "To Boost Gene Pool, Lions Artificially Inseminated" (On-line). National Geographic News. Accessed February 08, 2004 at http://news.nationalgeographic.com/news/2002/06/0612_020612_TVlion.html.

Urban, M., P. West. 2002. "Lion Research Center" (On-line). Accessed February 10, 2004 at http://www.lionresearch.org/.