There have been few efforts in the past to estimate the number of Lions in
The most quantitative historical estimate of the African Lion population in the recent past was made by Ferreras and Cousins (1996), who developed a GIS-based model to predict African Lion range and numbers, calibrated by surveying experts about the factors affecting Lion populations. First they correlated vegetation (Leaf Area Index) with Lion densities, using known values from 37 studies in 19 African protected areas, and mapped potential Lion range. Then the reduction effect of human activities on Lion range and numbers were estimated. Lion experts were surveyed in order to develop and rank a set of factors which would lead to lower Lion densities as well as Lion absence. These included agriculture, human population density, cattle grazing, and distance from a protected area, and were derived from GIS databases of varying age. For example, in areas identified as main cattle grazing areas Lion density was reduced by 90%, and in areas identified as having widespread agricultural cultivation or high human population density (> 2.5 people/km²) Lions were considered absent. Lion density was reduced by 50% in areas with low human population density (1-2.5 people/km²). Because of the age of their data sources on extent of agriculture and pastoralism, Ferreras and Cousins (1996) selected 1980 as the base year for their predicted African Lion population of 75,800. They emphasized the need for ground-truthing their estimate by censusing Lions, particularly outside protected areas.
Two recent surveys have provided current estimates of the African Lion population, with some ground-truthing. The African Lion Working Group, a network of specialists affiliated with the IUCN SSC Cat Specialist Group, conducted a mail survey and compiled estimates of 100 known African Lion populations. Not included were populations of known existence, but unknown or unestimated size. The ALWG African Lion population estimate is 23,000, with a range of 16,500-30,000 (Bauer and Van Der Merwe 2004). The second survey was carried out by Philippe Chardonnet and sponsored by the International Foundation for the Conservation of Wildlife and Conservation Force (Chardonnet 2002). He also compiled estimates for 144 individual African Lion populations, grouped into 36 largely isolated subpopulations. His methodology included extrapolation of estimates of known populations into areas where Lion status was unknown, and his total figure is not surprisingly larger: 39,000 Lions in
Approximately 30% of the individual population estimates compiled by the African Lion Working Group were based on scientific surveys. Techniques for these surveys included total count based on individually identified body features, sampling by use of calling stations playing recordings of hyaena and/or Lion prey, and mark-recapture methods including radio telemetry, photo databases, and spoor counts (Bauer and Van Der Merwe 2004). Seventy percent of their population figures were derived from expert opinion or guesstimate. In the other survey, 63% of Chardonnet's (2002) individual population estimates were based on expert opinions or guesstimates. Twelve percent of Chardonnet's (2002) estimates were based on scientific surveys, and a further 25% were derived from extrapolation of variables from nearby populations and catch-per-unit effort-estimates based on Lion trophy hunting.
Estimating the size of the African Lion population is an ambitious exercise involving many uncertainties. The three main efforts (Ferreras and Cousins 1996; Chardonnet 2002; Bauer and Van Der Merwe 2004) all use different methods. The African Lion Working Group compiled individual population estimates primarily from protected areas (23,000 Lions: Bauer and Van Der Merwe 2004). In 1980, Ferreras and Cousins (1996) predicted 18,600 Lions to occur in protected areas. This was probably an underestimate as not all protected areas inhabited by Lions at that time were included. Still, the comparison suggests that the number of Lions in African protected areas has remained stable or possibly increased over time. But Ferreras and Cousins (1996) predicted that most Lions in 1980 were found outside protected areas. Chardonnet (2002) finds that unprotected areas still comprise a significant portion (half) of the Lion's current African range. Comparison of Ferreras and Cousin's (1996) prediction of 75,800 Lions in 1980 (roughly three Lion generations ago) to Chardonnet's (2002) estimate of 39,000 Lions yields a suspected decline of 48.5%. This calculation suggests a substantial decline in Lions outside protected areas over the past two decades. Ferreras and Cousins (1996) may have over-estimated the African Lion population in 1980, as their number was derived from a model rather than actual Lion counts, and so it is possible that the rate of decline of the African Lion population may be lower. A group exercise led by WCS and the IUCN SSC Cat Specialist Group estimated that 42% of major Lion populations were declining (Bauer 2008). The rate of decline is most unlikely to have been as high as 90%, as reported in a series of news reports in 2003 (Kirby 2003, Frank and Parker 2003).
Genetic population models indicate that large populations (50-100 Lion prides) are necessary to conserve genetic diversity and avoid inbreeding, which increases significantly when populations fall below 10 prides. Male dispersal is also an important factor in conserving genetic variation (Bjorklund 2003). These conditions are met in few wild Lion populations, although there are at least 17 Lion "strongholds" >50,000 km² in extent (Bauer 2008).
Outside sub-Saharan Africa, the Asiatic Lion P. leo persica occurs as an isolated single wild population in