For the convenience of the reader, there are 2 accepted lion sub-species – Panthera leo persica (Asian/Asiatic/South Asian lion) and the African lion (P leo leo). These have differences in anatomy. The European lion (P l europaea) is now extinct. Sub-Saharan African lions are genetically and anatomically similar enough to be considered a single subspecies, but differences in size, mane, colour and behaviour has led to localised populations being considered subspecies by some taxonomists. They are possibly more analogous to "breeds" as found in domestic cats.

Regional strains or subspecies of African lion: Panthera leo azandica (North East Congo lion), P l bleyenberghi (Katanga/Southwest African lion), P l hollisteri (Congo lion), P l krugeri (South African/Southeast African lion of which the White lion is a colour variant), P l leo/P l berberisca (Barbary lion, extinct in the wild), P l melanochaita (extinct Cape lion), P l massaicus (Masai lion), P l nubica (Ethiopian/Nubian/East African lion), P l roosevelti (Abyssinian lion), P l somaliensis (Somali lion), P l senegalensis (Senegal/West African lion), P l verneyi (Kalahari lion).

There is only a remnant population of Asian (or Asiatic) lions remain in the wild. These are found in the Gir Forest Sanctuary in northwest India. They differ from African lions in several ways: smaller manes in males, an abdominal fold and pairing (or bifurcation) of the infraorbital foramen (i.e. 2 holes in the skull just below the eye while African lions have only one hole).

In the mid 1980s it was found that some "Asian" lions exported to the USA from Trivandrum Zoo, India were Asian/African hybrids. Paul Joslin, former assistant director of Chicago's Brookfield Zoo had noticed that many "Asian" lions in US zoos lacked the telltale belly fold. He also noticed an increase in infant mortality which is indicative of inbreeding depression. The captive population of Asian lions originated from only 5 founder animals, mostly hybrids. Research by O'Brien and Martenson (O'Brien, SJ, Joslin, P, Smith III, GL, Wolfe, R, Schaffer, N, Heath, E, Ott-Joslin, J, Rawal, PP, Bhattacharjee, KK and Martenson, JS, Zoo Biol, 1987, 6, 99-116) found that almost all "Asian" lions exhibited in US zoos and some in Asian ones as well were hybrids were hybrids. This may affect other zoos around the world due to the loan and trading of stock, however loans and transfers are traceable.

Analysis of mitochondrial DNA (which is normally contributed only by the mother) showed that African lionesses and Asian male lions were used in creating the hybrids. The hybrids inherited their mothers' African-type mitochondrial DNA (Pattabhiraman Shankaranarayanan and Lalji Singh, 1998). The two subspecies diverged around 80,000 to 100,000 years ago. Mitochondrial DNA analysis indicated that Asian lions underwent a population bottleneck about 10,000 years ago at the end of the Pleistocene ice age (Menotti-Raymond, MA and O'Brien, SJ, Proc National Acad Sci USA, 1993, 90, 3172-3176) which reduced the population to only a few breeding individuals.

In 2006 Chhatbir Zoo (at Chandigarh, Punjab in India) set up a sanctuary for its ageing and ill Asian/African hybrid lions. They had around 30 remaining hybrids, some of which will be kept in special enclosures separate from younger, more vigorous lions in the sanctuary. More than 300 hybrids housed in zoos and safari parks around India will be sterilised and allowed to die of old age or natural causes. India's Central Zoo Authority (CZA) has ordered the sterilisation of all hybrids so that the strain becomes extinct and does not taint purebred Asian lion stock.

The Asian/African breeding programme began in the late 1970s when captive Asian lions in Indian zoos were crossed with African lions from travelling circuses (not the best parental stock). At the time, the emphasis was on prolific breeding of "improved" lions for exhibition purposes rather than conservation of pure-bred Asian lions. The breeding programme was largely unsupervised, hence the unwise degree of inbreeding. The hybrids have characteristics of both the Asian and the African species, but have poor immune systems and are disease-prone.

Chhatbir Zoo was at the forefront of the programme and bred around 100 hybrid lions. Many sickened and died; almost 45 have died over the past 3 years including 13 cubs in one go. Around 30 of the hybrids remain there. The zoo's director, Kuldip Kumar, admitted that the subsequent inbreeding since the mid-1980s had weakened the bloodline and devastated the gene pool. Some have wounds that refuse to heal while other were born paralysed. Indian laws and tradition prohibit euthanasia and so the lions are kept as healthy and comfortable as possible.

It was originally hoped that the hybrids could be introduced into the wild to bolster the Asian lion stock, but instead of hybrid vigour, the programme resulted in inbreeding depression. The hybrids have apparently weakened the Asian lion's gene pool, resulting in lions with physical and mental defects and weakened immune systems. Reports are suggestive of postzygotic incompatibility between the lion subspecies, however some of the defects are probably attributable to inbreeding of a limited gene pool (hybrid or otherwise) for mass-production and not simply to the lions being hybrids.

The breeding programme ended in 2002 and all of the male mixed blood lions in zoos were sterilised to prevent further breeding of hybrids. The remaining hybrids are expected to die out before 2020.

It is known that hybrids between the Barbary lion and other African lion subspecies are held in zoos. There are only a few remaining pure-bred Barbary lions and careful management is required to avoid excessive inbreeding. It may, therefore, become necessary to analyse the DNA of hybrids and to use those with the greatest proportions of Barbary lion DNA and the closest resemblance to the Barbary lion's appearance. If the latter is the case, the Barabary lion would be a recreation of the type rather than a restoration of the subspecies.

REFERENCES AND FURTHER READING

For more information on the genetics of colour and pattern:
Robinson's Genetics for Cat Breeders & Veterinarians 4^th Ed (the current version)

For more information on genetics, inheritance and gene pools see:
The Pros and Cons of Inbreeding
The Pros and Cons of Cloning

For more information on anomalous colour and pattern forms in big cats see
Karl Shuker's "Mystery Cats of the World" (Robert Hale: London, 1989 - some of the genetics content is outdated)