An alert reader from the Netherlands has informed me that four white lions were just put on view in the Ouwehands zoo.
Here are the beautiful cats; you can see more pictures here (click on “volgende” to advance the photos):
White lions have been reported sporadically for several hundred years, but appeared in recent times in the 1920’s in the Timbavati Game Reserve in South Africa. They probably arose as a genetic result of matings between relatives (“inbreeding”), which exposes recessive alleles. According to The White Lion Protection Trust, because of their rarity and beauty these lions were selectively hunted as trophies and captured for breeding. The mutant form apparently disappeared from the wild in the 1990s, but is now being reintroduced from zoos and animal farms.
White lions carry a recessive mutation affecting coat color (this means that the mating of two white lions will produce only moar white lions). The condition caused by the mutation is called “leucism.” It’s not the same mutation that causes albinism in humans and other vertebrates, for the lions have fully pigmented retinas (unlike “normal” albinos, the lions’ eyes are not pink). And, just as true albinos occur in many vertebrate species, so do true leucistic mutants.
Several sites report that white lions don’t show any noticeable decrease of survival in the wild; reports of physical defects in mutant lions may simply reflect the fact that they’re inbred (to keep a line of white lions going, you have to mate them to each other, though you can outcross them to regular lions and recover white lions in in the second generation).
The mutant lions are often given a subspecies designation, considered members of Panthera leo krugeri (the subspecies name reflects Kruger Park, where they’re also found). But this is incorrect, for white lions aren’t members of a genetically and geographically distinct interbreeding population—which is how biologists define a subspecies. These lions simply share a single mutation affecting pigmentation. Calling them members of a subspecies is no more correct than calling all human albinos, or humans with blue eyes, members of a distinct subspecies.
The coat coloration varies among individuals, sometimes having tinges of orange (I call this the “creamsicle” phenotype). This dude is pretty white:
And some cute cubs (there’s no sound until the guy is talking):
As I said, leucism occurs in many species, for lots of vertebrates carry the gene that can mutate to that condition. Here’s an American alligator (Alligator mississippiensis) with leucism: