The rare but fascinating albino species
Aug 06 2014
Recently, I saw a spotted deer and it was completely white. Normally, a deer’s white spots are clearly visible on its brown coat, but in this one, it was all white on white. My friend in Cotigaon, Goa, is always inviting me to come see the black panther, a rare treat for any wildlife watcher. This beast is actually a normal leopard but with extra pigment. Similarly in 2007, forest officials at Simlipal Tiger Reserve, Odisha, found two tigers-moms and a small cub, all of whom had a special coat — they not only had many more stripes than normal tigers but these were extra thick as well.
If we dig deeper, we find that these abnormal pigment and colour formations are an example of albinism. It is an inborn disorder characterised by the complete or partial absence of pigment in the skin, hair and eyes due to absence or defect of the particular enzyme involved in the production of melanin. Melanin is a broad term for a group of natural pigments found in most organisms. In many birds, which have white feathers but black eyes, it is example of leucism. Albinism is a complete lack of the cells that produce pigments whereas these cells are “switched off'” or faulty in the leucistic state. Leucism differs from albinism in that the melanin is, at least, partially absent but the eyes retain their usual colour. Some leucistic animals are white or pale because of chromatophore (pigment cell) defects, and do not lack melanin.
Melanism is the direct opposite of albinism. An unusually high level of melanin pigmentation results in an appearance darker than non-melanistic specimens from the same gene pool. They are not albinos either; they do have black stripes, just that they are not capable of producing pheomelanin pigment that turns tigers orange–yellow. But they do produce eumelanin pigments that explain the black stripes. In other words, white tigers suffer a less severe mutation of genes than other albinos. So, due to genetic or cell disorders, they appear different.
(The writer is a conservation biologist at Tiger Watch, Ranthambore)