21 January 2014 - 1:48pm
Only a few days ago, a young white bottlenose dolphin was brutally ripped apart from her family by dolphin fishermen in Taiji, destined for a life in captivity. Although every whale, dolphin and porpoise is special and deserves to live a life free from pain and suffering, when something "different" comes along, it's only human nature that the focus of attention is to some extent, diverted towards the anomaly.
Hence, at the same time as being outraged at the goings-on in Taiji, people have been asking, "How rare is this condition amongst whales and dolphins?", "Why does it happen?", "Is it a true albino?" and "What does this abnormal colouration mean for its long-term survival?". Hopefully I can try to help answer some of these questions.
(Iceberg - the white orca spotted off the coast of Russia; (c) E. Lazareva, Far East Russia Orca Project (FEROP, WDC))
So let's begin with "Why does it happen, how rare is it and what's the cause?"
Albinism is a condition that can affect all vertebrates. It is a congenital disorder (meaning it is inherited from the parents) and is characterised by the complete or partial absence of pigmentation in the skin, hair and eyes. This pigmentation is called melanin and there are varying degrees of melanin expression in individuals. "True" albinism only occurs if both the parents carry the recessive gene for the condition and the offspring receives both copies of the recessive gene. Depending on the degree of albinism, the individual may have all or some of the following characteristics: white or pale skin (and hair), pink or red eye colouring and often, impaired vision and hearing.
Interestingly, the incidence of albinism can be artificially increased in fish by exposing the eggs to heavy metals (arsenic, cadmium, copper, mercury, selenium, zinc) and therefore whether this is a condition that we might see more of in marine mammals in the years to come is a question not yet answered.
Some animals can be white or lighter-coloured than usual but not be a "true albino". Unlike albinos, they have dark coloured eyes and usually possess a few dark patches of skin, for example on the dorsal fin or around the eyes. This condition is called leucism, and occurs when the melanin is partially absent, meaning that it is expressed in some regions of the body but not others.
To date, albinism has been documented in over 20 cetacean species, including humpback whales, bottlenose dolphins, orca and harbour porpoises. The inspiration for the classic "Moby Dick" for example was a white sperm whale.
"What challenges face albino whales, dolphins and porpoises?"
In general, those with albinism are as healthy as those without, however there can be some associated issues that affect their vision and/or hearing but this is not always the case. Albino or otherwise uniquely-coloured animals can also be subject to increased risk in the wild, for example they will have less camouflage to help them hide from predators and they may find it more difficult to attract a mate as they may be seen as being different or less attractive. Importantly, melanin is thought to protect skin cells from UVB light (the damaging kind) and therefore reduce the incidence of skin problems including cancer and so without the presence of melanin, light-coloured animals may face a higher risk of sun-damage.
Another and possibly the most important risk, is the additional (and unwanted) attention and disturbance from humans. As has become evident from the young calf in Taiji, they may pay the biggest price of all - that of a life away from its family, imprisoned in a concrete tank, at the mercy of humans. No-one knows how this calf will fare in captivity but one thing is for sure, she was better of where she was, living a life in the wild with her family around her.