What colour is your hen? A question as simple as that will leave Selvaraj fumbling for an answer.

The small time farmer is yet to figure out the real colour of the hen strutting about in the premises of his house at Mukkola near Vizhinjam here.

The six year old bird is now a celebrity of sorts, grabbing public attention for its capacity to change colour periodically from black to white and back. Scientists are studying the hen that has already changed colour four times.

It was after the first egg laying period that Mr.Selvaraj and family noticed the black hen gradually changing to white without completely shedding its feathers. In about an year’s time, the bird became completely white, starting from the downfeathers.

The newly white hen continued to lay eggs. The magic began to work again after one year when the bird started turning black. It was then that Mr. Selvaraj decided to notify the Zoology department of the University of Kerala about the recurring event. A team of researchers led by CSIR emeritus scientist, Zoology Department and Centre for Bioinformatics, Dr. Oommen V. Oommen, examined the hen in 2008. The team members including R. Dileep kumar, K. Ramachandran and L. Divya tagged the bird and collected blood samples for further investigation. They continued to observe the hen that was superficially black with patches of white underneath.

The bird turned black and white in 2009 and almost white in 2010. The blood samples collected in 2008, 2009 & 2010 were analyzed for several hormones including estrogens (female sex hormone). The team also consulted Dr. Chandana Haldar from the Benares Hindu University and other scientists.

The colour change in the bird was found to coincide with an abnormal increase in the level of estrogen, peaking at almost six times the normal for a hen. Coincidentally, an experiment conducted by Prof. Thapliyal (Dr. Oommen’s mentor) of BHU in the 1960’s had established that estrogens can inhibit pigmentation in females.

“Here is a natural situation of high concentration of estrogens inhibiting the colour pigmentation process to turn the bird’s black plumage to white”, says Dr. Oommen. However, the reversal of the process remains a mystery for the scientists. “It will require detailed genetic studies to unravel the science of this recurrent colour change”, Dr.Oommen says.

“It is definitely a freak phenomenon. What we have observed is that the feathers are changing colour and not moulting”, he said. The team has observed the colour changing process to be slowing down in the ageing hen.

The colour changing phenomenon is not unheard of in birds. There were reports of a normal blue Andalusian hen in Kansas, USA turning white in 1917- 1918. But the bird never returned to its original colour.

Incidentally, this is not the first time Dr. Oommen and his team have been on the trail of animals exhibiting abnormal colour characteristics.

In 2008, the scientists came across a black squirrel, a species not endemic to India. After DNA tests, the team, with the help of UK- based scientist Dr. Alison Thomas, identified the animal as a striped grey palm squirrel that could have possibly undergone genetic mutation. Efforts were also launched to identify the chromosome responsible for the mutation that gave the animal its unique black coat.