Saturday, 14 January 2012

An Interesting Phenomenon

Pepsi cruises by in April.
As devoted viewers of QI will no doubt recall, if you put a Siamese cat in a refrigerator it goes black. That is because the hair is temperature sensitive. The fur on the face, tail and feet ie the extremities, are always cooler, so always dark. However the body fur is warmer and stays pale.

Pepsi just released from a fortnight in the fridge*.
It's to do with an enzyme in the hair called tyrosine. The enzyme is involved in the production of melanin, a brown pigment, but it is heat sensitive, breaking down if the temperature goes up too much.


*Or possibly photographed visiting in the January cold.


  1. Pepsi looks a very nice cat... Baron is of Siamese parentage... mum was a Havana [all 'cigar' brown Siamese]. He's all black, all the time.... he tells me he's a cool cat... now I just have to believe him, don't I!!

  2. Pepsi is the coolest name and he seems like the coolest cat. I never knew the science behind the fur, so thank you for these great photos and an interesting story. -Lola from Et tu, Tofu

  3. What a handsome cat, and I never knew they changed colour. Cool !!

  4. Cool cat! Love the way the tabby markings show 'in the cold'. Great name too!
    Don't know if it is enzyme related[probably] but dark Persians can go 'rusty' in the sun. We had two black longhairs who had a bit of Persian in them and their fur always went rusty brown in the summer.

  5. Is it the reverse in humans? My hair has been white for years, no matter what is the temperature outside or inside. Since my head is supposed to be a cold extremity, my hair should be black. I’m hoping when I come back for good to these cold northern climes, my hair will turn much darker! BTW it is in the seventies right here in SoCal.

  6. This is the 'something new' for me to learn today ...

  7. N&A: it is exactly the same process apparently.
    CHM: don't fancy your chances :-)