BBC Learnings · Section 11

Why are some animals black and white

Neil, what do the following animals have in common? Zebras, giant pandas and magpies.

Level: B1 · 96 sentences

Transcript

  1. Neil, what do the following animals have in common?
  2. Zebras, giant pandas and magpies.
  3. That's… Pretty easy, Becca.
  4. They're all black and white.
  5. Right. But do you know why these animals evolved to be black and white?
  6. I'm not so sure. Probably something about survival.
  7. That's usually the answer, isn't it?
  8. It is. The animal world is full of colour –
  9. shiny blue peacocks and bright green frogs.
  10. But in fact, hundreds of animal species are black and white.
  11. In this episode, we'll try to find out why,
  12. According to one theory, some animals are black and white
  13. to warn potential predators that they're dangerous or they taste bad.
  14. But what is the scientific term for this?
  15. Is it a camouflage, b mimicry, or c aposematism?
  16. Well, Neil, I'm going to go with C
  17. just because I've never heard of that word before.
  18. OK. I like your style.
  19. Some scientists think zebra's distinctive black and white stripes prevent bites
  20. from flies and other insects.
  21. Zoologist Dr Martin Howe tested this theory by covering horses,
  22. a close relative of the zebra, in stripes.
  23. Here Martin discusses his experiment with Caroline Steele,
  24. from BBC World Service programme CrowdScience.
  25. Do we know what it is about the stripes that's putting them off?
  26. Is it somehow like visually confusing?
  27. We originally set out to test whether
  28. maybe there were these optical illusions at play.
  29. So we did a whole bunch of tests
  30. where we tried different patterns of rugs.
  31. But it turned out that practically every high contrast pattern,
  32. every black and white pattern we used,
  33. almost every pattern was really effective at stopping flies.
  34. Martin conducted a whole bunch of, meaning a lot of,
  35. tests using different colours and patterns.
  36. Black and white stripes created an optical illusion,
  37. a visual trick that makes your eyes see things differently
  38. from how they really are.
  39. As a result, the flies were put off.
  40. They lost interest and didn't bite.
  41. So zebra's stripes confuse insects,
  42. telling them to look elsewhere for food.
  43. But are there other reasons animals are black and white?
  44. Nobody who's seen giant pandas in a zoo would find them hard to spot.
  45. Against a grassy background, they stand out easily.
  46. But seen from a distance in the snowy mountain forests
  47. where they live, black and white makes the perfect disguise.
  48. Here's Professor Tim Caro, a world authority on animal behaviour,
  49. explaining more to Caroline Steele for BBC World Service's CrowdScience.
  50. The giveaway for me was 15 photos of giant pandas
  51. taken either fairly close up or at a distance.
  52. And in two of those photos
  53. I was unable to see anything
  54. in the picture other than rocks and snow.
  55. And then later on I realised that in fact there
  56. was a giant panda in the centre of that
  57. picture some distance away.
  58. Immediately that clicked in my mind.
  59. The pandas were so well camouflaged.
  60. Tim couldn't spot them in the photos.
  61. That's when something clicked in his mind,
  62. a phrase used when you suddenly understand something
  63. after trying for a long time.
  64. Tim understood that pandas use colour to hide.
  65. He calls this a giveaway, something that makes it easy for people to discover something secret or unknown.
  66. So, are animals black and white to repel insects, like zebras?
  67. Or for camouflage, like pandas?
  68. Let's give the final word to Hannah Rowland,
  69. a researcher into another black and white animal, penguins.
  70. Really, science never has a black and white answer.
  71. Excuse the pun with penguins being black and white.
  72. It's often a very complex mixture of reasons.
  73. The answer to why animals are black and white is not black and white.
  74. A situation described as black and white means
  75. one where it's easy to understand what's right and wrong.
  76. In fact, there's no one reason why animals are black and white.
  77. Zebras avoid bites. Pandas hide from predators.
  78. And some animals, like skunks, warn other animals they're dangerous.
  79. It all depends on the specific animal.
  80. And talking of skunks reminds me of my question, Bekka.
  81. According to one theory, some animals are black and white
  82. to warn potential predators they're dangerous or taste bad.
  83. But what is the scientific term?
  84. And I chose C, opossumatism, because I'd never heard of it before.
  85. Well, that's a great way of choosing.
  86. And it's done well for you because you're correct.
  87. OK, let's recap the vocabulary we've learned
  88. starting with optical illusion – a visual trick
  89. where your eyes perceive things differently from how they really are.
  90. A whole bunch of something means a lot of something.
  91. If something puts you off, it causes you to dislike
  92. it or lose interest.
  93. A giveaway is something that makes it easy for people to discover something secret or unknown.
  94. The phrase something clicked in my mind is used when you suddenly understand something at last.
  95. And finally, if you describe something as black and white,
  96. you mean it's easy to understand what is right and wrong.