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Video transcript: Bright eyes: Study finds reindeers’ eyes change colour with Arctic seasons

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October 2013

Video show stills of reindeer grazing

Professor Glen Jeffery, University College London
These beautiful animals are Artic reindeer and we have discovered the eyes of artic reindeer change colour throughout the seasons from gold to blue adapting to extreme changes in light levels in their environment which helps them detect predators like wolves. This is the first time a colour change of this kind in the eye has been shown in a mammal.

Video shows the six members of Prof Jeffery's team, then a series of landscapes for the Artic in different low-light conditions

My research team from University College London is funded by the BBSRC and with our colleagues at the University of Tromsø in Artic Norway we regularly travelled up to the Arctic Circle as you can see in these stunning vistas. By studying the reindeer many years over seasons we have shown that the colour change in their eyes help reindeer to see better in the 3 months continuous daylight of summer and the continuous darkness of the long Artic winters and the eyes manage this by changing the sensitivity of the retina to light.

Video shows the different animals with good night vision

Most people are familiar with the way the cats eyes reflect the light back to enhance night vision in fact many animals have this reflective layer it is called the tapetum lucidum (TL) for short.

Video shows the dissected eye of reindeer, followed by several a close-ups showing the colour change the reindeer's eyes go through

Artic reindeer process this reflective layer too and by changing its colour the TL reflects different wave lengths of light.

This image is a close up of a reindeer's eye and shows in the bright light of summer the TL in the Artic reindeer is gold similar to other manuals which reflects light mostly directly back through the retina.

This image shows the eye in winter as you can see it has changed to a deep blue which reflects less light out of the eye.

This change scatters more light through the photo receptors through the back of the eye increasing sensitivity of the retina in response to the limited winter light. We believe this would be an advantage in the prolonged murk of winter. This ties in nicely with our previous research that has shown that Artic reindeer can also see ultraviolet which is abundant in Artic light but it is invisible to humans and that they used this to find food and see predators. The blue reflection from the winter eye is likely to favour ultraviolet sensitivity.

Video shows stills from the Sami tribe, with their reindeer herd

In case you are wondering how we know so much about this huge animal it is by working with the Sami, the indigenous people of the area, and these animals are their primary source of income many reindeer are killed around the solstices for their meat and their eyes shown in this study come from these animals. It is one of the few parts of the animal not used by the Sami.

Video shows a sedated reindeer lying on a work surface, carefully being prepared for this research

The animal in this picture is not dead it has just been given a sedative it was brought directly from the Sami herders 73 degrees north outside of Tromsø, in Artic Norway it is being prepared to have a small gold foil electro placed under its eyelid to record the electro activity and sensitivity of the retina.

The animal is recovered and returned to the field but comes back consequent summer and winter solstices so that we can see how retinal sensitivity changes between the seasons in fact we never found the upper limit sensitivity in the winter eyes so it is likely to be significantly greater.

ENDS

Credits

In partnership with the UCL and University of Tromsø

Image credits:

  • All reindeer and reindeer eye images copyright: Glen Jeffery
  • Cat's eyes copyright Michael Semensonh
  • Racoon copyright Bowlhover
  • UV tree, shrooms copyright Siaron James
  • Tapetum lucidum copyright BalRutilant