How reindeer eyes transform in winter to give them twilight vision

[Still Waters]

Reindeer are loved the world over for their dark, expressive eyes, majestic antlers and magical association with Santa Claus. The moment you learn the cold, hard truth of how Christmas presents arrive under the tree is a harrowing one that blights many a childhood. But reindeer are more special than your cynical older sibling or classmates would have had you believe.

The Arctic reindeer, like its main predator the wolf, is incredibly well adapted to its snowy home, where winter conditions can see temperatures drop to -50°C and low levels of daylight. Reindeer have a second layer of fur, and wide crescent-shaped hooves that keep them stable and allow them to dig in the snow. And as our new study  shows, their eyes undergo physical change as the seasons turn which allows them to see clearly in the long winter twilight.

https://theconversation.com/how-reindeer-eyes-transform-in-winter-to-give-them-twilight-vision-185819

Reindeer eyes seasonally adapt to ozone-blue Arctic twilight by tuning a photonic tapetum lucidum

https://royalsocietypublishing.org/doi/10.1098/rspb.2022.1002