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Vision: What's He Thinking When He Walks Off the Table?
nice to think that ferrets, famous for their goofball antics, goof
around solely for the entertainment of their humans. The truth is, the
way their eyes work plays a big role in their "silliness."
Most ferrets have very bad depth perception
and will walk nonchalantly off a table, bookcase, or windowsill without
hesitation. Perhaps they can't see how far down the floor really is.
Though you might find this habit of theirs amusing, safety is an issue;
you should ferret-proof your home so your fuzzies can't climb up tall
objects and then fall off. Some ferrets are terribly afraid of heights
and will scramble away from the edge of a table, or be extremely
uncomfortable about riding on your shoulder unless supported by your
Ferrets have "binocular" or
"stereoscopic" vision, meaning that their eyes are placed more
to the sides of their heads than human eyes are. This gives ferrets much
better peripheral (side) vision. Because a ferret's eyes are one solid
color (usually black), people sometimes assume that the eyes are fixed
in the head (yes, I have actually been asked about this). This is of
course incorrect. Like humans, ferrets can move their eyes without
moving their head. Ferrets don't see much detail beyond a few feet, so
it's not likely that your ferrets see the specifics of your face when
they look up at you; they just know that you have a face.
All this might make it sound as if your
ferret is at a huge disadvantage as he makes his way around. But
overall, ferrets depend more on their senses of smell, hearing, and
touch than on their vision. Also, at close range (one or two ferret
lengths), your ferret actually sees better detail than you do—and
better detail than a cat does. Ferrets do have a blind spot right in
front of their nose, so they'll sniff when looking at something
Ferret eyes work best at twilight, an
ability that was probably inherited from wild polecat cousins who hunted
at dusk and dawn. Ferrets don't see well in pitch dark and have
difficulty adapting to sudden bright light. However, they see in
low-light conditions much better than humans do. This is because
ferrets, like cats and horses, have something called a "tapetum
lucidum" at the back of each eye—a reflective layer that shines
even the smallest amount of light back into the eye. It is also because
of the tapetum that a ferret's eyes seem to glow in the dark.
Pupil shape also helps ferrets see well in
low-light conditions. Unlike humans, who have round pupils, ferrets have
slit pupils. This enhances edge detection and makes objects more visible
in poor light. Cats, too, have slit pupils, but theirs are slit
vertically, while ferrets' are slit horizontally. Because of this, a
ball bouncing up and down is much more exciting for your ferret than for
your cat (who would prefer to see the ball zip across the floor). The
slit pupil makes up for the ferret's nearsightedness: Although ferrets
can't make out distance detail, they see movement quite well. So if you
stand still, your ferret may not see you across the room, but as soon as
you move, he will.
Red is the only color that domesticated
ferrets can see; other colors appear as shades of gray. This is not
surprising, because color is not important for seeing in low-light
conditions. So don't deliberate for too long over what color hammock to
get for your ferret.
Older ferrets lose their vision just like
older humans do, and they may become totally blind toward the end of
their life because of cataracts. Albino ferrets often suffer from being
cross-eyed, which reduces their ability to see. Also, some albinos have
an abnormality that sends scrambled signals from the eye to the brain,
which disrupts binocular vision and the ability to correctly process
visual stimuli. Colored ferrets with albino genes (especially cinnamons,
dark-eyed whites, and pandas) can also have this albino vision
abnormality. I have raised several ferrets with vision problems, but
they don't have many problems getting around—and they play just as
well as everyone else!