thin hair on rabbit ears

Question
I've found several similar questions like this on allexperts.com, but my
rabbit's symptoms do not seem to quite match.  

I have a roughly 13 week old female dwarf lop rabbit, whom I purchased from
a pet store.  When I bought her I noticed a very small area on both her ears
(in the same place) that had thinner hair.  I didn't think much of it at the
time.  Its been 4 weeks since I've brought her home, and the thin hair patch
has spread.  It now covers most of both her ears, in the same area. The fur is
so thin that you can easily see the skin and all the veins in her ears.  She isn't
balding, but it really doesn't look healthy.

There is no internal ear discharge.  There are no mites, either on her main
body or ears.  She does not shake her head, she does not scratch more than a
normal rabbit.  Her nails are properly trimmed.  She has been to a vet who
knows rabbits, and he has no idea what is wrong with her.  Other than her
conjunctivitis (for which she is currently receiving treatment), the vet says she
is perfectly healthy.  

Her diet is standard: unlimited hay, unlimited pellets (for another week, when
the rabbit books I have suggest that her pellet intake start to be limited),
fresh water, and an occasional yogurt treat.  I will also begin starting her on
veggies in a week.

Most sites on the web suggest ear mites as a cause for thinning hair on the
ears of rabbits.  However my rabbit has none of the secondary symptoms, and
also does not yet have any bald patches.  I would really like to know what is
going on, and how to stop it.  I appreciate any information you can give me.

Answer
Dear Jadina,

A normal rabbit ear has very little fur on the external surface that's closest to the head when the ears are cupped outwards.  If you view the picture here:

http://farm1.static.flickr.com/32/38152654_aad6be5f56.jpg?v=0

the area of the ear that should be nearly bald (but have a fine covering of very thin, silky fur) is visible as the pink part of the bunny's ear, to the left of the photo.

This is absolutely normal.  The rabbit ear is an important organ for thermoregulation, and the part with thinner fur allows the internal blood vessels to carry blood to the ear for convective cooling.  This is also why the blood vessels are so prominent in this part of the ear.

So please don't worry about the thin fur on her ears in the absence of any other signs of trouble (flakes, redness, scratching, etc.).  It's completely normal, and a necessary feature of rabbit anatomy.  (And it's very soft and silky to stroke with a gentle fingertip!)  :)

Hope that helps!

Dana