Male Bunny Losing LOTS of hair, very small

Question
I've had a male and female dutch lop rabbit for about 2 years now.  The male is neutered and the female isn't fixed at all (had 1 litter about a year and a half ago).  They seem to get along fine, but occasionally fight.

Other than that, I can't spot any problems.  Except that my male rabbit is practically half the size, or less, than the female.  Even when not comparing them, he looks incedibly small (I know females are bigger, but this is worse than usual.  either she's getting really fat, or he's getting very skinny).  I always feed them pellets and fresh water, but not always the hay they need (though I have been keeping up with this lately).  Occasionally, they get some honey nut cheerios as a treat.  Maybe 4 or 5 cheerios.

The male, besides being very small (no idea on weight as I don't own a scale) also loses a lot of hair and has done so steadily for over a year.  It comes out in clumps, but I never see any bald spots.  The hair is also turning from a darker gray, like his sister/buddy to a lighter gray, or almost white.  The hair is everywhere in my apartment.  If I clean up, there's visible dust bunnies on the floor within the day.  I can't even pick him up anymore as I end up getting covered in so much hair that it takes 10 minutes to clean myself off again.

And still, no bald spots.  

As far as behaviour goes, he seems to eat and drink normally and still interacts with his buddy.  Lately he seems to have become more calm and friendly, something I've attributed to gaining a roomate of my own so more people are around at a time, and more often.

I'm a bit puzzled as what I thought was some small seasonal molting hasn't stopped in more than a year and seems to me it's getting out of hand.

Do you have any ideas what could be causing this small size and excessive hair loss (without balding or scabbing etc).  Are there any checks I can perform (short of buying a scale) to access his physical condition and weight?  

I have noticed some large (2-5 cm long) clumps of 'greasy' (but not slimey)looking and smellier than usual clumps of poop occasionally.  But since both rabbits are together overnight and it's so rare, I can't tell which one of them is the culpret.  I know this is normal, and that they eat them, but when I come home from work, sometimes they're just there, and they haven't been eaten.  In 2 years this has never happened until the last month or 2.

Any and all help is appreciated, thank you.

- Jason -  

Answer
hi jason
There are many diseases that can lead to excessive hair loss including the following :

Nest building - rabbits will pull out hair to add to other materials in the nest
Dominance behaviour by other rabbits
Excessive grooming by overzealous owners
Behavioural vices - boredom, stress
Ectoparasites - eg mites which cause itchiness and self-trauma - rubbing or biting
Infections (bacteria or fungi) - causes localised hair oss, and self-trauma - rubbing or biting
Nutrional deficiency - eg inadequate fibre intake  has been reported to result in hair loss
check these out against yours and see if nything is appropriate
he should weigh between 4-5 lbs.
dave.