rabbits: all in the bunny family

Question
well im moved into my new house! My mother rabbit is free as usual, being
the angel housetrained pet she is. However ive had to separate the babies
completely from contact with her due to some very strange behavior. Im
hoping you might be able to make sense of this.
When by chance the mother and son rabbit meet, the son (8 months) runs
around frantically and starts nipping his sister (his bonded companion) which
gets her running around too. What is this? The girl baby has no issues being
around mom at all, but the boy goes nuts! Because of this my baby bunnies
are in a completely different room of the house in a playpen (6x4ft) and only
get out for playtime for roughly an hour a day. I feel terrible about it but i dont
know how to deal with this strange behavior. What do you think?

Also, i have a question about rabbit growth and development. At 8 months
my bunnies are still only half the size of their mom. A baby rabbit is still only
two handfuls, the size of two large grapefruits put together. I can get you
some concrete numbers tomorrow. When do rabbits get to full size??
Sometimes i feel like im raising peanuts!
thanks for everything!


Answer
Dear Lauren,

The behavior the boy is showing is typical of a bunny who's being very jealous.  He's nipping his sister to keep her away from mama, because he wants sister all to himself.  Once the babies are spayed/neutered (And you should do this soon, because they are old enough to be fertile!  You do NOT want incestuous relationships and the genetics problems that come with that!), this behavior should subside a bit.  But you might need to engage in some re-bonding tactics, once everyone is "fixed."  Tips can be found in the articles here:

http://search.atomz.com/search/?sp-a=00062824-sp00000000&sp-q=bonding&user=enter...

At the age of 8 months, the babies should be approaching the size of their mother.  You don't give precise size (e.g., weights) for the bunnies, but I wonder now if one of the parents had recessive genes for dwarfing.  Here's how it works, in a nutshell:

All of us carry two copies of every gene for every trait.  We get one copy from mom, and one from dad.  The two versions (alleles) of the gene may be the same, or they may be different.  An allele of a gene that masks the expression of a different allele of that gene is said to be dominant.  The one whose expression is masked is said to be recessive.

For example, freckles in humans are controlled by a single gene with two versions, F (dominant; codes for freckles) and f (recessive; no freckles).  A person with FF or Ff genotype will have freckles.  A person with ff will have none.

There is a dwarfing gene in rabbits we'll call "d".  It is the mutant form of a "normal size" gene calle "D".  If a rabbit has two copies of the normal gene (DD), the rabbit will be "normal" size for the breed.  And if the rabbit inherits two copies of the mutant gene (dd), then the condition is lethal, and the baby will die (these are the "peanuts").

In this case, though, D is *incompletely dominant* to d, meaning that if a rabbit inherits D from one parent and d from the other (the genotype for the gene will be Dd), then the rabbit will be a dwarf--the trait is sort of "in between" the two extremes, and the babies are viable, but small.

It's possible that if your mama bunny mated with a dwarf bunny, that the babies inherited the dwarfing gene from dad, and are dwarfs.

Peanuts usually don't survive, and they have lots of other congenital problems besides being very small, so I doubt your bunnies are peanuts.

If you send pictures of mama and babies, I might be able to look at their shapes and give you an idea of whether this could be the case.  (Send to dana@miami.edu or upload to AllExperts with their new photo function.)

Hope this helps.

Dana