It is very easy to tell the difference between male and female
rats. Males have large prominent testicles which are visible under the
tail from well before the age when they are ready to leave their
mother. They can draw their testicles up inside them if they are
afraid, but will not do this for a long period of time. A good rat
breeder or staff at a good pet shop will find it easy to tell which
sex baby rats are.
Both male and female rats make great companion animals, although they
have different characteristics. Does (females) are smaller, more lithe
and more active than Bucks (males). Does have a smoother coat (unless
they are rexes, in which case they have a less curly coat); they have
almost no discernible smell and rarely scent-mark
territory. Approximately once every five days a doe will be in heat
for around twelve hours. This usually happens in the evening. You will
notice that your doe is in heat by changes in her behaviour: she will
be jumpy, skittish, and may perform a mating 'dance' by freezing,
arching her back and fluttering her ears if you tickle her
haunches. Bucks are larger and more laid-back than does. Their coat is
coarser and has a slight musky smell to it. While they are as
affectionate as does, they are much lazier, and when left free-range
will often curl up in a corner or on your lap. Some bucks scent mark
almost everything that they run into -- including their human
companions -- but this is not as disgusting as it sounds as the
'scent' is only a few drops of urine and does not smell strongly. Very
rarely, a male may become overly aggressive towards his cage mate(s)
or hard to handle when he reaches 4-5 months of age (and sometimes
later) if his levels of male hormones are too high. This is not a
usual occurrence and should not be confused with the normal rough and
tumble of adolescent rats. A rat suffering from an excess of male
hormones will display "fight or flight" behaviour almost constantly:
he will puff up his fur, hiss and huff at other rats and people, and
may attack or bite cage-mates or his owners. This condition can
usually be cured by having the rat neutered, and his hormonal levels
and behaviour will soon return to normal. If you must have a buck
neutered, make sure that you use a vet who has done this operation on
rats before: rats have an internal muscular structure unlike that of
dogs and cats, and a slightly different procedure must be used (the
inguinal canal must be stitched closed). Neutering normally costs
about =A330 (at time of writing -- 1996). The National Fancy Rat
Society has a list of vets that have experience in dealing with rats.