Ship rats sleep extremely heavily. Don't just stick your hand into the nest without knocking first: even the most amiable ship rat may take a piece out of you if wakened from a deep sleep to find itself being grabbed.

Being a wild species, aggression is much commoner in ship rats than in fancy rats. In bucks this is normally due to over-dominance (i.e. excessive testosterone): they usually mellow slightly as they get older, but anyone who is going to keep an undomesticated animal must be prepared to cope with aggression. Nursing does in particular can be quite startlingly fierce.

Aggressive ship rats have a nasty habit of sitting gazing dreamily at you as if butter wouldn't melt in their mouth, and then leaping at you without warning as if fired from a gun, making horrible noises. Since they are an arboreal species, I imagine that they use this surprize attack to startle predators into falling out of their tree. It must be pretty effective: they are probably not a suitable animal for someone with a weak heart.

If an aggressive ship rat is still handleable, you can often convince them that you are the dominant animal by picking them up by the scruff, holding them up in the air and "grooming" (lightly rubbing and tickling) their stomachs - persuading them that you are Mother. A few ship rats, however, don't have the scruff reflex - and are likely to turn round in their own skin, hack you and run away.

Once age has calmed them down, over-dominant bucks often make wonderful friends - since the mere fact that they treat you as a rival means that they relate to you as another individual and not just as a meal-ticket.

If you have to clean a cage with an aggressive ship rat in situ, wear elbow-length heavy gloves or wrap a towel around the hand. They at least won't be able to bite straight through it as a Norway rat could.

Even if he isn't a biter, a dominant buck may become excessively territorial and go round scent-marking everything - including you - by urinating on it. This behaviour is harmless, if sticky: but your cat or dog may not be happy to find a mad rodent peeing on their head.

Ship rat fights normally consist of a lot of swearing and rodent kung fu, but no serious injury: in any case their bite is much weaker than that of the Norway rat. However, I do know of one case where a sick animal was eaten by its cage-mates - perhaps because it no longer smelt like the individual they knew - and bucks who seriously hate each other will chew the bases of each other's tails, mouse-fashion.