Most groups of rats will have one 'alpha' who> is the most dominant. A rat may remain alpha into old age purely by force of habit, and cages can erupt into dominance fighting after the death of an old alpha. This usually calms down once a new boss rat takes their place. If you find a particular rat is being bullied to the point where it is affecting their wellbeing, you may need to either split the group or have the bully neutered and let the group establish a new pecking order. This can lead to a cascade of neutering.
Rats rarely bite, and when they do they usually have a reason. This can be simply due to mistaking your hand for food, from fear if the rat has not been socialised well, or from hormonal aggression which if extreme can be solved by castration or spaying.
Many perfectly amenable rats will instinctively bite a finger put through the cage bars. It's a good idea never to offer food through the bars, as this will encourage this behaviour. Both adults and children seem to have an unthinking impulse to poke their fingers into cages, so it's wise to warn them in advance.
Tilting the head, circling and rolling are all signs of an inner ear infection. See the health care section.
Some rats, particularly those with paler eyes, will tend to weave their head from side to side. This is a way of coping with particularly poor eyesight, helping them to judge distance better.
Both males and females will mount rats of the same sex. Males use this as a form of dominance, whereas females will tend to chase and mount cage mates who are in season.
Rats from a reputable breeder should have been handled and socialised from an early age. If you have an unhandleable or biting rat, you will need to take time for them to learn to trust you. A jumpy rat can learn very quickly if you spend a lot of time together. Try wearing two layers of clothes and popping the rat between the layers while you go about your normal routine. Treats of a food such as pieces of puffed rice cereal can help too. If the rat bites when taking food, try putting a little yoghurt on a teaspoon. The jarring of biting down on a spoon soon teaches the rat to take care, and the nature of the food stops them running away with it.
Female rats come into season every four or five days. Some rats show strong signs of being in season such as squeakiness, fluttering their ears and arching their bodies (called lordosis), others give very little outward sign. Frequent biting and aggression during seasons, or being stuck in season, can be a sign of polycystic ovaries and is usually helped by spaying.
Boggling is a very strange rat habit. When a rat is happy it will grind its teeth together, called bruxing. Because the jawbone and its muscle are so close to the eye, extreme bruxing can turn into boggling, which is popping in and out of the eyes. It's harmless and very entertaining. Rats also brux when extremely unhappy, in the same way that cats sometimes purr when unhappy, presumably in an effort to soothe themselves.
An amusing term for the habit of fluffing the fur up when riled, often accompanied by scent marking from the flank glands and making a foofing sound. Bog brushing is a sign of aggression or hormonal upset. Be very careful when approaching a bog brushed rat; they may bite before they realise it's you.
Rats chew. It's what 'rodent' means. It's a good idea to have a set of clothes that you're not too fond of to wear with the rats. They will chew your clothes, your curtains, your chairs and even wallpaper and carpets. Block things off, hide things, or live with it.
Although your rat will appreciate wooden chew toys, they're not essential. They can keep their teeth perfectly well trimmed by bruxing and normal chewing.