Although pet rats tend to be sweet-natured and get on well with people, the odd one may bite. Your rat might be biting out of fear or as a form of rough play, but the most common explanation is just mistaken identity -- the rat has assumed your finger is a snack. This is especially likely if you make a habit of giving him treats through the cage bars.
Determine why your rat is biting. If he bites when you pick him up and acts nervous around people generally, he’s scared. Well-socialized rats won’t do this, but rescues might. If he bites occasionally when you’re handling him and not usually very hard, he’s probably playing. Rats play-fight a lot. If he bites fingers pushed through the bars, he thinks the fingers are treats. Gentle nibbling which doesn’t hurt in the least is not going to turn into biting. Your rat is just being inquisitive, trying to catch your attention or showing affection, and you do not need to do anything. If the biting rat is an unaltered male who seems to be territorial or aggressive, neutering might help, but discuss this with your vet first.
Stop feeding the rat snacks by hand, especially through the bars, if he’s biting from mistaken identity. Overenthusiastic rats might bite your fingers by accident or just assume that anything pushed into the cage is a treat. Remind visitors and other family members not to try and pet the rat through the bars.
Squeal loudly whenever he bites and pull your hand or other body part away rapidly, even if the bite is gentle and doesn’t really hurt you. Rats do this to let each other know when something is painful. Cry in a high-pitched tone so your rat hears you clearly. If this doesn’t stop the habit, rub a mint-scented hand cream into your hands or whichever body parts he bites. While the bitter spray for puppies doesn’t work well on rodents -- the bitterness doesn’t taste very strong to them -- rats hate the smell of mint. If he bites your feet, try a mint foot spray. To make your own mint hand cream, mix a plain unscented lotion with a few drops of peppermint essential oil. Note that your rats probably won’t like being touched once you’ve put this on your hands, so don’t handle them afterward. To make a mint foot spray, shake up some of the oil with water in a spray bottle. Also avoid playing nudging games with rats that get overexcited and end up biting too hard. Let your rats play that game together and make human-rat playtime a more sedate affair.
Avoid picking him up if he’s a scared rat. Instead, begin by spending time just near the cage, and later stroke him when he lets you. In this particular case, offering treats might help. Put on gloves on the occasions when picking him up is essential. Mother rats may bite to defend their babies. In this case, just leave her alone -- let her and her offspring approach you when they are ready. If a previously gentle rat suddenly starts biting, he might be ill or injured, so arrange an appointment with your vet as soon as possible.
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