If you have pet rats, you may have noticed that they like to lick your hands, kiss your earlobe, or even nibble on your fingernails. Have you ever wondered why they do this?
Rats are extremely social animals. They use their sense of smell and taste to communicate with each other1. This also applies to their interaction with humans – rats can gather a lot of information simply from the smell and taste of your skin. This is why they will often kiss, nibble and lick you.
When your pet rat gets “mouthy” with you, it’s probably because they want to communicate something.
Read on to find out six reasons why your rat likes to lick or nibble you!
6 Reasons Your Pet Rat May Lick & Nibble
1. Rats Like to Groom Each Other – And You
Grooming is very important behavior for rats2. Rats like to groom other members of their mischief (that’s what a group of rats is called).
Since rats can’t always reach every part of their own body – especially as they grow older and less flexible – it’s crucial that their cage mates help them keep clean. Grooming can also keep skin parasites at bay3.
If your rat sees you as a member of their pack, he or she will try to groom you, resulting in ratty kisses, nibbles, and thorough licks.
If you like, you can groom your rat back: Scratch them behind their ears, on their backs, or on their tummy (if they like being touched there).
2. Rats Want to Bond With You
Nibbling and kissing other rats isn’t only meant to keep them clean – it’s also a sign of rat affection.
Rats groom each other to re-establish their group bond. They learn this from their mothers when they are still pups.
Studies have shown that rats born to mothers who groom more are more relaxed later in life – the kisses they get from their mother helps them regulate their stress hormone levels4.
Your rat may want to extend this courtesy to you. When they kiss and nibble you, your pet rats are trying to bond with you and communicate their affection.
3. Rats Are Rodents and Like To Use Their Teeth
Nibbling and playful biting is very normal behavior for rats. Rats are rodents5 – derived from the latin word “rodere”: to gnaw. A fun fact about rats is that their incisor teeth keep growing continuously all their lives.
Rats need to keep chewing, biting, and gnawing to ensure that these teeth don’t grow too long or become deformed. Using their teeth is therefore daily business to them. In fact, rat teeth have complex nerve endings and can be used as sensory organs6.
It’s no wonder that rats like to explore objects with their teeth – and this can include your hands, ears, or anything that is within reach, really.
From time to time, your pet rat might accidentally chomp down a bit too hard. This is usually not done on purpose, and you can let your rat know that they hurt you by squeaking loudly.
4. Your Rat Can Smell Food on Your Fingers
If your hands still smell like food, it’s no wonder that your rat will nibble or lick them clean. Rats have a very keen sense of smell, so even if you washed your hands, they can probably still catch a whiff of your last meal on them.
In fact, rats are hard-wired to find out what other members of their mischief (including you) ate – this is their way of gathering information about which foods are safe for them7. They do this by observing, or by smelling the breath or paws (or hands) of others.
5. Your Rat Can Smell Other Rats on You
Rats cannot only smell food on you, but also other rats. Especially if you keep two separate mischiefs – bucks and does in separate groups, for example – your rats will be extremely interested to smell your hands after you handled other rats.
By “smelling” pheromones, they can gather information on the social status and reproductive cycle of other rats8.
Pheromones are not actually perceived through the olfactory sense: They are “smelled” in the vomeronasal organ, which is located in the septum of the nose9. And even though humans probably can’t perceive rat pheromone at all, they carry a lot of information for your rats and may encourage them to kiss and lick your hands all over.
6. Your Rats Thinks That You Smell Unfamiliar
On a similar note, rats can tell who belongs to their mischief and who doesn’t by a combination of smells and pheromones8.
If you spend enough time with your rats, your hands can take on the scent of the “pack” – but when you’ve been away, they will bring back all sorts of unfamiliar smells.
A typical characteristic of rats is their neophobia, which is fear of the unknown10. So, if a familiar rat – or human – suddenly stops smelling like their trusted environment, they will try to reverse this by licking and kissing them all over, thus covering them in “ratty smell”.
You may even notice that your rat tries to nibble any wounds or scabs that you might have on your hands, or gets particularly interested in unfamiliar jewellery or nail varnish.
Should You Let Your Pet Rat Lick You?
Now you know why your rat likes to kiss, nibble and lick you!
Another questions is: Should you let them?
There is no harm in letting your rat lick the skin of your hands, as long as it is intact and healthy. Just be sure not to touch your eyes or the insides of your nose and mouth, and wash your hands thoroughly after playing with your rats.
Don’t let your rats lick your wounds or your mouth, because this can introduce bacteria and potentially cause health issues for you. If you follow these basic guidelines, go ahead and enjoy all the ratty nibbles your can get!
Resources:
1. Schweinfurth MK. The social life of Norway rats (Rattus norvegicus). eLife 2020;9:e54020. https://pubmed.ncbi.nlm.nih.gov/32271713.
2. Calhoun JB. The ecology and sociology of the Norway rat: US Department of Health, Education, and Welfare, Public Health Service, 1963. https://archive.org/details/ecologysociology00calh/page/n7/mode/2up
3. Hart BL, Hart LA. How mammals stay healthy in nature: the evolution of behaviours to avoid parasites and pathogens. Philos Trans R Soc Lond B Biol Sci 2018;373. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6000140/.
4. Liu D, Diorio J, Tannenbaum B, et al. Maternal care, hippocampal glucocorticoid receptors, and hypothalamic-pituitary-adrenal responses to stress. Science 1997;277:1659-1662. https://pubmed.ncbi.nlm.nih.gov/9287218/.
5. Modlinska K, Pisula W. The Norway rat, from an obnoxious pest to a laboratory pet. eLife 2020;9:e50651. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6968928/.
6. Byers MR, Cornel LM. Multiple complex somatosensory systems in mature rat molars defined by immunohistochemistry. Arch Oral Biol 2018;85:84-97. https://pubmed.ncbi.nlm.nih.gov/29035722/.
7. Galef BG, Jr., Whiskin EE. Socially transmitted food preferences can be used to study long-term memory in rats. Learn Behav 2003;31:160-164. https://pubmed.ncbi.nlm.nih.gov/12882374/.
8. Otto GM, Franklin CL, Clifford CB. Biology and Diseases of Rats. Laboratory Animal Medicine 2015:151-207. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7158576/.
9. Liman ER. Pheromone transduction in the vomeronasal organ. Curr Opin Neurobiol 1996;6:487-493. https://pubmed.ncbi.nlm.nih.gov/8794101/.
10. Mitchell D. Experiments on neophobia in wild and laboratory rats: a reevaluation. J Comp Physiol Psychol 1976;90:190-197. https://pubmed.ncbi.nlm.nih.gov/1249271/.
Nina has a degree from the Veterinary School in Zurich, with a special focus on microbiological research. Nina has a passion for sports, nutrition and the outdoors and she loves all pets, but rats have a special place in her heart. When she’s not working or reading and writing about all things related to pet health, she loves to travel and surf.
As a small animal veterinarian, Nina is your go-to expert on pet health and nutrition.
