Dear Sinéad, Siouxsie and Thomas:
My name is Nicole and I am a seventh grader doing a science project on cats purring. Could you please tell me if a cat's environment -- for example, being in a loud room or a quiet room -- affects their purring?

Thanks for your help!
~ Nicole

Sinéad: Well, Nicole, we're always willing to help people out with their school projects, so we've decided to move your letter up in the pile and answer it this week.

Siouxsie: Quite a while ago we wrote an article about how cats purr, but we haven't written all that much about the effect of the environment on purring.

Thomas: We believe that emotional state has more bearing on our purring (that is, the loudness, frequency of purrs, or whether we purr at all) than the environment in which we live. However, certain environments can cause stress or make us feel more relaxed, and in that way maybe environment does have an effect on purring.

Sinéad: The noise level in a room will certainly make you more or less able to hear whether a cat is purring. If you're in a room and you're playing video games and listening to loud music, or there are a bunch of people talking while the TV is going, you probably won't be able to hear your cat even if he or she is purring.

Siouxsie: And depending on the cat, all that noise might be so stressful that a cat wouldn't want to purr. Some cats become very stressed in loud environments, and that emotional stress would keep a cat from feeling comfortable enough to purr.

Thomas: As a general rule, cats prefer quiet and order. This, of course, will vary from cat to cat. Some very outgoing and people-oriented cats, particularly those of us who were raised in busy, louder homes, will have little to no reaction to noise and high traffic. Speaking for myself, though, I like it quiet, and I tend to purr more when I get to curl up and relax in Mama's lap.

Sinéad: Other environmental factors that might affect a cat's emotional state, and therefore their willingness to purr, are the temperature of a room, whether there are familiar people around, and whether they feel safe. I'm always more likely to purr if I feel warm and safe, and especially if I'm curled up in Mama's arms under her blankets in bed. I purr really loudly then because I'm so happy and contented. Until Thomas walks on my head, that is!

Thomas: Hey, I get a turn under the blankets, too. We agreed, I get under the blankets at night and you get under the blankets in the morning!

Sinéad: Did not!

Thomas: Did too!

Siouxsie: You could both solve this problem if you stopped being such ninnies and curled up on top of the covers instead of under them.

Sinéad: Anyway, Nicole, back to the subject at hand. You probably know from your research that purring happens at the same time, and through the same passages, as breathing. We purr at the same rate we breathe. So any environmental changes that would change our respiration rate would change how fast or slowly we purr. For example, when I'm snuggling under the blankets, the level of carbon dioxide (CO₂) in the air I'm breathing increases every time I exhale (breathe out). And, like humans, as the level of carbon dioxide gets higher, my breathing gets faster because my body needs to take more breaths to get enough oxygen (O₂). Eventually I have to get out from under the blankets because I need more oxygen than I can get from the air there, and it's too uncomfortable to stay in a place where I can't get enough oxygen to breathe.

Siouxsie: Another thing that would affect how quickly or slowly we breathe (and purr) is heat. When it's very hot, cats breathe faster. That's the only way we have to get rid of excess body heat, since we don't sweat. So when we're too hot, we breathe faster, and if we're inclined to purr we'll purr faster, too.

Thomas: Basically, what we're saying is that any environmental factor that would affect a cat's breathing will affect their purring as well.

Sinéad: If you read our past column on how cats purr, you'll find out that we do in fact choose whether or not to purr. We think the factor that's most important in whether or not a cat purrs is the cat's emotional state and stress level.

Siouxsie: We hope this helps to answer your question, Nicole. Good luck on your science project, and if there's any other way we can help you, please let us know.

Got a question? Need some advice? E-mail us at advice@paws-and-effect.com. None of the material in this column is meant to be a substitute for regular veterinary care.