why do cats tails go big and thick when they run into a dog or a cat that they dont like?

yesterday my friends brought over their new puppy and our cats tail got so bushy and she was really tense and her pupils were massivewas she scared, or angry?

They are trying to make themselves look bigger to intimidate their foe.Thats why they arch their backs too.

they do it to make themselves look bigger.

Pure entertainment. Cats look ridiculous with big Christmas Tree tails.They do it to make us laugh.

Cats tails puffs up and they arch their back and hiss to tell the introder that they arent welcomed and also to make them llok bigger.As well, if the cat isnt used to other animals around they are protecting what they know as THEIR territory, she will get used to the dog over time.

When cats are scared or threatened, they bush up their tails and arch their backs to make themselves look bigger and more intimidating. If you see a cat doing that when you approach, take it as the cat saying "Leave me alone or you'll be sorry."

She was scared!! when they arch up like that many people think they are being aggressive but really they do it out of fear. If their eyes stay small and their ears go back however that means they are going to be aggressive, Its all about the face in cats whereas in dogs its about the body. Cats fur goes up weather they are scared or gonna attack, it makes them look bigger (and possibly less scared)! Just watch her face and then you will know!!

Scared, probably. My cat, when around new dogs goes crazy. Big tail, wide eyes. tense. Just keep that kitty away from puppies for now, or let her watch from a distance, so she cant get close to puppy. This will let her get used to the dog, and maybe that will help/

they are both scaried and angry...they puff up their tail to intimidate

theyu do it so they try to tell the other animal that they are not afraid of them but they are actually really afraid

she was scared the puff up to make themselfs look bigger. to scare there enemys. they can also arch thier back to. when they see someone they dont like there first thing that pops into their head is to defend themselfs, so they make themsefs look bigger to scare their opponints away.

their tail goes big and thick as a sign to show the other dog or cat to stay away. basically it's a warning sign and seeing as it was a dog your friends brought round i'd think she was angry that he was on her property.if ur friend brings their dog over more she wont be as angry your cat. hope this helps !

The same reason when you get scared you get goose pimples and your hair stands on end.

To make themselves look bigger