Cat Body Language
Cats are complex creatures & knowing what their body language is telling you is very important.
Tails up, ears down, paws curled. These all mean something, and you need to know what. Each cat is different and will exhibit their emotions in different ways.
It can be hard sometimes to figure out what the cats are telling you, and how to respond to them. It is a lot of patience, trial and error. Once you know what the cat is telling you it gets a little easier.
The various illustrations below have been taken from some very helpful websites. The internet is filled with sites on cat body language. It really helps your foster experience the more you learn about.

This Readers Digest & Sherry Haynes illustrations are a great starting place for learning cat behaviours. We all know that a hissing cat is not going to be friendly, but what does a tail up or down mean?
Take note of the following, and try to match it to the illustrations.
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Ears
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Tail
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Paws
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Eyes
Once you know what the emotional state of your cat is, you can proceed in the direction you need to. If you have an aggressive or shy cat, the Common Behavioural Issues page can help you start to socialize them.
Remember that most cats when you get them are stressed. They are reacting to being uprooted and placed in a new situation. This behaviour may last a few hours, a few days, or a few months depending on the cats situation.



This adorable poster from Catsu shows different cat postures.
Most scared cats will follow this chart pretty much in order as they socialize.
Ready to Run Poses
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Sitting up straight
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Sitting low well
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Curled feet
Relaxing A Little
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Front legs relaxed
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All legs relaxed
One Happy Cat
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Belly showing
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On their back

The Most Extreme Cat Body Language - Scared, Feral or Shy Cats
These cats are SCARED, and do not want you around. Feral cats are not socialized at all, and are the trickiest cases. Scared or shy cats usually have some socialization.
Eyes will be wide, ears flattened, body will be in a position to flee - tense with feet tucked under. These cats will generally hide and try to make themselves as invisible as possible, or get ready to attack. The tail could be lashing back and forth, or tucked. Some cats will also arch their backs and their fur will be on end. They will let you know they are not happy for you to be around by hissing, or swiping if you get too close.
Believe it or not, these cats can be socialized. They may, or may not end up as lap cats, but they can can learn to trust and be able to share a space with you successfully.
Other Resources
General Cat Body Language
Cats Protection https://www.cats.org.uk/help-and-advice/cat-behaviour/cat-body-language
RSPCA UK https://www.rspca.org.uk/adviceandwelfare/pets/cats/behaviour/understanding
Tail Body Language
Chewy https://be.chewy.com/cat-tail-language-what-your-cats-tail-says-about-her-mood/
Ear Body Language
Hills Pets https://www.hillspet.com/cat-care/behavior-appearance/cat-ear-language?lightboxfired=true#
Aggression in Cats
ASPCA https://www.aspca.org/pet-care/cat-care/common-cat-behavior-issues/aggression-cats