@coolboymew Basically our brain interprets poses and body language as a way to interpret threats from other people. This probably is the reason why "flirtatious" body language exists.
The brain goes so far with this that even non-human figures like stick figures and 3d wireframe images can have body language.
Naturally humans can interpret body language from animals too. So when drawing fantasy animals that don't exist you can draw them in real animal poses and body language to express the right emotion you want them to express. (Simple example: all animals show teeth with aggression)
stock-vector-body-language-basic-posture-simple-stick-silhouette-sketches-vector-614300075.jpg