These are really rad! The volume fo the form and the perspective is really well done here and the previous studying you've done is definitely showing! As you draw one thing I'd recommend to keep an eye on is the height and width relationships. Some things such as the horse and rhino's faces seem a bit wide, and the neck on the rooster is reading too thin. You can use comparative measurement to help check these. Remember to keep checking these relationships throughout the drawing process because things do have a way of "drifting" or mistakes from earlier that you didn't catch are now being caught.

Your foundation drawing looks really nice . keep it up

Hi Becky, the horse is the one that came out best, you realised that some parts are stiff and are useful to indicate the twisting of the torso. For the hen: I would advise you to treat the head more as a wedge, and the legs as more angular shapes, they are pretty much all bone, sinew and skin. The rhino's shoulders should be treated exactly as you did the horse's: they are a block connected to the spine into which the legs fit. When drawing animals, remember that there are constants (more than anything else, remembering this makes your life a lot easier). Everyone has a backbone (unless we are talking about invertebrates), if we are talking about animals (reptiles, amphibians or birds) with legs, the first thing to do is to identify the 4 main forms. The first two are the pelvis and the shoulders, which you can generally represent as boxes connected to the spine, and then an ovoid shape for the thoracic gabba, which is connected to the shoulders (just like for humans. If you have done the exercise for the human body you will also know how to do it for animals, the proportions change, the posture, but the base is the same). The last big shape is the head, which you can represent with a wedge, a circle or a combination of shapes and planes depending on the subject (and your experience). The legs (or fins or wings) fit into the shoulders and pelvis, start by defining the gesture and then building the structure on top of it. Don't fall into the habit of always representing them as cylinders or cones, because very often the legs, for example in herbivores (gazelles, deer, horses, etc.) are extremely thin and what you see is almost exclusively bone, tendon and skin, so closer to very thin boxes or wedges than to rounded shapes. Don't get me wrong, your sketches are very good, I only mention these things to help you take the next step if you are interested in continuing to draw animals. :)

Nice work!