All you need at the beginning is to take a fine-point black marker and cover the entire page with a gesture sketch of the animal in the image. Look closely at your reference photo or illustration and analyze the shapes that comprise the shape your animal. This is because the major problem in making images of live animals is getting them to hold still to pose. Put the photograph of the animal in front of you or a nearby wall where you can see it while drawing.
You need to improve your practice sketching to these basic shapes like oval head, a smaller oval for snout, triangles for ears and lengthy ovals or rounded rectangles for legs. By doing this, you are already emphasized the animal’s characteristics, increasing the believability of the animal and adding a personality. Pay attention when making paws and feet of the animal to make sure that they look real.
Check again on how to draw cartoon at your reference photograph or illustration to see the prominent features and details of your jungle animal. A chimpanzee would be having the long arms and expressive face and ears. A tiger has striped pattern on their body.
You may also want to add detail elements from the background. It is fine to erase and redraw again. You need to increase variety of drawing line intensity to make the eye to particular segments of the jungle animal.