I'm assuming, if there's just a piece of an animal, you just take your best guess and go on?
by wilderzone moderator
Exactly. If you can see part of the animal, start by going through the "looks like" filters to find what you think is the best match. In this case, the foreground animal is obviously quite tall, so selecting Build->Tall will give you a narrowed down set of options. Then check the horn shapes to match the animal resting in the background. It's most likely the two animals in the frame are the same species. In this case, they appear to be two hartebeest.
As you go on, you'll become pretty familiar with the basic habits and structures of the animals (height, color, build), but sometimes there's really not enough to go on in the image, so just give it your best guess. See this discussion in the FAQs for why your best guess is best.