There are various ways to define a study. One type of study is applying yourself to learn something. Another is an area of some branch of knowledge. Then that's also the room you see in old movies where the star sits in an easy chair surrounded by walls lined with books.
But in this case a study is a preliminary artwork that will later be developed into or made part of a larger and more complete work. Or it is a preliminary artwork that didn't go any further. We will not bother to distinguish what type of study we have here.
But if your want to know more about rhinoceri (if that's the plural) - or more accuate - rhinocerotidae - this is a designation of an animal family and is therefore even a broader designation than a genus. The genus rhinoceros is very specific for the one horned rhinoceri and so is not what this study - a pastel - represents. To CooperToons' untrained eye, this appears to be a rhinocerotidae diceros bicornis.
Rhinos, Sally Walker, Nature Watch, Lerner Publications, 2007.