Reasons of these paintings

Activities such as catching large fish and hunting large game animals with specialized tools connote increased group-wide cooperation and more elaborate social organization.

In addition to developing advanced cultural traits, humans also first began to take part in long-distance trade between groups for rare commodities (such as ochre (which was often used for religious purposes such as ritual and raw materials.

Evidence from archeology and comparative ethnography indicates that Middle Paleolithic people lived in small, egalitarian band societies, that is small groups similar to a family.

                                      
                                          Cave of Ramales de la Victoria, Cantabria,  España


That is the reason of their interset in animals! They hunted them to get food to eat, blood to paint and bones to make tools, together with the skin to have some clothes to wear...

Now think, children: if you paint something important in your life or in your existance, what would you paint??