Why do people study animals (and other creatures)? Here are some answers -
1. To improve animal welfare - Humans use animals for food, sport, labour, entertainment, etc. We need to ensure that these animals are treated well. That is, until we eat them (in the case of animals in the food industry). therefore, we research their living conditions in these working environments. Are they treated well before being processed, or while being used on farms or as livestock, or while being bred for shows or for races?
2. Conservation - Some creatures like insects are essential for ecosystem maintenance. We need to conduct studies to find out if their populations are changing and what factors affect this, in order to maintain optimum numbers to help us maintain our ecosystems to suit our personal economic and aesthetic interests. Studying physical differences between species and correlating these with our knowledge of genetics, geography, geology, etc. adds to our knowledge of physical evolution and the selection pressures involved, which in turn adds to our knowledge of biological processes, genetics and human and animal welfare and conservation.
3. Disease prevention - Many creatures are responsible for spreading disease. We need to study these to find out how we might control their numbers. Other creatures help us find cures for diseases by being test subjects in disease research, or by providing us with biochemical materials that help us lead safer and more comfortable lives.
4. To improve human welfare, by adding to our knowledge of our minds and evolutionary history - We need to study apes, dogs and other creatures to find out more about differences in behaviour patterns between them and us. This adds to our knowledge of how and why we might have evolved certain behaviours, based on our knowledge of how distantly related these animals are to us. Studying differences in individuals within a species also tells us about how personality differences and other mental abilities develop in different species. We can then determine causes and make predictions, which helps us figure out how mental processes work, and compare these with our own, to make studying our own species easier, and add to our knowledge of neuroscience, to make it easier to detect, predict and prevent abnormalities in human behaviour.