Not sure what animals have to do with this...
Germany has a population of around 80 million - about a quarter of the US population, but with a much higher population density.
- Have they learned how to get along better than we have?
- Are the cops there more likely to solve problems in a less violent way?
I think both are true. I lived in Germany for 12 years (ten of those years in the military). They certainly have conflicts, but don't seem to resort to violence as quickly as we do here.