"My God, look at the hooves, this was bovicide without any doubt."
Thus, murder is a species of homicide. The specific differences of murder relative to homicide is that it is voluntary, premeditated, and malicious.
The law merely recognizes this distinction. It doesn't construct some convention around homicide. Indeed, law in general is a particular determination of general moral principles within a particular jurisdiction.
So, a lion doesn't commit murder, because a lion's actions are involuntary and neither malicious nor premeditated. Also, while a lion can kill a person or non-person, it is not capable of homicide, because its meaning specifically pertains to the killing of one person by another.