The mammal group with the highest population is the mouse. With an estimated 30 per every human on earth, that means there are approximately 210 billion mice on the planet. The single mammal species with the highest population would be Humans. Cows number approximately 1.3 billion. Dogs number 500 million, cats number 300 million. In short, the animals whose specie has the highest numbers are the ones with the most importance to humans. humans.....yeah humans
