They’re still killing a few billion other animals yearly, just that those are “accidents” instead of being on purpose.

Very large numbers of mammals, birds, reptiles, amphibians and invertebrates are killed on the world’s roads every day. A Humane Society volunteer survey conducted over three Memorial Day weekends in the 1960s estimated that one million vertebrate animals are killed by vehicular traffic daily in the United States. A 2008 Federal Highway Administration report estimates that 1 to 2 million accidents occur each year between large animals and vehicles. Extrapolating globally based on total length of roads, roughly 5.5 million vertebrates are killed per day, or over 2 billion annually.