It doesnt even do that. All that being an atheist requires is a lack of belief in god(s). Any further implications of this lack of belief vary between individuals. Many atheists share a pro scientific humanist philosophy (and perhaps you could consider humanism a religion) but that does not mean we all share a common belief in the goodness of humanity, or that all atheists think that the scientific method is a good form of inquiry.
The way I see it even though you aren't consciously thinking of the number of drum beats as they pass by, you are still perceiving that number of beats and keeping track of it somewhere in your sub conscious. You may not use the same system to count, but I would argue that any method which is used to keep track of an incrementally increasing value even when not specifically defined as a number is a form of counting.
Music is probably the most common form of sub conscious counting we have, what is counting if not pattern recognition? When counting a series of number all you're really doing is keeping track of your position in an already recognized pattern and then continuing that pattern when you reach a number you have never used before. The same thing happens when you repeat a song that you know from memory, keeping your position in the music-space of a song is akin to keeping your position in given number space while counting. Were just aware of it in different ways.
Back on topic, I don't the ants are consciously thinking one... two
When bad men combine, the good must associate; else they will fall one by one, an unpitied sacrifice in a contemptible struggle. - Edmund Burke