That's a valid question, for which you shouldn't be downvoted, but you should know that it's not anything about it being a force of will by the animals, more th

That's a valid question, for which you shouldn't be downvoted, but you should know that it's not anything about it being a force of will by the animals, more that it's a new behavior of how the animal cells are diverse. In other words, maybe the animal is in higher temperatures that trigger a gene to begin executing this particular 'circuit', which causes proteins to form that make slightly more responsive nerve cell ion channels. Where previously we assumed that variation was spread mainly through genes in DNA, this headline shows that there are other ways beyond just DNA-> RNA-> protein. I may have totally borked this attempted analogy, so hope that helps.